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2024 |
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| 193. | X. Miao, Diemer K; Mitric, R J. Chem. Phys., 160 , pp. 124309-1 - 124309-11, 2024. @article{Mitric2024, title = {A CASSCF/MRCI trajectory surface hopping simulation of the photochemical dynamics and the gas phase ultrafast electron diffraction patterns of cyclobutanone}, author = {X. Miao, K. Diemer and R. Mitric}, url = {https://doi.org/10.1063/5.0197768}, doi = {10.1063/5.0197768}, year = {2024}, date = {2024-03-25}, journal = {J. Chem. Phys.}, volume = {160}, pages = { 124309-1 - 124309-11}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 192. | F. Sturm L. N. Philipp, Flock Fischer M I; Mitric, R The Electronic Structures of Azaphenanthrenes and Their Dimers Journal Article J. Phys. Chem. A, 128 (7), pp. 1250–1259, 2024. @article{Sturm2024, title = {The Electronic Structures of Azaphenanthrenes and Their Dimers}, author = {F. Sturm, L. N. Philipp, M. Flock, I. Fischer and R. Mitric}, url = {https://doi.org/10.1021/acs.jpca.3c07740}, doi = {10.1021/acs.jpca.3c07740}, year = {2024}, date = {2024-02-12}, journal = {J. Phys. Chem. A}, volume = {128}, number = {7}, pages = {1250–1259}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2023 |
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| 191. | Wenzel, Michael; Mitric, Roland Prediction of fluorescence quantum yields using the extended thawed Gaussian approximation Journal Article J. Chem. Phys., 159 , pp. 234113, 2023. @article{Wenzel2023, title = {Prediction of fluorescence quantum yields using the extended thawed Gaussian approximation}, author = {Michael Wenzel and Roland Mitric}, doi = {https://doi.org/10.1063/5.0178106}, year = {2023}, date = {2023-12-18}, journal = {J. Chem. Phys.}, volume = {159}, pages = {234113}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 190. | Fischermeier, David; Steinmetzger, Christian; Höbartner, Claudia; Mitrić, Roland Conformational preferences of modified nucleobases in RNA aptamers and their effect on Förster resonant energy transfer Journal Article Phys. Chem. Chem. Phys., pp. Advance Article, 2023. @article{Fischermeier2023b, title = {Conformational preferences of modified nucleobases in RNA aptamers and their effect on Förster resonant energy transfer}, author = {David Fischermeier and Christian Steinmetzger and Claudia Höbartner and Roland Mitrić}, doi = {https://doi.org/10.1039/D3CP04704K}, year = {2023}, date = {2023-11-24}, journal = {Phys. Chem. Chem. Phys.}, pages = {Advance Article}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 189. | Fischermeier, David; Turkin, Arthur; Selby, Joshua; Lambert, Christoph; Mitrić, Roland Simulation of exciton spectra in disordered supramolecular polymers: exciton localization in cisoid indolenine squaraine hexamers Journal Article Phys. Chem. Chem. Phys., pp. Advance Article, 2023. @article{Fischermeier2023, title = {Simulation of exciton spectra in disordered supramolecular polymers: exciton localization in cisoid indolenine squaraine hexamers}, author = {David Fischermeier and Arthur Turkin and Joshua Selby and Christoph Lambert and Roland Mitrić }, doi = {https://doi.org/10.1039/D3CP04557A}, year = {2023}, date = {2023-11-16}, journal = {Phys. Chem. Chem. Phys.}, pages = {Advance Article}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 188. | Issler, Kevin; Mitric, Roland; Petersen, Jens A trajectory surface hopping study of the vibration-induced autodetachment dynamics of the 1-nitropropane anion Journal Article Theo. Chem. Acc., 142 , pp. 123, 2023. @article{Issler2023c, title = {A trajectory surface hopping study of the vibration-induced autodetachment dynamics of the 1-nitropropane anion}, author = {Kevin Issler and Roland Mitric and Jens Petersen}, doi = {https://doi.org/10.1007/s00214-023-03063-z}, year = {2023}, date = {2023-11-08}, journal = {Theo. Chem. Acc.}, volume = {142}, pages = {123}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 187. | Issler, Kevin; Mitric, Roland; Petersen, Jens HORTENSIA, a program package for the simulation of nonadiabatic autoionization dynamics in molecules Journal Article J. Chem. Phys., 159 , pp. 134801, 2023. @article{Issler2023b, title = {HORTENSIA, a program package for the simulation of nonadiabatic autoionization dynamics in molecules}, author = {Kevin Issler and Roland Mitric and Jens Petersen}, doi = {https://doi.org/10.1063/5.0167412}, year = {2023}, date = {2023-10-03}, journal = {J. Chem. Phys.}, volume = {159}, pages = {134801}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 186. | Freytag, Emely; Kreimendahl, Lasse; Holzapfel, Marco; Petersen, Jens; Lackinger, Heiko; Stolte, Matthias; Würthner, Frank; Mitric, Roland; Lambert, Christoph Chiroptical Properties of Planar Benzobisthiazole-Bridged Squaraine Dimers Journal Article J. Org. Chem., 88 , pp. 10777-10788, 2023. @article{Freytag2023, title = {Chiroptical Properties of Planar Benzobisthiazole-Bridged Squaraine Dimers}, author = {Emely Freytag and Lasse Kreimendahl and Marco Holzapfel and Jens Petersen and Heiko Lackinger and Matthias Stolte and Frank Würthner and Roland Mitric and Christoph Lambert}, doi = {https://doi.org/10.1021/acs.joc.3c00821}, year = {2023}, date = {2023-07-24}, journal = {J. Org. Chem.}, volume = {88}, pages = {10777-10788}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 185. | Issler, Kevin; Sturm, Floriane; Petersen, Jens; Flock, Marco; Mitric, Roland; Fischer, Ingo; Barreau, Lou; Poisson, Lionel Time-resolved photoelectron spectroscopy of 4-(dimethylamino)benzethyne – an experimental and computational study Journal Article Phys. Chem. Chem. Phys., 25 , pp. 9837-9845, 2023. @article{Issler2023, title = {Time-resolved photoelectron spectroscopy of 4-(dimethylamino)benzethyne – an experimental and computational study}, author = {Kevin Issler and Floriane Sturm and Jens Petersen and Marco Flock and Roland Mitric and Ingo Fischer and Lou Barreau and Lionel Poisson}, doi = {https://doi.org/10.1039/D3CP00309D}, year = {2023}, date = {2023-03-27}, journal = {Phys. Chem. Chem. Phys.}, volume = {25}, pages = {9837-9845}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 184. | Karashima, Shutaro; Miao, Xincheng; Kanayama, Akio; Yamamoto, Yo-ichi; Nishitani, Junichi; Kavka, Nikita; Mitric, Roland; Suzuki, Toshinori Ultrafast Ring Closure Reaction of Gaseous cis-Stilbene from S1 (ππ*) Journal Article J. Am. Chem. Soc., 145 , pp. 3283–3288, 2023. @article{Karashima2023, title = {Ultrafast Ring Closure Reaction of Gaseous cis-Stilbene from S_{1} (ππ*)}, author = {Shutaro Karashima and Xincheng Miao and Akio Kanayama and Yo-ichi Yamamoto and Junichi Nishitani and Nikita Kavka and Roland Mitric and Toshinori Suzuki}, doi = {https://doi.org/10.1021/jacs.2c12266}, year = {2023}, date = {2023-02-06}, journal = {J. Am. Chem. Soc.}, volume = {145}, pages = {3283–3288}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 183. | Einsele, Richard; Hoche, Joscha; Mitric, Roland Long-range Corrected Fragment Molecular Orbital Density-FunctionalTight-binding Method for Excited States in Large Molecular Systems Journal Article J. Chem. Phys., 158 , pp. 044121, 2023. @article{Einsele2022, title = {Long-range Corrected Fragment Molecular Orbital Density-FunctionalTight-binding Method for Excited States in Large Molecular Systems}, author = {Richard Einsele and Joscha Hoche and Roland Mitric}, doi = {10.1063/5.0136844}, year = {2023}, date = {2023-01-27}, journal = {J. Chem. Phys.}, volume = {158}, pages = {044121}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 182. | Kirst, Christin; Knechtel, Fabian; Gensler, Manuel; Fischermeier, David; Petersen, Jens; Danaf, Nader A; Tietze, Jonathan; Wedel, Armin; Lamb, Don C; Mitrić, Roland; Karaghiosoff, Konstantin Aggregation-Induced Emission in a Flexible Phosphine Oxide and its Zn(II) Complexes—A Simple Approach to Blue Luminescent Materials Journal Article Adv. Funct. Mater., 33 , pp. 2212436, 2023. @article{Kirst2023, title = {Aggregation-Induced Emission in a Flexible Phosphine Oxide and its Zn(II) Complexes—A Simple Approach to Blue Luminescent Materials}, author = {Christin Kirst and Fabian Knechtel and Manuel Gensler and David Fischermeier and Jens Petersen and Nader A. Danaf and Jonathan Tietze and Armin Wedel and Don C. Lamb and Roland Mitrić and Konstantin Karaghiosoff}, doi = {https://doi.org/10.1002/adfm.202212436}, year = {2023}, date = {2023-01-24}, journal = {Adv. Funct. Mater.}, volume = {33}, pages = {2212436}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 181. | Issler, Kevin; Mitric, Roland; Petersen, Jens Quantum-classical Dynamics of Vibration-Induced Autoionization in Molecules Journal Article J. Chem. Phys., 158 , pp. 034107, 2023. @article{Issler2022, title = {Quantum-classical Dynamics of Vibration-Induced Autoionization in Molecules}, author = {Kevin Issler and Roland Mitric and Jens Petersen}, doi = {10.1063/5.0135392}, year = {2023}, date = {2023-01-19}, journal = {J. Chem. Phys.}, volume = {158}, pages = {034107}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 180. | Wenzel, Michael; Mitric, Roland Internal Conversion Rates from the Extended Thawed Gaussian Approximation: Theory and Validation Journal Article J. Chem. Phys., 158 , pp. 034105, 2023. @article{Wenzel2022, title = {Internal Conversion Rates from the Extended Thawed Gaussian Approximation: Theory and Validation}, author = {Michael Wenzel and Roland Mitric}, doi = {10.1063/5.0130340}, year = {2023}, date = {2023-01-18}, journal = {J. Chem. Phys.}, volume = {158}, pages = {034105}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2022 |
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| 179. | Miao, Xincheng; Preitschopf, Tobias; Sturm, Floriane; Fischer, Ingo; Lemmens, Alexander K; Limbacher, Moritz; Mitric, Roland Stacking Is Favored over Hydrogen Bonding in Azaphenanthrene Dimers Journal Article J. Phys. Chem. Lett., 13 , pp. 8939–8944, 2022. @article{Miao2022, title = {Stacking Is Favored over Hydrogen Bonding in Azaphenanthrene Dimers}, author = {Xincheng Miao and Tobias Preitschopf and Floriane Sturm and Ingo Fischer and Alexander K. Lemmens and Moritz Limbacher and Roland Mitric}, doi = {10.1021/acs.jpclett.2c02280}, year = {2022}, date = {2022-09-22}, journal = {J. Phys. Chem. Lett.}, volume = {13}, pages = {8939–8944}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 178. | Titov, E; Kopp, T; Hoche, J; Humeniuk, A; Mitric, R (De)localization dynamics of molecular excitons: comparison of mixed quantum-classical and fully quantum treatments Journal Article Phys. Chem. Chem. Phys., 24 , pp. 12136-12148, 2022. @article{Titov2022, title = {(De)localization dynamics of molecular excitons: comparison of mixed quantum-classical and fully quantum treatments}, author = {E. Titov and T. Kopp and J. Hoche and A. Humeniuk and R. Mitric}, doi = {10.1039/d2cp00586g}, year = {2022}, date = {2022-05-25}, journal = {Phys. Chem. Chem. Phys.}, volume = {24}, pages = {12136-12148}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 177. | Patalag, L J; Hoche, J; Mitric, R; Werz, D B; Feringa, B L Transforming Dyes Into Fluorophores: Exciton‐Induced Emission with Chain‐like Oligo‐BODIPY Superstructures Journal Article Angew. Chem. , 61 , pp. e202116834, 2022. @article{hoche_2022_a, title = {Transforming Dyes Into Fluorophores: Exciton‐Induced Emission with Chain‐like Oligo‐BODIPY Superstructures}, author = {L. J. Patalag and J. Hoche and R. Mitric and D. B. Werz and B. L. Feringa}, doi = {10.1002/ange.202116834}, year = {2022}, date = {2022-03-04}, journal = {Angew. Chem. }, volume = {61}, pages = {e202116834}, abstract = {Herein we present a systematic study demonstrating to which extent exciton formation can amplify fluorescence based on a series of ethylene-bridged oligo-BODIPYs. A set of non- and weakly fluorescent BODIPY motifs was selected and transformed into discrete, chain-like oligomers by linkage via a flexible ethylene tether. The prepared superstructures constitute excitonically active entities with non-conjugated, Coulomb-coupled oscillators. The non-radiative deactivation channels of Internal Conversion (IC), also combined with an upstream reductive Photoelectron Transfer (rPET) and Intersystem Crossing (ISC) were addressed at the monomeric state and the evolution of fluorescence and (non-)radiative decay rates studied along the oligomeric series. We demonstrate that a “masked” fluorescence can be fully reactivated irrespective of the imposed conformational rigidity. This work challenges the paradigm that a collective fluorescence enhancement is limited to sterically induced motional restrictions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Herein we present a systematic study demonstrating to which extent exciton formation can amplify fluorescence based on a series of ethylene-bridged oligo-BODIPYs. A set of non- and weakly fluorescent BODIPY motifs was selected and transformed into discrete, chain-like oligomers by linkage via a flexible ethylene tether. The prepared superstructures constitute excitonically active entities with non-conjugated, Coulomb-coupled oscillators. The non-radiative deactivation channels of Internal Conversion (IC), also combined with an upstream reductive Photoelectron Transfer (rPET) and Intersystem Crossing (ISC) were addressed at the monomeric state and the evolution of fluorescence and (non-)radiative decay rates studied along the oligomeric series. We demonstrate that a “masked” fluorescence can be fully reactivated irrespective of the imposed conformational rigidity. This work challenges the paradigm that a collective fluorescence enhancement is limited to sterically induced motional restrictions. |
| 176. | Rödel, M; Lisinetskaya, P; Rudloff, M; Stark, T; Manara, J; Mitric, R; Pflaum, J The Role of Molecular Arrangement on the Strongly Coupled Exciton–Plasmon Polariton Dispersion in Metal–Organic Hybrid Structures Journal Article J. Phys. Chem. C, 126 (8), pp. 4163-4167, 2022. @article{lisinetskaya_2022, title = {The Role of Molecular Arrangement on the Strongly Coupled Exciton–Plasmon Polariton Dispersion in Metal–Organic Hybrid Structures}, author = {M. Rödel and P. Lisinetskaya and M. Rudloff and T. Stark and J. Manara and R. Mitric and J. Pflaum}, doi = {10.1021/acs.jpcc.1c10084}, year = {2022}, date = {2022-02-23}, journal = {J. Phys. Chem. C}, volume = {126}, number = {8}, pages = {4163-4167}, abstract = {Metal–organic hybrid structures have been demonstrated to be a versatile platform to study primary aspects of light–matter interaction by means of emerging states comprising excitonic and plasmonic properties. Here we are studying the wave-vector-dependent photoexcitations in gold layers covered by molecular films of zinc phthalocyanine and its fluorinated derivatives (FnZnPc, with n = 0, 4, 8, 16). These layered metal–organic samples show up to four anticrossings in their dispersions correlating in energy with the respective degree of ZnPc fluorination. By means of complementary structural and theoretical data, we attribute the observed anticrossings to three main scenarios of surface plasmon coupling: (i) to aggregated α-phase regions within the FnZnPc layers at 1.75 and 1.85 eV, (ii) to a coexisting F16ZnPc β-polymorph at 1.51 eV, and (iii) to monomers, preferentially located at the metal interface, at 2.15 eV. Whereas energy and splitting of the monomer anticrossings depend on strength and average tilting of the molecular dipole moments, the aggregate-related anticrossings show a distinct variation with degree of fluorination. These observations can be consistently explained by a change in FnZnPc dipole density induced by an increased lattice spacing due to the larger molecular van der Waals radii upon fluorination. The reported results prove Au/FnZnPc bilayers a model system to demonstrate the high sensitivity of exciton–plasmon coupling on the molecular alignment at microscopic length scales.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Metal–organic hybrid structures have been demonstrated to be a versatile platform to study primary aspects of light–matter interaction by means of emerging states comprising excitonic and plasmonic properties. Here we are studying the wave-vector-dependent photoexcitations in gold layers covered by molecular films of zinc phthalocyanine and its fluorinated derivatives (FnZnPc, with n = 0, 4, 8, 16). These layered metal–organic samples show up to four anticrossings in their dispersions correlating in energy with the respective degree of ZnPc fluorination. By means of complementary structural and theoretical data, we attribute the observed anticrossings to three main scenarios of surface plasmon coupling: (i) to aggregated α-phase regions within the FnZnPc layers at 1.75 and 1.85 eV, (ii) to a coexisting F16ZnPc β-polymorph at 1.51 eV, and (iii) to monomers, preferentially located at the metal interface, at 2.15 eV. Whereas energy and splitting of the monomer anticrossings depend on strength and average tilting of the molecular dipole moments, the aggregate-related anticrossings show a distinct variation with degree of fluorination. These observations can be consistently explained by a change in FnZnPc dipole density induced by an increased lattice spacing due to the larger molecular van der Waals radii upon fluorination. The reported results prove Au/FnZnPc bilayers a model system to demonstrate the high sensitivity of exciton–plasmon coupling on the molecular alignment at microscopic length scales. |
2021 |
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| 175. | Miyazaki, M; Kamya, T; Wohlgemuth, M; Chatterjee, K; Mitric, R; Dopfer, O; Fujii, M Phys. Chem. Chem. Phys., 24 , pp. 73-85, 2021. @article{wohlgemuth2021, title = {Real-time observation of photoionization-induced water migration dynamics in 4-methylformanilide–water by picosecond time-resolved infrared spectroscopy and ab initio molecular dynamics simulations}, author = {M Miyazaki and T Kamya and M Wohlgemuth and K Chatterjee and R Mitric and O Dopfer and M Fujii}, url = {https://pubs.rsc.org/en/content/articlelanding/2022/CP/D1CP03327A}, doi = {https://doi.org/10.1039/D1CP03327A}, year = {2021}, date = {2021-10-01}, journal = {Phys. Chem. Chem. Phys.}, volume = {24}, pages = {73-85}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 174. | Schmitt, Hans-Christian; Fischer, Ingo; Ji, Lei; Merz, Julia; Marder, Todd B; Hoche, Joscha; Röhr, Merle I S; Mitric, Roland Isolated 2-hydroxypyrene and its dimer: a frequency- and time-resolved spectroscopic study Journal Article New J. Chem. , 45 , pp. 14949-14956, 2021. @article{hoche_2020_06_njchem, title = {Isolated 2-hydroxypyrene and its dimer: a frequency- and time-resolved spectroscopic study}, author = {Hans-Christian Schmitt and Ingo Fischer and Lei Ji and Julia Merz and Todd B. Marder and Joscha Hoche and Merle I. S. Röhr and Roland Mitric}, url = {https://pubs.rsc.org/en/content/articlelanding/2020/nj/d0nj02391d#!divAbstract}, doi = {10.1039/D0NJ02391D}, year = {2021}, date = {2021-09-07}, journal = {New J. Chem. }, volume = {45}, pages = {14949-14956}, abstract = {We investigated isolated 2-hydroxypyrene and its dimer in the gas phase by time- and frequency-resolved photoionisation with picosecond time-resolution. The experiments are supported by simulations that include an extensive conformational search based on the machine learning ANI-1ccx neural network potential combined with automatic structure classification using a data clustering algorithm. Vibrationally resolved spectra of the S1 ← S0 and S2 ← S0 transitions are reported which are in very good agreement with the simulated spectra at the TDDFT level. As expected from the molecular orbitals involved in the transitions, the red-shifts of the transitions are more pronounced for the S1 state compared to those of unsubstituted pyrene. While a ns-lifetime is observed for the S1 state, the lifetime decreases to 3 ps or less for the origin of the S2 state, indicating a strong interaction between the two states. For the dimer, a slightly V-shaped structure was computed, and intermolecular interactions are dominated by dispersion rather than hydrogen-bonding. The highest oscillator strength was computed for the transition to the S4 state, which deactivates within 4 ps to a lower-lying excited state.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigated isolated 2-hydroxypyrene and its dimer in the gas phase by time- and frequency-resolved photoionisation with picosecond time-resolution. The experiments are supported by simulations that include an extensive conformational search based on the machine learning ANI-1ccx neural network potential combined with automatic structure classification using a data clustering algorithm. Vibrationally resolved spectra of the S1 ← S0 and S2 ← S0 transitions are reported which are in very good agreement with the simulated spectra at the TDDFT level. As expected from the molecular orbitals involved in the transitions, the red-shifts of the transitions are more pronounced for the S1 state compared to those of unsubstituted pyrene. While a ns-lifetime is observed for the S1 state, the lifetime decreases to 3 ps or less for the origin of the S2 state, indicating a strong interaction between the two states. For the dimer, a slightly V-shaped structure was computed, and intermolecular interactions are dominated by dispersion rather than hydrogen-bonding. The highest oscillator strength was computed for the transition to the S4 state, which deactivates within 4 ps to a lower-lying excited state. |
| 173. | Hoche, J; Flock, M; Miao, X; Philipp, L N; Wenzel, M; Fischer, I; Mitric, R Excimer formation dynamics in the isolated tetracene dimer Journal Article Chem. Sci., 12 , pp. 11965-11975 , 2021. @article{hochej_tetracene_2021, title = {Excimer formation dynamics in the isolated tetracene dimer}, author = {J. Hoche and M. Flock and X. Miao and L. N. Philipp and M. Wenzel and I. Fischer and R. Mitric}, doi = {10.1039/D1SC03214C}, year = {2021}, date = {2021-08-03}, journal = {Chem. Sci.}, volume = {12}, pages = {11965-11975 }, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 172. | Karashima, S; Humeniuk, A; Uenishi, R; Horio, T; Kanno, M; Ohta, T; Nishitani, J; Mitrić, R; Suzuki, T Ultrafast Ring-Opening Reaction of 1, 3-Cyclohexadiene: Identification of Nonadiabatic Pathway via Doubly Excited State Journal Article J. Am. Chem. Soc., 143 (21), pp. 8034-8045, 2021. @article{humeniuk2021a, title = {Ultrafast Ring-Opening Reaction of 1, 3-Cyclohexadiene: Identification of Nonadiabatic Pathway via Doubly Excited State}, author = {S. Karashima and A. Humeniuk and R. Uenishi and T. Horio and M. Kanno and T. Ohta and J. Nishitani and R. Mitrić and T. Suzuki}, doi = {10.1021/jacs.1c01896}, year = {2021}, date = {2021-05-23}, journal = {J. Am. Chem. Soc.}, volume = {143}, number = {21}, pages = {8034-8045}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 171. | Patalag, L J; Hoche, J; Holzapfel, M; Schmiedel, A; Mitric, R; Lambert, C; Werz, D B Ultrafast Resonance Energy Transfer in Ethylene-Bridged BODIPY Heterooligomers: From Frenkel to Förster Coupling Limit Journal Article J. Am. Chem. Soc., 143 , pp. 7414-7425, 2021. @article{hoche_2021, title = {Ultrafast Resonance Energy Transfer in Ethylene-Bridged BODIPY Heterooligomers: From Frenkel to Förster Coupling Limit}, author = {L. J. Patalag and J. Hoche and M. Holzapfel and A. Schmiedel and R. Mitric and C. Lambert and D. B. Werz}, url = {https://pubs.acs.org/doi/10.1021/jacs.1c01279}, doi = {10.1021/jacs.1c01279}, year = {2021}, date = {2021-05-06}, journal = {J. Am. Chem. Soc.}, volume = {143}, pages = {7414-7425}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 170. | Petersen, J; Einsele, R; Mitric, R On the quantum and classical control of laser-driven isomerization in the Wigner representation Journal Article J. Chem. Phys. , 154 , pp. 174103, 2021. @article{petersen_2021, title = {On the quantum and classical control of laser-driven isomerization in the Wigner representation}, author = {J. Petersen and R. Einsele and R. Mitric}, url = {https://aip.scitation.org/doi/full/10.1063/5.0046030}, doi = {10.1063/5.0046030}, year = {2021}, date = {2021-05-04}, journal = {J. Chem. Phys. }, volume = {154}, pages = {174103}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 169. | Titov, Evgenii; Hummert, Johan; Ikonnikov, Evgenii; Mitric, Roland; Kornilov, Oleg Farad. Discuss., 228 , pp. 226-241, 2021. @article{titov2020aa, title = {Electronic relaxation of aqueous aminoazobenzenes studied by time-resolved photoelectron spectroscopy and surface hopping TDDFT dynamics calculations}, author = {Evgenii Titov and Johan Hummert and Evgenii Ikonnikov and Roland Mitric and Oleg Kornilov}, doi = {10.1039/D0FD00111B}, year = {2021}, date = {2021-05-01}, journal = {Farad. Discuss.}, volume = {228}, pages = {226-241}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 168. | Turkin, A; Holzapfel, M; Agarwal, M; Fischermeier, D; Mitric, R; Schweins, F; Gröhn, F; Lambert, C Solvent Induced Helix Folding of Defined Indolenine Squaraine Oligomers Journal Article Chem. Eur. J., 27 , pp. 8380-8389, 2021. @article{fischermeier1, title = {Solvent Induced Helix Folding of Defined Indolenine Squaraine Oligomers}, author = {A. Turkin and M. Holzapfel and M. Agarwal and D. Fischermeier and R. Mitric and F. Schweins and F. Gröhn and C. Lambert}, url = {https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202101063}, doi = {10.1002/chem.202101063}, year = {2021}, date = {2021-04-19}, journal = { Chem. Eur. J.}, volume = {27}, pages = {8380-8389}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 167. | Lambert, C; Hoche, J; Schreck, M H; Holzapfel, M; Schmiedel, A; Selby, J; Turkin, A; Mitric, R Ultrafast Energy Transfer Dynamics in a Squaraine Heterotriad Journal Article J. Phys. Chem. A, 125 (12), pp. 2504-2511, 2021. @article{hoche_2021b, title = {Ultrafast Energy Transfer Dynamics in a Squaraine Heterotriad}, author = {C. Lambert and J. Hoche and M. H. Schreck and M. Holzapfel and A. Schmiedel and J. Selby and A. Turkin and R. Mitric}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpca.1c00349}, doi = {10.1021/acs.jpca.1c00349}, year = {2021}, date = {2021-03-19}, journal = {J. Phys. Chem. A}, volume = {125}, number = {12}, pages = {2504-2511}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 166. | Darghouth, Ala Aldin M H M; Casida, Mark E; Zhu, Xi; Natarajan, Bhaarathi; Su, Haibin; Humeniuk, Alexander; Titov, Evgenii; Miao, Xincheng; Mitrić, Roland J. Chem. Phys., 154 , pp. 054102, 2021. @article{alaaldin2021, title = {Effect of varying the TD-lc-DFTB range-separation parameter on charge and energy transfer in a model pentacene/buckminsterfullerene heterojunction}, author = {Ala Aldin M. H. M. Darghouth and Mark E. Casida and Xi Zhu and Bhaarathi Natarajan and Haibin Su and Alexander Humeniuk and Evgenii Titov and Xincheng Miao and Roland Mitrić}, doi = {10.1063/5.0024559}, year = {2021}, date = {2021-02-02}, journal = {J. Chem. Phys.}, volume = {154}, pages = {054102}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2020 |
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| 165. | Humeniuk., A; Mitric, R; Bonacic-Koutecky, V Size Dependence of Non-Radiative Decay Rates in J-Aggregates Journal Article J. Phys. Chem. A, 124 , pp. 10143-10151, 2020. @article{humeniuk2020c, title = {Size Dependence of Non-Radiative Decay Rates in J-Aggregates}, author = {A. Humeniuk. and R. Mitric and V. Bonacic-Koutecky}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpca.0c09074}, doi = {10.1021/acs.jpca.0c09074}, year = {2020}, date = {2020-11-29}, journal = {J. Phys. Chem. A}, volume = {124}, pages = {10143-10151}, abstract = {Fluorophores that emit in the near-infrared (NIR, 700–1700 nm) and have high quantum yields are urgently needed for many technical applications such as organic light-emitting diodes or bioimaging. The design of such chromophores is hampered by the energy gap law, which states that shifting the emission to lower wavelengths is accompanied by a dramatic increase in the nonradiative decay rate. In this article we argue that linear oligomers with J-type excitonic coupling are ideal NIR fluorophores because of the advantageous dependence of the emission energy and the radiative and nonradiative rates on the length N over which the excitation is delocalized. The lowering of the emission energy due to exciton splitting and the linear increase of the radiative rate with length (super-radiance) are well understood. However, less attention has been paid to the decrease of the nonradiative rate with length, which can compensate for the exponential increase due to the energy gap law. According to the exciton model, the Huang–Rhys factors decrease like N–2 while the strength of the nonadiabatic coupling remains approximately constant. Plugging these relations into the Englman–Jortner’s energy gap law, we show that for excitonic coupling that is not too strong the nonradiative rate decreases quickly with N. This phenomenon explains the decrease of the nonradiative rate with length in J-aggregates of carbocyanine dyes and the exceptionally high fluorescence quantum yields of linear ethyne-linked zinc-porphyrin arrays, which seemed to defy the energy gap law.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Fluorophores that emit in the near-infrared (NIR, 700–1700 nm) and have high quantum yields are urgently needed for many technical applications such as organic light-emitting diodes or bioimaging. The design of such chromophores is hampered by the energy gap law, which states that shifting the emission to lower wavelengths is accompanied by a dramatic increase in the nonradiative decay rate. In this article we argue that linear oligomers with J-type excitonic coupling are ideal NIR fluorophores because of the advantageous dependence of the emission energy and the radiative and nonradiative rates on the length N over which the excitation is delocalized. The lowering of the emission energy due to exciton splitting and the linear increase of the radiative rate with length (super-radiance) are well understood. However, less attention has been paid to the decrease of the nonradiative rate with length, which can compensate for the exponential increase due to the energy gap law. According to the exciton model, the Huang–Rhys factors decrease like N–2 while the strength of the nonadiabatic coupling remains approximately constant. Plugging these relations into the Englman–Jortner’s energy gap law, we show that for excitonic coupling that is not too strong the nonradiative rate decreases quickly with N. This phenomenon explains the decrease of the nonradiative rate with length in J-aggregates of carbocyanine dyes and the exceptionally high fluorescence quantum yields of linear ethyne-linked zinc-porphyrin arrays, which seemed to defy the energy gap law. |
| 164. | Förstel, Marko; Pollow, Kai Mario; Saroukh, Karim; Najib, Este Ainun; Mitric, Roland; Dopfer, Otto The Optical Spectrum of Au2+ Journal Article Angew. Chem. Int. Ed., 59 , pp. 21403-21408, 2020. @article{mitricAU, title = {The Optical Spectrum of Au_{2}^{+}}, author = {Marko Förstel and Kai Mario Pollow and Karim Saroukh and Este Ainun Najib and Roland Mitric and Otto Dopfer}, doi = {https://doi.org/10.1002/ange.202011337}, year = {2020}, date = {2020-09-05}, journal = {Angew. Chem. Int. Ed.}, volume = {59}, pages = {21403-21408}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 163. | Ma, Xiaonan; Maier, Jan; Wenzel, Michael; Friedrich, Alexandra; Steffen, Andreas; Marder, Todd B; Mitric, Roland; Brixner, Tobias Direct observation of o-benzyne formation in photochemical hexadehydro-Diels–Alder (hν-HDDA) reactions Journal Article Chem. Sci., 11 , pp. 9198-9208, 2020. @article{wenzel2020a, title = {Direct observation of o-benzyne formation in photochemical hexadehydro-Diels–Alder (hν-HDDA) reactions}, author = {Xiaonan Ma and Jan Maier and Michael Wenzel and Alexandra Friedrich and Andreas Steffen and Todd B. Marder and Roland Mitric and Tobias Brixner }, url = {https://pubs.rsc.org/en/content/articlelanding/2020/sc/d0sc03184d#!divAbstract}, doi = {10.1039/D0SC03184D}, year = {2020}, date = {2020-08-14}, journal = {Chem. Sci.}, volume = {11}, pages = {9198-9208}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 162. | Li, Donghai; Titov, Evgenii; Roedel, Maximilian; Kolb, Verena; Goetz, Sebastian; Mitric, Roland; Pflaum, Jens; Brixner, Tobias Correlating nanoscale optical coherence length and microscale topography in organic materials by coherent two-dimensional micro-spectroscopy Journal Article Nano Lett., 20 , pp. 6452-6458, 2020. @article{titov2020b, title = {Correlating nanoscale optical coherence length and microscale topography in organic materials by coherent two-dimensional micro-spectroscopy}, author = {Donghai Li and Evgenii Titov and Maximilian Roedel and Verena Kolb and Sebastian Goetz and Roland Mitric and Jens Pflaum and Tobias Brixner}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.0c02146}, doi = {10.1021/acs.nanolett.0c02146}, year = {2020}, date = {2020-08-10}, journal = {Nano Lett.}, volume = {20}, pages = {6452-6458}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 161. | Hirsch, Florian; Pachner, Kai; Fischer, Ingo; Issler, Kevin; Petersen, Jens; Mitric, Roland; Bakels, Sjors; Rijs, Anouk Do Xylylenes isomerize in Pyrolysis? Journal Article ChemPhysChem, 21 (14), pp. 1515-1518, 2020. @article{isslerk_2020_05_06, title = {Do Xylylenes isomerize in Pyrolysis?}, author = {Florian Hirsch and Kai Pachner and Ingo Fischer and Kevin Issler and Jens Petersen and Roland Mitric and Sjors Bakels and Anouk Rijs}, url = {https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/cphc.202000317}, doi = {10.1002/cphc.202000317}, year = {2020}, date = {2020-06-05}, journal = {ChemPhysChem}, volume = {21}, number = {14}, pages = {1515-1518}, abstract = {A gas phase IR spectrum of para‐xylylene was recorded by IR/UV ion dip spectroscopy. The molecule was generated by flash pyrolysis. Ortho‐ and meta‐xylylene partially rearrange to benzocyclobutene and styrene. Their detection can be explained by the oscillator strength of the UV transition.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A gas phase IR spectrum of para‐xylylene was recorded by IR/UV ion dip spectroscopy. The molecule was generated by flash pyrolysis. Ortho‐ and meta‐xylylene partially rearrange to benzocyclobutene and styrene. Their detection can be explained by the oscillator strength of the UV transition. |
| 160. | Wohlgemuth, Matthias; Mitric, Roland Excitation energy transport in DNA modelled by multi-chromophoric field-induced surface hopping Journal Article Phys. Chem. Chem. Phys. , 22 , pp. 16536-16551 , 2020. @article{wohlgemu_2020_jun, title = {Excitation energy transport in DNA modelled by multi-chromophoric field-induced surface hopping}, author = {Matthias Wohlgemuth and Roland Mitric}, url = {https://pubs.rsc.org/en/content/articlelanding/2020/cp/d0cp02255a#!divAbstract}, doi = {10.1039/D0CP02255A}, year = {2020}, date = {2020-06-03}, journal = {Phys. Chem. Chem. Phys. }, volume = {22}, pages = {16536-16551 }, abstract = {Absorption of ultraviolet light is known as a major source of carcinogenic mutations of DNA. The underlying processes of excitation energy dissipation are yet not fully understood. In this work we provide a new and generally applicable route for studying the excitation energy transport in multi-chromophoric complexes at an atomistic level. The surface-hopping approach in the frame of the extended Frenkel exciton model combined with QM/MM techniques allowed us to simulate the photodynamics of the alternating (dAdT)_{10}:(dAdT)_{10} double-stranded DNA. In accordance with recent experiments, we find that the excited state decay is multiexponential, involving a long and a short component which are due to two distinct mechanisms: formation of long-lived delocalized excitonic and charge transfer states vs. ultrafast decaying localized states resembling those of the bare nucleobases. Our simulations explain all stages of the ultrafast photodynamics including initial photoexcitation, dynamical evolution out of the Franck–Condon region, excimer formation and nonradiative relaxation to the ground state.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Absorption of ultraviolet light is known as a major source of carcinogenic mutations of DNA. The underlying processes of excitation energy dissipation are yet not fully understood. In this work we provide a new and generally applicable route for studying the excitation energy transport in multi-chromophoric complexes at an atomistic level. The surface-hopping approach in the frame of the extended Frenkel exciton model combined with QM/MM techniques allowed us to simulate the photodynamics of the alternating (dAdT)10:(dAdT)10 double-stranded DNA. In accordance with recent experiments, we find that the excited state decay is multiexponential, involving a long and a short component which are due to two distinct mechanisms: formation of long-lived delocalized excitonic and charge transfer states vs. ultrafast decaying localized states resembling those of the bare nucleobases. Our simulations explain all stages of the ultrafast photodynamics including initial photoexcitation, dynamical evolution out of the Franck–Condon region, excimer formation and nonradiative relaxation to the ground state. |
| 159. | Meza-Chincha, Ana-Luca; Lindner, Joachim O; Schindler, Dorothee; Schmidt, David; Krause, Ana-Mariua; Röhr, Merle I S; Mitric, Roland; Würthner, Frank Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation Journal Article Chem. Sci. , 11 , pp. 7654-7664, 2020. @article{röhr_2020_a, title = {Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation}, author = {Ana-Luca Meza-Chincha and Joachim O. Lindner and Dorothee Schindler and David Schmidt and Ana-Mariua Krause and Merle I. S. Röhr and Roland Mitric and Frank Würthner}, url = {https://pubs.rsc.org/en/content/articlehtml/2020/sc/d0sc01097a}, doi = {10.1039/D0SC01097A}, year = {2020}, date = {2020-04-29}, journal = {Chem. Sci. }, volume = {11}, pages = {7654-7664}, abstract = {Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites. |
| 158. | Muessig, Jonas; Lisinetskaya, Polina; Dewhurst, Rian; Bertermann, Rüdiger; Thaler, Melanie; Mitrić, Roland; Braunschweig, Holger Tetraiododiborane(4) (B2I4) is a Polymer based on sp3 Boron in the Solid State Journal Article Angew. Chem., 132 , pp. 1-7, 2020. @article{polina19b, title = {Tetraiododiborane(4) (B_{2}I_{4}) is a Polymer based on sp^{3} Boron in the Solid State}, author = {Jonas Muessig and Polina Lisinetskaya and Rian Dewhurst and Rüdiger Bertermann and Melanie Thaler and Roland Mitrić and Holger Braunschweig }, doi = {10.1002/ange.201913590}, year = {2020}, date = {2020-03-27}, journal = {Angew. Chem.}, volume = {132}, pages = {1-7}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 157. | Humeniuk, Alexander; Bužančić, Margarita; Hoche, Joscha; Cerezo, Javier; Mitrić, Roland; Santoro, Fabrizio; Bonačić-Koutecký, Vlasta J. Chem. Phys., 152 , pp. 054107, 2020. @article{humeniuk_2020a, title = {Predicting fluorescence quantum yields for molecules in solution: A critical assessment of the harmonic approximation and the choice of the lineshape function}, author = {Alexander Humeniuk and Margarita Bužančić and Joscha Hoche and Javier Cerezo and Roland Mitrić and Fabrizio Santoro and Vlasta Bonačić-Koutecký}, url = {https://aip.scitation.org/doi/full/10.1063/1.5143212}, doi = {10.1063/1.5143212}, year = {2020}, date = {2020-02-05}, journal = {J. Chem. Phys.}, volume = {152}, pages = {054107}, abstract = {For the rational design of new fluorophores, reliable predictions of fluorescence quantum yields from first principles would be of great help. However, efficient computational approaches for predicting transition rates usually assume that the vibrational structure is harmonic. While the harmonic approximation has been used successfully to predict vibrationally resolved spectra and radiative rates, its reliability for non- radiative rates is much more questionable. Since non-adiabatic transitions convert large amounts of electronic energy into vibrational energy, the highly excited final vibrational states deviate greatly from harmonic oscillator eigenfunctions. We employ a time-dependent formalism to compute radiative and non-radiative rates for transitions and study the dependence on model parameters. For several coumarin dyes, we compare different adiabatic and vertical harmonic models (AS, ASF, AH, VG, VGF, and VH), in order to dissect the importance of displacements, frequency changes, and Duschinsky rotations. In addition, we analyze the effect of different broadening functions (Gaussian, Lorentzian, or Voigt). Moreover, to assess the qualitative influence of anharmonicity on the internal conversion rate, we develop a simplified anharmonic model. We address the reliability of these models considering the potential errors introduced by the harmonic approximation and the phenomenological width of the broadening function.}, keywords = {}, pubstate = {published}, tppubtype = {article} } For the rational design of new fluorophores, reliable predictions of fluorescence quantum yields from first principles would be of great help. However, efficient computational approaches for predicting transition rates usually assume that the vibrational structure is harmonic. While the harmonic approximation has been used successfully to predict vibrationally resolved spectra and radiative rates, its reliability for non- radiative rates is much more questionable. Since non-adiabatic transitions convert large amounts of electronic energy into vibrational energy, the highly excited final vibrational states deviate greatly from harmonic oscillator eigenfunctions. We employ a time-dependent formalism to compute radiative and non-radiative rates for transitions and study the dependence on model parameters. For several coumarin dyes, we compare different adiabatic and vertical harmonic models (AS, ASF, AH, VG, VGF, and VH), in order to dissect the importance of displacements, frequency changes, and Duschinsky rotations. In addition, we analyze the effect of different broadening functions (Gaussian, Lorentzian, or Voigt). Moreover, to assess the qualitative influence of anharmonicity on the internal conversion rate, we develop a simplified anharmonic model. We address the reliability of these models considering the potential errors introduced by the harmonic approximation and the phenomenological width of the broadening function. |
| 156. | Titov, Evgenii; Humeniuk, Alexander; Mitric, Roland Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections Journal Article Chem. Phys., 528 , pp. 110526, 2020. @article{titov19a, title = {Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections}, author = {Evgenii Titov and Alexander Humeniuk and Roland Mitric}, doi = {10.1016/j.chemphys.2019.110526}, year = {2020}, date = {2020-01-01}, journal = {Chem. Phys.}, volume = {528}, pages = {110526}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2019 |
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| 155. | Hoche, Joscha; Schulz, Alexander; Dietrich, Lysanne Monika; Humeniuk, Alexander; Stolte, Matthias; Schmidt, David; Brixner, Tobias; Würthner, Frank; Mitric, Roland The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes Journal Article Chem. Sci., 10 , pp. 11013-11022, 2019. @article{hoche19b, title = {The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes}, author = {Joscha Hoche and Alexander Schulz and Lysanne Monika Dietrich and Alexander Humeniuk and Matthias Stolte and David Schmidt and Tobias Brixner and Frank Würthner and Roland Mitric}, url = {https://pubs.rsc.org/en/content/articlepdf/2019/sc/c9sc05012d}, doi = {10.1039/c9sc05012d}, year = {2019}, date = {2019-12-04}, journal = {Chem. Sci.}, volume = {10}, pages = {11013-11022}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 154. | Lisinetskaya, Polina G; Mitric, Roland Collective Response in DNA-Stabilized Silver Cluster Assemblies from First-Principles Simulations Journal Article J. Phys. Chem. Lett., 10 , pp. 7884-7889, 2019. @article{polina19jpcl, title = {Collective Response in DNA-Stabilized Silver Cluster Assemblies from First-Principles Simulations}, author = {Polina G Lisinetskaya and Roland Mitric}, url = {https://pubs.acs.org/doi/10.1021/acs.jpclett.9b03136}, doi = {10.1021/acs.jpclett.9b03136}, year = {2019}, date = {2019-11-27}, journal = {J. Phys. Chem. Lett.}, volume = {10}, pages = {7884-7889}, abstract = {We investigate fluorescence resonant energy transfer and concurrent electron dynamics in a pair of DNA-stabilized silver clusters. For this purpose we introduce a methodology for the simulation of collective opto-electronic properties of coupled molecular aggregates starting from first-principles quantum chemistry, which can be further applied to a broad range of coupled molecular systems to study their electrooptical response. Our simulations reveal the existence of a low-energy coupled excitonic states, which enable ultrafast energy transport between subunits, and give an insight into the origin of the fluorescence signal in coupled DNA-stabilized silver clusters, that have been recently experimentally detected. Hence we demonstrate the possibility to construct an ultrasmall energy transmission lines and optical converters based on these hybrid molecular systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate fluorescence resonant energy transfer and concurrent electron dynamics in a pair of DNA-stabilized silver clusters. For this purpose we introduce a methodology for the simulation of collective opto-electronic properties of coupled molecular aggregates starting from first-principles quantum chemistry, which can be further applied to a broad range of coupled molecular systems to study their electrooptical response. Our simulations reveal the existence of a low-energy coupled excitonic states, which enable ultrafast energy transport between subunits, and give an insight into the origin of the fluorescence signal in coupled DNA-stabilized silver clusters, that have been recently experimentally detected. Hence we demonstrate the possibility to construct an ultrasmall energy transmission lines and optical converters based on these hybrid molecular systems. |
| 153. | Röder, Anja; Petersen, Jens; Issler, Kevin; Fischer, Ingo; Mitric, Roland; Poisson, Lionel J. Phys. Chem. A, 123 (50), pp. 10643-10662, 2019. @article{feature_jpca_19, title = {Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals and Carbenes Using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations}, author = {Anja Röder and Jens Petersen and Kevin Issler and Ingo Fischer and Roland Mitric and Lionel Poisson}, doi = {10.1021/acs.jpca.9b06346}, year = {2019}, date = {2019-09-05}, journal = {J. Phys. Chem. A}, volume = {123}, number = {50}, pages = {10643-10662}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 152. | O, Lindner J; Sultangaleeva, K; Röhr, M I S; Mitric, R metaFALCON: A program package for automatic sampling of conical intersection seams using multistate metadynamics Journal Article J. Chem. Theor. Comput., 15 (6), pp. 3450-3460, 2019. @article{lindner_19, title = {metaFALCON: A program package for automatic sampling of conical intersection seams using multistate metadynamics}, author = {Lindner J O and Sultangaleeva, K and Röhr, M I S and Mitric, R}, doi = {10.1021/acs.jctc.9b00029}, year = {2019}, date = {2019-04-17}, journal = {J. Chem. Theor. Comput.}, volume = {15}, number = {6}, pages = {3450-3460}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 151. | Auerhammer, N; Schulz, A; Schmiedel, A; Holzapfel, M; Hoche, J; Röhr, M I S; Lambert, C; Mitric, R Dynamic exciton localisation in a pyrene-BODIPY-pyrene dye conjugate Journal Article Phys. Chem. Chem. Phys., 21 , pp. 9013-9025, 2019. @article{pccpbodipy, title = {Dynamic exciton localisation in a pyrene-BODIPY-pyrene dye conjugate}, author = {N. Auerhammer and A. Schulz and A. Schmiedel and M. Holzapfel and J. Hoche and M. I. S. Röhr and C. Lambert and R. Mitric}, url = {https://pubs.rsc.org/en/content/articlelanding/2019/cp/c9cp00908f#!divAbstract}, year = {2019}, date = {2019-03-21}, journal = {Phys. Chem. Chem. Phys.}, volume = {21}, pages = {9013-9025}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 150. | Walter, Michael; Vogel, Marlene; Zamudio-Bayer, Vicente; Lindblad, Rebecka; Reichenbach, Thomas; Hirsch, Konstantin; Langenberg, Andreas; Rittmann, Jochen; Kulesza, Alexander; Mitric, Roland; Moseler, Michael; Möller, Thomas; von Issendorff, Bernd; Lau, Tobias J Phys. Chem. Chem. Phys., 21 , pp. 6651-6661 , 2019. @article{kulezsa19, title = {Experimental and theoretical 2p core-level spectra of size-selected gas-phase aluminum and silicon cluster cations: chemical shifts, geometric structure, and coordination-dependent screening}, author = {Michael Walter and Marlene Vogel and Vicente Zamudio-Bayer and Rebecka Lindblad and Thomas Reichenbach and Konstantin Hirsch and Andreas Langenberg and Jochen Rittmann and Alexander Kulesza and Roland Mitric and Michael Moseler and Thomas Möller and Bernd von Issendorff and Tobias J Lau}, doi = {10.1039/c8cp07169a}, year = {2019}, date = {2019-02-24}, journal = {Phys. Chem. Chem. Phys.}, volume = {21}, pages = {6651-6661 }, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2018 |
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| 149. | Darghouth, A A M H M; Correa, Calinao G; Juillard, S; Casida, M E; Humeniuk, A; Mitric, R J. Chem. Phys., 149 , pp. 134111, 2018. @article{dargouth2018, title = {Davydov-Type Excitonic Effects on the Absorption Spectra of Parallel-Stacked and Herringbone Aggregates of Pentacene: Time-Dependent Density-Functional Theory and Time-Dependent Density-Functional Tight Binding}, author = {A A M H M Darghouth and G Calinao Correa and S Juillard and M E Casida and A Humeniuk and R Mitric}, url = {https://arxiv.org/abs/1803.00056}, doi = {10.1063/1.5025624}, year = {2018}, date = {2018-10-04}, journal = {J. Chem. Phys.}, volume = {149}, pages = {134111}, organization = {Arxiv.org}, abstract = {Exciton formation leads to J-bands in solid pentacene. Describing these exciton bands represents a challenge for both time-dependent (TD) density-functional theory (DFT) and for its semi-empirical analog, namely, for TD density-functional tight binding (DFTB) for three reasons: (i) solid pentacene and pentacene aggregates are bound only by van der Waals forces which are notoriously difficult to describe with DFT and DFTB, (ii) the proper description of the long-range coupling between molecules, needed to describe Davydov splitting, is not easy to include in TD-DFT with traditional functionals and in TD-DFTB, and (iii) mixing may occur between local and charge transfer excitons, which may, in turn, require special functionals. We assess how far TD-DFTB has progressed toward a correct description of this type of exciton by including both a dispersion correction for the ground state and a range-separated hybrid functional for the excited state and comparing the results against corresponding TD-CAM-B3LYP/CAM-B3LYP+D3 results. Analytic results for parallel-stacked ethylene are derived which go beyond Kasha’s exciton model [M. Kasha, H. R. Rawls, and A. El-Bayoumi, Pure Appl. Chem. 11, 371 (1965)] in that we are able to make a clear distinction between charge transfer and energy transfer excitons. This is further confirmed when it is shown that range-separated hybrids have a markedly greater effect on charge-transfer excitons than on energy-transfer excitons in the case of parallel-stacked pentacenes. TD-DFT calculations with the CAM-B3LYP functional and TD-lc-DFT calculations lead to negligible excitonic corrections for the herringbone crystal structure, possibly because of an overcorrection of charge-transfer effects (CAM refers to Coulomb attenuated method). In this case, TD-DFT calculations with the B3LYP functional or TD-DFTB calculations parameterized to B3LYP give the best results for excitonic corrections for the herringbone crystal structure as judged from comparison with experimental spectra and with Bethe-Salpeter equation calculations from the literature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Exciton formation leads to J-bands in solid pentacene. Describing these exciton bands represents a challenge for both time-dependent (TD) density-functional theory (DFT) and for its semi-empirical analog, namely, for TD density-functional tight binding (DFTB) for three reasons: (i) solid pentacene and pentacene aggregates are bound only by van der Waals forces which are notoriously difficult to describe with DFT and DFTB, (ii) the proper description of the long-range coupling between molecules, needed to describe Davydov splitting, is not easy to include in TD-DFT with traditional functionals and in TD-DFTB, and (iii) mixing may occur between local and charge transfer excitons, which may, in turn, require special functionals. We assess how far TD-DFTB has progressed toward a correct description of this type of exciton by including both a dispersion correction for the ground state and a range-separated hybrid functional for the excited state and comparing the results against corresponding TD-CAM-B3LYP/CAM-B3LYP+D3 results. Analytic results for parallel-stacked ethylene are derived which go beyond Kasha’s exciton model [M. Kasha, H. R. Rawls, and A. El-Bayoumi, Pure Appl. Chem. 11, 371 (1965)] in that we are able to make a clear distinction between charge transfer and energy transfer excitons. This is further confirmed when it is shown that range-separated hybrids have a markedly greater effect on charge-transfer excitons than on energy-transfer excitons in the case of parallel-stacked pentacenes. TD-DFT calculations with the CAM-B3LYP functional and TD-lc-DFT calculations lead to negligible excitonic corrections for the herringbone crystal structure, possibly because of an overcorrection of charge-transfer effects (CAM refers to Coulomb attenuated method). In this case, TD-DFT calculations with the B3LYP functional or TD-DFTB calculations parameterized to B3LYP give the best results for excitonic corrections for the herringbone crystal structure as judged from comparison with experimental spectra and with Bethe-Salpeter equation calculations from the literature. |
| 148. | Adachi, S; Schatteburg, T; Humeniuk, A; Mitric, R; Suzuki, T Probing ultrafast dynamics during and after passing through conical intersections Journal Article Phys. Chem. Chem. Phys., 21 , pp. 13902-13905 , 2018. @article{humeniuk2018f, title = {Probing ultrafast dynamics during and after passing through conical intersections}, author = {S. Adachi and T. Schatteburg and A. Humeniuk and R. Mitric and T. Suzuki}, url = {https://pubs.rsc.org/en/content/articlelanding/2018/cp/c8cp04426k#!divAbstract}, year = {2018}, date = {2018-09-24}, journal = {Phys. Chem. Chem. Phys.}, volume = {21}, pages = {13902-13905 }, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 147. | Schleier, D; Humeniuk, A; Reusch, E; Holzmeier, F; Nunez-Reyes, D; Alcaraz, C; Garcia, G A; Loison, J -C; Fischer, I; Mitric, R Diborene: Generation and Photoelectron Spectroscopy of an Inorganic Biradical Journal Article J. Phys. Chem. Lett., 9 (20), pp. 5921–5925, 2018. @article{humeniuk2018e, title = {Diborene: Generation and Photoelectron Spectroscopy of an Inorganic Biradical}, author = {D Schleier and A Humeniuk and E Reusch and F Holzmeier and D Nunez-Reyes and C Alcaraz and G A Garcia and J -C Loison and I Fischer and R Mitric}, url = {https://pubs.acs.org/doi/10.1021/acs.jpclett.8b02338}, doi = {10.1021/acs.jpclett.8b02338}, year = {2018}, date = {2018-09-20}, journal = {J. Phys. Chem. Lett.}, volume = {9}, number = {20}, pages = {5921–5925}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 146. | Titov, E; Humeniuk, A; Mitric, R Exciton localization in excited-state dynamics of a tetracene trimer: A surface hopping LC-TDDFTB study Journal Article Phys. Chem. Chem. Phys., 20 , pp. 25995-26007, 2018. @article{titov_2018, title = {Exciton localization in excited-state dynamics of a tetracene trimer: A surface hopping LC-TDDFTB study}, author = {E Titov and A Humeniuk and R Mitric}, url = {https://pubs.rsc.org/en/content/articlehtml/2018/cp/c8cp05240a}, doi = {10.1039/C8CP05240A}, year = {2018}, date = {2018-09-17}, journal = {Phys. Chem. Chem. Phys.}, volume = {20}, pages = {25995-26007}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 145. | Ma, X; Wenzel, M; Schmitt, H -C; Flock, M; Reusch, E; Mitric, R; Fischer, I; Brixner, T Disentangling the photochemistry of benzocyclobutenedione Journal Article Phys. Chem. Chem. Phys., 20 , pp. 15434-15444, 2018. @article{wenzel2018a, title = {Disentangling the photochemistry of benzocyclobutenedione}, author = {X Ma and M Wenzel and H -C Schmitt and M Flock and E Reusch and R Mitric and I Fischer and T Brixner}, url = {http://pubs.rsc.org/en/Content/ArticleLanding/2018/CP/C8CP01937A?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FCP+%28RSC+-+Phys.+Chem.+Chem.+Phys.+latest+articles%29#!divAbstract}, doi = {10.1039/C8CP01937A}, year = {2018}, date = {2018-05-25}, journal = {Phys. Chem. Chem. Phys.}, volume = {20}, pages = {15434-15444}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 144. | Humeniuk, A; Mitric, R A block Jacobi method for complex skew-symmetric matrices with applications in the time-dependent variational principle Journal Article Comput. Phys. Comm., 231 , pp. 187-197, 2018. @article{humeniuk2018c, title = {A block Jacobi method for complex skew-symmetric matrices with applications in the time-dependent variational principle}, author = {A Humeniuk and R Mitric}, url = {https://www.sciencedirect.com/science/article/pii/S0010465518301425}, year = {2018}, date = {2018-05-09}, journal = {Comput. Phys. Comm.}, volume = {231}, pages = {187-197}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 143. | Issler, K; Röder, A; Hirsch, F; Poisson, L; Fischer, I; Mitric, R; Petersen, J Excited state dynamics and time-resolved photoelectron spectroscopy of para-xylylene Journal Article Faraday. Discuss., 212 , pp. 83-100, 2018. @article{issler2018a, title = {Excited state dynamics and time-resolved photoelectron spectroscopy of para-xylylene}, author = {K Issler and A Röder and F Hirsch and L Poisson and I Fischer and R Mitric and J Petersen}, url = {http://pubs.rsc.org/en/content/articlelanding/2018/fd/c8fd00083b#!divAbstract}, year = {2018}, date = {2018-05-08}, journal = {Faraday. Discuss.}, volume = {212}, pages = {83-100}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 142. | Lindner, J O; Röhr, M I S; Mitric, R Multistate metadynamics for automatic exploration of conical intersections Journal Article Phys. Rev. A, 97 , pp. 052502, 2018. @article{lindner2018a, title = {Multistate metadynamics for automatic exploration of conical intersections}, author = {J O Lindner and M I S Röhr and R Mitric}, url = {https://arxiv.org/abs/1803.05631}, doi = {10.1103/PhysRevA.97.052502}, year = {2018}, date = {2018-05-07}, journal = {Phys. Rev. A}, volume = {97}, pages = {052502}, organization = {Arxiv.org}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 141. | Röhr, M I S; Marciniak, H; Hoche, J; Schreck, M; Ceymann, H; Mitric, R; Lambert, C Exciton Dynamics from Strong to Weak Coupling Limit Illustrated on a Series of Squaraine Dimers Journal Article J. Phys. Chem. C, 122 , pp. 8082–8093, 2018. @article{Röhr2018a, title = {Exciton Dynamics from Strong to Weak Coupling Limit Illustrated on a Series of Squaraine Dimers}, author = {M I S Röhr and H Marciniak and J Hoche and M Schreck and H Ceymann and R Mitric and C Lambert}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.8b00847?journalCode=jpccck}, doi = {10.1021/acs.jpcc.8b00847}, year = {2018}, date = {2018-04-04}, journal = {J. Phys. Chem. C}, volume = {122}, pages = {8082–8093}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 140. | Darghouth, A A M H M; Casida, M E; Zhu, X; Natarajan, B; Su, H; A., Humeniuk; Mitric, R Arxiv.org 2018. @online{darghouth2018b, title = {How Long Do Energy and Charge Transfer Take in a Model Buckminsterfullerene/Pentacene Heterojunction? Assessment of Fewest Switches Time-Dependent Density-Functional Tight-Binding with and without Long-Range Correction}, author = {A A M H M Darghouth and M E Casida and X Zhu and B Natarajan and H Su and Humeniuk A. and R Mitric}, url = {https://arxiv.org/abs/1803.11121}, year = {2018}, date = {2018-03-29}, organization = {Arxiv.org}, keywords = {}, pubstate = {published}, tppubtype = {online} } |
| 139. | Böhnke, J; Dellermann, T; Celik, M A; Krummenacher, I; Dewhurst, R D; Demeshko, S; Ewing, W C; Hammond, K; Heß, M; Bill, E; Welz, E; Röhr, M I S; Mitric, R; Engels, B; Meyer, F; Braunschweig, H Isolation of diborenes and their 90°-twisted diradical congeners Journal Article Nat. Comm., 2018. @article{boehnke2018, title = {Isolation of diborenes and their 90°-twisted diradical congeners}, author = {J. Böhnke and T. Dellermann and M. A. Celik and I. Krummenacher and R. D. Dewhurst and S. Demeshko and W. C. Ewing and K. Hammond and M. Heß and E. Bill and E. Welz and M. I. S. Röhr and R. Mitric and B. Engels and F. Meyer and H. Braunschweig}, url = {http://dx.doi.org/10.1038/s41467-018-02998-3}, year = {2018}, date = {2018-03-22}, journal = {Nat. Comm.}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 138. | Petersen, J; Lindner, J; R., Mitric Ultrafast Photodynamics of Glucose Journal Article J. Phys. Chem. B, 122 , pp. 19-27, 2018. @article{petersen2018a, title = {Ultrafast Photodynamics of Glucose}, author = {J Petersen and J Lindner and Mitric R.}, url = {http://dx.doi.org/10.1021/acs.jpcb.7b08602}, year = {2018}, date = {2018-01-01}, journal = {J. Phys. Chem. B}, volume = {122}, pages = {19-27}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2017 |
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| 137. | Kunz, V; Lindner, J O; Schulze, M; Röhr, M I S; Schmidt, D; Mitric, R; Würthner, F Cooperative water oxidation catalysis in a series of trinuclear metallosupramolecular ruthenium macrocycles Journal Article Energy Environ. Sci., 10 , pp. 2137-2153, 2017. @article{kunz2017a, title = {Cooperative water oxidation catalysis in a series of trinuclear metallosupramolecular ruthenium macrocycles}, author = {V Kunz and J O Lindner and M Schulze and M I S Röhr and D Schmidt and R Mitric and F Würthner}, url = {http://dx.doi.org/10.1039/C7EE01557G}, year = {2017}, date = {2017-09-04}, journal = {Energy Environ. Sci.}, volume = {10}, pages = {2137-2153}, abstract = {A series of trinuclear metallosupramolecular Ru(bda) macrocycles has been synthesized and the impact of the ring size on the catalytic activity in homogeneous water oxidation has been elucidated (bda = 2,2′-bipyridine-6,6′-dicarboxylate). Kinetic experiments revealed that for all macrocyclic catalysts a proton-coupled oxidation event is rate-determining. Distinct H/D kinetic isotope effects (KIE) have been observed for the individual macrocycles, which follow the same tendency like the catalytic activity where an intermediate ring size exhibits the best performance. To get insight into the different molecular properties, molecular dynamics simulations using a QM/MM approach have been performed for all reaction steps, revealing that the size of the cavity strongly influences the hydrogen-bonded water network inside the macrocyclic structure and thus, important proton-coupled reaction steps of the catalytic cycle. For the most active catalysts, all reactive sites point into the interior of the cavity, which is supported by a single crystal X-ray analysis of the largest macrocycle, and a cooperative effect between the individual Ru(bda) centers facilitating proton abstraction has been substantiated. On the other hand, different structural conformations predominate the smaller macrocycles, which prevent efficient interactions between the Ru(bda) centers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A series of trinuclear metallosupramolecular Ru(bda) macrocycles has been synthesized and the impact of the ring size on the catalytic activity in homogeneous water oxidation has been elucidated (bda = 2,2′-bipyridine-6,6′-dicarboxylate). Kinetic experiments revealed that for all macrocyclic catalysts a proton-coupled oxidation event is rate-determining. Distinct H/D kinetic isotope effects (KIE) have been observed for the individual macrocycles, which follow the same tendency like the catalytic activity where an intermediate ring size exhibits the best performance. To get insight into the different molecular properties, molecular dynamics simulations using a QM/MM approach have been performed for all reaction steps, revealing that the size of the cavity strongly influences the hydrogen-bonded water network inside the macrocyclic structure and thus, important proton-coupled reaction steps of the catalytic cycle. For the most active catalysts, all reactive sites point into the interior of the cavity, which is supported by a single crystal X-ray analysis of the largest macrocycle, and a cooperative effect between the individual Ru(bda) centers facilitating proton abstraction has been substantiated. On the other hand, different structural conformations predominate the smaller macrocycles, which prevent efficient interactions between the Ru(bda) centers. |
| 136. | Hoche, J; Schmitt, H -C; Humeniuk, A; Fischer, I; Mitric, R; Röhr, M I S The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer Journal Article Phys. Chem. Chem. Phys., 19 , pp. 25002-25015, 2017. @article{hoche2017, title = {The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer}, author = {J Hoche and H -C Schmitt and A Humeniuk and I Fischer and R Mitric and M I S Röhr}, url = {http://dx.doi.org/10.1039/C7CP03990E}, year = {2017}, date = {2017-08-30}, journal = {Phys. Chem. Chem. Phys.}, volume = {19}, pages = {25002-25015}, abstract = {The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck–Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6–7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale}, keywords = {}, pubstate = {published}, tppubtype = {article} } The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck–Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6–7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale |
| 135. | Wohlgemuth, M; Miyazaki, M; Tsukuda, K; Weiler, M; Dopfer, O; Fujii, M; Mitric, R Deciphering environment effects in peptide bond solvation dynamics by experiment and theory Journal Article Phys. Chem. Chem. Phys., 19 , pp. 22564, 2017. @article{wohlgemuth2017, title = {Deciphering environment effects in peptide bond solvation dynamics by experiment and theory}, author = {M Wohlgemuth and M Miyazaki and K Tsukuda and M Weiler and O Dopfer and M Fujii and R Mitric}, url = {http://dx.doi.org/10.1039/C7CP03992A}, doi = {10.1039/C7CP03992A}, year = {2017}, date = {2017-08-04}, journal = {Phys. Chem. Chem. Phys.}, volume = {19}, pages = {22564}, abstract = {Most proteins work in aqueous solution and the interaction with water strongly affects their structure and function. However, experimentally the motion of a specific single water molecule is difficult to trace by conventional methods, because they average over the heterogeneous solvation structure of bulk water surrounding the protein. Here, we provide a detailed atomistic picture of the water rearrangement dynamics around the –CONH– peptide linkage in the two model systems formanilide and acetanilide, which simply differ by the presence of a methyl group at the peptide linkage. The combination of picosecond pump–probe time-resolved infrared spectroscopy and molecular dynamics simulations demonstrates that the solvation dynamics at the molecular level is strongly influenced by this small structural difference. The effective timescales for solvent migration triggered by ionization are mainly controlled by the efficiency of the kinetic energy redistribution rather than the shape of the potential energy surface. This approach provides a fundamental understanding of protein hydration and may help to design functional molecules in solution with tailored properties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Most proteins work in aqueous solution and the interaction with water strongly affects their structure and function. However, experimentally the motion of a specific single water molecule is difficult to trace by conventional methods, because they average over the heterogeneous solvation structure of bulk water surrounding the protein. Here, we provide a detailed atomistic picture of the water rearrangement dynamics around the –CONH– peptide linkage in the two model systems formanilide and acetanilide, which simply differ by the presence of a methyl group at the peptide linkage. The combination of picosecond pump–probe time-resolved infrared spectroscopy and molecular dynamics simulations demonstrates that the solvation dynamics at the molecular level is strongly influenced by this small structural difference. The effective timescales for solvent migration triggered by ionization are mainly controlled by the efficiency of the kinetic energy redistribution rather than the shape of the potential energy surface. This approach provides a fundamental understanding of protein hydration and may help to design functional molecules in solution with tailored properties. |
| 134. | Kunz, V; Schmidt, D; Röhr, M I S; Mitric, R; Würthner, F Supramolecular Approaches to Improve the Performance of Ruthenium‐Based Water Oxidation Catalysts Journal Article Adv. Energy Mater., 7 , pp. 1602939, 2017. @article{kunz2017b, title = {Supramolecular Approaches to Improve the Performance of Ruthenium‐Based Water Oxidation Catalysts}, author = {V Kunz and D Schmidt and M I S Röhr and R Mitric and F Würthner}, url = {https://doi.org/10.1002/aenm.201602939}, doi = {10.1002/aenm.201602939}, year = {2017}, date = {2017-06-06}, journal = {Adv. Energy Mater.}, volume = {7}, pages = {1602939}, abstract = {Supramolecular principles have been widely applied to enhance the activity of homogeneous ruthenium-based water oxidation catalysts. For catalytic systems in which the O[BOND]O bond is formed via radical coupling of two metal oxyl subunits, self-assembly of mononuclear catalysts into vesicles or fibrous aggregates can be used to improve the interaction of two catalytic centers. Similarly, the catalytic subunits can be brought into spatial proximity by coordination chemistry, which allows the construction of highly efficient metallosupramolecular multinuclear structures. However, if the O[BOND]O bond is formed by the nucleophilic attack of water at a metal oxide species, the interaction of the catalytic center with substrate water molecules has to be improved. Here, by introducing tailored ligand systems, the second coordination sphere can be adjusted specifically to preorganize water for O[BOND]O bond formation whereas the implementation of proton accepting residues can be used to lower the activation barrier of crucial proton-coupled reaction steps. In a particularly outstanding example, both principles were combined in a multinuclear metallosupramolecular macrocycle.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Supramolecular principles have been widely applied to enhance the activity of homogeneous ruthenium-based water oxidation catalysts. For catalytic systems in which the O[BOND]O bond is formed via radical coupling of two metal oxyl subunits, self-assembly of mononuclear catalysts into vesicles or fibrous aggregates can be used to improve the interaction of two catalytic centers. Similarly, the catalytic subunits can be brought into spatial proximity by coordination chemistry, which allows the construction of highly efficient metallosupramolecular multinuclear structures. However, if the O[BOND]O bond is formed by the nucleophilic attack of water at a metal oxide species, the interaction of the catalytic center with substrate water molecules has to be improved. Here, by introducing tailored ligand systems, the second coordination sphere can be adjusted specifically to preorganize water for O[BOND]O bond formation whereas the implementation of proton accepting residues can be used to lower the activation barrier of crucial proton-coupled reaction steps. In a particularly outstanding example, both principles were combined in a multinuclear metallosupramolecular macrocycle. |
| 133. | Röder, A; Humeniuk, A; Giegerich, J; Fischer, I; Poisson, L; Mitric, R Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical Journal Article Phys. Chem. Chem. Phys., 19 , pp. 12365-12374, 2017. @article{humeniuk2017f, title = {Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical}, author = {A Röder and A Humeniuk and J Giegerich and I Fischer and L Poisson and R Mitric}, url = {https://pubs.rsc.org/en/content/articlelanding/2017/cp/c7cp01437f#!divAbstract}, doi = {10.1039/C7CP01437F}, year = {2017}, date = {2017-04-12}, journal = {Phys. Chem. Chem. Phys.}, volume = {19}, pages = {12365-12374}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 132. | Humeniuk, Roland Mitric Alexander DFTBaby: A software package for non-adiabatic molecular dynamics simulations based on long-range corrected tight-binding TD-DFT(B) Journal Article Comput. Phys. Commun., 221 , pp. 174-202, 2017. @article{Humeniuk2017b, title = {DFTBaby: A software package for non-adiabatic molecular dynamics simulations based on long-range corrected tight-binding TD-DFT(B)}, author = {Roland Mitric Alexander Humeniuk}, url = {https://arxiv.org/pdf/1703.04049.pdf}, doi = {10.1016/j.cpc.2017.08.012}, year = {2017}, date = {2017-03-12}, journal = {Comput. Phys. Commun.}, volume = {221}, pages = {174-202}, organization = {arXiv.org, e-Print Archive, Physics}, abstract = {A software package, called DFTBaby, is published, which provides the electronic structure needed for running non-adiabatic molecular dynamics simulations at the level of charge-consistent tight-binding DFT. A long-range correction is incorporated to avoid spurious charge transfer states. Excited state energies, their analytic gradients and scalar non-adiabatic couplings are computed using tight-binding TD-DFT. These quantities are fed into a molecular dynamics code, which integrates Newton's equations of motion for the nuclei together with the electronic Schrödinger equation. Non-adiabatic effects are included by surface hopping. As an example, the program is applied to the optimization of excited states and non-adiabatic dynamics of polyfluorene.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A software package, called DFTBaby, is published, which provides the electronic structure needed for running non-adiabatic molecular dynamics simulations at the level of charge-consistent tight-binding DFT. A long-range correction is incorporated to avoid spurious charge transfer states. Excited state energies, their analytic gradients and scalar non-adiabatic couplings are computed using tight-binding TD-DFT. These quantities are fed into a molecular dynamics code, which integrates Newton's equations of motion for the nuclei together with the electronic Schrödinger equation. Non-adiabatic effects are included by surface hopping. As an example, the program is applied to the optimization of excited states and non-adiabatic dynamics of polyfluorene. |
| 131. | Roeder, Anja; Issler, Kevin; Poisson, Lionel; Humeniuk, Alexander; Wohlgemuth, Matthias; Comte, Michel; Lepetit, Fabien; Fischer, Ingo; Mitric, Roland; Petersen, Jens. Femtosecond dynamics of the 2-methylallyl radical: A computational and experimental study. Journal Article Journal of Chemical Physics, 147 , pp. 013902, 2017. @article{Roeder2017, title = {Femtosecond dynamics of the 2-methylallyl radical: A computational and experimental study.}, author = {Anja Roeder and Kevin Issler and Lionel Poisson and Alexander Humeniuk and Matthias Wohlgemuth and Michel Comte and Fabien Lepetit and Ingo Fischer and Roland Mitric and Jens. Petersen}, url = {http://doi.org/10.1063/1.4974150}, doi = {10.1063/1.4974150}, year = {2017}, date = {2017-02-02}, journal = {Journal of Chemical Physics}, volume = {147}, pages = {013902}, publisher = {American Institute of Physics}, abstract = {We investigate the photodynamics of the 2-methylallyl radical by femtosecond time-resolved photoelectron imaging. The expts. are accompanied by field-induced surface hopping dynamics calcns. and the simulation of time-resolved photoelectron intensities and anisotropies, giving insight into the photochem. and nonradiative relaxation of the radical. 2-methylallyl is excited at 236 nm, 238 nm, and 240.6 nm into a 3p Rydberg state, and the subsequent dynamics is probed by multiphoton ionization using photons of 800 nm. The photoelectron image exhibits a prominent band with considerable anisotropy, which is compatible with the result of theory. The simulations show that the initially excited 3p state is rapidly depopulated to a 3s Rydberg state, from which photoelectrons of high anisotropy are produced. The 3s state then decays within several 100 fs to the D1 (n$pi$) state, followed by the deactivation of the D1 to the electronic ground state on the ps time scale. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate the photodynamics of the 2-methylallyl radical by femtosecond time-resolved photoelectron imaging. The expts. are accompanied by field-induced surface hopping dynamics calcns. and the simulation of time-resolved photoelectron intensities and anisotropies, giving insight into the photochem. and nonradiative relaxation of the radical. 2-methylallyl is excited at 236 nm, 238 nm, and 240.6 nm into a 3p Rydberg state, and the subsequent dynamics is probed by multiphoton ionization using photons of 800 nm. The photoelectron image exhibits a prominent band with considerable anisotropy, which is compatible with the result of theory. The simulations show that the initially excited 3p state is rapidly depopulated to a 3s Rydberg state, from which photoelectrons of high anisotropy are produced. The 3s state then decays within several 100 fs to the D1 (n$pi$) state, followed by the deactivation of the D1 to the electronic ground state on the ps time scale. [on SciFinder(R)] |
2016 |
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| 130. | Wohlgemuth, Matthias; Mitric, Roland. Photochemical Chiral Symmetry Breaking in Alanine. Journal Article Journal of Physical Chemistry A, 120 (45), pp. 8976–8982, 2016, ISSN: 1089-5639. @article{Wohlgemuth2016, title = {Photochemical Chiral Symmetry Breaking in Alanine.}, author = {Matthias Wohlgemuth and Roland. Mitric}, doi = {10.1021/acs.jpca.6b07611}, issn = {1089-5639}, year = {2016}, date = {2016-01-01}, journal = {Journal of Physical Chemistry A}, volume = {120}, number = {45}, pages = {8976--8982}, publisher = {American Chemical Society}, abstract = {We introduce a general theor. approach for the simulation of photochem. dynamics under the influence of circularly polarized light to explore the possibility of generating enantiomeric enrichment through polarized-light-selective photochem. The method is applied to the simulation of the photolysis of alanine, a prototype chiral amino acid. It is shown that a systematic enantiomeric enrichment can be obtained depending on the helicity of the circularly polarized light that induces the excited-state photochem. of alanine. By analyzing the patterns of the photoinduced fragmentation of alanine we find an inducible enantiomeric enrichment up to 1.7%, which is also in good correspondence to the exptl. findings. This method is generally applicable to complex systems and might serve to systematically explore the photochem. origin of homochirality. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We introduce a general theor. approach for the simulation of photochem. dynamics under the influence of circularly polarized light to explore the possibility of generating enantiomeric enrichment through polarized-light-selective photochem. The method is applied to the simulation of the photolysis of alanine, a prototype chiral amino acid. It is shown that a systematic enantiomeric enrichment can be obtained depending on the helicity of the circularly polarized light that induces the excited-state photochem. of alanine. By analyzing the patterns of the photoinduced fragmentation of alanine we find an inducible enantiomeric enrichment up to 1.7%, which is also in good correspondence to the exptl. findings. This method is generally applicable to complex systems and might serve to systematically explore the photochem. origin of homochirality. [on SciFinder(R)] |
| 129. | Humeniuk, Alexander; Mitric, Roland. Fully quantum non-adiabatic dynamics in electronic-nuclear coherent state basis. Online arXiv.org, e-Print Archive, Physics 2016. @online{Humeniuk2016, title = {Fully quantum non-adiabatic dynamics in electronic-nuclear coherent state basis.}, author = {Alexander Humeniuk and Roland. Mitric}, url = {http://arxiv.org/pdf/1604.07185.pdf}, year = {2016}, date = {2016-01-01}, journal = {arXiv.org, e-Print Archive, Physics}, pages = {1--18}, publisher = {Cornell University Library}, organization = {arXiv.org, e-Print Archive, Physics}, abstract = {Direct dynamics methods using Gaussian wavepackets have to rely only on local properties, such as gradients and hessians at the center of the wavepacket, so as to be compatible with the usual quantum chem. methods. Matrix elements of the potential energy surfaces between wavepackets therefore usually have to be approximated. It is shown, that if a modified form of valence bond theory is used instead of the usual MO-based theories, the matrix elements can be obtained exactly. This is so because the mol. Hamiltonian only contains the Coulomb potential, for which matrix elements between different basis functions (consisting of Gaussian nuclear and electronic orbitals) are all well-known. In valence bond theory the SCF calcn. can be avoided so that the matrix elements are anal. functions of the nuclear coordinates. A method for simulating non-adiabatic quantum dynamics is sketched, where coherent state trajectories are propagated "on the fly" on adiabatic potential energy surfaces without making approxns. to the matrix elements responsible for the coupling between trajectories. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {online} } Direct dynamics methods using Gaussian wavepackets have to rely only on local properties, such as gradients and hessians at the center of the wavepacket, so as to be compatible with the usual quantum chem. methods. Matrix elements of the potential energy surfaces between wavepackets therefore usually have to be approximated. It is shown, that if a modified form of valence bond theory is used instead of the usual MO-based theories, the matrix elements can be obtained exactly. This is so because the mol. Hamiltonian only contains the Coulomb potential, for which matrix elements between different basis functions (consisting of Gaussian nuclear and electronic orbitals) are all well-known. In valence bond theory the SCF calcn. can be avoided so that the matrix elements are anal. functions of the nuclear coordinates. A method for simulating non-adiabatic quantum dynamics is sketched, where coherent state trajectories are propagated "on the fly" on adiabatic potential energy surfaces without making approxns. to the matrix elements responsible for the coupling between trajectories. [on SciFinder(R)] |
| 128. | Humeniuk, Alexander; Mitric, Roland. Non-adiabatic dynamics around a conical intersection with surface-hopping coupled coherent states. Journal Article J. Chem. Phys., 144 , pp. 234108, 2016. @article{Humeniuk2016a, title = {Non-adiabatic dynamics around a conical intersection with surface-hopping coupled coherent states.}, author = {Alexander Humeniuk and Roland. Mitric}, url = {http://arxiv.org/pdf/1602.04083.pdf}, doi = {10.1063/1.4954189}, year = {2016}, date = {2016-01-01}, journal = {J. Chem. Phys.}, volume = {144}, pages = {234108}, publisher = {Cornell University Library}, abstract = {An extension of the CCS-method for simulating non-adiabatic dynamics with quantum effects of the nuclei is put forward. The time-dependent Schrödinger equation for the motion of the nuclei is solved in a moving basis set. The basis set is guided by classical trajectories, which can hop stochastically between different electronic potential energy surfaces. The non-adiabatic transitions are modelled by a modified version of Tully's fewest switches algorithm. The trajectories consist of Gaussians in the phase space of the nuclei (coherent states) combined with amplitudes for an electronic wave function. The time-dependent matrix elements between different coherent states det. the amplitude of each trajectory in the total multistate wave function; the diagonal matrix elements det. the hopping probabilities and gradients. In this way, both intereference effects and non-adiabatic transitions can be described in a very compact fashion, leading to the exact soln. if convergence with respect to the no. of trajectories is achieved and the potential energy surfaces are known globally. The method is tested on a 2D model for a conical intersection, where a nuclear wavepacket encircles the point of degeneracy between two potential energy surfaces and intereferes with itself. These intereference effects are absent in classical trajectory-based mol. dynamics but can be fully incorporated if trajectories are replaced by surface hopping coupled coherent states. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } An extension of the CCS-method for simulating non-adiabatic dynamics with quantum effects of the nuclei is put forward. The time-dependent Schrödinger equation for the motion of the nuclei is solved in a moving basis set. The basis set is guided by classical trajectories, which can hop stochastically between different electronic potential energy surfaces. The non-adiabatic transitions are modelled by a modified version of Tully's fewest switches algorithm. The trajectories consist of Gaussians in the phase space of the nuclei (coherent states) combined with amplitudes for an electronic wave function. The time-dependent matrix elements between different coherent states det. the amplitude of each trajectory in the total multistate wave function; the diagonal matrix elements det. the hopping probabilities and gradients. In this way, both intereference effects and non-adiabatic transitions can be described in a very compact fashion, leading to the exact soln. if convergence with respect to the no. of trajectories is achieved and the potential energy surfaces are known globally. The method is tested on a 2D model for a conical intersection, where a nuclear wavepacket encircles the point of degeneracy between two potential energy surfaces and intereferes with itself. These intereference effects are absent in classical trajectory-based mol. dynamics but can be fully incorporated if trajectories are replaced by surface hopping coupled coherent states. [on SciFinder(R)] |
| 127. | Lisinetskaya, Polina G; Röhr, Merle I S; Mitric, Roland. First-principles simulation of light propagation and exciton dynamics in metal cluster nanostructures. Journal Article Applied Physics B: Lasers and Optics, 122 (6), pp. 1–12, 2016, ISSN: 0946-2171. @article{Lisinetskaya2016, title = {First-principles simulation of light propagation and exciton dynamics in metal cluster nanostructures.}, author = {Polina G Lisinetskaya and Merle I S Röhr and Roland. Mitric}, doi = {10.1007/s00340-016-6436-6}, issn = {0946-2171}, year = {2016}, date = {2016-01-01}, journal = {Applied Physics B: Lasers and Optics}, volume = {122}, number = {6}, pages = {1--12}, publisher = {Springer}, abstract = {We present a theor. approach for the simulation of the elec. field and exciton propagation in ordered arrays constructed of mol.-sized noble metal clusters bound to org. polymer templates. In order to describe the electronic coupling between individual constituents of the nanostructure we use the ab initio parameterized transition charge method which is more accurate than the usual dipole-dipole coupling. The electronic population dynamics in the nanostructure under an external laser pulse excitation is simulated by numerical integration of the time-dependent Schrodinger equation employing the fully coupled Hamiltonian. The soln. of the TDSE gives rise to time-dependent partial point charges for each subunit of the nanostructure, and the spatio-temporal elec. field distribution is evaluated by means of classical electrodynamics methods. The time-dependent partial charges are detd. based on the stationary partial and transition charges obtained in the framework of the TDDFT. In order to treat large plasmonic nanostructures constructed of many constituents, the approx. self-consistent iterative approach presented in (Lisinetskaya and Mitric in Phys Rev B 89:035433, 2014) is modified to include the transition-charge-based interaction. The developed methods are used to study the optical response and exciton dynamics of Ag+3 and porphyrin-Ag4 dimers. Subsequently, the spatio-temporal elec. field distribution in a ring constructed of ten porphyrin-Ag4 subunits under the action of circularly polarized laser pulse is simulated. The presented methodol. provides a theor. basis for the investigation of coupled light-exciton propagation in nanoarchitectures built from mol. size metal nanoclusters in which quantum confinement effects are important. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a theor. approach for the simulation of the elec. field and exciton propagation in ordered arrays constructed of mol.-sized noble metal clusters bound to org. polymer templates. In order to describe the electronic coupling between individual constituents of the nanostructure we use the ab initio parameterized transition charge method which is more accurate than the usual dipole-dipole coupling. The electronic population dynamics in the nanostructure under an external laser pulse excitation is simulated by numerical integration of the time-dependent Schrodinger equation employing the fully coupled Hamiltonian. The soln. of the TDSE gives rise to time-dependent partial point charges for each subunit of the nanostructure, and the spatio-temporal elec. field distribution is evaluated by means of classical electrodynamics methods. The time-dependent partial charges are detd. based on the stationary partial and transition charges obtained in the framework of the TDDFT. In order to treat large plasmonic nanostructures constructed of many constituents, the approx. self-consistent iterative approach presented in (Lisinetskaya and Mitric in Phys Rev B 89:035433, 2014) is modified to include the transition-charge-based interaction. The developed methods are used to study the optical response and exciton dynamics of Ag+3 and porphyrin-Ag4 dimers. Subsequently, the spatio-temporal elec. field distribution in a ring constructed of ten porphyrin-Ag4 subunits under the action of circularly polarized laser pulse is simulated. The presented methodol. provides a theor. basis for the investigation of coupled light-exciton propagation in nanoarchitectures built from mol. size metal nanoclusters in which quantum confinement effects are important. [on SciFinder(R)] |
| 126. | Gerbich, Thiemo; Schmitt, Hans-Christian; Fischer, Ingo; Mitric, Roland; Petersen, Jens. Dynamics of Isolated 1,8-Naphthalimide and N-Methyl-1,8-naphthalimide: An Experimental and Computational Study. Journal Article Journal of Physical Chemistry A, 120 (13), pp. 2089–2095, 2016, ISSN: 1089-5639. @article{Gerbich2016, title = {Dynamics of Isolated 1,8-Naphthalimide and N-Methyl-1,8-naphthalimide: An Experimental and Computational Study.}, author = {Thiemo Gerbich and Hans-Christian Schmitt and Ingo Fischer and Roland Mitric and Jens. Petersen}, doi = {10.1021/acs.jpca.6b01226}, issn = {1089-5639}, year = {2016}, date = {2016-01-01}, journal = {Journal of Physical Chemistry A}, volume = {120}, number = {13}, pages = {2089--2095}, publisher = {American Chemical Society}, abstract = {The excited-state structures and dynamics of 1,8-naphthalimide (NI) and N-methyl-1,8-naphthalimide (Me-NI) have been studied in the gas phase by picosecond time- and frequency-resolved multiphoton ionization spectroscopy. The energies of several electronically excited singlet and triplet states and the S1 vibrational wavenumbers were calcd. Nonadiabatic dynamics simulations support the anal. of the radiationless deactivation processes. The origin of the S1 ← S0 ($pi$$pi$*) transition was found at 30,082 cm-1 for NI and at 29,920 cm-1 for Me-NI. Furthermore, a couple of low-lying vibrational bands were resolved in the spectra of both mols. In the time-resolved scans a biexponential decay was apparent for both Me-NI and NI. The fast time const. is in the range of 10-20 ps, whereas the second one is in the nanosecond range. In accordance with the dynamics simulations, intersystem crossing to the fourth triplet state S1 ($pi$$pi$*) → T4 (n$pi$*) is the main deactivation process for Me-NI due to a large spin-orbit coupling between these states. Only for significant vibrational excitation internal conversion via a conical intersection becomes a relevant deactivation pathway. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The excited-state structures and dynamics of 1,8-naphthalimide (NI) and N-methyl-1,8-naphthalimide (Me-NI) have been studied in the gas phase by picosecond time- and frequency-resolved multiphoton ionization spectroscopy. The energies of several electronically excited singlet and triplet states and the S1 vibrational wavenumbers were calcd. Nonadiabatic dynamics simulations support the anal. of the radiationless deactivation processes. The origin of the S1 ← S0 ($pi$$pi$*) transition was found at 30,082 cm-1 for NI and at 29,920 cm-1 for Me-NI. Furthermore, a couple of low-lying vibrational bands were resolved in the spectra of both mols. In the time-resolved scans a biexponential decay was apparent for both Me-NI and NI. The fast time const. is in the range of 10-20 ps, whereas the second one is in the nanosecond range. In accordance with the dynamics simulations, intersystem crossing to the fourth triplet state S1 ($pi$$pi$*) → T4 (n$pi$*) is the main deactivation process for Me-NI due to a large spin-orbit coupling between these states. Only for significant vibrational excitation internal conversion via a conical intersection becomes a relevant deactivation pathway. [on SciFinder(R)] |
| 125. | Röhr, Merle I S; Mitric, Roland; Petersen, Jens. Vibrationally resolved optical spectra and ultrafast electronic relaxation dynamics of diamantane. Journal Article Physical Chemistry Chemical Physics, 18 (12), pp. 8701–8709, 2016, ISSN: 1463-9076. @article{Röhr2016a, title = {Vibrationally resolved optical spectra and ultrafast electronic relaxation dynamics of diamantane.}, author = {Merle I S Röhr and Roland Mitric and Jens. Petersen}, doi = {10.1039/C6CP00137H}, issn = {1463-9076}, year = {2016}, date = {2016-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {18}, number = {12}, pages = {8701--8709}, publisher = {Royal Society of Chemistry}, abstract = {We present theor. simulations of the vibrationally resolved photoabsorption and photoemission spectra of diamantane combined with nonadiabatic dynamics simulations in order to identify the state responsible for the measured photoluminescence of diamantane and to det. the mechanism and the time-scales of the electronic state relaxation. Diamantane is a prototype representative of the diamondoid class of hydrocarbons which have recently gained significant interest due to their unique electronic properties. This mol. is characterized by an almost dark first excited state, which therefore cannot be directly excited. Moreover, the calcd. vertical transition from the geometrically relaxed first excited state to the ground state also bears no intensity. However, recent expts. suggest that the obsd. photoluminescence originates from the lowest excited state. We have performed spectral simulations in the frame of the Herzberg-Teller approxn. for vibronic transitions, which goes beyond the Franck-Condon approxn. of const. transition dipole moments and takes into account their linear dependence on the geometrical deformations. In this way, the available exptl. spectrum could be fully reproduced, resolving the issue about the origin of the photoluminescence. Moreover, the photoemission from the first excited state also implies that ultrafast nonradiative processes have to take place after the initial excitation of the bright electronic states. We have detd. the mechanism and time-scales of these relaxation processes by performing nonadiabatic dynamics simulations in the manifold of s- and p-type Rydberg excited states. The simulations demonstrate that the lowest excited electronic state of diamantane gains significant population from higher-lying states already after several hundreds of femtoseconds. Thus, our dynamics simulations combined with spectra calcd. using the Herzberg-Teller approxn. allow us to fully explain the obsd. photoabsorption and photoemission properties of diamantane. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present theor. simulations of the vibrationally resolved photoabsorption and photoemission spectra of diamantane combined with nonadiabatic dynamics simulations in order to identify the state responsible for the measured photoluminescence of diamantane and to det. the mechanism and the time-scales of the electronic state relaxation. Diamantane is a prototype representative of the diamondoid class of hydrocarbons which have recently gained significant interest due to their unique electronic properties. This mol. is characterized by an almost dark first excited state, which therefore cannot be directly excited. Moreover, the calcd. vertical transition from the geometrically relaxed first excited state to the ground state also bears no intensity. However, recent expts. suggest that the obsd. photoluminescence originates from the lowest excited state. We have performed spectral simulations in the frame of the Herzberg-Teller approxn. for vibronic transitions, which goes beyond the Franck-Condon approxn. of const. transition dipole moments and takes into account their linear dependence on the geometrical deformations. In this way, the available exptl. spectrum could be fully reproduced, resolving the issue about the origin of the photoluminescence. Moreover, the photoemission from the first excited state also implies that ultrafast nonradiative processes have to take place after the initial excitation of the bright electronic states. We have detd. the mechanism and time-scales of these relaxation processes by performing nonadiabatic dynamics simulations in the manifold of s- and p-type Rydberg excited states. The simulations demonstrate that the lowest excited electronic state of diamantane gains significant population from higher-lying states already after several hundreds of femtoseconds. Thus, our dynamics simulations combined with spectra calcd. using the Herzberg-Teller approxn. allow us to fully explain the obsd. photoabsorption and photoemission properties of diamantane. [on SciFinder(R)] |
| 124. | Lisinetskaya, Polina G; Braun, Christian; Proch, Sebastian; Kim, Young Dok; Gantefoer, Gerd; Mitric, Roland. Excited state nonadiabatic dynamics of bare and hydrated anionic gold clusters Au3-[H2O]n (n = 0-2). Journal Article Physical Chemistry Chemical Physics, 18 (9), pp. 6411–6419, 2016, ISSN: 1463-9076. @article{Lisinetskaya2016a, title = {Excited state nonadiabatic dynamics of bare and hydrated anionic gold clusters Au3-[H2O]n (n = 0-2).}, author = {Polina G Lisinetskaya and Christian Braun and Sebastian Proch and Young Dok Kim and Gerd Gantefoer and Roland. Mitric}, doi = {10.1039/C5CP04297F}, issn = {1463-9076}, year = {2016}, date = {2016-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {18}, number = {9}, pages = {6411--6419}, publisher = {Royal Society of Chemistry}, abstract = {We present a joint theor. and exptl. study of excited state dynamics in pure and hydrated anionic gold clusters Au3-[H2O]n (n = 0-2). We employ mixed quantum-classical dynamics combined with femtosecond time-resolved photoelectron spectroscopy in order to investigate the influence of hydration on excited state lifetimes and photo-dissocn. dynamics. A gradual decrease of the excited state lifetime with the no. of adsorbed water mols. as well as gold cluster fragmentation quenching by two or more water mols. are obsd. both in expt. and in simulations. Nonradiative relaxation and dissocn. in excited states are found to be responsible for the excited state population depletion. Time consts. of these two processes strongly depend on the no. of water mols. leading to the possibility to modulate excited state dynamics and fragmentation of the anionic cluster by adsorption of water mols. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a joint theor. and exptl. study of excited state dynamics in pure and hydrated anionic gold clusters Au3-[H2O]n (n = 0-2). We employ mixed quantum-classical dynamics combined with femtosecond time-resolved photoelectron spectroscopy in order to investigate the influence of hydration on excited state lifetimes and photo-dissocn. dynamics. A gradual decrease of the excited state lifetime with the no. of adsorbed water mols. as well as gold cluster fragmentation quenching by two or more water mols. are obsd. both in expt. and in simulations. Nonradiative relaxation and dissocn. in excited states are found to be responsible for the excited state population depletion. Time consts. of these two processes strongly depend on the no. of water mols. leading to the possibility to modulate excited state dynamics and fragmentation of the anionic cluster by adsorption of water mols. [on SciFinder(R)] |
| 123. | Röhr, Merle I S; Lisinetskaya, Polina G; Mitric, Roland. Excitonic Properties of Ordered Metal Nanocluster Arrays: 2D Silver Clusters at Multiporphyrin Templates. Journal Article J. Phys. Chem. A, 120 (26), pp. 4465–4472, 2016, ISSN: 1089-5639. @article{Röhr2016, title = {Excitonic Properties of Ordered Metal Nanocluster Arrays: 2D Silver Clusters at Multiporphyrin Templates.}, author = {Merle I S Röhr and Polina G Lisinetskaya and Roland. Mitric}, doi = {10.1021/acs.jpca.6b04243}, issn = {1089-5639}, year = {2016}, date = {2016-01-01}, journal = {J. Phys. Chem. A}, volume = {120}, number = {26}, pages = {4465--4472}, publisher = {American Chemical Society}, abstract = {The design of ordered arrays of metal nanoclusters such as, for example, two-dimensional cluster-org. frameworks might open a new route toward the development of materials with tailored optical properties. Such systems could serve as plasmonically enhanced light-harvesting materials, sensors, or catalysts. The authors present here a theor. approach for the simulation of the optical properties of ordered arrays of metal clusters that is based on the ab initio parametrized Frenkel exciton model. Small atomically precise Ag clusters can be assembled in 1- and two-dimensional arrays on suitably designed porphyrin templates exhibiting remarkable optical properties. By employing explicit time-dependent d. functional theory calcns. on smaller homologs, the intrinsic optical properties of metal clusters are largely preserved but undergo J- and H-type excitonic coupling that results in controllable splitting of their excited states. Also, ab initio parametrized Frenkel exciton model calcns. allow the authors to predict an energetic splitting of up to 0.77 eV in extended two-dimensional square arrays and 0.79 eV in tilted square aggregates contg. up to 25 cluster-porphyrin subunits. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The design of ordered arrays of metal nanoclusters such as, for example, two-dimensional cluster-org. frameworks might open a new route toward the development of materials with tailored optical properties. Such systems could serve as plasmonically enhanced light-harvesting materials, sensors, or catalysts. The authors present here a theor. approach for the simulation of the optical properties of ordered arrays of metal clusters that is based on the ab initio parametrized Frenkel exciton model. Small atomically precise Ag clusters can be assembled in 1- and two-dimensional arrays on suitably designed porphyrin templates exhibiting remarkable optical properties. By employing explicit time-dependent d. functional theory calcns. on smaller homologs, the intrinsic optical properties of metal clusters are largely preserved but undergo J- and H-type excitonic coupling that results in controllable splitting of their excited states. Also, ab initio parametrized Frenkel exciton model calcns. allow the authors to predict an energetic splitting of up to 0.77 eV in extended two-dimensional square arrays and 0.79 eV in tilted square aggregates contg. up to 25 cluster-porphyrin subunits. [on SciFinder(R)] |
2015 |
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| 122. | Humeniuk, Alexander; Mitric, Roland. Long-range correction for tight-binding TD-DFT. Journal Article Journal of Chemical Physics, 143 (13), pp. 134120/1–134120/21, 2015, ISSN: 0021-9606. @article{Humeniuk2015, title = {Long-range correction for tight-binding TD-DFT.}, author = {Alexander Humeniuk and Roland. Mitric}, doi = {10.1063/1.4931179}, issn = {0021-9606}, year = {2015}, date = {2015-01-01}, journal = {Journal of Chemical Physics}, volume = {143}, number = {13}, pages = {134120/1--134120/21}, publisher = {American Institute of Physics}, abstract = {We present two improvements to the tight-binding approxn. of time-dependent d. functional theory (TD-DFTB): First, we add an exact Hartree-Fock exchange term, which is switched on at large distances, to the ground state Hamiltonian and similarly to the coupling matrix that enters the linear response equations for the calcn. of excited electronic states. We show that the excitation energies of charge transfer states are improved relative to the std. approach without the long-range correction by testing the method on a set of mols. from the database in Peach et al. [J. Chem. Phys. 128, 044118 (2008)] which are known to exhibit problematic charge transfer states. The degree of spatial overlap between occupied and virtual orbitals indicates where TD-DFTB and long-range cor. TD-DFTB (lc-TD-DFTB) can be expected to produce large errors. Second, we improve the calcn. of oscillator strengths. The transition dipoles are obtained from Slater Koster files for the dipole matrix elements between valence orbitals. In particular, excitations localized on a single atom, which appear dark when using Mulliken transition charges, acquire a more realistic oscillator strength in this way. These extensions pave the way for using lc-TD-DFTB to describe the electronic structure of large chromophoric polymers, where uncorrected TD-DFTB fails to describe the high degree of conjugation and produces spurious low-lying charge transfer states. (c) 2015 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present two improvements to the tight-binding approxn. of time-dependent d. functional theory (TD-DFTB): First, we add an exact Hartree-Fock exchange term, which is switched on at large distances, to the ground state Hamiltonian and similarly to the coupling matrix that enters the linear response equations for the calcn. of excited electronic states. We show that the excitation energies of charge transfer states are improved relative to the std. approach without the long-range correction by testing the method on a set of mols. from the database in Peach et al. [J. Chem. Phys. 128, 044118 (2008)] which are known to exhibit problematic charge transfer states. The degree of spatial overlap between occupied and virtual orbitals indicates where TD-DFTB and long-range cor. TD-DFTB (lc-TD-DFTB) can be expected to produce large errors. Second, we improve the calcn. of oscillator strengths. The transition dipoles are obtained from Slater Koster files for the dipole matrix elements between valence orbitals. In particular, excitations localized on a single atom, which appear dark when using Mulliken transition charges, acquire a more realistic oscillator strength in this way. These extensions pave the way for using lc-TD-DFTB to describe the electronic structure of large chromophoric polymers, where uncorrected TD-DFTB fails to describe the high degree of conjugation and produces spurious low-lying charge transfer states. (c) 2015 American Institute of Physics. [on SciFinder(R)] |
| 121. | Miyazaki, Mitsuhiko; Nakamura, Takashi; Wohlgemuth, Matthias; Mitric, Roland; Dopfer, Otto; Fujii, Masaaki. Single water solvation dynamics in the 4-aminobenzonitrile-water cluster cation revealed by picosecond time-resolved infrared spectroscopy. Journal Article Physical Chemistry Chemical Physics, 17 (44), pp. 29969–29977, 2015, ISSN: 1463-9076. @article{Miyazaki2015, title = {Single water solvation dynamics in the 4-aminobenzonitrile-water cluster cation revealed by picosecond time-resolved infrared spectroscopy.}, author = {Mitsuhiko Miyazaki and Takashi Nakamura and Matthias Wohlgemuth and Roland Mitric and Otto Dopfer and Masaaki. Fujii}, doi = {10.1039/C5CP05400A}, issn = {1463-9076}, year = {2015}, date = {2015-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {17}, number = {44}, pages = {29969--29977}, publisher = {Royal Society of Chemistry}, abstract = {The dynamics of a solvent is important for many chem. and biol. processes. Here, the migration dynamics of a single water mol. is triggered by the photoionization of the 4-aminobenzonitrile-water (4ABN-W) cluster and monitored in real time by picosecond time-resolved IR (ps TRIR) spectroscopy. In the neutral cluster, water is hydrogen-bonded to the CN group. When this CN-bound cluster is selectively ionized with an excess energy of 1238 cm-1, water migrates with a lifetime of $tau$ = 17 ps from the CN to the NH2 group, forming a more stable 4ABN+-W(NH) isomer with a yield of unity. By decreasing the ionization excess energy, the yield of the CN → NH2 reaction is reduced. The relatively slow migration in comparison to the ionization-induced solvent dynamics in the related acetanilide-water cluster cation ($tau$ = 5 ps) is discussed in terms of the internal excess energy after photoionization and the shape of the potential energy surface. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamics of a solvent is important for many chem. and biol. processes. Here, the migration dynamics of a single water mol. is triggered by the photoionization of the 4-aminobenzonitrile-water (4ABN-W) cluster and monitored in real time by picosecond time-resolved IR (ps TRIR) spectroscopy. In the neutral cluster, water is hydrogen-bonded to the CN group. When this CN-bound cluster is selectively ionized with an excess energy of 1238 cm-1, water migrates with a lifetime of $tau$ = 17 ps from the CN to the NH2 group, forming a more stable 4ABN+-W(NH) isomer with a yield of unity. By decreasing the ionization excess energy, the yield of the CN → NH2 reaction is reduced. The relatively slow migration in comparison to the ionization-induced solvent dynamics in the related acetanilide-water cluster cation ($tau$ = 5 ps) is discussed in terms of the internal excess energy after photoionization and the shape of the potential energy surface. [on SciFinder(R)] |
| 120. | Lisinetskaya, Polina G; Mitric, Roland. Optimal control of light propagation and exciton transfer in arrays of molecular-like noble-metal clusters. Journal Article Physical Review B: Condensed Matter and Materials Physics, 91 (12), pp. 125436/1–125436/8, 2015, ISSN: 1098-0121. @article{Lisinetskaya2015, title = {Optimal control of light propagation and exciton transfer in arrays of molecular-like noble-metal clusters.}, author = {Polina G Lisinetskaya and Roland. Mitric}, doi = {10.1103/PhysRevB.91.125436}, issn = {1098-0121}, year = {2015}, date = {2015-01-01}, journal = {Physical Review B: Condensed Matter and Materials Physics}, volume = {91}, number = {12}, pages = {125436/1--125436/8}, publisher = {American Physical Society}, abstract = {We demonstrate theor. the possibility of optimal control of light propagation and exciton transfer in arrays constructed of subnanometer sized noble-metal clusters by using phase-shaped laser pulses and analyze the mechanism underlying this process. The theor. approach for simulation of light propagation in the arrays is based on the numerical soln. of the coupled time-dependent Schrodinger equation and the classical elec. field propagation in an iterative self-consistent manner. The electronic eigenstates of individual clusters and the dipole couplings are obtained from ab initio TDDFT calcns. The total elec. field is propagated along the array by coupling an external excitation elec. field with the elec. fields produced by all clusters. A genetic algorithm is used to det. optimal pulse shapes which drive the excitation in a desired direction. The described theor. approach is applied to control the light propagation and exciton transfer dynamics into a T-shaped structure built of seven Ag8 clusters. We demonstrate that a selective switching of light localization is possible in ∼5 nm sized cluster arrays which might serve as a building block for plasmonic devices with an ultrafast operation regime. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate theor. the possibility of optimal control of light propagation and exciton transfer in arrays constructed of subnanometer sized noble-metal clusters by using phase-shaped laser pulses and analyze the mechanism underlying this process. The theor. approach for simulation of light propagation in the arrays is based on the numerical soln. of the coupled time-dependent Schrodinger equation and the classical elec. field propagation in an iterative self-consistent manner. The electronic eigenstates of individual clusters and the dipole couplings are obtained from ab initio TDDFT calcns. The total elec. field is propagated along the array by coupling an external excitation elec. field with the elec. fields produced by all clusters. A genetic algorithm is used to det. optimal pulse shapes which drive the excitation in a desired direction. The described theor. approach is applied to control the light propagation and exciton transfer dynamics into a T-shaped structure built of seven Ag8 clusters. We demonstrate that a selective switching of light localization is possible in ∼5 nm sized cluster arrays which might serve as a building block for plasmonic devices with an ultrafast operation regime. [on SciFinder(R)] |
| 119. | Lambert, Christoph; Koch, Federico; Voelker, Sebastian F; Schmiedel, Alexander; Holzapfel, Marco; Humeniuk, Alexander; Röhr, Merle I S; Mitric, Roland; Brixner, Tobias. Energy Transfer Between Squaraine Polymer Sections: From Helix to Zigzag and All the Way Back. Journal Article Journal of the American Chemical Society, 137 (24), pp. 7851–7861, 2015, ISSN: 0002-7863. @article{Lambert2015, title = {Energy Transfer Between Squaraine Polymer Sections: From Helix to Zigzag and All the Way Back.}, author = {Christoph Lambert and Federico Koch and Sebastian F Voelker and Alexander Schmiedel and Marco Holzapfel and Alexander Humeniuk and Merle I S Röhr and Roland Mitric and Tobias. Brixner}, doi = {10.1021/jacs.5b03644}, issn = {0002-7863}, year = {2015}, date = {2015-01-01}, journal = {Journal of the American Chemical Society}, volume = {137}, number = {24}, pages = {7851--7861}, publisher = {American Chemical Society}, abstract = {We provide a joint exptl. and theor. study of squaraine polymers in soln. The absorption spectra show evidence that two different conformations are present in the polymer: a helix and a zigzag structure. This unique situation allows investigating ultrafast energy-transfer processes between different structural segments within a single polymer chain in soln. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. Here, we combine femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy in order to demonstrate that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zigzag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the d. of states between donor and acceptor polymer segments because of the very small reorganization energy in these cyanine-like chromophores. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We provide a joint exptl. and theor. study of squaraine polymers in soln. The absorption spectra show evidence that two different conformations are present in the polymer: a helix and a zigzag structure. This unique situation allows investigating ultrafast energy-transfer processes between different structural segments within a single polymer chain in soln. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. Here, we combine femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy in order to demonstrate that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zigzag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the d. of states between donor and acceptor polymer segments because of the very small reorganization energy in these cyanine-like chromophores. [on SciFinder(R)] |
| 118. | Gerbich, Thiemo; Schmitt, Hans-Christian; Fischer, Ingo; Petersen, Jens; Albert, Julian; Mitric, Roland. Time-Resolved Study of 1,8-Naphthalic Anhydride and 1,4,5,8-Naphthalene-tetracarboxylic Dianhydride. Journal Article Journal of Physical Chemistry A, 119 (23), pp. 6006–6016, 2015, ISSN: 1089-5639. @article{Gerbich2015, title = {Time-Resolved Study of 1,8-Naphthalic Anhydride and 1,4,5,8-Naphthalene-tetracarboxylic Dianhydride.}, author = {Thiemo Gerbich and Hans-Christian Schmitt and Ingo Fischer and Jens Petersen and Julian Albert and Roland. Mitric}, doi = {10.1021/jp511843q}, issn = {1089-5639}, year = {2015}, date = {2015-01-01}, journal = {Journal of Physical Chemistry A}, volume = {119}, number = {23}, pages = {6006--6016}, publisher = {American Chemical Society}, abstract = {We investigate the excited electronic states of 1,8-naphthalic anhydride (NDCA) and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) by time- and frequency-resolved electronic spectroscopy in the gas phase using picosecond lasers and by femtosecond time-resolved transient absorption in cyclohexane. The expts. are accompanied by calcns. that yield the energy of the excited singlet and triplet states as well as by surface hopping dynamics simulations and calcns. of spin-orbit couplings that give insight into the photochem. The origin of the A 1A1 ← X 1A1 ($pi$$pi$*) transition in isolated NDCA was found at 30 260 cm-1, and several low-lying vibrational bands were obsd. The lifetime drops sharply from 1.2 ns at the origin to around 30 ps at an excess energy of 800 cm-1. Both internal conversion (IC) and intersystem crossing (ISC) are possible deactivation pathways as found in coupled electron-nuclear dynamics simulations. In cyclohexane soln., two time consts. were obsd. Deactivation of the initially excited state by ISC seems to dominate as supported by computations. For NTCDA we obsd. a gas phase lifetime of 16 ps upon excitation at 351 nm. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate the excited electronic states of 1,8-naphthalic anhydride (NDCA) and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) by time- and frequency-resolved electronic spectroscopy in the gas phase using picosecond lasers and by femtosecond time-resolved transient absorption in cyclohexane. The expts. are accompanied by calcns. that yield the energy of the excited singlet and triplet states as well as by surface hopping dynamics simulations and calcns. of spin-orbit couplings that give insight into the photochem. The origin of the A 1A1 ← X 1A1 ($pi$$pi$*) transition in isolated NDCA was found at 30 260 cm-1, and several low-lying vibrational bands were obsd. The lifetime drops sharply from 1.2 ns at the origin to around 30 ps at an excess energy of 800 cm-1. Both internal conversion (IC) and intersystem crossing (ISC) are possible deactivation pathways as found in coupled electron-nuclear dynamics simulations. In cyclohexane soln., two time consts. were obsd. Deactivation of the initially excited state by ISC seems to dominate as supported by computations. For NTCDA we obsd. a gas phase lifetime of 16 ps upon excitation at 351 nm. [on SciFinder(R)] |
| 117. | Megow, Joerg; Röhr, Merle I S; Schmidt am Busch, Marcel ; Renger, Thomas; Mitric, Roland; Kirstein, Stefan; Rabe, Juergen P; May, Volkhard. Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates. Journal Article Physical Chemistry Chemical Physics, 17 (10), pp. 6741–6747, 2015, ISSN: 1463-9076. @article{Megow2015, title = {Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates.}, author = {Joerg Megow and Merle I S Röhr and Marcel {Schmidt am Busch} and Thomas Renger and Roland Mitric and Stefan Kirstein and Juergen P Rabe and Volkhard. May}, doi = {10.1039/C4CP05945J}, issn = {1463-9076}, year = {2015}, date = {2015-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {17}, number = {10}, pages = {6741--6747}, publisher = {Royal Society of Chemistry}, abstract = {The simulation of the optical properties of supramol. aggregates requires the development of methods, which are able to treat a large no. of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chem., the Frenkel exciton model is a valuable alternative. The Frenkel exciton model can be extended to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding mols. The exptl. obsd. splitting is well explained by the site-dependent energy shift of mols. placed at the inner or outer side of the double-walled tube, resp. Therefore inclusion of the site-dependent dispersive effect in the theor. description of optical properties of nanoscaled dye aggregates is mandatory. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The simulation of the optical properties of supramol. aggregates requires the development of methods, which are able to treat a large no. of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chem., the Frenkel exciton model is a valuable alternative. The Frenkel exciton model can be extended to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding mols. The exptl. obsd. splitting is well explained by the site-dependent energy shift of mols. placed at the inner or outer side of the double-walled tube, resp. Therefore inclusion of the site-dependent dispersive effect in the theor. description of optical properties of nanoscaled dye aggregates is mandatory. [on SciFinder(R)] |
| 116. | Richter, Robert; Röhr, Merle I S; Zimmermann, Tobias; Petersen, Jens; Heidrich, Christoph; Rahner, Ramon; Moeller, Thomas; Dahl, Jeremy E; Carlson, Robert M K; Mitric, Roland; Rander, Torbjoern; Merli, Andrea. Laser-induced fluorescence of free diamondoid molecules. Journal Article Physical Chemistry Chemical Physics, 17 (6), pp. 4739–4749, 2015, ISSN: 1463-9076. @article{Richter2015a, title = {Laser-induced fluorescence of free diamondoid molecules.}, author = {Robert Richter and Merle I S Röhr and Tobias Zimmermann and Jens Petersen and Christoph Heidrich and Ramon Rahner and Thomas Moeller and Jeremy E Dahl and Robert M K Carlson and Roland Mitric and Torbjoern Rander and Andrea. Merli}, doi = {10.1039/C4CP04423A}, issn = {1463-9076}, year = {2015}, date = {2015-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {17}, number = {6}, pages = {4739--4749}, publisher = {Royal Society of Chemistry}, abstract = {We observe the fluorescence of pristine diamondoids in the gas phase, excited using narrow band UV laser light. The emission spectra show well-defined features, which can be attributed to transitions from the excited electronic state into different vibrational modes of the electronic ground state. We assign the normal modes responsible for the vibrational bands, and det. the geometry of the excited states. Calcns. indicate that for large diamondoids, the spectral bands do not result from progressions of single modes, but rather from combination bands composed of a large no. of $Delta$v = 1 transitions. The vibrational modes detg. the spectral envelope can mainly be assigned to wagging and twisting modes of the surface atoms. We conclude that our theor. approach accurately describes the photophysics in diamondoids and possibly other hydrocarbons in general. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We observe the fluorescence of pristine diamondoids in the gas phase, excited using narrow band UV laser light. The emission spectra show well-defined features, which can be attributed to transitions from the excited electronic state into different vibrational modes of the electronic ground state. We assign the normal modes responsible for the vibrational bands, and det. the geometry of the excited states. Calcns. indicate that for large diamondoids, the spectral bands do not result from progressions of single modes, but rather from combination bands composed of a large no. of $Delta$v = 1 transitions. The vibrational modes detg. the spectral envelope can mainly be assigned to wagging and twisting modes of the surface atoms. We conclude that our theor. approach accurately describes the photophysics in diamondoids and possibly other hydrocarbons in general. [on SciFinder(R)] |
2014 |
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| 115. | Wohlgemuth, Matthias; Miyazaki, Mitsuhiko; Weiler, Martin; Sakai, Makoto; Dopfer, Otto; Fujii, Masaaki; Mitric, Roland. Solvation Dynamics of a Single Water Molecule Probed by Infrared Spectra-Theory Meets Experiment. Journal Article Angewandte Chemie, International Edition, 53 (52), pp. 14601–14604, 2014, ISSN: 1433-7851. @article{Wohlgemuth2014, title = {Solvation Dynamics of a Single Water Molecule Probed by Infrared Spectra-Theory Meets Experiment.}, author = {Matthias Wohlgemuth and Mitsuhiko Miyazaki and Martin Weiler and Makoto Sakai and Otto Dopfer and Masaaki Fujii and Roland. Mitric}, doi = {10.1002/anie.201409047}, issn = {1433-7851}, year = {2014}, date = {2014-01-01}, journal = {Angewandte Chemie, International Edition}, volume = {53}, number = {52}, pages = {14601--14604}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {The dynamics and energetics of water at interfaces or in biol. systems plays a fundamental role in all solvation and biol. phenomena in aq. soln. In particular, the migration of water mols. is the first step that controls the overall process in the time domain. Exptl., the dynamics of individual water mols. is nearly impossible to follow in soln., because signals from mols. in heterogeneous environments overlap. Although mol. dynamics simulations do not have this restriction, there is a lack of exptl. data to validate the calcd. dynamics. Here, we demonstrate a new strategy, in which the calcd. dynamics are verified by measured time-resolved IR spectra. The coexistence of fast and slow migrations of water mols. around a CONH peptide linkage is revealed for a model system representative of a hydrate peptide. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamics and energetics of water at interfaces or in biol. systems plays a fundamental role in all solvation and biol. phenomena in aq. soln. In particular, the migration of water mols. is the first step that controls the overall process in the time domain. Exptl., the dynamics of individual water mols. is nearly impossible to follow in soln., because signals from mols. in heterogeneous environments overlap. Although mol. dynamics simulations do not have this restriction, there is a lack of exptl. data to validate the calcd. dynamics. Here, we demonstrate a new strategy, in which the calcd. dynamics are verified by measured time-resolved IR spectra. The coexistence of fast and slow migrations of water mols. around a CONH peptide linkage is revealed for a model system representative of a hydrate peptide. [on SciFinder(R)] |
| 114. | Humeniuk, Alexander; Mitric, Roland. Excited states from quantum Monte Carlo in the basis of Slater determinants. Journal Article Journal of Chemical Physics, 141 (19), pp. 194104/1–194104/13, 2014, ISSN: 0021-9606. @article{Humeniuk2014, title = {Excited states from quantum Monte Carlo in the basis of Slater determinants.}, author = {Alexander Humeniuk and Roland. Mitric}, doi = {10.1063/1.4901020}, issn = {0021-9606}, year = {2014}, date = {2014-01-01}, journal = {Journal of Chemical Physics}, volume = {141}, number = {19}, pages = {194104/1--194104/13}, publisher = {American Institute of Physics}, abstract = {Building on the full CI quantum Monte Carlo (FCIQMC) algorithm introduced recently by Booth et al. [J. Chem. Phys.131, 054106 (2009)] to compute the ground state of correlated many-electron systems, an extension to the computation of excited states (exFCIQMC) is presented. The Hilbert space is divided into a large part consisting of pure Slater determinants and a much smaller orthogonal part (the size of which is controlled by a cut-off threshold), from which the lowest eigenstates can be removed efficiently. In this way, the quantum Monte Carlo algorithm is restricted to the orthogonal complement of the lower excited states and projects out the next highest excited state. Starting from the ground state, higher excited states can be found one after the other. The Schrodinger equation in imaginary time is solved by the same population dynamics as in the ground state algorithm with modified probabilities and matrix elements, for which working formulas are provided. As a proof of principle, the method is applied to lithium hydride in the 3-21G basis set and to the helium dimer in the aug-cc-pVDZ basis set. It is shown to give the correct electronic structure for all bond lengths. Much more testing will be required before the applicability of this method to electron correlation problems of interesting size can be assessed. (c) 2014 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Building on the full CI quantum Monte Carlo (FCIQMC) algorithm introduced recently by Booth et al. [J. Chem. Phys.131, 054106 (2009)] to compute the ground state of correlated many-electron systems, an extension to the computation of excited states (exFCIQMC) is presented. The Hilbert space is divided into a large part consisting of pure Slater determinants and a much smaller orthogonal part (the size of which is controlled by a cut-off threshold), from which the lowest eigenstates can be removed efficiently. In this way, the quantum Monte Carlo algorithm is restricted to the orthogonal complement of the lower excited states and projects out the next highest excited state. Starting from the ground state, higher excited states can be found one after the other. The Schrodinger equation in imaginary time is solved by the same population dynamics as in the ground state algorithm with modified probabilities and matrix elements, for which working formulas are provided. As a proof of principle, the method is applied to lithium hydride in the 3-21G basis set and to the helium dimer in the aug-cc-pVDZ basis set. It is shown to give the correct electronic structure for all bond lengths. Much more testing will be required before the applicability of this method to electron correlation problems of interesting size can be assessed. (c) 2014 American Institute of Physics. [on SciFinder(R)] |
| 113. | Yamamoto, Yo-ichi; Suzuki, Yoshi-ichi; Tomasello, Gaia; Horio, Takuya; Karashima, Shutaro; Mitric, Roland; Suzuki, Toshinori. Time- and angle-resolved photoemission spectroscopy of hydrated electrons near a liquid water surface. Journal Article Physical Review Letters, 112 (18), pp. 187603/1–187603/5, 5 pp., 2014, ISSN: 0031-9007. @article{Yamamoto2014, title = {Time- and angle-resolved photoemission spectroscopy of hydrated electrons near a liquid water surface.}, author = {Yo-ichi Yamamoto and Yoshi-ichi Suzuki and Gaia Tomasello and Takuya Horio and Shutaro Karashima and Roland Mitric and Toshinori. Suzuki}, doi = {10.1103/PhysRevLett.112.187603}, issn = {0031-9007}, year = {2014}, date = {2014-01-01}, journal = {Physical Review Letters}, volume = {112}, number = {18}, pages = {187603/1--187603/5, 5 pp.}, publisher = {American Physical Society}, abstract = {We present time- and angle-resolved photoemission spectroscopy of trapped electrons near liq. surfaces. Photoemission from the ground state of a hydrated electron at 260 nm is found to be isotropic, while anisotropic photoemission is obsd. for the excited states of 1,4-diazabicyclo[2,2,2]octane and I- in aq. solns. Our results indicate that surface and subsurface species create hydrated electrons in the bulk side. No signature of a surface-bound electron has been obsd. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present time- and angle-resolved photoemission spectroscopy of trapped electrons near liq. surfaces. Photoemission from the ground state of a hydrated electron at 260 nm is found to be isotropic, while anisotropic photoemission is obsd. for the excited states of 1,4-diazabicyclo[2,2,2]octane and I- in aq. solns. Our results indicate that surface and subsurface species create hydrated electrons in the bulk side. No signature of a surface-bound electron has been obsd. [on SciFinder(R)] |
| 112. | Tomasello, Gaia; Humeniuk, Alexander; Mitric, Roland. Exploring Ultrafast Dynamics of Pyrazine by Time-Resolved Photoelectron Imaging. Journal Article Journal of Physical Chemistry A, 118 (37), pp. 8437–8445, 2014, ISSN: 1089-5639. @article{Tomasello2014, title = {Exploring Ultrafast Dynamics of Pyrazine by Time-Resolved Photoelectron Imaging.}, author = {Gaia Tomasello and Alexander Humeniuk and Roland. Mitric}, doi = {10.1021/jp5017328}, issn = {1089-5639}, year = {2014}, date = {2014-01-01}, journal = {Journal of Physical Chemistry A}, volume = {118}, number = {37}, pages = {8437--8445}, publisher = {American Chemical Society}, abstract = {The authors present the simulation of time-resolved photoelectron imaging spectra of pyrazine in the gas phase. The approach the authors have adopted is based on the combination of the ab initio nonadiabatic mol. dynamics on the fly with an approx. treatment of the photoionization process using Dyson orbitals and Coulomb functions to describe the bound and ionized states of the photoelectron. The method was implemented (Humeniuk, A.; et al. J. Chem. Phys., 2013, 139, 134104) in the framework of the time-dependent d. functional theory and was applied here to interrogate the ultrafast internal conversion between the S2 and S1 states in pyrazine. Conventional time-resolved photoelectron spectra without angular resoln. fail to locate the S2 → S1 internal conversion, because the ionization potentials relevant for the photoionization channels S2 → D1 ($pi$-1) and S1 → D0 (n-1) are almost identical. Introducing the angular resoln. in the photoelectron spectra reveals evidence of such ultrafast internal conversion and provides a more detailed picture of the overall dynamics. The simulated time- and energy-dependent anisotropy map obtained within the Dyson/time-dependent d. functional theory approach is in good agreement with its exptl. counterpart provided by Horio et al. (Horio, T.; et al. J. Am. Chem. Soc.2009, 131, 10932). Theor. approach represents a general tool for mapping the time- and angle-resolved photoelectron spectra in complex systems and thus can be used to study the ultrafast relaxation processes occurring in isolated mols. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present the simulation of time-resolved photoelectron imaging spectra of pyrazine in the gas phase. The approach the authors have adopted is based on the combination of the ab initio nonadiabatic mol. dynamics on the fly with an approx. treatment of the photoionization process using Dyson orbitals and Coulomb functions to describe the bound and ionized states of the photoelectron. The method was implemented (Humeniuk, A.; et al. J. Chem. Phys., 2013, 139, 134104) in the framework of the time-dependent d. functional theory and was applied here to interrogate the ultrafast internal conversion between the S2 and S1 states in pyrazine. Conventional time-resolved photoelectron spectra without angular resoln. fail to locate the S2 → S1 internal conversion, because the ionization potentials relevant for the photoionization channels S2 → D1 ($pi$-1) and S1 → D0 (n-1) are almost identical. Introducing the angular resoln. in the photoelectron spectra reveals evidence of such ultrafast internal conversion and provides a more detailed picture of the overall dynamics. The simulated time- and energy-dependent anisotropy map obtained within the Dyson/time-dependent d. functional theory approach is in good agreement with its exptl. counterpart provided by Horio et al. (Horio, T.; et al. J. Am. Chem. Soc.2009, 131, 10932). Theor. approach represents a general tool for mapping the time- and angle-resolved photoelectron spectra in complex systems and thus can be used to study the ultrafast relaxation processes occurring in isolated mols. [on SciFinder(R)] |
| 111. | Holz, M; Wichmann, J; Mitric, R; Woeste, L; Lindinger, A Photo-oxidation by laser pulse induced desorption of phthalocyanines. Journal Article International Journal of Mass Spectrometry, 365-366 , pp. 89–92, 2014, ISSN: 1387-3806. @article{Holz2014, title = {Photo-oxidation by laser pulse induced desorption of phthalocyanines.}, author = {M Holz and J Wichmann and R Mitric and L Woeste and A Lindinger}, doi = {10.1016/j.ijms.2014.03.005}, issn = {1387-3806}, year = {2014}, date = {2014-01-01}, journal = {International Journal of Mass Spectrometry}, volume = {365-366}, pages = {89--92}, publisher = {Elsevier B.V.}, abstract = {Photo-oxidn. of iron(II)-phthalocyanine (PcFe) has been obsd. in matrix assisted laser desorption/ionization (MALDI) and laser desorption/ionization (LDI) and is interpreted by theor. mol. dynamics simulations. The two ionization methods show different amts. of $mu$-oxo-bridged PcFe-dimer and deliver evidence that MALDI produces less mech. stress on the analyte. The typical proton-transfer in the MALDI-process does not occur which leads to the assumption of a released electron of the delocalized $pi$-system. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Photo-oxidn. of iron(II)-phthalocyanine (PcFe) has been obsd. in matrix assisted laser desorption/ionization (MALDI) and laser desorption/ionization (LDI) and is interpreted by theor. mol. dynamics simulations. The two ionization methods show different amts. of $mu$-oxo-bridged PcFe-dimer and deliver evidence that MALDI produces less mech. stress on the analyte. The typical proton-transfer in the MALDI-process does not occur which leads to the assumption of a released electron of the delocalized $pi$-system. [on SciFinder(R)] |
| 110. | Lisinetskaya, Polina G; Mitric, Roland. Ab initio simulations of light propagation in silver cluster nanostructures. Journal Article Physical Review B: Condensed Matter and Materials Physics, 89 (3), pp. 035433/1–035433/13, 2014, ISSN: 1098-0121. @article{Lisinetskaya2014, title = {Ab initio simulations of light propagation in silver cluster nanostructures.}, author = {Polina G Lisinetskaya and Roland. Mitric}, doi = {10.1103/PhysRevB.89.035433}, issn = {1098-0121}, year = {2014}, date = {2014-01-01}, journal = {Physical Review B: Condensed Matter and Materials Physics}, volume = {89}, number = {3}, pages = {035433/1--035433/13}, publisher = {American Physical Society}, abstract = {We present a theor. approach for the simulation of the optical response and light propagation in aggregates and in ordered arrays of small noble-metal clusters with discrete electronic structure. We construct the Hamiltonian for the aggregate system based on the time-dependent d. functional theory electronic states of the individual subunits and describe the interaction between them using the dipole approxn. The time evolution of the aggregate under the influence of the external elec. field is obtained from the numerical soln. of the time-dependent Schroedinger equation with the coupled excitonic Hamiltonian. For each subunit, the time-dependent dipole moment is calcd. using the reduced d. matrix formalism. Such quantum-mech. detd. dipole moments are used to simulate the spatiotemporal distribution of the elec. field produced by the array. Addnl., we introduce an approx. self-consistent iterative approach to treat arrays consisting of many subunits which are of interest in the context of nanoplasmonics, nano-optical applications, and development of light-harvesting materials. The developed methodol. is illustrated 1st on the example of Ag2 and Ag8 cluster pairs. Subsequently, light propagation in a triangular-shaped array consisting of six Ag8 clusters is simulated. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a theor. approach for the simulation of the optical response and light propagation in aggregates and in ordered arrays of small noble-metal clusters with discrete electronic structure. We construct the Hamiltonian for the aggregate system based on the time-dependent d. functional theory electronic states of the individual subunits and describe the interaction between them using the dipole approxn. The time evolution of the aggregate under the influence of the external elec. field is obtained from the numerical soln. of the time-dependent Schroedinger equation with the coupled excitonic Hamiltonian. For each subunit, the time-dependent dipole moment is calcd. using the reduced d. matrix formalism. Such quantum-mech. detd. dipole moments are used to simulate the spatiotemporal distribution of the elec. field produced by the array. Addnl., we introduce an approx. self-consistent iterative approach to treat arrays consisting of many subunits which are of interest in the context of nanoplasmonics, nano-optical applications, and development of light-harvesting materials. The developed methodol. is illustrated 1st on the example of Ag2 and Ag8 cluster pairs. Subsequently, light propagation in a triangular-shaped array consisting of six Ag8 clusters is simulated. [on SciFinder(R)] |
| 109. | Giegerich, Jens; Petersen, Jens; Mitric, Roland; Fischer, Ingo. Photodissociation dynamics of propargylene, HCCCH. Journal Article Physical Chemistry Chemical Physics, 16 (13), pp. 6294–6302, 2014, ISSN: 1463-9076. @article{Giegerich2014, title = {Photodissociation dynamics of propargylene, HCCCH.}, author = {Jens Giegerich and Jens Petersen and Roland Mitric and Ingo. Fischer}, doi = {10.1039/c3cp53213e}, issn = {1463-9076}, year = {2014}, date = {2014-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {16}, number = {13}, pages = {6294--6302}, publisher = {Royal Society of Chemistry}, abstract = {We report a joint theor. and exptl. study on the photodissocn. of the C3H2 isomer propargylene, HCCCH, combining velocity map imaging with nonadiabatic trajectory surface hopping calcns. Propargylene loses an H-atom, after laser excitation at around 250 nm, presumably to the T6 state. The photofragment angular distribution exhibits only a very small anisotropy, but the H-atom translational energy distribution extends to high energies and shows an expectation value of 〈fT〉, the fraction of excess energy released as translation, of 48%, outside the range expected for a statistical reaction mechanism. The computations suggest a predissocn. in the T4-T6 state and lead to a translational energy distribution and photofragment angular distribution that match the exptl. obsd. ones very well. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report a joint theor. and exptl. study on the photodissocn. of the C3H2 isomer propargylene, HCCCH, combining velocity map imaging with nonadiabatic trajectory surface hopping calcns. Propargylene loses an H-atom, after laser excitation at around 250 nm, presumably to the T6 state. The photofragment angular distribution exhibits only a very small anisotropy, but the H-atom translational energy distribution extends to high energies and shows an expectation value of 〈fT〉, the fraction of excess energy released as translation, of 48%, outside the range expected for a statistical reaction mechanism. The computations suggest a predissocn. in the T4-T6 state and lead to a translational energy distribution and photofragment angular distribution that match the exptl. obsd. ones very well. [on SciFinder(R)] |
| 108. | Richter, Robert; Wolter, David; Zimmermann, Tobias; Landt, Lasse; Knecht, Andre; Heidrich, Christoph; Merli, Andrea; Dopfer, Otto; Reiss, Philipp; Ehresmann, Arno; Petersen, Jens; Dahl, Jeremy E; Carlson, Robert M K; Bostedt, Christoph; Moeller, Thomas; Mitric, Roland; Rander, Torbjoern. Size and shape dependent photoluminescence and excited state decay rates of diamondoids. Journal Article Physical Chemistry Chemical Physics, 16 (7), pp. 3070–3076, 2014, ISSN: 1463-9076. @article{Richter2014, title = {Size and shape dependent photoluminescence and excited state decay rates of diamondoids.}, author = {Robert Richter and David Wolter and Tobias Zimmermann and Lasse Landt and Andre Knecht and Christoph Heidrich and Andrea Merli and Otto Dopfer and Philipp Reiss and Arno Ehresmann and Jens Petersen and Jeremy E Dahl and Robert M K Carlson and Christoph Bostedt and Thomas Moeller and Roland Mitric and Torbjoern. Rander}, doi = {10.1039/C3CP54570A}, issn = {1463-9076}, year = {2014}, date = {2014-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {16}, number = {7}, pages = {3070--3076}, publisher = {Royal Society of Chemistry}, abstract = {We present photoluminescence spectra and excited state decay rates of a series of diamondoids, which represent mol. structural analogs to H-passivated bulk diamond. Specific isomers of the 5 smallest diamondoids (adamantane-pentamantane) were brought into the gas phase and irradiated with synchrotron radiation. All investigated compds. show intrinsic photoluminescence in the UV spectral region. The emission spectra exhibit pronounced vibrational fine structure which is analyzed using quantum chem. calcns. We show that the geometrical relaxation of the 1st excited state of adamantane, exhibiting Rydberg character, leads to the loss of Td symmetry. The luminescence of adamantane is attributed to a transition from the delocalized 1st excited state into different vibrational modes of the electronic ground state. Similar geometrical changes of the excited state structure were also identified in the other investigated diamondoids. The excited state decay rates show a clear dependence on the size of the diamondoid, but are independent of the particle geometry, further indicating a loss of particle symmetry upon electronic excitation. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present photoluminescence spectra and excited state decay rates of a series of diamondoids, which represent mol. structural analogs to H-passivated bulk diamond. Specific isomers of the 5 smallest diamondoids (adamantane-pentamantane) were brought into the gas phase and irradiated with synchrotron radiation. All investigated compds. show intrinsic photoluminescence in the UV spectral region. The emission spectra exhibit pronounced vibrational fine structure which is analyzed using quantum chem. calcns. We show that the geometrical relaxation of the 1st excited state of adamantane, exhibiting Rydberg character, leads to the loss of Td symmetry. The luminescence of adamantane is attributed to a transition from the delocalized 1st excited state into different vibrational modes of the electronic ground state. Similar geometrical changes of the excited state structure were also identified in the other investigated diamondoids. The excited state decay rates show a clear dependence on the size of the diamondoid, but are independent of the particle geometry, further indicating a loss of particle symmetry upon electronic excitation. [on SciFinder(R)] |
| 107. | Sanader, Zeljka; Mitric, Roland; Bonacic-Koutecky, Vlasta; Bellina, Bruno; Antoine, Rodolphe; Dugourd, Philippe. The nature of electronic excitations at the metal-bioorganic interface illustrated on histidine-silver hybrids. Journal Article Physical Chemistry Chemical Physics, 16 (3), pp. 1257–1261, 2014, ISSN: 1463-9076. @article{Sanader2014, title = {The nature of electronic excitations at the metal-bioorganic interface illustrated on histidine-silver hybrids.}, author = {Zeljka Sanader and Roland Mitric and Vlasta Bonacic-Koutecky and Bruno Bellina and Rodolphe Antoine and Philippe. Dugourd}, doi = {10.1039/C3CP52712C}, issn = {1463-9076}, year = {2014}, date = {2014-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {16}, number = {3}, pages = {1257--1261}, publisher = {Royal Society of Chemistry}, abstract = {The authors present a joint theor. and exptl. study of the structure selective optical properties of cationic and anionic histidine-silver complexes with Ag and Ag3 which were prepd. in the gas phase using mass spectroscopy coupled to electrospray ion source. The authors' TDDFT calcns. provide general insight into the nature of electronic excitations at the metal-bioorg. interface that involve $pi$-$pi$* excitation within bioorg. subunits, charge transfer between two subunits and intrametallic excitations. The binding of silver to histidine, one of the most important amino acids, induces red shift in the optical absorption of protonated histidine particularly for anionic species. The presence of the smallest metallic subunit Ag3 increases the intensity of low energy transitions of histidine illustrating a metal cluster-induced enhancement of absorption of biomols. in hybrid systems. Comparison of calcd. absorption spectra with exptl. photofragmentation yield provides structural assignment of the measured spectroscopic patterns. The authors' findings may serve to establish silver-labeling as the tool for the detection of histidine or histidine-tagged proteins. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a joint theor. and exptl. study of the structure selective optical properties of cationic and anionic histidine-silver complexes with Ag and Ag3 which were prepd. in the gas phase using mass spectroscopy coupled to electrospray ion source. The authors' TDDFT calcns. provide general insight into the nature of electronic excitations at the metal-bioorg. interface that involve $pi$-$pi$* excitation within bioorg. subunits, charge transfer between two subunits and intrametallic excitations. The binding of silver to histidine, one of the most important amino acids, induces red shift in the optical absorption of protonated histidine particularly for anionic species. The presence of the smallest metallic subunit Ag3 increases the intensity of low energy transitions of histidine illustrating a metal cluster-induced enhancement of absorption of biomols. in hybrid systems. Comparison of calcd. absorption spectra with exptl. photofragmentation yield provides structural assignment of the measured spectroscopic patterns. The authors' findings may serve to establish silver-labeling as the tool for the detection of histidine or histidine-tagged proteins. [on SciFinder(R)] |
2013 |
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| 106. | Humeniuk, Alexander; Wohlgemuth, Matthias; Suzuki, Toshinori; Mitric, Roland. Time-resolved photoelectron imaging spectra from non-adiabatic molecular dynamics simulations. Journal Article Journal of Chemical Physics, 139 (13), pp. 134104/1–134104/9, 2013, ISSN: 0021-9606. @article{Humeniuk2013, title = {Time-resolved photoelectron imaging spectra from non-adiabatic molecular dynamics simulations.}, author = {Alexander Humeniuk and Matthias Wohlgemuth and Toshinori Suzuki and Roland. Mitric}, doi = {10.1063/1.4820238}, issn = {0021-9606}, year = {2013}, date = {2013-01-01}, journal = {Journal of Chemical Physics}, volume = {139}, number = {13}, pages = {134104/1--134104/9}, publisher = {American Institute of Physics}, abstract = {We present an efficient method for the simulation of time-resolved photoelectron imaging (TRPEI) spectra in polyat. mols. Our approach combines trajectory-based mol. dynamics that account for non-adiabatic effects using surface hopping, with an approx. treatment of the photoionization process using Dyson orbitals as initial and Coulomb waves as final electron states. The method has been implemented in the frame of linear response time-dependent d. functional theory. As an illustration, we simulate time- and energy-resolved anisotropy maps for the furan mol. and compare them with recent exptl. data . Our method can be generally used for the interpretation of TRPEI expts. allowing to shed light into the fundamental photochem. processes in complex mols. (c) 2013 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present an efficient method for the simulation of time-resolved photoelectron imaging (TRPEI) spectra in polyat. mols. Our approach combines trajectory-based mol. dynamics that account for non-adiabatic effects using surface hopping, with an approx. treatment of the photoionization process using Dyson orbitals as initial and Coulomb waves as final electron states. The method has been implemented in the frame of linear response time-dependent d. functional theory. As an illustration, we simulate time- and energy-resolved anisotropy maps for the furan mol. and compare them with recent exptl. data . Our method can be generally used for the interpretation of TRPEI expts. allowing to shed light into the fundamental photochem. processes in complex mols. (c) 2013 American Institute of Physics. [on SciFinder(R)] |
| 105. | Gell, Lars; Kulesza, Alexander; Petersen, Jens; Röhr, Merle I S; Mitric, Roland; Bonacic-Koutecky, Vlasta. Tuning Structural and Optical Properties of Thiolate-Protected Silver Clusters by Formation of a Silver Core with Confined Electrons. Journal Article Journal of Physical Chemistry C, 117 (28), pp. 14824–14831, 2013, ISSN: 1932-7447. @article{Gell2013, title = {Tuning Structural and Optical Properties of Thiolate-Protected Silver Clusters by Formation of a Silver Core with Confined Electrons.}, author = {Lars Gell and Alexander Kulesza and Jens Petersen and Merle I S Röhr and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp402931w}, issn = {1932-7447}, year = {2013}, date = {2013-01-01}, journal = {Journal of Physical Chemistry C}, volume = {117}, number = {28}, pages = {14824--14831}, publisher = {American Chemical Society}, abstract = {The authors present a systematic theor. study of the structural and optical properties of thiolate-protected Ag clusters with the goal to design species exhibiting strong absorption and fluorescence in the UV-visible spectral range. The optical properties can be tuned by creating systems with different counts of confined electrons within the cluster core. Liganded Ag complexes with n Ag atoms (Agn) and x ligands (Lx) in anionic complexes [AgnLx]- with L = SMe are considered. Variation of the compn. ratio gives rise to systems with (i) zero confined electrons for x = n + 1, (ii) 2 confined electrons for x = n - 1, and (iii) 4 confined electrons for x = n - 3. The no. of confined electrons within the cluster core and the geometric structure of the latter are responsible for the spectral patterns, giving rise to intense absorption transitions and fluorescence in the visible or even IR range. The results open a perspective for the rational design of stable ligand-protected Ag cluster chromophores that might find numerous applications in the field of biosensing. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a systematic theor. study of the structural and optical properties of thiolate-protected Ag clusters with the goal to design species exhibiting strong absorption and fluorescence in the UV-visible spectral range. The optical properties can be tuned by creating systems with different counts of confined electrons within the cluster core. Liganded Ag complexes with n Ag atoms (Agn) and x ligands (Lx) in anionic complexes [AgnLx]- with L = SMe are considered. Variation of the compn. ratio gives rise to systems with (i) zero confined electrons for x = n + 1, (ii) 2 confined electrons for x = n - 1, and (iii) 4 confined electrons for x = n - 3. The no. of confined electrons within the cluster core and the geometric structure of the latter are responsible for the spectral patterns, giving rise to intense absorption transitions and fluorescence in the visible or even IR range. The results open a perspective for the rational design of stable ligand-protected Ag cluster chromophores that might find numerous applications in the field of biosensing. [on SciFinder(R)] |
| 104. | Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Gell, Lars; Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Synthesis, characterization and optical properties of low nuclearity liganded silver clusters. Ag31(SG)19 and Ag15(SG)11. Journal Article Nanoscale, 5 (12), pp. 5637–5643, 2013, ISSN: 2040-3372. @article{Bertorelle2013, title = {Synthesis, characterization and optical properties of low nuclearity liganded silver clusters. Ag31(SG)19 and Ag15(SG)11.}, author = {Franck Bertorelle and Ramzi Hamouda and Driss Rayane and Michel Broyer and Rodolphe Antoine and Philippe Dugourd and Lars Gell and Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1039/c3nr00677h}, issn = {2040-3372}, year = {2013}, date = {2013-01-01}, journal = {Nanoscale}, volume = {5}, number = {12}, pages = {5637--5643}, publisher = {Royal Society of Chemistry}, abstract = {A simple synthesis of silver:glutathione (Ag:SG) clusters using a cyclic redn. under oxidative conditions is reported. Two syntheses are described which lead to solns. contg. well-defined Ag31(SG)19 and Ag15(SG)11 clusters that have been characterized by mass spectrometry. The optical properties of Ag:SG cluster solns. were investigated exptl. In particular, the soln. contg. Ag15(SG)11 clusters shows a bright and photostable emission. For Ag31(SG)19 and Ag15(SG)11 clusters, the comparison of exptl. findings with DFT and TDDFT calcns. allowed us to reveal the structural and electronic properties of such low nuclearity liganded Ag clusters. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A simple synthesis of silver:glutathione (Ag:SG) clusters using a cyclic redn. under oxidative conditions is reported. Two syntheses are described which lead to solns. contg. well-defined Ag31(SG)19 and Ag15(SG)11 clusters that have been characterized by mass spectrometry. The optical properties of Ag:SG cluster solns. were investigated exptl. In particular, the soln. contg. Ag15(SG)11 clusters shows a bright and photostable emission. For Ag31(SG)19 and Ag15(SG)11 clusters, the comparison of exptl. findings with DFT and TDDFT calcns. allowed us to reveal the structural and electronic properties of such low nuclearity liganded Ag clusters. [on SciFinder(R)] |
| 103. | Bellina, Bruno; Antoine, Rodolphe; Broyer, Michel; Gell, Lars; Sanader, Zeljka; Mitric, Roland; Bonacic-Koutecky, Vlasta; Dugourd, Philippe. Formation and characterization of thioglycolic acid-silver cluster complexes. Journal Article Dalton Transactions, 42 (23), pp. 8328–8333, 2013, ISSN: 1477-9226. @article{Bellina2013, title = {Formation and characterization of thioglycolic acid-silver cluster complexes.}, author = {Bruno Bellina and Rodolphe Antoine and Michel Broyer and Lars Gell and Zeljka Sanader and Roland Mitric and Vlasta Bonacic-Koutecky and Philippe. Dugourd}, doi = {10.1039/c3dt50485a}, issn = {1477-9226}, year = {2013}, date = {2013-01-01}, journal = {Dalton Transactions}, volume = {42}, number = {23}, pages = {8328--8333}, publisher = {Royal Society of Chemistry}, abstract = {Gas phase reactivity obsd. in an ion trap was used to produce silver clusters protected with thioglycolic acid. Fragmentation pathways as well as optical properties were explored exptl. and theor. Sequential losses of SCH2 and CO2 in the ion trap lead to redox reactions with charge transfers between the metal part and the carboxylate and thiolate groups. This allows the authors to control the no. of electrons in the metallic subunit and thus optical properties of the complexes. The presented formation process can be used as a prototype for tuning optical and chem. properties of ligated metal clusters by varying the no. of confined electrons within the metallic subunit. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Gas phase reactivity obsd. in an ion trap was used to produce silver clusters protected with thioglycolic acid. Fragmentation pathways as well as optical properties were explored exptl. and theor. Sequential losses of SCH2 and CO2 in the ion trap lead to redox reactions with charge transfers between the metal part and the carboxylate and thiolate groups. This allows the authors to control the no. of electrons in the metallic subunit and thus optical properties of the complexes. The presented formation process can be used as a prototype for tuning optical and chem. properties of ligated metal clusters by varying the no. of confined electrons within the metallic subunit. [on SciFinder(R)] |
| 102. | Sanader, Zeljka; Brunet, Claire; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Mitric, Roland; Bonacic-Koutecky, Vlasta. Cation induced electrochromism in 2,4-dinitrophenylhydrazine (DNPH): Tuning optical properties of aromatic rings. Journal Article Chemical Physics Letters, 570 , pp. 22–25, 2013, ISSN: 0009-2614. @article{Sanader2013, title = {Cation induced electrochromism in 2,4-dinitrophenylhydrazine (DNPH): Tuning optical properties of aromatic rings.}, author = {Zeljka Sanader and Claire Brunet and Michel Broyer and Rodolphe Antoine and Philippe Dugourd and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1016/j.cplett.2013.03.049}, issn = {0009-2614}, year = {2013}, date = {2013-01-01}, journal = {Chemical Physics Letters}, volume = {570}, pages = {22--25}, publisher = {Elsevier B.V.}, abstract = {We have theor. investigated the influence of protons and noble metal cations on optical properties of 2,4-dinitrophenylhydrazine (DNPH). We show that optical properties of arom. rings can be tuned by cation-induced electrochromism in DNPH due to binding to specific NO2 groups. Our findings on cation-induced electrochromism in DNPH may open new routes in two different application areas, due to the fact that DNPH can easily bind to biol. mols. and surface materials through carbonyl groups. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have theor. investigated the influence of protons and noble metal cations on optical properties of 2,4-dinitrophenylhydrazine (DNPH). We show that optical properties of arom. rings can be tuned by cation-induced electrochromism in DNPH due to binding to specific NO2 groups. Our findings on cation-induced electrochromism in DNPH may open new routes in two different application areas, due to the fact that DNPH can easily bind to biol. mols. and surface materials through carbonyl groups. [on SciFinder(R)] |
| 101. | Röhr, Merle I S; Petersen, Jens; Wohlgemuth, Matthias; Bonacic-Koutecky, Vlasta; Mitric, Roland. Nonlinear Absorption Dynamics Using Field-Induced Surface Hopping: Zinc Porphyrin in Water. Journal Article ChemPhysChem, 14 (7), pp. 1377–1386, 2013, ISSN: 1439-4235. @article{Röhr2013, title = {Nonlinear Absorption Dynamics Using Field-Induced Surface Hopping: Zinc Porphyrin in Water.}, author = {Merle I S Röhr and Jens Petersen and Matthias Wohlgemuth and Vlasta Bonacic-Koutecky and Roland. Mitric}, doi = {10.1002/cphc.201300053}, issn = {1439-4235}, year = {2013}, date = {2013-01-01}, journal = {ChemPhysChem}, volume = {14}, number = {7}, pages = {1377--1386}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {The authors present the application of their field-induced surface-hopping (FISH) method to simulate nonlinear absorption dynamics induced by strong nonresonant laser fields. The authors provide a systematic comparison of the FISH approach with exact quantum dynamics simulations on a multi-state model system and demonstrate that FISH allows for accurate simulations of nonlinear excitation processes including multiphoton electronic transitions. In particular, two different approaches for simulating two-photon transitions are compared. The first approach is essentially exact and involves the soln. of the time-dependent Schrodinger equation in an extended manifold of excited states, while in the second one only transiently populated nonessential states are replaced by an effective quadratic coupling term, and dynamics is performed in a considerably smaller manifold of states. The authors illustrate the applicability of this method to complex mol. systems by simulating the linear and nonlinear laser-driven dynamics in zinc porphyrin in the gas phase and in water. For this purpose, the FISH approach is connected with the quantum mech.-mol. mech. approach (QM/MM) which is generally applicable to large classes of complex systems. The finding that multiphoton absorption and dynamics increase the population of higher excited states of Zn porphyrin in the nonlinear regime, in particular in soln., provides a means for manipulating excited-state properties, such as transient absorption dynamics and electronic relaxation. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present the application of their field-induced surface-hopping (FISH) method to simulate nonlinear absorption dynamics induced by strong nonresonant laser fields. The authors provide a systematic comparison of the FISH approach with exact quantum dynamics simulations on a multi-state model system and demonstrate that FISH allows for accurate simulations of nonlinear excitation processes including multiphoton electronic transitions. In particular, two different approaches for simulating two-photon transitions are compared. The first approach is essentially exact and involves the soln. of the time-dependent Schrodinger equation in an extended manifold of excited states, while in the second one only transiently populated nonessential states are replaced by an effective quadratic coupling term, and dynamics is performed in a considerably smaller manifold of states. The authors illustrate the applicability of this method to complex mol. systems by simulating the linear and nonlinear laser-driven dynamics in zinc porphyrin in the gas phase and in water. For this purpose, the FISH approach is connected with the quantum mech.-mol. mech. approach (QM/MM) which is generally applicable to large classes of complex systems. The finding that multiphoton absorption and dynamics increase the population of higher excited states of Zn porphyrin in the nonlinear regime, in particular in soln., provides a means for manipulating excited-state properties, such as transient absorption dynamics and electronic relaxation. [on SciFinder(R)] |
| 100. | Mitric, Roland. Theoretical chemistry 2012. Light-induced quantum dynamics in complex systems. Journal Article Nachrichten aus der Chemie, 61 (3), pp. 325–329, 2013, ISSN: 1439-9598. @article{Mitric2013, title = {Theoretical chemistry 2012. Light-induced quantum dynamics in complex systems.}, author = {Roland. Mitric}, issn = {1439-9598}, year = {2013}, date = {2013-01-01}, journal = {Nachrichten aus der Chemie}, volume = {61}, number = {3}, pages = {325--329}, publisher = {Walter de Gruyter GmbH & Co. KG}, abstract = {A review. The development of exptl. techniques and simulation methods in femto-chem. and atto-second physics will make it possible to describe coupled motions of electrons and nuclei in mols. Furthermore, there are continuous research efforts to question how photochem. reactions and other dynamic processes are coherently controlled with molded light pulses. It is expected that the development of high-performance ultrafast techniques as spectroscopy of higher harmonics will allow direct investigation of the correlated electron dynamics, leading to further challenges to theory and new quantum dynamical methods. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A review. The development of exptl. techniques and simulation methods in femto-chem. and atto-second physics will make it possible to describe coupled motions of electrons and nuclei in mols. Furthermore, there are continuous research efforts to question how photochem. reactions and other dynamic processes are coherently controlled with molded light pulses. It is expected that the development of high-performance ultrafast techniques as spectroscopy of higher harmonics will allow direct investigation of the correlated electron dynamics, leading to further challenges to theory and new quantum dynamical methods. [on SciFinder(R)] |
2012 |
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| 99. | Bellina, Bruno; Compagnon, Isabelle; MacAleese, Luke; Chirot, Fabien; Lemoine, Jerome; Maitre, Philippe; Broyer, Michel; Antoine, Rodolphe; Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta; Dugourd, Philippe. Binding motifs of silver in prion octarepeat model peptides: a joint ion mobility, IR and UV spectroscopies, and theoretical approach. Journal Article Physical Chemistry Chemical Physics, 14 (32), pp. 11433–11440, 2012, ISSN: 1463-9076. @article{Bellina2012, title = {Binding motifs of silver in prion octarepeat model peptides: a joint ion mobility, IR and UV spectroscopies, and theoretical approach.}, author = {Bruno Bellina and Isabelle Compagnon and Luke MacAleese and Fabien Chirot and Jerome Lemoine and Philippe Maitre and Michel Broyer and Rodolphe Antoine and Alexander Kulesza and Roland Mitric and Vlasta Bonacic-Koutecky and Philippe. Dugourd}, doi = {10.1039/c2cp40924k}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {32}, pages = {11433--11440}, publisher = {Royal Society of Chemistry}, abstract = {Transition metal-ion complexation is essential to the function and structural stability of many proteins. We studied silver complexation with the octarepeat motif ProHisGlyGlyGlyTrpGlyGln of the prion protein, which shows competitive sites for metal chelation including amide, indole and imidazole groups. This octapeptide is known as a favorable transition metal binding site in prion protein. We used ion mobility spectrometry (IMS), IR multiple photon dissocn. (IRMPD) spectroscopy and d. functional theory calcns. (DFT) to identify the binding motifs of a silver cation on HisGlyGlyGlyTrp peptide as well as on peptide subsequences. Ultra-violet photodissocn. (UVPD) and collision induced dissocn. mass spectrometry together with the time-dependent d. functional method was then exploited to study the influence of binding sites on optical properties and on the ground and excited states reactivity of the peptide. We show that the metal cation is bound to the $pi$-system of the indole group and a nitrogen atom of the imidazole group and that charge transfers from the indole group to the silver cation occur in excited electronic states. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Transition metal-ion complexation is essential to the function and structural stability of many proteins. We studied silver complexation with the octarepeat motif ProHisGlyGlyGlyTrpGlyGln of the prion protein, which shows competitive sites for metal chelation including amide, indole and imidazole groups. This octapeptide is known as a favorable transition metal binding site in prion protein. We used ion mobility spectrometry (IMS), IR multiple photon dissocn. (IRMPD) spectroscopy and d. functional theory calcns. (DFT) to identify the binding motifs of a silver cation on HisGlyGlyGlyTrp peptide as well as on peptide subsequences. Ultra-violet photodissocn. (UVPD) and collision induced dissocn. mass spectrometry together with the time-dependent d. functional method was then exploited to study the influence of binding sites on optical properties and on the ground and excited states reactivity of the peptide. We show that the metal cation is bound to the $pi$-system of the indole group and a nitrogen atom of the imidazole group and that charge transfers from the indole group to the silver cation occur in excited electronic states. [on SciFinder(R)] |
| 98. | Vogel, M; Kasigkeit, C; Hirsch, K; Langenberg, A; Rittmann, J; Zamudio-Bayer, V; Kulesza, A; Mitric, R; Moeller, T; von Issendorff, B; Lau, J T 2p core-level binding energies of size-selected free silicon clusters: chemical shifts and cluster structure. Journal Article Physical Review B: Condensed Matter and Materials Physics, 85 (19), pp. 195454/1–195454/5, 2012, ISSN: 1098-0121. @article{Vogel2012, title = {2p core-level binding energies of size-selected free silicon clusters: chemical shifts and cluster structure.}, author = {M Vogel and C Kasigkeit and K Hirsch and A Langenberg and J Rittmann and V Zamudio-Bayer and A Kulesza and R Mitric and T Moeller and B von Issendorff and J T Lau}, doi = {10.1103/PhysRevB.85.195454}, issn = {1098-0121}, year = {2012}, date = {2012-01-01}, journal = {Physical Review B: Condensed Matter and Materials Physics}, volume = {85}, number = {19}, pages = {195454/1--195454/5}, publisher = {American Physical Society}, abstract = {The 2p core-level electron binding energies of size-selected silicon cluster ions have been detd. from soft x-ray photoionization efficiency curves. Local chem. shifts and global charging energy contributions to the 2p binding energy can be sepd., because core-level and valence-band electron binding energies exhibit the same inverse radius dependence. The exptl. 2p binding energy distributions show characteristic size-specific patterns that are well reproduced by the corresponding electronic d. of states obtained from d. functional theory modeling. These results demonstrate that 2p binding energies in silicon clusters are dominated by initial state effects, i.e., by the interaction with the local valence electron d., and can thus be used to corroborate structural assignments. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The 2p core-level electron binding energies of size-selected silicon cluster ions have been detd. from soft x-ray photoionization efficiency curves. Local chem. shifts and global charging energy contributions to the 2p binding energy can be sepd., because core-level and valence-band electron binding energies exhibit the same inverse radius dependence. The exptl. 2p binding energy distributions show characteristic size-specific patterns that are well reproduced by the corresponding electronic d. of states obtained from d. functional theory modeling. These results demonstrate that 2p binding energies in silicon clusters are dominated by initial state effects, i.e., by the interaction with the local valence electron d., and can thus be used to corroborate structural assignments. [on SciFinder(R)] |
| 97. | Goetze, Jan P; Greco, Claudio; Mitric, Roland; Bonacic-Koutecky, Vlasta; Saalfrank, Peter. BLUF Hydrogen network dynamics and UV/Vis spectra: A combined molecular dynamics and quantum chemical study. Journal Article Journal of Computational Chemistry, 33 (28), pp. 2233–2242, 2012, ISSN: 0192-8651. @article{Goetze2012, title = {BLUF Hydrogen network dynamics and UV/Vis spectra: A combined molecular dynamics and quantum chemical study.}, author = {Jan P Goetze and Claudio Greco and Roland Mitric and Vlasta Bonacic-Koutecky and Peter. Saalfrank}, doi = {10.1002/jcc.23056}, issn = {0192-8651}, year = {2012}, date = {2012-01-01}, journal = {Journal of Computational Chemistry}, volume = {33}, number = {28}, pages = {2233--2242}, publisher = {John Wiley & Sons, Inc.}, abstract = {Blue light sensing using flavin (BLUF) protein photoreceptor domains change their hydrogen bond network after photoexcitation. To explore this phenomenon, BLUF domains from R. sphaeroides were simulated using Amber99 mol. dynamics (MD). Five starting configurations were considered, to study different BLUF proteins (AppA/BlrB), Trp conformations ("Win"/"Wout"), structure detn. (X-ray/NMR), and finally, His protonation states. We found dependencies of the hydrogen bonds on almost all parameters. Our data show an esp. strong correlation of the Trp position and hydrogen bonds involving Gln63. The latter is in some contradiction to earlier results (Obanayama et al., Photochem. Photobiol. 2008, 84 10031010). Possible origins and implications are discussed. Our calcns. support conjectures that Gln63 is more flexible with Trp104 in Win position. Using snapshots from MD and time-dependent d. functional theory, UV/vis spectra for the chromophore were detd., which account for mol. motion of the protein under ambient conditions. In accord with expt., it is found that the UV/vis spectra of BLUF bound flavin are red-shifted and thermally broadened for all calcd. $pi$ → $pi$* transitions, relative to gas phase flavin at T = 0 K. However, differences in the spectra between the various BLUF configurations cannot be resolved with the present approach. textcopyright 2012 Wiley Periodicals, Inc. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Blue light sensing using flavin (BLUF) protein photoreceptor domains change their hydrogen bond network after photoexcitation. To explore this phenomenon, BLUF domains from R. sphaeroides were simulated using Amber99 mol. dynamics (MD). Five starting configurations were considered, to study different BLUF proteins (AppA/BlrB), Trp conformations ("Win"/"Wout"), structure detn. (X-ray/NMR), and finally, His protonation states. We found dependencies of the hydrogen bonds on almost all parameters. Our data show an esp. strong correlation of the Trp position and hydrogen bonds involving Gln63. The latter is in some contradiction to earlier results (Obanayama et al., Photochem. Photobiol. 2008, 84 10031010). Possible origins and implications are discussed. Our calcns. support conjectures that Gln63 is more flexible with Trp104 in Win position. Using snapshots from MD and time-dependent d. functional theory, UV/vis spectra for the chromophore were detd., which account for mol. motion of the protein under ambient conditions. In accord with expt., it is found that the UV/vis spectra of BLUF bound flavin are red-shifted and thermally broadened for all calcd. $pi$ → $pi$* transitions, relative to gas phase flavin at T = 0 K. However, differences in the spectra between the various BLUF configurations cannot be resolved with the present approach. textcopyright 2012 Wiley Periodicals, Inc. [on SciFinder(R)] |
| 96. | Tomasello, Gaia; Wohlgemuth, Matthias; Petersen, Jens; Mitric, Roland. Photodynamics of Free and Solvated Tyrosine. Journal Article Journal of Physical Chemistry B, 116 (30), pp. 8762–8770, 2012, ISSN: 1520-5207. @article{Tomasello2012, title = {Photodynamics of Free and Solvated Tyrosine.}, author = {Gaia Tomasello and Matthias Wohlgemuth and Jens Petersen and Roland. Mitric}, doi = {10.1021/jp302179m}, issn = {1520-5207}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry B}, volume = {116}, number = {30}, pages = {8762--8770}, publisher = {American Chemical Society}, abstract = {We present a theor. simulation, physicochem. of the ultrafast nonadiabatic photodynamics of tyrosine in the gas phase and in water. For this purpose, we combine our TDDFT/MM nonadiabatic dynamics (Wohlgemuth et al. J. Chem. Phys. 2011, 135, 054105) with the field-induced surface hopping method (Mitric, et al. Phys. Rev. A 2009, 79, 053416) allowing us to explicitly include the nonadiabatic effects as well as femtosecond laser radiation excitation into the simulation, physicochem. Our results reveal an ultrafast deactivation of the initially excited bright $pi$$pi$* state by internal conversion to a dark n$pi$* state. We observe deactivation channels along the O-H stretching coordinate as well as involving the N-H bond cleavage of the amino group followed by proton transfer to the phenol ring, which is in agreement with previous static energy path calcns. However, since in the gas phase the canonical form of tyrosine is the most stable one, the proton transfer proceeds in two steps, starting from the carboxyl group that first passes its proton to the amino group, from where it finally moves to the phenol ring. Furthermore, we also investigate the influence of water on the relaxation processes. For the system of tyrosine with three explicit water mols. solvating the amino group, embedded in a classical water sphere, we also observe a relaxation channel involving proton transfer to the phenol ring. However, in aq. environment, a water mol. near the protonated amino group of tyrosine acts as a mediator for the proton transfer, underlining the importance of the solvent in nonradiative relaxation processes of amino acids. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a theor. simulation, physicochem. of the ultrafast nonadiabatic photodynamics of tyrosine in the gas phase and in water. For this purpose, we combine our TDDFT/MM nonadiabatic dynamics (Wohlgemuth et al. J. Chem. Phys. 2011, 135, 054105) with the field-induced surface hopping method (Mitric, et al. Phys. Rev. A 2009, 79, 053416) allowing us to explicitly include the nonadiabatic effects as well as femtosecond laser radiation excitation into the simulation, physicochem. Our results reveal an ultrafast deactivation of the initially excited bright $pi$$pi$* state by internal conversion to a dark n$pi$* state. We observe deactivation channels along the O-H stretching coordinate as well as involving the N-H bond cleavage of the amino group followed by proton transfer to the phenol ring, which is in agreement with previous static energy path calcns. However, since in the gas phase the canonical form of tyrosine is the most stable one, the proton transfer proceeds in two steps, starting from the carboxyl group that first passes its proton to the amino group, from where it finally moves to the phenol ring. Furthermore, we also investigate the influence of water on the relaxation processes. For the system of tyrosine with three explicit water mols. solvating the amino group, embedded in a classical water sphere, we also observe a relaxation channel involving proton transfer to the phenol ring. However, in aq. environment, a water mol. near the protonated amino group of tyrosine acts as a mediator for the proton transfer, underlining the importance of the solvent in nonradiative relaxation processes of amino acids. [on SciFinder(R)] |
| 95. | Wichmann, J M; Mitric, R; Weise, C; Holz, M; Lindinger, A Modification of the secondary structure of angiotensin II by substitution of hydrogen with Cs cations: an experimental and theoretical study. Journal Article Physical Chemistry Chemical Physics, 14 (26), pp. 9301–9305, 2012, ISSN: 1463-9076. @article{Wichmann2012, title = {Modification of the secondary structure of angiotensin II by substitution of hydrogen with Cs cations: an experimental and theoretical study.}, author = {J M Wichmann and R Mitric and C Weise and M Holz and A Lindinger}, doi = {10.1039/c2cp22808d}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {26}, pages = {9301--9305}, publisher = {Royal Society of Chemistry}, abstract = {MALDI mass spectrometry in combination with post-source decay (PSD) anal. is a fast and easy to apply method for peptide sequencing. The PSD technique was used to study the influence of the adaptation of one, two, and three cesium cations to angiotensin II in the gas phase. The PSD spectra of cesium-aggregated angiotensin II show far less fragmentation in comparison to the protonated one. In the case of singly (doubly) Cs+ substituted angiotensin II, the PSD mass spectrum shows only fragments with one (two) Cs cation(s). These results are interpreted in terms of addnl. interactions of the cesium cation(s) with the peptide. In order to study this suggestion, the mol. structures were calcd. with semi-empirical mol. dynamic (MD) simulations and further optimized at the quantum chem. level (BP86, SVP) of theory. On the one hand, secondary structures of Cs+ substituted angiotensin II are more compact than the structure of protonated angiotensin II, indicating electrostatic interactions of the Cs cations and the heterocyclic structures. Moreover, oxyphilic interactions of the cations with the oxygen atoms of the peptide backbone also contribute as further van-der-Waals interactions of the Cs+ substituted angiotensin II. These interactions are able to explain its higher stability due to reduced dissocn. in comparison to the protonated angiotensin II. However, most MD simulations of doubly and triply Cs+ substituted angiotensin II show a formation of a [2 Cs] cluster, surrounded by the peptide mol. The formation of this cluster would explain the lack of singly Cs+ substituted fragments in the PSD mass spectrum of doubly Cs+ substituted angiotensin II. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } MALDI mass spectrometry in combination with post-source decay (PSD) anal. is a fast and easy to apply method for peptide sequencing. The PSD technique was used to study the influence of the adaptation of one, two, and three cesium cations to angiotensin II in the gas phase. The PSD spectra of cesium-aggregated angiotensin II show far less fragmentation in comparison to the protonated one. In the case of singly (doubly) Cs+ substituted angiotensin II, the PSD mass spectrum shows only fragments with one (two) Cs cation(s). These results are interpreted in terms of addnl. interactions of the cesium cation(s) with the peptide. In order to study this suggestion, the mol. structures were calcd. with semi-empirical mol. dynamic (MD) simulations and further optimized at the quantum chem. level (BP86, SVP) of theory. On the one hand, secondary structures of Cs+ substituted angiotensin II are more compact than the structure of protonated angiotensin II, indicating electrostatic interactions of the Cs cations and the heterocyclic structures. Moreover, oxyphilic interactions of the cations with the oxygen atoms of the peptide backbone also contribute as further van-der-Waals interactions of the Cs+ substituted angiotensin II. These interactions are able to explain its higher stability due to reduced dissocn. in comparison to the protonated angiotensin II. However, most MD simulations of doubly and triply Cs+ substituted angiotensin II show a formation of a [2 Cs] cluster, surrounded by the peptide mol. The formation of this cluster would explain the lack of singly Cs+ substituted fragments in the PSD mass spectrum of doubly Cs+ substituted angiotensin II. [on SciFinder(R)] |
| 94. | Bonacic-Koutecky, Vlasta; Kulesza, Alexander; Gell, Lars; Mitric, Roland; Antoine, Rodolphe; Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Broyer, Michel; Tabarin, Thibault; Dugourd, Philippe. Silver cluster-biomolecule hybrids: from basics towards sensors. Journal Article Physical Chemistry Chemical Physics, 14 (26), pp. 9282–9290, 2012, ISSN: 1463-9076. @article{Bonacic-Koutecky2012, title = {Silver cluster-biomolecule hybrids: from basics towards sensors.}, author = {Vlasta Bonacic-Koutecky and Alexander Kulesza and Lars Gell and Roland Mitric and Rodolphe Antoine and Franck Bertorelle and Ramzi Hamouda and Driss Rayane and Michel Broyer and Thibault Tabarin and Philippe. Dugourd}, doi = {10.1039/c2cp00050d}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {26}, pages = {9282--9290}, publisher = {Royal Society of Chemistry}, abstract = {The authors focus on the functional role of small silver clusters in model hybrid systems involving peptides in the context of a new generation of nanostructured materials for biosensing. The optical properties of hybrids in the gas phase and at support will be addressed with the aim to bridge fundamental and application aspects. Extension and enhancement of absorption of peptides can be achieved by small silver clusters due to the interaction of intense intracluster excitations with the $pi$-$pi$* excitations of chromophoric amino acids. Moreover, the binding of a peptide to a supported silver cluster can be detected by the optical fingerprint. This illustrates that supported silver clusters can serve as building blocks for biosensing materials. Moreover, the clusters can be used simultaneously to immobilize biomols. and to increase the sensitivity of detection, thus replacing the std. use of org. dyes and providing label-free detection. Complementary to that, protected silver clusters contg. a cluster core and a shell liganded by thiolates exhibit absorption properties with intense transitions in the visible regime which are also suitable for biosensing applications. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors focus on the functional role of small silver clusters in model hybrid systems involving peptides in the context of a new generation of nanostructured materials for biosensing. The optical properties of hybrids in the gas phase and at support will be addressed with the aim to bridge fundamental and application aspects. Extension and enhancement of absorption of peptides can be achieved by small silver clusters due to the interaction of intense intracluster excitations with the $pi$-$pi$* excitations of chromophoric amino acids. Moreover, the binding of a peptide to a supported silver cluster can be detected by the optical fingerprint. This illustrates that supported silver clusters can serve as building blocks for biosensing materials. Moreover, the clusters can be used simultaneously to immobilize biomols. and to increase the sensitivity of detection, thus replacing the std. use of org. dyes and providing label-free detection. Complementary to that, protected silver clusters contg. a cluster core and a shell liganded by thiolates exhibit absorption properties with intense transitions in the visible regime which are also suitable for biosensing applications. [on SciFinder(R)] |
| 93. | Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Theoretical study of structural and optical properties of noble metal cluster-dipeptide hybrids at defect centers of MgO. Journal Article Physical Chemistry Chemical Physics, 14 (26), pp. 9330–9335, 2012, ISSN: 1463-9076. @article{Kulesza2012, title = {Theoretical study of structural and optical properties of noble metal cluster-dipeptide hybrids at defect centers of MgO.}, author = {Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1039/c2cp23500e}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {26}, pages = {9330--9335}, publisher = {Royal Society of Chemistry}, abstract = {The authors present the theor. study of structural and optical properties of silver and gold cluster-dipeptide hybrids bound to the FS defect of the MgO (100) surface. The authors use DFT and its TDDFT variant combined with the polarizable embedded cluster model for the description of the extended MgO environment. As model peptide the authors have chosen CysTrp since the cysteine residue interacts strongly with metal particles through the sulfur atom and tryptophan is the most important chromophoric amino acid. The authors' results show that in the case of CysTrp bound to the supported Ag4 cluster an intense optical signal arises at 400 nm. In contrast, in the case of gold no strongly localized absorption is present since the optical response of supported gold-peptide hybrids is dominated by a large no. of low intensity d-electron excitations spread over a broad energy range. Such a localized optical signal which is present in supported silver hybrids can be exploited for the optical detection of peptides and thus can serve as basis for the development of biosensing materials. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present the theor. study of structural and optical properties of silver and gold cluster-dipeptide hybrids bound to the FS defect of the MgO (100) surface. The authors use DFT and its TDDFT variant combined with the polarizable embedded cluster model for the description of the extended MgO environment. As model peptide the authors have chosen CysTrp since the cysteine residue interacts strongly with metal particles through the sulfur atom and tryptophan is the most important chromophoric amino acid. The authors' results show that in the case of CysTrp bound to the supported Ag4 cluster an intense optical signal arises at 400 nm. In contrast, in the case of gold no strongly localized absorption is present since the optical response of supported gold-peptide hybrids is dominated by a large no. of low intensity d-electron excitations spread over a broad energy range. Such a localized optical signal which is present in supported silver hybrids can be exploited for the optical detection of peptides and thus can serve as basis for the development of biosensing materials. [on SciFinder(R)] |
| 92. | Petersen, Jens; Mitric, Roland. Electronic coherence within the semiclassical field-induced surface hopping method: strong field quantum control in K2. Journal Article Physical Chemistry Chemical Physics, 14 (23), pp. 8299–8306, 2012, ISSN: 1463-9076. @article{Petersen2012, title = {Electronic coherence within the semiclassical field-induced surface hopping method: strong field quantum control in K2.}, author = {Jens Petersen and Roland. Mitric}, doi = {10.1039/c2cp40747g}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {23}, pages = {8299--8306}, publisher = {Royal Society of Chemistry}, abstract = {We demonstrate that the semiclassical field-induced surface hopping (FISH) method (Mitric et al., Phys. Rev. A: At., Mol., Opt. Phys., 2009, 79, 053416.) accurately describes the selective coherent control of electronic state populations. With the example of the strong field control in the potassium dimer using phase-coherent double pulse sequences, we present a detailed comparison between FISH simulations and exact quantum dynamics. We show that for short pulses the variation of the time delay between the subpulses allows for a selective population of the desired final state with high efficiency. Furthermore, also for pulses of longer time duration, when substantial nuclear motion takes place during the action of the pulse, optimized pulse shapes can be obtained which lead to selective population transfer. For both types of pulses, the FISH method almost perfectly reproduces the exact quantum mech. electronic population dynamics, fully taking account of the electronic coherence, and describes the leading features of the nuclear dynamics accurately. Due to the significantly higher computational efficiency of FISH as a trajectory-based method compared to full quantum dynamics simulations, this offers the possibility to theor. investigate control expts. on realistic systems including all nuclear degrees of freedom. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate that the semiclassical field-induced surface hopping (FISH) method (Mitric et al., Phys. Rev. A: At., Mol., Opt. Phys., 2009, 79, 053416.) accurately describes the selective coherent control of electronic state populations. With the example of the strong field control in the potassium dimer using phase-coherent double pulse sequences, we present a detailed comparison between FISH simulations and exact quantum dynamics. We show that for short pulses the variation of the time delay between the subpulses allows for a selective population of the desired final state with high efficiency. Furthermore, also for pulses of longer time duration, when substantial nuclear motion takes place during the action of the pulse, optimized pulse shapes can be obtained which lead to selective population transfer. For both types of pulses, the FISH method almost perfectly reproduces the exact quantum mech. electronic population dynamics, fully taking account of the electronic coherence, and describes the leading features of the nuclear dynamics accurately. Due to the significantly higher computational efficiency of FISH as a trajectory-based method compared to full quantum dynamics simulations, this offers the possibility to theor. investigate control expts. on realistic systems including all nuclear degrees of freedom. [on SciFinder(R)] |
| 91. | Bruschi, Maurizio; Bertini, Luca; Bonacic-Koutecky, Vlasta; De Gioia, Luca ; Mitric, Roland; Zampella, Giuseppe; Fantucci, Piercarlo. Speciation of Copper-Peptide Complexes in Water Solution Using DFTB and DFT Approaches: Case of the [Cu(HGGG)(Py)] Complex. Journal Article Journal of Physical Chemistry B, 116 (22), pp. 6250–6260, 2012, ISSN: 1520-5207. @article{Bruschi2012, title = {Speciation of Copper-Peptide Complexes in Water Solution Using DFTB and DFT Approaches: Case of the [Cu(HGGG)(Py)] Complex.}, author = {Maurizio Bruschi and Luca Bertini and Vlasta Bonacic-Koutecky and Luca {De Gioia} and Roland Mitric and Giuseppe Zampella and Piercarlo. Fantucci}, doi = {10.1021/jp210409c}, issn = {1520-5207}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry B}, volume = {116}, number = {22}, pages = {6250--6260}, publisher = {American Chemical Society}, abstract = {The DFTB and DFT methods are applied to the study of different forms of the [Cu(HGGG)(Py)] complex in water, with the aim of identifying the most stable isomer. The DFTB calcns. were possible thanks to a careful parametrization of the atom-atom repulsive energy terms for Cu-H, Cu-C, Cu-N, and Cu-O. The speciation process is carried out by computing different DFTB-steered mol. dynamics (SMD) trajectories, each of which ends in a well-defined different form. The last frame of each trajectory is subjected to geometry optimization at both DFTB and DFT levels, leading to a different isomer. From the corresponding energy values, a rank of relative stability of the isomers can be established. The computational protocol developed here is of general applicability to other metal-peptide systems and represents a new powerful tool for the study of speciation of metal-contg. systems in water soln., particularly useful when the full characterization of the compd. cannot be carried out on the basis of exptl. results only. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The DFTB and DFT methods are applied to the study of different forms of the [Cu(HGGG)(Py)] complex in water, with the aim of identifying the most stable isomer. The DFTB calcns. were possible thanks to a careful parametrization of the atom-atom repulsive energy terms for Cu-H, Cu-C, Cu-N, and Cu-O. The speciation process is carried out by computing different DFTB-steered mol. dynamics (SMD) trajectories, each of which ends in a well-defined different form. The last frame of each trajectory is subjected to geometry optimization at both DFTB and DFT levels, leading to a different isomer. From the corresponding energy values, a rank of relative stability of the isomers can be established. The computational protocol developed here is of general applicability to other metal-peptide systems and represents a new powerful tool for the study of speciation of metal-contg. systems in water soln., particularly useful when the full characterization of the compd. cannot be carried out on the basis of exptl. results only. [on SciFinder(R)] |
| 90. | Noessler, Melanie; Mitric, Roland; Bonacic-Koutecky, Vlasta. Binary Neutral Metal Oxide Clusters with Oxygen Radical Centers for Catalytic Oxidation Reactions: From Cluster Models Toward Surfaces. Journal Article Journal of Physical Chemistry C, 116 (21), pp. 11570–11574, 2012, ISSN: 1932-7447. @article{Noessler2012, title = {Binary Neutral Metal Oxide Clusters with Oxygen Radical Centers for Catalytic Oxidation Reactions: From Cluster Models Toward Surfaces.}, author = {Melanie Noessler and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp301553s}, issn = {1932-7447}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {21}, pages = {11570--11574}, publisher = {American Chemical Society}, abstract = {We present theor. results based on DFT calcns. of the reactivity of binary neutral stoichiometric Zrn-1ScO2n clusters with oxygen radical centers toward CO and acetylene with the aim to build a bridge between clusters and surface models. Following the concept of the same total valence electron count, the studied series of binary clusters mimics cationic stoichiometric (ZrO2)n+ species characterized also by the presence of an oxygen radical center. In the case of Zr11ScO24, representing a section of the (ZrO2)n bulk, in addn. to the oxygen radical center, the presence of neighboring Zr atoms effectively promotes oxidn. reactions toward CO and acetylene, showing the importance of the surrounding of active centers. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present theor. results based on DFT calcns. of the reactivity of binary neutral stoichiometric Zrn-1ScO2n clusters with oxygen radical centers toward CO and acetylene with the aim to build a bridge between clusters and surface models. Following the concept of the same total valence electron count, the studied series of binary clusters mimics cationic stoichiometric (ZrO2)n+ species characterized also by the presence of an oxygen radical center. In the case of Zr11ScO24, representing a section of the (ZrO2)n bulk, in addn. to the oxygen radical center, the presence of neighboring Zr atoms effectively promotes oxidn. reactions toward CO and acetylene, showing the importance of the surrounding of active centers. [on SciFinder(R)] |
| 89. | Röhr, M I S; Petersen, J; Brunet, C; Antoine, R; Broyer, M; Dugourd, P; Bonacic-Koutecky, V; OHair, R A J; Mitric, R Synthesis and Spectroscopic Characterization of Diphenylargentate, [(C6H5)2Ag]-. Journal Article Journal of Physical Chemistry Letters, 3 (9), pp. 1197–1201, 2012, ISSN: 1948-7185. @article{Röhr2012, title = {Synthesis and Spectroscopic Characterization of Diphenylargentate, [(C6H5)2Ag]-.}, author = {M I S Röhr and J Petersen and C Brunet and R Antoine and M Broyer and P Dugourd and V Bonacic-Koutecky and R A J OHair and R Mitric}, doi = {10.1021/jz300280f}, issn = {1948-7185}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {3}, number = {9}, pages = {1197--1201}, publisher = {American Chemical Society}, abstract = {The structural and optical properties are presented of the isolated Ph2Ag-, which was synthesized by multistage mass spectrometry in a quadrupole ion trap. The exptl. photodetachment spectrum was obtained by action spectroscopy. Comparison with quantum chem. calcns. of the electronic absorption spectrum allows for a precise characterization of the spectroscopic features, showing that in the low-energy regime, the optical properties of diphenylargentate bear a significant resemblance to those of at. Ag. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The structural and optical properties are presented of the isolated Ph2Ag-, which was synthesized by multistage mass spectrometry in a quadrupole ion trap. The exptl. photodetachment spectrum was obtained by action spectroscopy. Comparison with quantum chem. calcns. of the electronic absorption spectrum allows for a precise characterization of the spectroscopic features, showing that in the low-energy regime, the optical properties of diphenylargentate bear a significant resemblance to those of at. Ag. [on SciFinder(R)] |
| 88. | Petersen, Jens; Wohlgemuth, Matthias; Sellner, Bernhard; Bonacic-Koutecky, Vlasta; Lischka, Hans; Mitric, Roland. Laser pulse trains for controlling excited state dynamics of adenine in water. Journal Article Physical Chemistry Chemical Physics, 14 (14), pp. 4687–4694, 2012, ISSN: 1463-9076. @article{Petersen2012a, title = {Laser pulse trains for controlling excited state dynamics of adenine in water.}, author = {Jens Petersen and Matthias Wohlgemuth and Bernhard Sellner and Vlasta Bonacic-Koutecky and Hans Lischka and Roland. Mitric}, doi = {10.1039/c2cp24002e}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {14}, pages = {4687--4694}, publisher = {Royal Society of Chemistry}, abstract = {The authors investigate theor. the control of the ultrafast excited state dynamics of adenine in water by laser pulse trains, with the aim to extend the excited state lifetime and to suppress nonradiative relaxation processes. For this purpose, the authors introduce the combination of their field-induced surface hopping method (FISH) with the quantum mech.-mol. mech. (QM/MM) technique for simulating the laser-driven dynamics in the condensed phase under explicit inclusion of the solvent environment. Moreover, the authors employ parametric pulse shaping in the frequency domain to design simplified laser pulse trains allowing to establish a direct link between the pulse parameters and the controlled dynamics. The authors construct pulse trains which achieve a high excitation efficiency and at the same time keep a high excited state population for a significantly extended time period compared to the uncontrolled dynamics. The control mechanism involves a sequential cycling of the population between the lowest and higher excited states, thereby utilizing the properties of the corresponding potential energy surfaces to avoid conical intersections and thus to suppress the nonradiative decay to the ground state. The authors' findings provide a means to increase the fluorescence yield of mols. with an intrinsically very short excited state lifetime, which can lead to novel applications of shaped laser fields in the context of biosensing. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors investigate theor. the control of the ultrafast excited state dynamics of adenine in water by laser pulse trains, with the aim to extend the excited state lifetime and to suppress nonradiative relaxation processes. For this purpose, the authors introduce the combination of their field-induced surface hopping method (FISH) with the quantum mech.-mol. mech. (QM/MM) technique for simulating the laser-driven dynamics in the condensed phase under explicit inclusion of the solvent environment. Moreover, the authors employ parametric pulse shaping in the frequency domain to design simplified laser pulse trains allowing to establish a direct link between the pulse parameters and the controlled dynamics. The authors construct pulse trains which achieve a high excitation efficiency and at the same time keep a high excited state population for a significantly extended time period compared to the uncontrolled dynamics. The control mechanism involves a sequential cycling of the population between the lowest and higher excited states, thereby utilizing the properties of the corresponding potential energy surfaces to avoid conical intersections and thus to suppress the nonradiative decay to the ground state. The authors' findings provide a means to increase the fluorescence yield of mols. with an intrinsically very short excited state lifetime, which can lead to novel applications of shaped laser fields in the context of biosensing. [on SciFinder(R)] |
| 87. | Stanzel, Joerg; Neeb, Matthias; Eberhardt, Wolfgang; Lisinetskaya, Polina G; Petersen, Jens; Mitric, Roland. Switching from molecular to bulk-like dynamics in electronic relaxation of a small gold cluster. Journal Article Physical Review A: Atomic, Molecular, and Optical Physics, 85 (1-A), pp. 013201/1–013201/6, 2012, ISSN: 1050-2947. @article{Stanzel2012, title = {Switching from molecular to bulk-like dynamics in electronic relaxation of a small gold cluster.}, author = {Joerg Stanzel and Matthias Neeb and Wolfgang Eberhardt and Polina G Lisinetskaya and Jens Petersen and Roland. Mitric}, doi = {10.1103/PhysRevA.85.013201}, issn = {1050-2947}, year = {2012}, date = {2012-01-01}, journal = {Physical Review A: Atomic, Molecular, and Optical Physics}, volume = {85}, number = {1-A}, pages = {013201/1--013201/6}, publisher = {American Physical Society}, abstract = {We have investigated the ultrafast electronic relaxation of Au7- using time-resolved photoelectron spectroscopy combined with first-principles simulations of the excited-state dynamics. Unlike previous findings, which have demonstrated molecularlike excited-state relaxation in Au7- at low excitation energy (1.56 eV), we show here that excitation with 3.12 eV leads to bulklike electronic relaxation without a considerable change of geometry. The exptl. findings are fully supported by theor. simulations, which reveal a bulklike electron-hole relaxation mechanism in a far band-gap cluster. Our findings demonstrate that small gold clusters in the sub-nm size range can exhibit either molecularlike or bulklike properties, depending on the excitation energy. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have investigated the ultrafast electronic relaxation of Au7- using time-resolved photoelectron spectroscopy combined with first-principles simulations of the excited-state dynamics. Unlike previous findings, which have demonstrated molecularlike excited-state relaxation in Au7- at low excitation energy (1.56 eV), we show here that excitation with 3.12 eV leads to bulklike electronic relaxation without a considerable change of geometry. The exptl. findings are fully supported by theor. simulations, which reveal a bulklike electron-hole relaxation mechanism in a far band-gap cluster. Our findings demonstrate that small gold clusters in the sub-nm size range can exhibit either molecularlike or bulklike properties, depending on the excitation energy. [on SciFinder(R)] |
| 86. | Tyo, Eric C; Noessler, Melanie; Rabe, Sabine; Harmon, Christopher L; Mitric, Roland; Bonacic-Koutecky, Vlasta; Castleman, A W Exploring similarities in reactivity of superatom species: a combined theoretical and experimental investigation. Journal Article Physical Chemistry Chemical Physics, 14 (6), pp. 1846–1849, 2012, ISSN: 1463-9076. @article{Tyo2012, title = {Exploring similarities in reactivity of superatom species: a combined theoretical and experimental investigation.}, author = {Eric C Tyo and Melanie Noessler and Sabine Rabe and Christopher L Harmon and Roland Mitric and Vlasta Bonacic-Koutecky and A W Castleman}, doi = {10.1039/c2cp23243j}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {6}, pages = {1846--1849}, publisher = {Royal Society of Chemistry}, abstract = {The replacement of group 10-based materials by superatoms has gained great attention due to studies presenting similarities in electronic character and reactive nature between pairs. The current study extends the concept to systems of larger and varied compn. as the pairs PdO+ and ZrO2+ as well as NiO+ and TiO2+ are interacted with C2H4 and CO through DFT calcns. and guided-ion-beam mass spectrometry. It is detd. that the pairs readily oxidize C2H4 while oxygen transfer is limited towards CO. Interestingly, within the reaction profiles for oxidn. of C2H4 by PdO+ and NiO+, a spin crossover is obsd. which greatly increases the exothermicity of the process. This investigation presents a major step in identifying replacements for expensive group 10 metals in catalytic materials. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The replacement of group 10-based materials by superatoms has gained great attention due to studies presenting similarities in electronic character and reactive nature between pairs. The current study extends the concept to systems of larger and varied compn. as the pairs PdO+ and ZrO2+ as well as NiO+ and TiO2+ are interacted with C2H4 and CO through DFT calcns. and guided-ion-beam mass spectrometry. It is detd. that the pairs readily oxidize C2H4 while oxygen transfer is limited towards CO. Interestingly, within the reaction profiles for oxidn. of C2H4 by PdO+ and NiO+, a spin crossover is obsd. which greatly increases the exothermicity of the process. This investigation presents a major step in identifying replacements for expensive group 10 metals in catalytic materials. [on SciFinder(R)] |
| 85. | Megow, Joerg; Zelinskyy, Yaroslav; Roeder, Beate; Kulesza, Alexander; Mitric, Roland; May, Volkhard. Chemical Physics Letters, 522 , pp. 103–107, 2012, ISSN: 0009-2614. @article{Megow2012, title = {Transient absorption spectra of excitation energy transfer in supramolecular complexes: A mixed quantum-classical description of pheophorbide-a systems.}, author = {Joerg Megow and Yaroslav Zelinskyy and Beate Roeder and Alexander Kulesza and Roland Mitric and Volkhard. May}, doi = {10.1016/j.cplett.2011.11.074}, issn = {0009-2614}, year = {2012}, date = {2012-01-01}, journal = {Chemical Physics Letters}, volume = {522}, pages = {103--107}, publisher = {Elsevier B.V.}, abstract = {A mixed quantum-classical methodol. is used to compute transient optical spectra reflecting excitation energy transfer in large pheophorbide-a complexes dissolved in EtOH. Room-temp. mol. dynamics simulations are used to describe the nuclear dynamics of the whole solvent-solute complex. The electronic excitation energy dynamics is accounted for by solving the time-dependent electronic Schroedinger equation. All computations are carried out in the framework of the ground-state classical path approxn. and in the presence of optical excitations to det. the nonlinear response. A specification to a pump-probe scheme allows to det. spectra of transient anisotropy which offer signatures of a 10 ps excitation energy redistribution already found in earlier studies. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A mixed quantum-classical methodol. is used to compute transient optical spectra reflecting excitation energy transfer in large pheophorbide-a complexes dissolved in EtOH. Room-temp. mol. dynamics simulations are used to describe the nuclear dynamics of the whole solvent-solute complex. The electronic excitation energy dynamics is accounted for by solving the time-dependent electronic Schroedinger equation. All computations are carried out in the framework of the ground-state classical path approxn. and in the presence of optical excitations to det. the nonlinear response. A specification to a pump-probe scheme allows to det. spectra of transient anisotropy which offer signatures of a 10 ps excitation energy redistribution already found in earlier studies. [on SciFinder(R)] |
2011 |
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| 84. | Mitric, Roland; Petersen, Jens; Bonacic-Koutecky, Vlasta. Multistate nonadiabatic dynamics Journal Article Advanced Series in Physical Chemistry, 17 (Conical Intersections), pp. 497–568, 2011, ISSN: 0219-1784. @article{Mitric2011, title = {Multistate nonadiabatic dynamics}, author = {Roland Mitric and Jens Petersen and Vlasta. Bonacic-Koutecky}, issn = {0219-1784}, year = {2011}, date = {2011-01-01}, journal = {Advanced Series in Physical Chemistry}, volume = {17}, number = {Conical Intersections}, pages = {497--568}, publisher = {World Scientific Publishing Co. Pte. Ltd.}, abstract = {A review presents the development of theor. methods for the simulation of nonadiabatic dynamics and its manipulation by laser fields in complex systems accounting for all degrees of freedom. It describes nonadiabatic dynamics 'on the fly' in the frame of time-dependent d. functional theory and its approx. tight-binding version. It outlines the procedure for the simulation of time-resolved photoelectron spectra based on the nonadiabatic dynamics 'on the fly' and the field-induced surface hopping method which is based on the combination of quantum electronic state population dynamics with classical nuclear dynamics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A review presents the development of theor. methods for the simulation of nonadiabatic dynamics and its manipulation by laser fields in complex systems accounting for all degrees of freedom. It describes nonadiabatic dynamics 'on the fly' in the frame of time-dependent d. functional theory and its approx. tight-binding version. It outlines the procedure for the simulation of time-resolved photoelectron spectra based on the nonadiabatic dynamics 'on the fly' and the field-induced surface hopping method which is based on the combination of quantum electronic state population dynamics with classical nuclear dynamics. [on SciFinder(R)] |
| 83. | Bellina, Bruno; Compagnon, Isabelle; Bertorelle, Franck; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Gell, Lars; Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Structural and Optical Properties of Isolated Noble Metal-Glutathione Complexes: Insight into the Chemistry of Liganded Nanoclusters. Journal Article Journal of Physical Chemistry C, 115 (50), pp. 24549–24554, 2011, ISSN: 1932-7447. @article{Bellina2011, title = {Structural and Optical Properties of Isolated Noble Metal-Glutathione Complexes: Insight into the Chemistry of Liganded Nanoclusters.}, author = {Bruno Bellina and Isabelle Compagnon and Franck Bertorelle and Michel Broyer and Rodolphe Antoine and Philippe Dugourd and Lars Gell and Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp207158v}, issn = {1932-7447}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {50}, pages = {24549--24554}, publisher = {American Chemical Society}, abstract = {Au(I)- and Ag(I)-thiolate oligomers generated under nanoparticle growth conditions have been suggested to play an important role in the growth mechanism of thiolate-protected noble metal clusters. The authors explore the formation of isolated noble metal-glutathione complexes by complementing electrospray mass spectrometry and optical action spectroscopy with TDDFT calcns. The authors have isolated and recorded action spectra of [Au+GSH-2H]-, [Ag+GSH-2H]-, and [3Ag+2GSH-4H]- complexes. Competition between photofragmentation and photodetachment channels related to electron binding energies was obsd. The authors' findings show that, although structural properties of Ag and Au metal-glutathione oligomers are similar, their optical properties in the UV range differ substantially. The exptl. spectra were interpreted and assigned by comparison with TDDFT simulations, which allowed the authors to identify the key role of O-metal-S subunits and characterize their optical properties depending on the choice of metal. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Au(I)- and Ag(I)-thiolate oligomers generated under nanoparticle growth conditions have been suggested to play an important role in the growth mechanism of thiolate-protected noble metal clusters. The authors explore the formation of isolated noble metal-glutathione complexes by complementing electrospray mass spectrometry and optical action spectroscopy with TDDFT calcns. The authors have isolated and recorded action spectra of [Au+GSH-2H]-, [Ag+GSH-2H]-, and [3Ag+2GSH-4H]- complexes. Competition between photofragmentation and photodetachment channels related to electron binding energies was obsd. The authors' findings show that, although structural properties of Ag and Au metal-glutathione oligomers are similar, their optical properties in the UV range differ substantially. The exptl. spectra were interpreted and assigned by comparison with TDDFT simulations, which allowed the authors to identify the key role of O-metal-S subunits and characterize their optical properties depending on the choice of metal. [on SciFinder(R)] |
| 82. | Tyo, Eric C; Nossler, Melanie; Harmon, Christopher L; Mitric, Roland; Bonacic-Koutecky, Vlasta; Castleman, A W Investigating Reactive Superoxide Units Bound to Zirconium Oxide Cations. Journal Article Journal of Physical Chemistry C, 115 (44), pp. 21559–21566, 2011, ISSN: 1932-7447. @article{Tyo2011, title = {Investigating Reactive Superoxide Units Bound to Zirconium Oxide Cations.}, author = {Eric C Tyo and Melanie Nossler and Christopher L Harmon and Roland Mitric and Vlasta Bonacic-Koutecky and A W Castleman}, doi = {10.1021/jp204453a}, issn = {1932-7447}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {44}, pages = {21559--21566}, publisher = {American Chemical Society}, abstract = {The structure and reactivity properties of a series of clusters ZrxO2x+1+ (x = 1-3) are investigated using DFT calcns. and guided-ion-beam mass spectrometry. Calcns. det. the cluster structures contg. two oxygen atoms sharing a spin unpaired electron known as a superoxide (O2-). Expt. and theory provide evidence that the size of the cluster has marked influence over the reactivity properties toward C3H6, C4H6, and C2H2. In particular, Zr2O5+ is highly reactive for the oxidn. of the three hydrocarbons, while ZrO3+ only presents substantial reactivity toward butadiene. In addn., Zr3O7+ primarily assocs. the reactants, revealing minor oxidn. channels. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The structure and reactivity properties of a series of clusters ZrxO2x+1+ (x = 1-3) are investigated using DFT calcns. and guided-ion-beam mass spectrometry. Calcns. det. the cluster structures contg. two oxygen atoms sharing a spin unpaired electron known as a superoxide (O2-). Expt. and theory provide evidence that the size of the cluster has marked influence over the reactivity properties toward C3H6, C4H6, and C2H2. In particular, Zr2O5+ is highly reactive for the oxidn. of the three hydrocarbons, while ZrO3+ only presents substantial reactivity toward butadiene. In addn., Zr3O7+ primarily assocs. the reactants, revealing minor oxidn. channels. [on SciFinder(R)] |
| 81. | Melko, Joshua J; Werner, Ute; Mitric, Roland; Bonacic-Koutecky, Vlasta; Castleman, A W Electronic Structure Similarities in PbxSby- and SnxBiy- Clusters. Journal Article Journal of Physical Chemistry A, 115 (37), pp. 10276–10280, 2011, ISSN: 1089-5639. @article{Melko2011, title = {Electronic Structure Similarities in PbxSby- and SnxBiy- Clusters.}, author = {Joshua J Melko and Ute Werner and Roland Mitric and Vlasta Bonacic-Koutecky and A W Castleman}, doi = {10.1021/jp207474h}, issn = {1089-5639}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry A}, volume = {115}, number = {37}, pages = {10276--10280}, publisher = {American Chemical Society}, abstract = {The geometric and electronic structure of PbxSby- and SnxBiy- clusters were investigated by photoelectron spectroscopic and DFT-PBE0 methods. PbSb2- and SnBi2- have similar spectroscopic patterns, reflecting correlations in electronic nature that are a result of their isoelectronic character and common geometries. Analogous findings are presented for Pb2Sb2- and Sn2Bi2-. We investigate the effect of altering the total valence count, and sep. the geometry, on spectroscopic patterns. We concluded that these heavy p-block elements are interchangeable and that the electronic structure correspondence can be preserved regardless of elemental compn. This represents an extension of the traditional concepts of periodicity, where elements of similar valence configuration are grouped into columns. Instead, elements from different columns may be combined to yield similarities in chem., given the overall valence count is preserved. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The geometric and electronic structure of PbxSby- and SnxBiy- clusters were investigated by photoelectron spectroscopic and DFT-PBE0 methods. PbSb2- and SnBi2- have similar spectroscopic patterns, reflecting correlations in electronic nature that are a result of their isoelectronic character and common geometries. Analogous findings are presented for Pb2Sb2- and Sn2Bi2-. We investigate the effect of altering the total valence count, and sep. the geometry, on spectroscopic patterns. We concluded that these heavy p-block elements are interchangeable and that the electronic structure correspondence can be preserved regardless of elemental compn. This represents an extension of the traditional concepts of periodicity, where elements of similar valence configuration are grouped into columns. Instead, elements from different columns may be combined to yield similarities in chem., given the overall valence count is preserved. [on SciFinder(R)] |
| 80. | Wohlgemuth, Matthias; Bonacic-Koutecky, Vlasta; Mitric, Roland. Journal of Chemical Physics, 135 (5), pp. 054105/1–054105/10, 2011, ISSN: 0021-9606. @article{Wohlgemuth2011, title = {Time-dependent density functional theory excited state nonadiabatic dynamics combined with quantum mechanical/molecular mechanical approach: Photodynamics of indole in water.}, author = {Matthias Wohlgemuth and Vlasta Bonacic-Koutecky and Roland. Mitric}, doi = {10.1063/1.3622563}, issn = {0021-9606}, year = {2011}, date = {2011-01-01}, journal = {Journal of Chemical Physics}, volume = {135}, number = {5}, pages = {054105/1--054105/10}, publisher = {American Institute of Physics}, abstract = {We present a combination of time-dependent d. functional theory with the quantum mech./mol. mech. approach which can be applied to study nonadiabatic dynamical processes in mol. systems interacting with the environment. Our method is illustrated on the example of ultrafast excited state dynamics of indole in water. We compare the mechanisms of nonradiative relaxation and the electronic state lifetimes for isolated indole, indole in a sphere of classical water, and indole + 3H2O embedded in a classical water sphere. In the case of isolated indole, the initial excitation to the S2 electronic state is followed by an ultrafast internal conversion to the S1 state with a time const. of 17 fs. The S1 state is long living ( textgreater 30 ps) and deactivates to the ground state along the N-H stretching coordinate. This deactivation mechanism remains unchanged for indole in a classical water sphere. However, the lifetimes of the S2 and S1 electronic states are extended. The inclusion of three explicit water mols. opens a new relaxation channel which involves the electron transfer to the solvent, leading eventually to the formation of a solvated electron. The relaxation to the ground state takes place on a time scale of 60 fs and contributes to the lowering of the fluorescence quantum yield. Our simulations demonstrate the importance of including explicit water mols. in the theor. treatment of solvated systems. (c) 2011 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a combination of time-dependent d. functional theory with the quantum mech./mol. mech. approach which can be applied to study nonadiabatic dynamical processes in mol. systems interacting with the environment. Our method is illustrated on the example of ultrafast excited state dynamics of indole in water. We compare the mechanisms of nonradiative relaxation and the electronic state lifetimes for isolated indole, indole in a sphere of classical water, and indole + 3H2O embedded in a classical water sphere. In the case of isolated indole, the initial excitation to the S2 electronic state is followed by an ultrafast internal conversion to the S1 state with a time const. of 17 fs. The S1 state is long living ( textgreater 30 ps) and deactivates to the ground state along the N-H stretching coordinate. This deactivation mechanism remains unchanged for indole in a classical water sphere. However, the lifetimes of the S2 and S1 electronic states are extended. The inclusion of three explicit water mols. opens a new relaxation channel which involves the electron transfer to the solvent, leading eventually to the formation of a solvated electron. The relaxation to the ground state takes place on a time scale of 60 fs and contributes to the lowering of the fluorescence quantum yield. Our simulations demonstrate the importance of including explicit water mols. in the theor. treatment of solvated systems. (c) 2011 American Institute of Physics. [on SciFinder(R)] |
| 79. | Brunet, C; Antoine, R; Broyer, M; Dugourd, P; Kulesza, A; Petersen, J; Röhr, M I S; Mitric, R; Bonacic-Koutecky, V; O'Hair, R A J Structural and Photochemical Properties of Organosilver Reactive Intermediates MeAg2+ and PhAg2+. Journal Article Journal of Physical Chemistry A, 115 (33), pp. 9120–9127, 2011, ISSN: 1089-5639. @article{Brunet2011, title = {Structural and Photochemical Properties of Organosilver Reactive Intermediates MeAg2+ and PhAg2+.}, author = {C Brunet and R Antoine and M Broyer and P Dugourd and A Kulesza and J Petersen and M I S Röhr and R Mitric and V Bonacic-Koutecky and R A J O'Hair}, doi = {10.1021/jp205716a}, issn = {1089-5639}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry A}, volume = {115}, number = {33}, pages = {9120--9127}, publisher = {American Chemical Society}, abstract = {Although there is growing interest in silver promoted carbon-carbon bond formation, a key challenge in developing robust and reliable organosilver reagents is that thermal and photochem. decompn. reactions can compete with the desired coupling reaction. These undesirable reactions have been poorly understood due to complications arising from factors such as solvent effects and aggregation. Here the unimol. decompn. reactions of organosilver cations, RAg2+, where R = Me and Ph, are examd. in the gas phase using a combination of mass spectrometry based expts. and theor. calcns. to explore differences between thermal and photochem. decompns. Under collision-induced dissocn. conditions, which mimic thermal decompn., both PhAg2+ and MeAg2+ fragment via formation of Ag+. The new ionic products, RAg+textperiodcentered and Ag2+textperiodcentered, which arise via bond homolysis, are obsd. when RAg2+ is subject to photolysis using a UV-vis tunable laser OPO. Furthermore, comparisons between the theor. and exptl. UV-vis spectra allow us to unambiguously det. the most stable structures of PhAg2+ and MeAg2+ and to identify the central role of the silver part in the optical absorption of these species. The new photoproducts result from fragmentation in electronic excited states. In particular, potential energy surface calcns. together with the fragment charges highlight the role of triplet states in these new fragmentation schemes. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Although there is growing interest in silver promoted carbon-carbon bond formation, a key challenge in developing robust and reliable organosilver reagents is that thermal and photochem. decompn. reactions can compete with the desired coupling reaction. These undesirable reactions have been poorly understood due to complications arising from factors such as solvent effects and aggregation. Here the unimol. decompn. reactions of organosilver cations, RAg2+, where R = Me and Ph, are examd. in the gas phase using a combination of mass spectrometry based expts. and theor. calcns. to explore differences between thermal and photochem. decompns. Under collision-induced dissocn. conditions, which mimic thermal decompn., both PhAg2+ and MeAg2+ fragment via formation of Ag+. The new ionic products, RAg+textperiodcentered and Ag2+textperiodcentered, which arise via bond homolysis, are obsd. when RAg2+ is subject to photolysis using a UV-vis tunable laser OPO. Furthermore, comparisons between the theor. and exptl. UV-vis spectra allow us to unambiguously det. the most stable structures of PhAg2+ and MeAg2+ and to identify the central role of the silver part in the optical absorption of these species. The new photoproducts result from fragmentation in electronic excited states. In particular, potential energy surface calcns. together with the fragment charges highlight the role of triplet states in these new fragmentation schemes. [on SciFinder(R)] |
| 78. | Mitric, Roland; Petersen, Jens; Wohlgemuth, Matthias; Werner, Ute; Bonacic-Koutecky, Vlasta. Field-induced surface hopping method for probing transition state nonadiabatic dynamics of Ag3. Journal Article Physical Chemistry Chemical Physics, 13 (19), pp. 8690–8696, 2011, ISSN: 1463-9076. @article{Mitric2011a, title = {Field-induced surface hopping method for probing transition state nonadiabatic dynamics of Ag3.}, author = {Roland Mitric and Jens Petersen and Matthias Wohlgemuth and Ute Werner and Vlasta. Bonacic-Koutecky}, doi = {10.1039/c0cp02935a}, issn = {1463-9076}, year = {2011}, date = {2011-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {19}, pages = {8690--8696}, publisher = {Royal Society of Chemistry}, abstract = {We present the simulation of time-resolved photoelectron spectra of Ag3 involving excitation from the linear transition state, where nonadiabatic relaxation takes place in a complex manifold of electronic states. Thus, we address ultrafast processes reachable by neg. ion-to neutral-to pos. ion (NeNePo) spectroscopy starting from the linear Ag3- anionic species. For this purpose we use our newly developed field-induced surface hopping method (FISH) augmented for the description of photoionization processes. Furthermore we employ our method for nonadiabatic mol. dynamics "on the fly" in the framework of time-dependent d. functional theory generalized for open shell systems. Our presented approach is generally applicable for the prediction of time-resolved photoelectron spectra and their anal. in systems with complex electronic structure as well as many nuclear degrees freedom. This theor. development should serve to stimulate new ultrafast expts. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present the simulation of time-resolved photoelectron spectra of Ag3 involving excitation from the linear transition state, where nonadiabatic relaxation takes place in a complex manifold of electronic states. Thus, we address ultrafast processes reachable by neg. ion-to neutral-to pos. ion (NeNePo) spectroscopy starting from the linear Ag3- anionic species. For this purpose we use our newly developed field-induced surface hopping method (FISH) augmented for the description of photoionization processes. Furthermore we employ our method for nonadiabatic mol. dynamics "on the fly" in the framework of time-dependent d. functional theory generalized for open shell systems. Our presented approach is generally applicable for the prediction of time-resolved photoelectron spectra and their anal. in systems with complex electronic structure as well as many nuclear degrees freedom. This theor. development should serve to stimulate new ultrafast expts. [on SciFinder(R)] |
| 77. | Lisinetskaya, Polina G; Mitric, Roland. Simulation of laser-induced coupled electron-nuclear dynamics and time-resolved harmonic spectra in complex systems. Journal Article Physical Review A: Atomic, Molecular, and Optical Physics, 83 (3, Pt. B), pp. 033408/1–033408/13, 2011, ISSN: 1050-2947. @article{Lisinetskaya2011, title = {Simulation of laser-induced coupled electron-nuclear dynamics and time-resolved harmonic spectra in complex systems.}, author = {Polina G Lisinetskaya and Roland. Mitric}, doi = {10.1103/PhysRevA.83.033408}, issn = {1050-2947}, year = {2011}, date = {2011-01-01}, journal = {Physical Review A: Atomic, Molecular, and Optical Physics}, volume = {83}, number = {3, Pt. B}, pages = {033408/1--033408/13}, publisher = {American Physical Society}, abstract = {The authors present a theor. approach for the simulation of time-resolved harmonic spectra, including the effect of nuclear dynamics, which is applicable to complex systems involving many nuclear degrees of freedom. The method is based on the combination of semiclassical field-induced surface hopping approach for the treatment of laser-induced nuclear dynamics with the time-dependent d. functional theory for electron dynamics. The authors apply method to the simulation of ultrafast nonadiabatic dynamics and time-resolved harmonic spectra in small Ag clusters (Ag2 and Ag8), which exhibit discrete molecularlike electronic transitions. The harmonic signal is highly sensitive to the nuclear dynamics and thus can be used as a probe of coupled electron-nuclear dynamics, which is complementary to common pump-probe methods such as time-resolved photoelectron spectroscopy. Simulations allowed one also to det. the mechanism and the time scale of nonradiative relaxation in the magic Ag8 cluster and provided a fundamental insight into ultrafast dynamics of metal nanoclusters in the size regime where each atom counts. The excited-state dynamics of Ag8 involves an isomerization process from the initial structure with Td symmetry to the quadratic antiprism structure with D4d symmetry which takes place on a time scale of ∼600 fs and is clearly identified in a time-resolved harmonic signal. Theor. approach is generally applicable for the prediction of time-resolved harmonic spectra in complex systems with many nuclear degrees freedom and should serve to stimulate new ultrafast expts. using harmonic signals as a probe for nonadiabatic processes in mol. systems. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a theor. approach for the simulation of time-resolved harmonic spectra, including the effect of nuclear dynamics, which is applicable to complex systems involving many nuclear degrees of freedom. The method is based on the combination of semiclassical field-induced surface hopping approach for the treatment of laser-induced nuclear dynamics with the time-dependent d. functional theory for electron dynamics. The authors apply method to the simulation of ultrafast nonadiabatic dynamics and time-resolved harmonic spectra in small Ag clusters (Ag2 and Ag8), which exhibit discrete molecularlike electronic transitions. The harmonic signal is highly sensitive to the nuclear dynamics and thus can be used as a probe of coupled electron-nuclear dynamics, which is complementary to common pump-probe methods such as time-resolved photoelectron spectroscopy. Simulations allowed one also to det. the mechanism and the time scale of nonradiative relaxation in the magic Ag8 cluster and provided a fundamental insight into ultrafast dynamics of metal nanoclusters in the size regime where each atom counts. The excited-state dynamics of Ag8 involves an isomerization process from the initial structure with Td symmetry to the quadratic antiprism structure with D4d symmetry which takes place on a time scale of ∼600 fs and is clearly identified in a time-resolved harmonic signal. Theor. approach is generally applicable for the prediction of time-resolved harmonic spectra in complex systems with many nuclear degrees freedom and should serve to stimulate new ultrafast expts. using harmonic signals as a probe for nonadiabatic processes in mol. systems. [on SciFinder(R)] |
| 76. | Tyo, Eric C; Nossler, Melanie; Mitric, Roland; Bonacic-Koutecky, Vlasta; Castleman Jr., A W Reactivity of stoichiometric titanium oxide cations. Journal Article Physical Chemistry Chemical Physics, 13 (10), pp. 4243–4249, 2011, ISSN: 1463-9076. @article{Tyo2011a, title = {Reactivity of stoichiometric titanium oxide cations.}, author = {Eric C Tyo and Melanie Nossler and Roland Mitric and Vlasta Bonacic-Koutecky and A W {Castleman Jr.}}, doi = {10.1039/c0cp02170a}, issn = {1463-9076}, year = {2011}, date = {2011-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {10}, pages = {4243--4249}, publisher = {Royal Society of Chemistry}, abstract = {We present the results of a reactivity study of titanium cationic clusters towards CO, C2H2, C2H4 and C3H6 based on guided-ion-beam mass spectrometry and DFT calcns. We identified Ti2O4+ and to a lesser extent TiO2+ species which preferentially undergo oxidn. reactions. An oxygen centered radical of Ti2O4+ is responsible for selective oxidn. Energy profiles and MD simulations reveal the mechanisms of the reactions. Regeneration of the oxygen centered radical was achieved exptl. and theor. through the reaction of N2O with Ti2O3+. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present the results of a reactivity study of titanium cationic clusters towards CO, C2H2, C2H4 and C3H6 based on guided-ion-beam mass spectrometry and DFT calcns. We identified Ti2O4+ and to a lesser extent TiO2+ species which preferentially undergo oxidn. reactions. An oxygen centered radical of Ti2O4+ is responsible for selective oxidn. Energy profiles and MD simulations reveal the mechanisms of the reactions. Regeneration of the oxygen centered radical was achieved exptl. and theor. through the reaction of N2O with Ti2O3+. [on SciFinder(R)] |
| 75. | Mitric, R; Petersen, J; Kulesza, A; Röhr, M I S; Bonacic-Koutecky, V; Brunet, C; Antoine, R; Dugourd, P; Broyer, M; O'Hair, R A J Gas-phase synthesis and vibronic action spectroscopy of Ag2H+. Journal Article Journal of Physical Chemistry Letters, 2 (6), pp. 548–552, 2011, ISSN: 1948-7185. @article{Mitric2011b, title = {Gas-phase synthesis and vibronic action spectroscopy of Ag2H+.}, author = {R Mitric and J Petersen and A Kulesza and M I S Röhr and V Bonacic-Koutecky and C Brunet and R Antoine and P Dugourd and M Broyer and R A J O'Hair}, doi = {10.1021/jz101733v}, issn = {1948-7185}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {2}, number = {6}, pages = {548--552}, publisher = {American Chemical Society}, abstract = {The authors present the first vibrationally resolved electronic spectrum for the isolated silver hydride cation Ag2H+, which has been synthesized by multistage mass spectrometry in a quadrupole ion trap. The exptl. photofragmentation spectrum has been obtained by action spectroscopy. High-level ab initio simulations reproduce exptl. findings and provide precise assignment of structural properties of ground and excited electronic states of Ag2H+, which serves as an intermediate in important chem. reactions such as carbon-carbon coupling. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present the first vibrationally resolved electronic spectrum for the isolated silver hydride cation Ag2H+, which has been synthesized by multistage mass spectrometry in a quadrupole ion trap. The exptl. photofragmentation spectrum has been obtained by action spectroscopy. High-level ab initio simulations reproduce exptl. findings and provide precise assignment of structural properties of ground and excited electronic states of Ag2H+, which serves as an intermediate in important chem. reactions such as carbon-carbon coupling. [on SciFinder(R)] |
| 74. | Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta; Bellina, Bruno; Compagnon, Isabelle; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe. Doubly Charged Silver Clusters Stabilized by Tryptophan: Ag42+ as an Optical Marker for Monitoring Particle Growth. Journal Article Angewandte Chemie, International Edition, 50 (4), pp. 878–881, S878/1–S878/5, 2011, ISSN: 1433-7851. @article{Kulesza2011, title = {Doubly Charged Silver Clusters Stabilized by Tryptophan: Ag42+ as an Optical Marker for Monitoring Particle Growth.}, author = {Alexander Kulesza and Roland Mitric and Vlasta Bonacic-Koutecky and Bruno Bellina and Isabelle Compagnon and Michel Broyer and Rodolphe Antoine and Philippe. Dugourd}, doi = {10.1002/anie.201005419}, issn = {1433-7851}, year = {2011}, date = {2011-01-01}, journal = {Angewandte Chemie, International Edition}, volume = {50}, number = {4}, pages = {878--881, S878/1--S878/5}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {Gas phase electronic spectroscopy has succeeded in giving structural information on isolated and microhydrated mol. ions. Combined with theor. investigations, it provides a conceptual framework to unravel optical properties of multiply charged clusters and in particular the influence of. We demonstrate that this hybrid system exhibits an unambiguous optical fingerprint of the doubly charged silver cluster (Ag42+)stabilized by a salt-bridge (SB) interaction with the org. moiety. Thus, we propose the use of its optical signature as marker to monitor early stages of seeding processes for particle growth. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Gas phase electronic spectroscopy has succeeded in giving structural information on isolated and microhydrated mol. ions. Combined with theor. investigations, it provides a conceptual framework to unravel optical properties of multiply charged clusters and in particular the influence of. We demonstrate that this hybrid system exhibits an unambiguous optical fingerprint of the doubly charged silver cluster (Ag42+)stabilized by a salt-bridge (SB) interaction with the org. moiety. Thus, we propose the use of its optical signature as marker to monitor early stages of seeding processes for particle growth. [on SciFinder(R)] |
| 73. | Popolan, Denisia M; Nossler, Melanie; Mitric, Roland; Bernhardt, Thorsten M; Bonacic-Koutecky, Vlasta. Journal of Physical Chemistry A, 115 (6), pp. 951–959, 2011, ISSN: 1089-5639. @article{Popolan2011, title = {Tuning Cluster Reactivity by Charge State and Composition: Experimental and Theoretical Investigation of CO Binding Energies to AgnAum+/-(n + m = 3).}, author = {Denisia M Popolan and Melanie Nossler and Roland Mitric and Thorsten M Bernhardt and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp106884p}, issn = {1089-5639}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry A}, volume = {115}, number = {6}, pages = {951--959}, publisher = {American Chemical Society}, abstract = {Temp.-dependent gas-phase reaction kinetics measurements and equil. thermodn. under multicollision conditions in conjunction with ab initio DFT calcns. were employed to det. the binding energies of carbon monoxide to triat. silver-gold binary cluster cations and anions. The binding energies of the first CO mol. to the trimer clusters increase with increasing gold content and with changing charge from neg. to pos. Thus, the reactivity of the binary clusters can be sensitively tuned by varying charge state and compn. Also, multiple CO adsorption on the clusters was investigated. The max. no. of adsorbed CO mols. was found to strongly depend on cluster charge and compn. as well. Most interestingly, the cationic carbonyl complex Au3(CO)4+ is formed at cryogenic temp., whereas for the anion, only two CO mols. are adsorbed, leading to Au3(CO)2-. All other trimer clusters adsorb three CO mols. in the case of the cations and are completely inert to CO in our expt. in the case of the anions. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Temp.-dependent gas-phase reaction kinetics measurements and equil. thermodn. under multicollision conditions in conjunction with ab initio DFT calcns. were employed to det. the binding energies of carbon monoxide to triat. silver-gold binary cluster cations and anions. The binding energies of the first CO mol. to the trimer clusters increase with increasing gold content and with changing charge from neg. to pos. Thus, the reactivity of the binary clusters can be sensitively tuned by varying charge state and compn. Also, multiple CO adsorption on the clusters was investigated. The max. no. of adsorbed CO mols. was found to strongly depend on cluster charge and compn. as well. Most interestingly, the cationic carbonyl complex Au3(CO)4+ is formed at cryogenic temp., whereas for the anion, only two CO mols. are adsorbed, leading to Au3(CO)2-. All other trimer clusters adsorb three CO mols. in the case of the cations and are completely inert to CO in our expt. in the case of the anions. [on SciFinder(R)] |
| 72. | Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Unique optical properties of silver cluster-biochromophore hybrids: Comparison with copper and gold. Journal Article Chemical Physics Letters, 501 (4-6), pp. 211–214, 2011, ISSN: 0009-2614. @article{Kulesza2011a, title = {Unique optical properties of silver cluster-biochromophore hybrids: Comparison with copper and gold.}, author = {Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1016/j.cplett.2010.11.026}, issn = {0009-2614}, year = {2011}, date = {2011-01-01}, journal = {Chemical Physics Letters}, volume = {501}, number = {4-6}, pages = {211--214}, publisher = {Elsevier B.V.}, abstract = {Ag cluster-biochromophore hybrids exhibit markedly different optical properties than analog Cu and Au hybrids. This is reflected in a localized resonance at ≈320 nm enhancing strongly the absorption of biomols. In contrast, Cu and Au hybrid systems exhibit very different behavior due to a small s-d energy gap leading to a high d. of states with low intensities spread in a broad energy interval. The authors' results provide insight into the factors governing the proper choice of metallic labels for bioanal. applications based on localized enhancement of absorption and fluorescence. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ag cluster-biochromophore hybrids exhibit markedly different optical properties than analog Cu and Au hybrids. This is reflected in a localized resonance at ≈320 nm enhancing strongly the absorption of biomols. In contrast, Cu and Au hybrid systems exhibit very different behavior due to a small s-d energy gap leading to a high d. of states with low intensities spread in a broad energy interval. The authors' results provide insight into the factors governing the proper choice of metallic labels for bioanal. applications based on localized enhancement of absorption and fluorescence. [on SciFinder(R)] |
| 71. | Mitric, Roland; Petersen, Jens; Wohlgemuth, Matthias; Werner, Ute; Bonacic-Koutecky, Vlasta; Woeste, Ludger; Jortner, Joshua. Time-Resolved Femtosecond Photoelectron Spectroscopy by Field-Induced Surface Hopping. Journal Article Journal of Physical Chemistry A, 115 (16), pp. 3755–3765, 2011, ISSN: 1089-5639. @article{Mitric2011c, title = {Time-Resolved Femtosecond Photoelectron Spectroscopy by Field-Induced Surface Hopping.}, author = {Roland Mitric and Jens Petersen and Matthias Wohlgemuth and Ute Werner and Vlasta Bonacic-Koutecky and Ludger Woeste and Joshua. Jortner}, doi = {10.1021/jp106355n}, issn = {1089-5639}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry A}, volume = {115}, number = {16}, pages = {3755--3765}, publisher = {American Chemical Society}, abstract = {The authors present the extension of field-induced surface hopping method for the description of the photoionization process and the simulation of time-resolved photoelectron spectra (TRPES). This is based on the combination of nonadiabatic mol. dynamics on the fly in the framework of TDDFT generalized for open shell systems under the influence of laser fields with the approx. quantum mech. description of the photoionization process. Since arbitrary pulse shapes can be employed, this method can be also combined with the optimal control theory to steer the photoionization or to shape the outgoing electronic wavepackets. The authors illustrate method for the simulation of TRPES on the prototype system of Ag3, which involves excitation from the equil. triangular geometry, as well as excitation from the linear transition state, where in both cases nonadiabatic relaxation takes place in a complex manifold of electronic states. Approach represents a generally applicable method for the prediction of time-resolved photoelectron spectra and their anal. in systems with complex electronic structure as well as many nuclear degrees freedom. This theor. development should serve to stimulate new ultrafast expts. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present the extension of field-induced surface hopping method for the description of the photoionization process and the simulation of time-resolved photoelectron spectra (TRPES). This is based on the combination of nonadiabatic mol. dynamics on the fly in the framework of TDDFT generalized for open shell systems under the influence of laser fields with the approx. quantum mech. description of the photoionization process. Since arbitrary pulse shapes can be employed, this method can be also combined with the optimal control theory to steer the photoionization or to shape the outgoing electronic wavepackets. The authors illustrate method for the simulation of TRPES on the prototype system of Ag3, which involves excitation from the equil. triangular geometry, as well as excitation from the linear transition state, where in both cases nonadiabatic relaxation takes place in a complex manifold of electronic states. Approach represents a generally applicable method for the prediction of time-resolved photoelectron spectra and their anal. in systems with complex electronic structure as well as many nuclear degrees freedom. This theor. development should serve to stimulate new ultrafast expts. [on SciFinder(R)] |
2010 |
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| 70. | Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta; Bellina, Bruno; Compagnon, Isabelle; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe Doubly Charged Silver Clusters Stabilized by Tryptophan: Ag(4) (2+) as an Optical Marker for Monitoring Particle Growth Journal Article Angewandte Chemie (International ed. in English), 2010, ISSN: 1521-3773. @article{Kulesza2010, title = {Doubly Charged Silver Clusters Stabilized by Tryptophan: Ag(4) (2+) as an Optical Marker for Monitoring Particle Growth}, author = {Alexander Kulesza and Roland Mitric and Vlasta Bonacic-Koutecky and Bruno Bellina and Isabelle Compagnon and Michel Broyer and Rodolphe Antoine and Philippe Dugourd}, issn = {1521-3773}, year = {2010}, date = {2010-01-01}, journal = {Angewandte Chemie (International ed. in English)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 69. | Nossler, Melanie; Mitric, Roland; Bonacic-Koutecky, Vlasta; Johnson, Grant E; Tyo, Eric C; Castleman, Welford Jr A Generation of oxygen radical centers in binary neutral metal oxide clusters for catalytic oxidation reactions Journal Article Angewandte Chemie (International ed. in English), 49 (2), pp. 407–410, 2010, ISSN: 1521-3773. @article{Nossler2010, title = {Generation of oxygen radical centers in binary neutral metal oxide clusters for catalytic oxidation reactions}, author = {Melanie Nossler and Roland Mitric and Vlasta Bonacic-Koutecky and Grant E Johnson and Eric C Tyo and Welford Jr A Castleman}, issn = {1521-3773}, year = {2010}, date = {2010-01-01}, journal = {Angewandte Chemie (International ed. in English)}, volume = {49}, number = {2}, pages = {407--410}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 68. | Fuji, Takao; Suzuki, Yoshi-ichi; Horio, Takuya; Suzuki, Toshinori; Mitric, Roland; Werner, Ute; Bonacic-Koutecky, Vlasta. Ultrafast photodynamics of furan. Journal Article Journal of Chemical Physics, 133 (23), pp. 234303/1–234303/9, 2010, ISSN: 0021-9606. @article{Fuji2010, title = {Ultrafast photodynamics of furan.}, author = {Takao Fuji and Yoshi-ichi Suzuki and Takuya Horio and Toshinori Suzuki and Roland Mitric and Ute Werner and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.3518441}, issn = {0021-9606}, year = {2010}, date = {2010-01-01}, journal = {Journal of Chemical Physics}, volume = {133}, number = {23}, pages = {234303/1--234303/9}, publisher = {American Institute of Physics}, abstract = {Ultrafast photodynamics of furan was studied by time-resolved photoelectron imaging (TRPEI) spectroscopy with an unprecedented time resoln. of 22 fs. The simulation of the time-dependent photoelectron kinetic energy distribution (PKED) was performed with ab initio nonadiabatic dynamics on the fly in the frame of time-dependent d. functional theory. Based on the agreement between exptl. and theor. time-dependent photoelectron signal intensity as well as on PKED, precise time scales of ultrafast internal conversion from S2 over S1 to the ground state S0 of furan were revealed for the 1st time. Upon initial excitation of the S2 state which has $pi$-$pi$* character, a nonadiabatic transition to the S1 state occurs within 10 fs. Subsequent dynamics invokes the excitation of the C-O stretching and C-O-C out of plane vibrations which lead to the internal conversion to the ground state after 60 fs. Thus, the TRPEI combined with high level nonadiabatic dynamics calcns. provide fundamental insight into ultrafast photodynamics of chem. and biol. relevant chromophores. (c) 2010 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ultrafast photodynamics of furan was studied by time-resolved photoelectron imaging (TRPEI) spectroscopy with an unprecedented time resoln. of 22 fs. The simulation of the time-dependent photoelectron kinetic energy distribution (PKED) was performed with ab initio nonadiabatic dynamics on the fly in the frame of time-dependent d. functional theory. Based on the agreement between exptl. and theor. time-dependent photoelectron signal intensity as well as on PKED, precise time scales of ultrafast internal conversion from S2 over S1 to the ground state S0 of furan were revealed for the 1st time. Upon initial excitation of the S2 state which has $pi$-$pi$* character, a nonadiabatic transition to the S1 state occurs within 10 fs. Subsequent dynamics invokes the excitation of the C-O stretching and C-O-C out of plane vibrations which lead to the internal conversion to the ground state after 60 fs. Thus, the TRPEI combined with high level nonadiabatic dynamics calcns. provide fundamental insight into ultrafast photodynamics of chem. and biol. relevant chromophores. (c) 2010 American Institute of Physics. [on SciFinder(R)] |
| 67. | Barbatti, Mario; Pittner, Jiri; Pederzoli, Marek; Werner, Ute; Mitric, Roland; Bonacic-Koutecky, Vlasta; Lischka, Hans. Non-adiabatic dynamics of pyrrole: Dependence of deactivation mechanisms on the excitation energy. Journal Article Chemical Physics, 375 (1), pp. 26–34, 2010, ISSN: 0301-0104. @article{Barbatti2010, title = {Non-adiabatic dynamics of pyrrole: Dependence of deactivation mechanisms on the excitation energy.}, author = {Mario Barbatti and Jiri Pittner and Marek Pederzoli and Ute Werner and Roland Mitric and Vlasta Bonacic-Koutecky and Hans. Lischka}, doi = {10.1016/j.chemphys.2010.07.014}, issn = {0301-0104}, year = {2010}, date = {2010-01-01}, journal = {Chemical Physics}, volume = {375}, number = {1}, pages = {26--34}, publisher = {Elsevier B.V.}, abstract = {Nonadiabatic dynamics simulations were performed for pyrrole at time-dependent d. functional theory level using the trajectory surface hopping approach. Initial conditions were prepd. based on the UV-absorption spectrum so as to simulate monochromatic absorption in 3 distinct spectral regions. The results showed predominance of the NH-stretch mechanism for excited-state relaxation. With increasing initial energy, however, other mechanisms are activated as well, even though they still occurred for a minor fraction of the trajectories. Dynamics starting at the origin of the absorption spectrum exhibited internal conversion to the ground state with a time const. of 20 fs. But dynamics starting at higher energies gave rise to much longer time consts. for internal conversion near 200 fs. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Nonadiabatic dynamics simulations were performed for pyrrole at time-dependent d. functional theory level using the trajectory surface hopping approach. Initial conditions were prepd. based on the UV-absorption spectrum so as to simulate monochromatic absorption in 3 distinct spectral regions. The results showed predominance of the NH-stretch mechanism for excited-state relaxation. With increasing initial energy, however, other mechanisms are activated as well, even though they still occurred for a minor fraction of the trajectories. Dynamics starting at the origin of the absorption spectrum exhibited internal conversion to the ground state with a time const. of 20 fs. But dynamics starting at higher energies gave rise to much longer time consts. for internal conversion near 200 fs. [on SciFinder(R)] |
| 66. | Petersen, Jens; Mitric, Roland; Bonacic-Koutecky, Vlasta; Wolf, Jean-Pierre; Roslund, Jonathan; Rabitz, Herschel. How shaped light discriminates nearly identical biochromophores. Journal Article Physical Review Letters, 105 (7), pp. 073003/1–073003/4, 2010, ISSN: 0031-9007. @article{Petersen2010, title = {How shaped light discriminates nearly identical biochromophores.}, author = {Jens Petersen and Roland Mitric and Vlasta Bonacic-Koutecky and Jean-Pierre Wolf and Jonathan Roslund and Herschel. Rabitz}, doi = {10.1103/PhysRevLett.105.073003}, issn = {0031-9007}, year = {2010}, date = {2010-01-01}, journal = {Physical Review Letters}, volume = {105}, number = {7}, pages = {073003/1--073003/4}, publisher = {American Physical Society}, abstract = {A review. We present a general mechanism for successful discrimination of spectroscopically indistinguishable biochromophores by shaped light. For this purpose we use nonadiabatic dynamics in excited electronic states in the frame of the field-induced surface hopping method driven by the exptl. shaped laser fields. Our findings show that optimal laser fields drive low-frequency vibrational modes localized in the side chains of two biochromophores, thus selecting the parts of their potential energy surfaces characterized by different transition dipole moments leading to different ionization probabilities. The presented mechanism leads to selective fluorescence depletion which serves as a discrimination signal. Our findings offer a promising perspective for using optimally shaped laser pulses in bioanal. applications by increasing the selectivity beyond the current capability. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A review. We present a general mechanism for successful discrimination of spectroscopically indistinguishable biochromophores by shaped light. For this purpose we use nonadiabatic dynamics in excited electronic states in the frame of the field-induced surface hopping method driven by the exptl. shaped laser fields. Our findings show that optimal laser fields drive low-frequency vibrational modes localized in the side chains of two biochromophores, thus selecting the parts of their potential energy surfaces characterized by different transition dipole moments leading to different ionization probabilities. The presented mechanism leads to selective fluorescence depletion which serves as a discrimination signal. Our findings offer a promising perspective for using optimally shaped laser pulses in bioanal. applications by increasing the selectivity beyond the current capability. [on SciFinder(R)] |
| 65. | Popolan, Denisia M; Noessler, Melanie; Mitric, Roland; Bernhardt, Thorsten M; Bonacic-Koutecky, Vlasta. Composition dependent adsorption of multiple CO molecules on binary silver-gold clusters AgnAum+ (n + m = 5): theory and experiment. Journal Article Physical Chemistry Chemical Physics, 12 (28), pp. 7865–7873, 2010, ISSN: 1463-9076. @article{Popolan2010, title = {Composition dependent adsorption of multiple CO molecules on binary silver-gold clusters AgnAum+ (n + m = 5): theory and experiment.}, author = {Denisia M Popolan and Melanie Noessler and Roland Mitric and Thorsten M Bernhardt and Vlasta. Bonacic-Koutecky}, doi = {10.1039/b924022e}, issn = {1463-9076}, year = {2010}, date = {2010-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {12}, number = {28}, pages = {7865--7873}, publisher = {Royal Society of Chemistry}, abstract = {The binding energies of multiple CO mols. to five-atom silver-gold cluster cations were obtained employing temp. dependent gas phase ion trap measurements and ab initio calcns. The CO binding energies to AgnAum+ (n + m = 5) decrease with increasing no. of silver atoms. Most strikingly, after the adsorption of the 4th CO to Au5+ and of the 3rd CO to Ag5+, resp., a pronounced decrease in the binding energies of further CO mols. was obsd. This is related to a CO-induced structural transformation yielding more compact metal cluster geometries. First principles calcns. revealed that the exact structure of the carbonyl complexes with multiple CO and the nature of the CO-induced structural transformation strongly depend on the compn. of the metal cluster as well as on the no. of adsorbed CO mols. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The binding energies of multiple CO mols. to five-atom silver-gold cluster cations were obtained employing temp. dependent gas phase ion trap measurements and ab initio calcns. The CO binding energies to AgnAum+ (n + m = 5) decrease with increasing no. of silver atoms. Most strikingly, after the adsorption of the 4th CO to Au5+ and of the 3rd CO to Ag5+, resp., a pronounced decrease in the binding energies of further CO mols. was obsd. This is related to a CO-induced structural transformation yielding more compact metal cluster geometries. First principles calcns. revealed that the exact structure of the carbonyl complexes with multiple CO and the nature of the CO-induced structural transformation strongly depend on the compn. of the metal cluster as well as on the no. of adsorbed CO mols. [on SciFinder(R)] |
| 64. | Buergel, Christian; Mitric, Roland; Bonacic-Koutecky, Vlasta. Theoretical study of structural and optical properties of small silver and gold clusters at defect centers of MgO. Journal Article Physica Status Solidi B: Basic Solid State Physics, 247 (5), pp. 1099–1108, 2010, ISSN: 0370-1972. @article{Buergel2010, title = {Theoretical study of structural and optical properties of small silver and gold clusters at defect centers of MgO.}, author = {Christian Buergel and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1002/pssb.200945503}, issn = {0370-1972}, year = {2010}, date = {2010-01-01}, journal = {Physica Status Solidi B: Basic Solid State Physics}, volume = {247}, number = {5}, pages = {1099--1108}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {In this contribution we present the structural and optical properties of small noble-metal clusters at the FS-center defect of the MgO (100) support. We focus on comparing absorption and emission properties of supported silver and gold clusters. It will be shown that the leading absorption features in the low energy regime are similar for supported silver and gold clusters of the same size, in spite of the direct involvement of d electrons from Au atoms due to strong relativistic effects. Mol. dynamics (MD) simulations in the excited electronic states allow us to unravel relaxation mechanism and to propose the smallest noble-metal clusters at the FS-center defect, Ag2,4@F5c and Au2,4@F5c, as good candidates for emissive centers. In contrast, larger supported Ag8@F5c and Au8@F5c clusters are unlikely to fluoresce. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this contribution we present the structural and optical properties of small noble-metal clusters at the FS-center defect of the MgO (100) support. We focus on comparing absorption and emission properties of supported silver and gold clusters. It will be shown that the leading absorption features in the low energy regime are similar for supported silver and gold clusters of the same size, in spite of the direct involvement of d electrons from Au atoms due to strong relativistic effects. Mol. dynamics (MD) simulations in the excited electronic states allow us to unravel relaxation mechanism and to propose the smallest noble-metal clusters at the FS-center defect, Ag2,4@F5c and Au2,4@F5c, as good candidates for emissive centers. In contrast, larger supported Ag8@F5c and Au8@F5c clusters are unlikely to fluoresce. [on SciFinder(R)] |
| 63. | Werner, Ute; Mitric, Roland; Bonacic-Koutecky, Vlasta. Simulation of time resolved photoelectron spectra with Stieltjes imaging illustrated on ultrafast internal conversion in pyrazine. Journal Article Journal of Chemical Physics, 132 (17), pp. 174301/1–174301/8, 2010, ISSN: 0021-9606. @article{Werner2010, title = {Simulation of time resolved photoelectron spectra with Stieltjes imaging illustrated on ultrafast internal conversion in pyrazine.}, author = {Ute Werner and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.3395160}, issn = {0021-9606}, year = {2010}, date = {2010-01-01}, journal = {Journal of Chemical Physics}, volume = {132}, number = {17}, pages = {174301/1--174301/8}, publisher = {American Institute of Physics}, abstract = {We present an approach for the simulation of time resolved photoelectron spectra based on the combination of the ab initio nonadiabatic mol. dynamics "on the fly" with the Stieltjes imaging method utilizing discrete neutral states above the ionization limit for the approx. description of the ionization continuum. Our approach has been implemented in the framework of the time-dependent d. functional theory and has been applied to interrogate the ultrafast internal conversion between the S2 and S1 states in pyrazine. The simulations reveal that, parallel to the S2→S1 internal conversion, a change in the dominant ionization process (S2→D1 vs. S1→D0) occurs on the time scale of 20 fs such that no significant change in the photoelectron kinetic energy distribution is obsd. The presented results are in full agreement with the exptl. results presented in the accompanying paper and provide an insight into the interplay between the nonradiative relaxation and the photoionization process in pyrazine as reflected in the time resolved photoelectron spectrum. Our approach represents a general tool for the investigation of ultrafast photoionization processes in complex systems and thus can be used to investigate the ultrafast femtochem. of complex mol. systems including all degrees of freedom. (c) 2010 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present an approach for the simulation of time resolved photoelectron spectra based on the combination of the ab initio nonadiabatic mol. dynamics "on the fly" with the Stieltjes imaging method utilizing discrete neutral states above the ionization limit for the approx. description of the ionization continuum. Our approach has been implemented in the framework of the time-dependent d. functional theory and has been applied to interrogate the ultrafast internal conversion between the S2 and S1 states in pyrazine. The simulations reveal that, parallel to the S2→S1 internal conversion, a change in the dominant ionization process (S2→D1 vs. S1→D0) occurs on the time scale of 20 fs such that no significant change in the photoelectron kinetic energy distribution is obsd. The presented results are in full agreement with the exptl. results presented in the accompanying paper and provide an insight into the interplay between the nonradiative relaxation and the photoionization process in pyrazine as reflected in the time resolved photoelectron spectrum. Our approach represents a general tool for the investigation of ultrafast photoionization processes in complex systems and thus can be used to investigate the ultrafast femtochem. of complex mol. systems including all degrees of freedom. (c) 2010 American Institute of Physics. [on SciFinder(R)] |
| 62. | Landt, Lasse; Bostedt, Christoph; Wolter, David; Moeller, Thomas; Dahl, Jeremy E P; Carlson, Robert M K; Tkachenko, Boryslav A; Fokin, Andrey A; Schreiner, Peter R; Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Experimental and theoretical study of the absorption properties of thiolated diamondoids. Journal Article Journal of Chemical Physics, 132 (14), pp. 144305/1–144305/6, 2010, ISSN: 0021-9606. @article{Landt2010, title = {Experimental and theoretical study of the absorption properties of thiolated diamondoids.}, author = {Lasse Landt and Christoph Bostedt and David Wolter and Thomas Moeller and Jeremy E P Dahl and Robert M K Carlson and Boryslav A Tkachenko and Andrey A Fokin and Peter R Schreiner and Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.3356034}, issn = {0021-9606}, year = {2010}, date = {2010-01-01}, journal = {Journal of Chemical Physics}, volume = {132}, number = {14}, pages = {144305/1--144305/6}, publisher = {American Institute of Physics}, abstract = {Nanoscale hybrid systems are a new class of mol. aggregates that offer numerous new possibilities in materials design. Diamondoid thiols are promising nanoscale building blocks for such hybrid systems. They allow the incorporation of functional groups and the study of their effects on the unique materials' properties of diamondoids. Here the authors combine exptl. data with ab initio theory to explore the optical properties of diamondoid thiols and their dependence on size and shape. Agreement between theor. and exptl. obtained absorption spectra allows the identification of the nature of the optical transitions that are responsible for some photophys. and photochem. processes. The optical properties of diamondoid thiols in the deep UV regime depend on the functionalization site but are largely size independent. Findings provide an explanation for the disappearance of diamondoid UV photoluminescence upon thiolation for smaller diamondoids. However, theor. results indicate that for larger diamondoid thiols beyond the crit. size of 6 diamondoid cages the lowest energy transitions are characterized by diamondoidlike states suggesting that UV luminescence may be regained. (c) 2010 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Nanoscale hybrid systems are a new class of mol. aggregates that offer numerous new possibilities in materials design. Diamondoid thiols are promising nanoscale building blocks for such hybrid systems. They allow the incorporation of functional groups and the study of their effects on the unique materials' properties of diamondoids. Here the authors combine exptl. data with ab initio theory to explore the optical properties of diamondoid thiols and their dependence on size and shape. Agreement between theor. and exptl. obtained absorption spectra allows the identification of the nature of the optical transitions that are responsible for some photophys. and photochem. processes. The optical properties of diamondoid thiols in the deep UV regime depend on the functionalization site but are largely size independent. Findings provide an explanation for the disappearance of diamondoid UV photoluminescence upon thiolation for smaller diamondoids. However, theor. results indicate that for larger diamondoid thiols beyond the crit. size of 6 diamondoid cages the lowest energy transitions are characterized by diamondoidlike states suggesting that UV luminescence may be regained. (c) 2010 American Institute of Physics. [on SciFinder(R)] |
| 61. | Noessler, Melanie; Mitric, Roland; Bonacic-Koutecky, Vlasta; Johnson, Grant E; Tyo, Eric C; Castleman Jr., Welford A Generation of Oxygen Radical Centers in Binary Neutral Metal Oxide Clusters for Catalytic Oxidation Reactions. Journal Article Angewandte Chemie, International Edition, 49 (2), pp. 407–410, S407/1–S407/2, 2010, ISSN: 1433-7851. @article{Noessler2010a, title = {Generation of Oxygen Radical Centers in Binary Neutral Metal Oxide Clusters for Catalytic Oxidation Reactions.}, author = {Melanie Noessler and Roland Mitric and Vlasta Bonacic-Koutecky and Grant E Johnson and Eric C Tyo and Welford A {Castleman Jr.}}, doi = {10.1002/anie.200905434}, issn = {1433-7851}, year = {2010}, date = {2010-01-01}, journal = {Angewandte Chemie, International Edition}, volume = {49}, number = {2}, pages = {407--410, S407/1--S407/2}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {Oxidns. of carbon monoxide and acetylene by binary neutral metal oxide clusters, ZrScO4 and ZrNbO5, were studied using the DFT method with the hybrid B3LYP functional. ZrScO4 and ZrNbO5, contg. a radical oxygen center, are isoelectronic with previously studied Zr2O4+ and Zr2O5-, resp. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Oxidns. of carbon monoxide and acetylene by binary neutral metal oxide clusters, ZrScO4 and ZrNbO5, were studied using the DFT method with the hybrid B3LYP functional. ZrScO4 and ZrNbO5, contg. a radical oxygen center, are isoelectronic with previously studied Zr2O4+ and Zr2O5-, resp. [on SciFinder(R)] |
2009 |
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| 60. | Antoine, Rodolphe; Bertorelle, Franck; Broyer, Michel; Compagnon, Isabelle; Dugourd, Philippe; Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Gas-Phase Synthesis and Intense Visible Absorption of Tryptophan-Gold Cations. Journal Article Angewandte Chemie, International Edition, 48 (42), pp. 7829–7832, S7829/1–S7829/5, 2009, ISSN: 1433-7851. @article{Antoine2009, title = {Gas-Phase Synthesis and Intense Visible Absorption of Tryptophan-Gold Cations.}, author = {Rodolphe Antoine and Franck Bertorelle and Michel Broyer and Isabelle Compagnon and Philippe Dugourd and Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1002/anie.200902882}, issn = {1433-7851}, year = {2009}, date = {2009-01-01}, journal = {Angewandte Chemie, International Edition}, volume = {48}, number = {42}, pages = {7829--7832, S7829/1--S7829/5}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {Electrospray of a precursor soln. consisting of tryptophan, hydrogen tetrachloroaurarte and ascorbic acid led to [(Trp)2Au]+ complex cations which, upon collisional fragmentation, afforded [TrpAu]+. MS3 CAD or laser irradn. of the latter resulted in loss of AuH. Theor. calcns. revealed that the lower energy isomer of [TrpAu]+ exhibited amino and indole ring coordination and according to MD simulations, loss of AuH was obsd. in 6/20 trajectories at 1700-2500 K over a time scale of approx. 1.3 ps. The exptl. photodissocn. spectrum of [TrpAu]+ with its intense band around 400 nm was in full agreement with the theor. absorption spectrum in which the 400 nm band was identified as a HOMO-LUMO excitation dominated by CT excitation from indole $pi$ to Au s orbitals. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrospray of a precursor soln. consisting of tryptophan, hydrogen tetrachloroaurarte and ascorbic acid led to [(Trp)2Au]+ complex cations which, upon collisional fragmentation, afforded [TrpAu]+. MS3 CAD or laser irradn. of the latter resulted in loss of AuH. Theor. calcns. revealed that the lower energy isomer of [TrpAu]+ exhibited amino and indole ring coordination and according to MD simulations, loss of AuH was obsd. in 6/20 trajectories at 1700-2500 K over a time scale of approx. 1.3 ps. The exptl. photodissocn. spectrum of [TrpAu]+ with its intense band around 400 nm was in full agreement with the theor. absorption spectrum in which the 400 nm band was identified as a HOMO-LUMO excitation dominated by CT excitation from indole $pi$ to Au s orbitals. [on SciFinder(R)] |
| 59. | Mitric, Roland; Werner, Ute; Wohlgemuth, Matthias; Seifert, Gotthard; Bonacic-Koutecky, Vlasta. Nonadiabatic Dynamics within Time-Dependent Density Functional Tight Binding Method. Journal Article Journal of Physical Chemistry A, 113 (45), pp. 12700–12705, 2009, ISSN: 1089-5639. @article{Mitric2009, title = {Nonadiabatic Dynamics within Time-Dependent Density Functional Tight Binding Method.}, author = {Roland Mitric and Ute Werner and Matthias Wohlgemuth and Gotthard Seifert and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp905600w}, issn = {1089-5639}, year = {2009}, date = {2009-01-01}, journal = {Journal of Physical Chemistry A}, volume = {113}, number = {45}, pages = {12700--12705}, publisher = {American Chemical Society}, abstract = {A nonadiabatic mol. dynamics is implemented in the framework of the time-dependent d. functional tight binding method (TDDFTB) combined with Tully's stochastic surface hopping algorithm. The applicability of our method to complex mol. systems is illustrated on the example of the ultrafast excited state dynamics of microsolvated adenine. Our results demonstrate that in the presence of water, upon initial excitation to the S3 ($pi$-$pi$*) state at 260 nm, an ultrafast relaxation to the S1 state with a time const. of 16 fs is induced, followed by the radiationless decay to the ground state with a time const. of 200 fs. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A nonadiabatic mol. dynamics is implemented in the framework of the time-dependent d. functional tight binding method (TDDFTB) combined with Tully's stochastic surface hopping algorithm. The applicability of our method to complex mol. systems is illustrated on the example of the ultrafast excited state dynamics of microsolvated adenine. Our results demonstrate that in the presence of water, upon initial excitation to the S3 ($pi$-$pi$*) state at 260 nm, an ultrafast relaxation to the S1 state with a time const. of 16 fs is induced, followed by the radiationless decay to the ground state with a time const. of 200 fs. [on SciFinder(R)] |
| 58. | Joly, Laure; Antoine, Rodolphe; Albrieux, Florian; Ballivian, Renaud; Broyer, Michel; Chirot, Fabien; Lemoine, Jerome; Dugourd, Philippe; Greco, Claudio; Mitric, Roland; Bonacic-Koutecky, Vlasta. Optical and Structural Properties of Copper-Oxytocin Dications in the Gas Phase. Journal Article Journal of Physical Chemistry B, 113 (32), pp. 11293–11300, 2009, ISSN: 1520-6106. @article{Joly2009, title = {Optical and Structural Properties of Copper-Oxytocin Dications in the Gas Phase.}, author = {Laure Joly and Rodolphe Antoine and Florian Albrieux and Renaud Ballivian and Michel Broyer and Fabien Chirot and Jerome Lemoine and Philippe Dugourd and Claudio Greco and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp9037478}, issn = {1520-6106}, year = {2009}, date = {2009-01-01}, journal = {Journal of Physical Chemistry B}, volume = {113}, number = {32}, pages = {11293--11300}, publisher = {American Chemical Society}, abstract = {The authors present a joint exptl. and theor. study of the structural and optical properties of copper-oxytocin dications in the gas phase. Ion mobility and UV photodissocn. expts. were performed, allowing the study of the influence of the Cu2+ ion on the structural and optical properties of oxytocin. D. functional theory calcns. were performed to find low energy structures for the bare and complexed peptide and to characterize optical spectral features. Copper complexation induces a drastic change in the structure of the oxytocin peptide. In particular, the authors predict a 4N chelation of the copper cation which leads to a contraction of the oxytocin ring. The gas phase lowest-energy structures are compared with the x-ray crystal structure of the oxytocin mol. bound to its receptor protein. The optical spectrum of oxytocin complexed with the copper cation displays a global enhancement of the photofragmentation yield as compared to the one recorded for the doubly protonated oxytocin. Also, exptl. and calcd. optical spectra of protonated tyrosine also were detd., since its leading features are present in oxytocin as well. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a joint exptl. and theor. study of the structural and optical properties of copper-oxytocin dications in the gas phase. Ion mobility and UV photodissocn. expts. were performed, allowing the study of the influence of the Cu2+ ion on the structural and optical properties of oxytocin. D. functional theory calcns. were performed to find low energy structures for the bare and complexed peptide and to characterize optical spectral features. Copper complexation induces a drastic change in the structure of the oxytocin peptide. In particular, the authors predict a 4N chelation of the copper cation which leads to a contraction of the oxytocin ring. The gas phase lowest-energy structures are compared with the x-ray crystal structure of the oxytocin mol. bound to its receptor protein. The optical spectrum of oxytocin complexed with the copper cation displays a global enhancement of the photofragmentation yield as compared to the one recorded for the doubly protonated oxytocin. Also, exptl. and calcd. optical spectra of protonated tyrosine also were detd., since its leading features are present in oxytocin as well. [on SciFinder(R)] |
| 57. | Mitric, Roland; Petersen, Jens; Bonacic-Koutecky, Vlasta. Laser-field-induced surface-hopping method for the simulation and control of ultrafast photodynamics. Journal Article Physical Review A: Atomic, Molecular, and Optical Physics, 79 (5, Pt. A), pp. 053416/1–053416/6, 2009, ISSN: 1050-2947. @article{Mitric2009a, title = {Laser-field-induced surface-hopping method for the simulation and control of ultrafast photodynamics.}, author = {Roland Mitric and Jens Petersen and Vlasta. Bonacic-Koutecky}, doi = {10.1103/PhysRevA.79.053416}, issn = {1050-2947}, year = {2009}, date = {2009-01-01}, journal = {Physical Review A: Atomic, Molecular, and Optical Physics}, volume = {79}, number = {5, Pt. A}, pages = {053416/1--053416/6}, publisher = {American Physical Society}, abstract = {The authors present the semiclassical laser-field-induced surface-hopping method for the simulation and control of coupled electron-nuclear dynamics in complex mol. systems including all degrees of freedom. The authors approach is based on the Wigner representation of quantum mechanics. The combination of the mol. dynamics "on the fly" employing quantum initial conditions with the surface-hopping procedure allows for the treatment of the electronic transitions induced by the laser field. The authors semiclassical approach reproduced accurately exact quantum dynamics in a two-electronic-state model system. The authors demonstrate the scope of their method on the example of the optimal pump-dump control of the trans-cis isomerization of a prototypical Schiff base mol. switch. The authors results show that selective photochem. can be achieved by shaped laser pulses which open new dynamical pathways by suppressing the isomerization through the conical intersections between electronic states. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present the semiclassical laser-field-induced surface-hopping method for the simulation and control of coupled electron-nuclear dynamics in complex mol. systems including all degrees of freedom. The authors approach is based on the Wigner representation of quantum mechanics. The combination of the mol. dynamics "on the fly" employing quantum initial conditions with the surface-hopping procedure allows for the treatment of the electronic transitions induced by the laser field. The authors semiclassical approach reproduced accurately exact quantum dynamics in a two-electronic-state model system. The authors demonstrate the scope of their method on the example of the optimal pump-dump control of the trans-cis isomerization of a prototypical Schiff base mol. switch. The authors results show that selective photochem. can be achieved by shaped laser pulses which open new dynamical pathways by suppressing the isomerization through the conical intersections between electronic states. [on SciFinder(R)] |
| 56. | Johnson, Grant E; Mitric, Roland; Bonacic-Koutecky, Vlasta; Castleman, A W Clusters as model systems for investigating nanoscale oxidation catalysis. Journal Article Chemical Physics Letters, 475 (1-3), pp. 1–9, 2009, ISSN: 0009-2614. @article{Johnson2009, title = {Clusters as model systems for investigating nanoscale oxidation catalysis.}, author = {Grant E Johnson and Roland Mitric and Vlasta Bonacic-Koutecky and A W Castleman}, doi = {10.1016/j.cplett.2009.04.003}, issn = {0009-2614}, year = {2009}, date = {2009-01-01}, journal = {Chemical Physics Letters}, volume = {475}, number = {1-3}, pages = {1--9}, publisher = {Elsevier B.V.}, abstract = {A review; gas-phase cluster reactivity expts., combined with theor. calcns., provide insight into how factors such as size, stoichiometry and charging effects influence reactions promoted by metal and metal oxide catalysts. In this Letter, we describe the use of clusters to investigate the role of different types of oxygen centers in catalytic oxidn. reactions. First, we focus on recent results from our lab. concerning the oxidn. of carbon monoxide by gold clusters and how the charge state of the cluster dets. the mechanism of oxidn. We then discuss how radical oxygen centers in zirconium oxide clusters promote the oxidn. of carbon monoxide, ethylene and acetylene and how charge state may be used to tune the selectivity of these reactions. An overview of future directions for the research is given in conclusion. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A review; gas-phase cluster reactivity expts., combined with theor. calcns., provide insight into how factors such as size, stoichiometry and charging effects influence reactions promoted by metal and metal oxide catalysts. In this Letter, we describe the use of clusters to investigate the role of different types of oxygen centers in catalytic oxidn. reactions. First, we focus on recent results from our lab. concerning the oxidn. of carbon monoxide by gold clusters and how the charge state of the cluster dets. the mechanism of oxidn. We then discuss how radical oxygen centers in zirconium oxide clusters promote the oxidn. of carbon monoxide, ethylene and acetylene and how charge state may be used to tune the selectivity of these reactions. An overview of future directions for the research is given in conclusion. [on SciFinder(R)] |
| 55. | Kulesza, A; Mitric, R; Bonacic-Koutecky, V Silver cluster induced absorption enhancement and conformation control of peptides. Journal Article European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, 52 (1-3), pp. 203–206, 2009, ISSN: 1434-6060. @article{Kulesza2009, title = {Silver cluster induced absorption enhancement and conformation control of peptides.}, author = {A Kulesza and R Mitric and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2009-00056-2}, issn = {1434-6060}, year = {2009}, date = {2009-01-01}, journal = {European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics}, volume = {52}, number = {1-3}, pages = {203--206}, publisher = {EDP Sciences}, abstract = {We present a theor. study of the structural and optical properties of isolated silver clustertripeptide hybrid systems. We show that small silver clusters induce enhancement of the optical absorption of peptides. Moreover, silver clusters bound to peptides can reduce the conformational flexibility and invoke changes of the secondary structure. Thus, they might serve as local optical probes in biolabelling applications. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a theor. study of the structural and optical properties of isolated silver clustertripeptide hybrid systems. We show that small silver clusters induce enhancement of the optical absorption of peptides. Moreover, silver clusters bound to peptides can reduce the conformational flexibility and invoke changes of the secondary structure. Thus, they might serve as local optical probes in biolabelling applications. [on SciFinder(R)] |
| 54. | Johnson, Grant E; Mitric, Roland; Noessler, Melanie; Tyo, Eric C; Bonacic-Koutecky, Vlasta; Castleman Jr., A W Influence of Charge State on Catalytic Oxidation Reactions at Metal Oxide Clusters Containing Radical Oxygen Centers. Journal Article Journal of the American Chemical Society, 131 (15), pp. 5460–5470, 2009, ISSN: 0002-7863. @article{Johnson2009a, title = {Influence of Charge State on Catalytic Oxidation Reactions at Metal Oxide Clusters Containing Radical Oxygen Centers.}, author = {Grant E Johnson and Roland Mitric and Melanie Noessler and Eric C Tyo and Vlasta Bonacic-Koutecky and A W {Castleman Jr.}}, doi = {10.1021/ja807499z}, issn = {0002-7863}, year = {2009}, date = {2009-01-01}, journal = {Journal of the American Chemical Society}, volume = {131}, number = {15}, pages = {5460--5470}, publisher = {American Chemical Society}, abstract = {Evidence obtained by guided-ion-beam mass spectrometry expts. and d. functional theory calcns. indicates that by adding one oxygen atom with a full octet of valence electrons (O2-) to stoichiometric cationic zirconium oxide clusters (ZrO2)x+ (x = 1-4), a series of anionic clusters (ZrxO2x+1)- (x = 1-4) are formed which contain radical oxygen centers with elongated (elongation ≈ 0.24 ± 0.02 AA) metal-oxygen bonds. These anionic clusters oxidize carbon monoxide, strongly assoc. acetylene, and weakly assoc. ethylene, in contrast to the cationic species which were found previously to be highly active toward the oxidn. of all three mols. Theor. investigations indicate that a crit. hydrogen transfer step necessary for the oxidn. of ethylene and acetylene at metal oxide clusters contg. radical oxygen centers is energetically favorable for cationic clusters but unfavorable for the corresponding anionic species. The calcd. electrostatic potential of the cluster reveals that in the case of cations, a favorable interaction with nucleophilic mols. takes place over the whole surface of the (ZrO2)x+ (x = 1-4) clusters, compared to a restricted interaction of ethylene and acetylene with the less coordinated zirconium atom in the case of the anionic (ZrxO2x+1)- (x = 1-4) species. Therefore, in spite of the common presence of a radical oxygen center in specific anionic and cationic stoichiometries, the extent to which various classes of reactions are promoted is influenced by charge state. Moreover, the (ZrxO2x+1)- (x = 1-4) series of anionic clusters may be regenerated by reacting oxygen deficient clusters with a strong oxidizer. This indicates that not only cationic species, as shown previously, but also anionic clusters may promote multiple cycles of carbon monoxide oxidn. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Evidence obtained by guided-ion-beam mass spectrometry expts. and d. functional theory calcns. indicates that by adding one oxygen atom with a full octet of valence electrons (O2-) to stoichiometric cationic zirconium oxide clusters (ZrO2)x+ (x = 1-4), a series of anionic clusters (ZrxO2x+1)- (x = 1-4) are formed which contain radical oxygen centers with elongated (elongation ≈ 0.24 ± 0.02 AA) metal-oxygen bonds. These anionic clusters oxidize carbon monoxide, strongly assoc. acetylene, and weakly assoc. ethylene, in contrast to the cationic species which were found previously to be highly active toward the oxidn. of all three mols. Theor. investigations indicate that a crit. hydrogen transfer step necessary for the oxidn. of ethylene and acetylene at metal oxide clusters contg. radical oxygen centers is energetically favorable for cationic clusters but unfavorable for the corresponding anionic species. The calcd. electrostatic potential of the cluster reveals that in the case of cations, a favorable interaction with nucleophilic mols. takes place over the whole surface of the (ZrO2)x+ (x = 1-4) clusters, compared to a restricted interaction of ethylene and acetylene with the less coordinated zirconium atom in the case of the anionic (ZrxO2x+1)- (x = 1-4) species. Therefore, in spite of the common presence of a radical oxygen center in specific anionic and cationic stoichiometries, the extent to which various classes of reactions are promoted is influenced by charge state. Moreover, the (ZrxO2x+1)- (x = 1-4) series of anionic clusters may be regenerated by reacting oxygen deficient clusters with a strong oxidizer. This indicates that not only cationic species, as shown previously, but also anionic clusters may promote multiple cycles of carbon monoxide oxidn. [on SciFinder(R)] |
| 53. | Kulesza, Alexander; Mitric, Roland; Bonacic-Koutecky, Vlasta. Silver Cluster Chromophores for Absorption Enhancement of Peptides. Journal Article Journal of Physical Chemistry A, 113 (16), pp. 3783–3788, 2009, ISSN: 1089-5639. @article{Kulesza2009a, title = {Silver Cluster Chromophores for Absorption Enhancement of Peptides.}, author = {Alexander Kulesza and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp809118q}, issn = {1089-5639}, year = {2009}, date = {2009-01-01}, journal = {Journal of Physical Chemistry A}, volume = {113}, number = {16}, pages = {3783--3788}, publisher = {American Chemical Society}, abstract = {The authors present a theor. study of the structural and optical properties of tripeptide-silver cluster hybrid systems which shows that silver clusters induce significant absorption enhancement in the spectral region between 225 and 350 nm with respect to the pure peptide. This allows the use of clusters as chromophores for absorption enhancement of peptides and proteins and offers a potential for different applications in biosensing. Furthermore, the authors demonstrate that cluster binding can change the conformational preference for the secondary structure type leading possibly to new functional properties. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a theor. study of the structural and optical properties of tripeptide-silver cluster hybrid systems which shows that silver clusters induce significant absorption enhancement in the spectral region between 225 and 350 nm with respect to the pure peptide. This allows the use of clusters as chromophores for absorption enhancement of peptides and proteins and offers a potential for different applications in biosensing. Furthermore, the authors demonstrate that cluster binding can change the conformational preference for the secondary structure type leading possibly to new functional properties. [on SciFinder(R)] |
2008 |
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| 52. | Tabarin, Thibault; Kulesza, Alexander; Antoine, Rodolphe; Mitric, Roland; Broyer, Michel; Dugourd, Philippe; Bonacic-Koutecky, Vlasta. Absorption Enhancement and Conformational Control of Peptides by Small Silver Clusters. Journal Article Physical Review Letters, 101 (21), pp. 213001/1–213001/4, 2008, ISSN: 0031-9007. @article{Tabarin2008, title = {Absorption Enhancement and Conformational Control of Peptides by Small Silver Clusters.}, author = {Thibault Tabarin and Alexander Kulesza and Rodolphe Antoine and Roland Mitric and Michel Broyer and Philippe Dugourd and Vlasta. Bonacic-Koutecky}, doi = {10.1103/PhysRevLett.101.213001}, issn = {0031-9007}, year = {2008}, date = {2008-01-01}, journal = {Physical Review Letters}, volume = {101}, number = {21}, pages = {213001/1--213001/4}, publisher = {American Physical Society}, abstract = {We explored exptl. and theor. the optical properties of isolated silver trimer-dipeptide bioconjugates. The metallic moiety induces a strong enhancement of the optical absorption of the peptide. We also show that its binding to a peptide can reduce the conformational flexibility and induce transitions between secondary structures. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We explored exptl. and theor. the optical properties of isolated silver trimer-dipeptide bioconjugates. The metallic moiety induces a strong enhancement of the optical absorption of the peptide. We also show that its binding to a peptide can reduce the conformational flexibility and induce transitions between secondary structures. [on SciFinder(R)] |
| 51. | Mitric, Roland; Werner, Ute; Bonacic-Koutecky, Vlasta. Journal of Chemical Physics, 129 (16), pp. 164118/1–164118/9, 2008, ISSN: 0021-9606. @article{Mitric2008, title = {Nonadiabatic dynamics and simulation of time resolved photoelectron spectra within time-dependent density functional theory: Ultrafast photoswitching in benzylideneaniline.}, author = {Roland Mitric and Ute Werner and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.3000012}, issn = {0021-9606}, year = {2008}, date = {2008-01-01}, journal = {Journal of Chemical Physics}, volume = {129}, number = {16}, pages = {164118/1--164118/9}, publisher = {American Institute of Physics}, abstract = {The authors present a theor. approach for the nonadiabatic dynamics "on the fly" based on the combination of the time-dependent d. functional theory (TDDFT) with Tully's stochastic surface hopping method. The formulation is based on localized Gaussian basis sets and is suitable for the simulation of ultrafast processes in complex mol. systems including all degrees of freedom. The authors approach is used for the simulation of time resolved photoelectron spectra in the framework of the Wigner distribution approach. In order to illustrate the scope of the method, the authors study the ultrafast photoswitching dynamics of the prototype Schiff base benzylideneaniline (BAN). The nonradiative lifetime of the S1 state of BAN is detd. to be ∼200 fs. The mechanism of the photoisomerization has been investigated and a connection between the time resolved photoelectron signal and the underlying nonadiabatic processes has been established. (c) 2008 American Institute of Physics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a theor. approach for the nonadiabatic dynamics "on the fly" based on the combination of the time-dependent d. functional theory (TDDFT) with Tully's stochastic surface hopping method. The formulation is based on localized Gaussian basis sets and is suitable for the simulation of ultrafast processes in complex mol. systems including all degrees of freedom. The authors approach is used for the simulation of time resolved photoelectron spectra in the framework of the Wigner distribution approach. In order to illustrate the scope of the method, the authors study the ultrafast photoswitching dynamics of the prototype Schiff base benzylideneaniline (BAN). The nonradiative lifetime of the S1 state of BAN is detd. to be ∼200 fs. The mechanism of the photoisomerization has been investigated and a connection between the time resolved photoelectron signal and the underlying nonadiabatic processes has been established. (c) 2008 American Institute of Physics. [on SciFinder(R)] |
| 50. | Johnson, Grant E; Mitric, Roland; Tyo, Eric C; Bonacic-Koutecky, Vlasta; Castleman, A W Stoichiometric Zirconium Oxide Cations as Potential Building Blocks for Cluster Assembled Catalysts. Journal Article Journal of the American Chemical Society, 130 (42), pp. 13912–13920, 2008, ISSN: 0002-7863. @article{Johnson2008, title = {Stoichiometric Zirconium Oxide Cations as Potential Building Blocks for Cluster Assembled Catalysts.}, author = {Grant E Johnson and Roland Mitric and Eric C Tyo and Vlasta Bonacic-Koutecky and A W Castleman}, doi = {10.1021/ja803246n}, issn = {0002-7863}, year = {2008}, date = {2008-01-01}, journal = {Journal of the American Chemical Society}, volume = {130}, number = {42}, pages = {13912--13920}, publisher = {American Chemical Society}, abstract = {Employing guided-ion-beam mass spectrometry, we identified a series of pos. charged stoichiometric zirconium oxide clusters that exhibit enhanced activity and selectivity for three oxidn. reactions of widespread chem. importance. D. functional theory calcns. reveal that these clusters all contain the same active site consisting of a radical oxygen center with an elongated zirconium-oxygen bond. Calcd. energy profiles demonstrate that each oxidn. reaction is highly favorable energetically and involves easily surmountable barriers. Furthermore, the active stoichiometric clusters may be regenerated by reacting oxygen-deficient clusters with a strong oxidizer. This indicates that these species may promote multiple cycles of oxidn. reactions and, therefore, exhibit true catalytic behavior. The stoichiometric clusters, having structures that resemble specific sites in bulk zirconia, are promising candidates for potential incorporation into a cluster assembled catalyst material. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Employing guided-ion-beam mass spectrometry, we identified a series of pos. charged stoichiometric zirconium oxide clusters that exhibit enhanced activity and selectivity for three oxidn. reactions of widespread chem. importance. D. functional theory calcns. reveal that these clusters all contain the same active site consisting of a radical oxygen center with an elongated zirconium-oxygen bond. Calcd. energy profiles demonstrate that each oxidn. reaction is highly favorable energetically and involves easily surmountable barriers. Furthermore, the active stoichiometric clusters may be regenerated by reacting oxygen-deficient clusters with a strong oxidizer. This indicates that these species may promote multiple cycles of oxidn. reactions and, therefore, exhibit true catalytic behavior. The stoichiometric clusters, having structures that resemble specific sites in bulk zirconia, are promising candidates for potential incorporation into a cluster assembled catalyst material. [on SciFinder(R)] |
| 49. | Bruschi, Maurizio; De Gioia, Luca ; Mitric, Roland; Bonacic-Koutecky, Vlasta; Fantucci, Piercarlo. A DFT study of EPR parameters in Cu(II) complexes of the octarepeat region of the prion protein. Journal Article Physical Chemistry Chemical Physics, 10 (31), pp. 4573–4583, 2008, ISSN: 1463-9076. @article{Bruschi2008, title = {A DFT study of EPR parameters in Cu(II) complexes of the octarepeat region of the prion protein.}, author = {Maurizio Bruschi and Luca {De Gioia} and Roland Mitric and Vlasta Bonacic-Koutecky and Piercarlo. Fantucci}, doi = {10.1039/b718603g}, issn = {1463-9076}, year = {2008}, date = {2008-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {10}, number = {31}, pages = {4573--4583}, publisher = {Royal Society of Chemistry}, abstract = {The present paper shows how theor. detd. ESR parameters can help in assigning the most favorable structure of Cu(II) complexes in octarepeat (OR) regions (PHGGGWGQ) of the prion protein (PrP). This could contribute to a better understanding of the mol. structure of the Cu(OR) complexes, as some features of such species in soln. are still unclear. The present theor. investigation on [Cu(II)(HGGG)] and [Cu(II)(HGGGW)] complexes was carried out to confirm the stability of relevant isomers, and in particular, to evaluate the hyperfine coupling consts. (hcc) with 63Cu, 14N and 17O nuclei, as well as the g values. The hcc (and to a lesser extent the g components) are useful probes for checking whether the computed EPR parameters for specific isomers fit the exptl. data, thus permitting the assocn. of the obsd. spectra with a specific complex structure. The results obtained suggest that the Cu(II) ion in the [Cu(HGGG)] isomers prefers a square pyramidal coordination with three nitrogen atoms of the peptide and one carbonyl oxygen atom in the basal plane. Also the Cu(II) ion in the [Cu(HGGGW)] complex is penta-coordinated. The penta-coordination does not actually involve the tryptophan residue but an addnl. water mol., forced to occupy the axial coordination position by a rather extended hydrogen-bond network, promoted by the tryptophan residue. The comparison between the calcd. and exptl. values of EPR parameters allows one to suggest the assignment of the coordination mode of the Cu(II) ion in the considered peptide ligands. The computed values of the g components seem to be little affected by a particular coordination mode. In particular, the g‖ component is always underestimated by about 0.1 with respect to the expt. The calcd. values of the hcc, in contrast, are in acceptable agreement with the exptl. values, in spite of the fact that the large size of the species under consideration forced us to accept a certain level of approxn. in the computational procedure. Nevertheless, the present study must be considered as one of the first examples of truly ab initio calcns. of EPR parameters for systems as large as the Cu(OR)-type complexes. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present paper shows how theor. detd. ESR parameters can help in assigning the most favorable structure of Cu(II) complexes in octarepeat (OR) regions (PHGGGWGQ) of the prion protein (PrP). This could contribute to a better understanding of the mol. structure of the Cu(OR) complexes, as some features of such species in soln. are still unclear. The present theor. investigation on [Cu(II)(HGGG)] and [Cu(II)(HGGGW)] complexes was carried out to confirm the stability of relevant isomers, and in particular, to evaluate the hyperfine coupling consts. (hcc) with 63Cu, 14N and 17O nuclei, as well as the g values. The hcc (and to a lesser extent the g components) are useful probes for checking whether the computed EPR parameters for specific isomers fit the exptl. data, thus permitting the assocn. of the obsd. spectra with a specific complex structure. The results obtained suggest that the Cu(II) ion in the [Cu(HGGG)] isomers prefers a square pyramidal coordination with three nitrogen atoms of the peptide and one carbonyl oxygen atom in the basal plane. Also the Cu(II) ion in the [Cu(HGGGW)] complex is penta-coordinated. The penta-coordination does not actually involve the tryptophan residue but an addnl. water mol., forced to occupy the axial coordination position by a rather extended hydrogen-bond network, promoted by the tryptophan residue. The comparison between the calcd. and exptl. values of EPR parameters allows one to suggest the assignment of the coordination mode of the Cu(II) ion in the considered peptide ligands. The computed values of the g components seem to be little affected by a particular coordination mode. In particular, the g‖ component is always underestimated by about 0.1 with respect to the expt. The calcd. values of the hcc, in contrast, are in acceptable agreement with the exptl. values, in spite of the fact that the large size of the species under consideration forced us to accept a certain level of approxn. in the computational procedure. Nevertheless, the present study must be considered as one of the first examples of truly ab initio calcns. of EPR parameters for systems as large as the Cu(OR)-type complexes. [on SciFinder(R)] |
| 48. | Werner, Ute; Mitric, Roland; Suzuki, Toshinori; Bonacic-Koutecky, Vlasta. Nonadiabatic dynamics within the time dependent density functional theory: Ultrafast photodynamics in pyrazine. Journal Article Chemical Physics, 349 (1-3), pp. 319–324, 2008, ISSN: 0301-0104. @article{Werner2008, title = {Nonadiabatic dynamics within the time dependent density functional theory: Ultrafast photodynamics in pyrazine.}, author = {Ute Werner and Roland Mitric and Toshinori Suzuki and Vlasta. Bonacic-Koutecky}, doi = {10.1016/j.chemphys.2008.02.061}, issn = {0301-0104}, year = {2008}, date = {2008-01-01}, journal = {Chemical Physics}, volume = {349}, number = {1-3}, pages = {319--324}, publisher = {Elsevier B.V.}, abstract = {We present a formulation of nonadiabatic dynamics "on the fly" combining time-dependent d. functional theory using localized Gaussian basis sets with Tully's stochastic fewest switches surface hopping procedure. The aim is to provide a suitable approach for studying ultrafast photoinduced dynamics over a manifold of excited states in complex systems based on semiclassical dynamics, which takes into account all nuclear degrees of freedom. The reliability of the approach has been illustrated on the example of photodynamics in pyrazine by carrying out nonadiabatic dynamics over four excited electronic states. The calcd. nonradiative lifetime of the optically allowed S 2 state of 20 fs is in a good agreement with the results obtained from full quantum dynamical treatment and with available exptl. data. Our simulated time-resolved photoelectron spectrum of pyrazine represents the observable which can be exptl. measured providing the time scales of nonadiabatic processes. Therefore, the presented theor. results should stimulate the exptl. work in the future. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a formulation of nonadiabatic dynamics "on the fly" combining time-dependent d. functional theory using localized Gaussian basis sets with Tully's stochastic fewest switches surface hopping procedure. The aim is to provide a suitable approach for studying ultrafast photoinduced dynamics over a manifold of excited states in complex systems based on semiclassical dynamics, which takes into account all nuclear degrees of freedom. The reliability of the approach has been illustrated on the example of photodynamics in pyrazine by carrying out nonadiabatic dynamics over four excited electronic states. The calcd. nonradiative lifetime of the optically allowed S 2 state of 20 fs is in a good agreement with the results obtained from full quantum dynamical treatment and with available exptl. data. Our simulated time-resolved photoelectron spectrum of pyrazine represents the observable which can be exptl. measured providing the time scales of nonadiabatic processes. Therefore, the presented theor. results should stimulate the exptl. work in the future. [on SciFinder(R)] |
| 47. | Bonacic-Koutecky, Vlasta; Mitric, Roland; Buergel, Christian; Noessler, Melanie. Ultrafast dynamics in noble metal clusters: The role of internal vibrational redistribution. Journal Article Chemical Physics, 350 (1-3), pp. 111–117, 2008, ISSN: 0301-0104. @article{Bonacic-Koutecky2008, title = {Ultrafast dynamics in noble metal clusters: The role of internal vibrational redistribution.}, author = {Vlasta Bonacic-Koutecky and Roland Mitric and Christian Buergel and Melanie. Noessler}, doi = {10.1016/j.chemphys.2008.01.009}, issn = {0301-0104}, year = {2008}, date = {2008-01-01}, journal = {Chemical Physics}, volume = {350}, number = {1-3}, pages = {111--117}, publisher = {Elsevier B.V.}, abstract = {We present a theor. study of the ultrafast dynamics in noble metal clusters interacting with mol. oxygen which is of fundamental importance for the understanding and design of cluster-based heterogeneous nanocatalysts. We demonstrate that intrinsic dynamical properties can significantly promote the reactivity of small noble metal clusters towards O2. This concept is illustrated by performing collision simulations between Ag6(1-) and Au6(1-) clusters and O2 in the framework of the ab initio mol. dynamics (MD) using d. functional theory (DFT). We show that different nature and efficiency of the internal vibrational energy redistribution (IVR) during the collisions with O2 are responsible for considerably different sticking probabilities of O2 to silver and gold clusters, resp. In the case of Au6(1-) + O2 , resonant IVR between the cluster and the O2 subunit activates the O-O bond and promotes the subsequent oxidn. reaction. In contrast, in the case of Ag6(1-) + O2 fast dissipative IVR on the time scale of ∼1 ps leads to a higher sticking probability for O2 but the O-O bond is very rapidly deactivated and cannot participate in further oxidn. processes. These findings allow us to introduce the nature of IVR as a criterion for promoting the reactivity of noble metal clusters. Such different behavior of silver and gold clusters colliding with O2 originates from difference in relativistic effects which are considerably more pronounced in the case of gold clusters causing more directional rigid bonding in contrast to silver clusters with more s-metallic floppy character. Moreover, we demonstrate that breaking of O-O bond can be induced in Au6O2(1-) by a selective excitation of the O-O bond with an ultrashort pulse in the IR spectral range. This opens the perspective to control the action of nanocatalysts by employing shaped laser pulses and thus bridges the fields of femtochem. and cluster nanocatalysis. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a theor. study of the ultrafast dynamics in noble metal clusters interacting with mol. oxygen which is of fundamental importance for the understanding and design of cluster-based heterogeneous nanocatalysts. We demonstrate that intrinsic dynamical properties can significantly promote the reactivity of small noble metal clusters towards O2. This concept is illustrated by performing collision simulations between Ag6(1-) and Au6(1-) clusters and O2 in the framework of the ab initio mol. dynamics (MD) using d. functional theory (DFT). We show that different nature and efficiency of the internal vibrational energy redistribution (IVR) during the collisions with O2 are responsible for considerably different sticking probabilities of O2 to silver and gold clusters, resp. In the case of Au6(1-) + O2 , resonant IVR between the cluster and the O2 subunit activates the O-O bond and promotes the subsequent oxidn. reaction. In contrast, in the case of Ag6(1-) + O2 fast dissipative IVR on the time scale of ∼1 ps leads to a higher sticking probability for O2 but the O-O bond is very rapidly deactivated and cannot participate in further oxidn. processes. These findings allow us to introduce the nature of IVR as a criterion for promoting the reactivity of noble metal clusters. Such different behavior of silver and gold clusters colliding with O2 originates from difference in relativistic effects which are considerably more pronounced in the case of gold clusters causing more directional rigid bonding in contrast to silver clusters with more s-metallic floppy character. Moreover, we demonstrate that breaking of O-O bond can be induced in Au6O2(1-) by a selective excitation of the O-O bond with an ultrashort pulse in the IR spectral range. This opens the perspective to control the action of nanocatalysts by employing shaped laser pulses and thus bridges the fields of femtochem. and cluster nanocatalysis. [on SciFinder(R)] |
| 46. | Mitric, Roland; Petersen, Jens; Kulesza, Alexander; Bonacic-Koutecky, Vlasta; Tabarin, Thibault; Compagnon, Isabelle; Antoine, Rodolphe; Broyer, Michel; Dugourd, Philippe. Chemical Physics, 343 (2-3), pp. 372–380, 2008, ISSN: 0301-0104. @article{Mitric2008a, title = {Absorption properties of cationic silver cluster-tryptophan complexes: A model for photoabsorption and photoemission enhancement in nanoparticle-biomolecule systems.}, author = {Roland Mitric and Jens Petersen and Alexander Kulesza and Vlasta Bonacic-Koutecky and Thibault Tabarin and Isabelle Compagnon and Rodolphe Antoine and Michel Broyer and Philippe. Dugourd}, doi = {10.1016/j.chemphys.2007.09.033}, issn = {0301-0104}, year = {2008}, date = {2008-01-01}, journal = {Chemical Physics}, volume = {343}, number = {2-3}, pages = {372--380}, publisher = {Elsevier B.V.}, abstract = {The authors present a joint theor. and exptl. study of the size and structure selective absorption properties of cationic silver cluster-tryptophan (Trp-Ag+n}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a joint theor. and exptl. study of the size and structure selective absorption properties of cationic silver cluster-tryptophan (Trp-Ag+n |
| 45. | Buergel, Christian; Reilly, Nelly M; Johnson, Grant E; Mitric, Roland; Kimble, Michele L; Castleman Jr., A W; Bonacic-Koutecky, Vlasta. Influence of Charge State on the Mechanism of CO Oxidation on Gold Clusters. Journal Article Journal of the American Chemical Society, 130 (5), pp. 1694–1698, 2008, ISSN: 0002-7863. @article{Buergel2008, title = {Influence of Charge State on the Mechanism of CO Oxidation on Gold Clusters.}, author = {Christian Buergel and Nelly M Reilly and Grant E Johnson and Roland Mitric and Michele L Kimble and A W {Castleman Jr.} and Vlasta. Bonacic-Koutecky}, doi = {10.1021/ja0768542}, issn = {0002-7863}, year = {2008}, date = {2008-01-01}, journal = {Journal of the American Chemical Society}, volume = {130}, number = {5}, pages = {1694--1698}, publisher = {American Chemical Society}, abstract = {We present results from our joint exptl. and theor. study of the reactivity of anionic and cationic gold oxide clusters toward CO, focusing on the role of at. oxygen, different charge states, and mechanisms for oxidn. We show that anionic clusters react by an Eley-Rideal-like mechanism involving the preferential attack of CO on oxygen rather than gold. In contrast, the oxidn. of CO on cationic gold oxide clusters can occur by both an Eley-Rideal-like and a Langmuir-Hinshelwood-like mechanism at multiple collision conditions as a result of the high adsorption energy of two CO mols. This large energy of CO adsorption on cationic gold oxide clusters is the driving force for the CO oxidn. Therefore, in the presence of cationic gold species at high pressures of CO, the oxidn. reaction is self-promoting (i.e., the oxidn. of one CO mol. is promoted by the binding of a second CO). Our findings provide new insight into the role of charge state in gold-cluster-based nanocatalysis. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present results from our joint exptl. and theor. study of the reactivity of anionic and cationic gold oxide clusters toward CO, focusing on the role of at. oxygen, different charge states, and mechanisms for oxidn. We show that anionic clusters react by an Eley-Rideal-like mechanism involving the preferential attack of CO on oxygen rather than gold. In contrast, the oxidn. of CO on cationic gold oxide clusters can occur by both an Eley-Rideal-like and a Langmuir-Hinshelwood-like mechanism at multiple collision conditions as a result of the high adsorption energy of two CO mols. This large energy of CO adsorption on cationic gold oxide clusters is the driving force for the CO oxidn. Therefore, in the presence of cationic gold species at high pressures of CO, the oxidn. reaction is self-promoting (i.e., the oxidn. of one CO mol. is promoted by the binding of a second CO). Our findings provide new insight into the role of charge state in gold-cluster-based nanocatalysis. [on SciFinder(R)] |
2007 |
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| 44. | Mitric, R; Werner, U; Buergel, C; Bonacic-Koutecky, V Dynamical aspects and the role of IVR for the reactivity of noble metal clusters towards molecular oxygen. Journal Article European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, 43 (1-3), pp. 201–204, 2007, ISSN: 1434-6060. @article{Mitric2007, title = {Dynamical aspects and the role of IVR for the reactivity of noble metal clusters towards molecular oxygen.}, author = {R Mitric and U Werner and C Buergel and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2007-00113-x}, issn = {1434-6060}, year = {2007}, date = {2007-01-01}, journal = {European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics}, volume = {43}, number = {1-3}, pages = {201--204}, publisher = {EDP Sciences}, abstract = {Here, we present the dynamical aspects and the role of internal energy redistribution (IVR) in the reactivity of noble metal clusters towards O2. We show on the example of Ag3O-2 / Ag3O2 / Ag3O+2 that NeNePo spectroscopy carried out under zero electron kinetic energy (ZEKE) conditions can be a powerful tool to investigate the geometry relaxation and IVR induced by photodetachment in real time. Furthermore, we demonstrate that difference in the reactivity of Ag-6 and Au-6 towards O2 can be attributed to different nature of the IVR process. Dissipative IVR in Ag-6 favors fast complex stabilization, whereas resonant IVR found for Au-6 might be an important factor detg. the catalytic activity of Au-6 cluster in the CO oxidn. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here, we present the dynamical aspects and the role of internal energy redistribution (IVR) in the reactivity of noble metal clusters towards O2. We show on the example of Ag3O-2 / Ag3O2 / Ag3O+2 that NeNePo spectroscopy carried out under zero electron kinetic energy (ZEKE) conditions can be a powerful tool to investigate the geometry relaxation and IVR induced by photodetachment in real time. Furthermore, we demonstrate that difference in the reactivity of Ag-6 and Au-6 towards O2 can be attributed to different nature of the IVR process. Dissipative IVR in Ag-6 favors fast complex stabilization, whereas resonant IVR found for Au-6 might be an important factor detg. the catalytic activity of Au-6 cluster in the CO oxidn. [on SciFinder(R)] |
| 43. | Kimble, M L; Moore, N A; Castleman Jr., A W; Buergel, C; Mitric, R; Bonacic-Koutecky, V Reactivity of anionic gold oxide clusters towards CO: experiment and theory. Journal Article European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, 43 (1-3), pp. 205–208, 2007, ISSN: 1434-6060. @article{Kimble2007, title = {Reactivity of anionic gold oxide clusters towards CO: experiment and theory.}, author = {M L Kimble and N A Moore and A W {Castleman Jr.} and C Buergel and R Mitric and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2007-00119-4}, issn = {1434-6060}, year = {2007}, date = {2007-01-01}, journal = {European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics}, volume = {43}, number = {1-3}, pages = {205--208}, publisher = {EDP Sciences}, abstract = {In this paper, we present results from our joint exptl. and theor. study of the reactivity of anionic gold oxide clusters Au2,3O-1-4 towards CO. We provide clear evidence that, although O-O bond weakening/dissocn. is important to enable CO oxidn., the presence of at. oxygen can be favorable but is not always sufficient. Furthermore, we show that with the addn. of a single gold atom the reactivity channels can be changed. As a consequence, in contrast to CO oxidn. in the case of anionic gold dimer oxides, assocn. of CO or replacement of O2 by CO become the dominant reaction channels for Au3O-n. This demonstrates the nonscalable properties of gold clusters in the size regime in which each atom counts. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, we present results from our joint exptl. and theor. study of the reactivity of anionic gold oxide clusters Au2,3O-1-4 towards CO. We provide clear evidence that, although O-O bond weakening/dissocn. is important to enable CO oxidn., the presence of at. oxygen can be favorable but is not always sufficient. Furthermore, we show that with the addn. of a single gold atom the reactivity channels can be changed. As a consequence, in contrast to CO oxidn. in the case of anionic gold dimer oxides, assocn. of CO or replacement of O2 by CO become the dominant reaction channels for Au3O-n. This demonstrates the nonscalable properties of gold clusters in the size regime in which each atom counts. [on SciFinder(R)] |
| 42. | Tabarin, T; Antoine, R; Compagnon, I; Broyer, M; Dugourd, P; Mitric, R; Petersen, J; Bonacic-Koutecky, V Optical absorption of isolated silver cluster-tryptophan: A joint experimental and theoretical study. Journal Article European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, 43 (1-3), pp. 275–278, 2007, ISSN: 1434-6060. @article{Tabarin2007, title = {Optical absorption of isolated silver cluster-tryptophan: A joint experimental and theoretical study.}, author = {T Tabarin and R Antoine and I Compagnon and M Broyer and P Dugourd and R Mitric and J Petersen and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2007-00118-5}, issn = {1434-6060}, year = {2007}, date = {2007-01-01}, journal = {European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics}, volume = {43}, number = {1-3}, pages = {275--278}, publisher = {EDP Sciences}, abstract = {The authors present a joint exptl. and theor. gas phase study of photoabsorption and photofragmentation of Ag cluster-biomol. complexes. The authors demonstrate on the example of [Trp.Ag3]+ that binding of the metal cluster to a biomol. leads to a significant enhancement of the photoabsorption in comparison with [Trp.H]+ and [Trp.Ag]+. This enhancement arises due to the coupling between the excitations in the metallic subunit with charge transfer excitations between Ag cluster and tryptophan. The authors' exptl. studies show that Ag clusters up to eleven atoms can be bound to tryptophan and the authors present 1st results on the photofragmentation of the Trp.Ag+11 complex cation, in which properties of cluster subunit remain preserved. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a joint exptl. and theor. gas phase study of photoabsorption and photofragmentation of Ag cluster-biomol. complexes. The authors demonstrate on the example of [Trp.Ag3]+ that binding of the metal cluster to a biomol. leads to a significant enhancement of the photoabsorption in comparison with [Trp.H]+ and [Trp.Ag]+. This enhancement arises due to the coupling between the excitations in the metallic subunit with charge transfer excitations between Ag cluster and tryptophan. The authors' exptl. studies show that Ag clusters up to eleven atoms can be bound to tryptophan and the authors present 1st results on the photofragmentation of the Trp.Ag+11 complex cation, in which properties of cluster subunit remain preserved. [on SciFinder(R)] |
| 41. | Gleitsmann, T; Vaida, M E; Bernhardt, T M; Bonacic-Koutecky, V; Buergel, C; Kuznetsov, A E; Mitric, R Mass-selected Ag3 clusters soft-landed onto MgO/Mo(100). Femtosecond photoemission and 1st-principles simulations. Journal Article European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, 45 (3), pp. 477–483, 2007, ISSN: 1434-6060. @article{Gleitsmann2007, title = {Mass-selected Ag3 clusters soft-landed onto MgO/Mo(100). Femtosecond photoemission and 1st-principles simulations.}, author = {T Gleitsmann and M E Vaida and T M Bernhardt and V Bonacic-Koutecky and C Buergel and A E Kuznetsov and R Mitric}, doi = {10.1140/epjd/e2007-00257-7}, issn = {1434-6060}, year = {2007}, date = {2007-01-01}, journal = {European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics}, volume = {45}, number = {3}, pages = {477--483}, publisher = {EDP Sciences}, abstract = {The electronic structure of supported mass-selected Ag3 clusters is analyzed by joint femtosecond photoemission spectroscopy and ab initio theor. investigations. A wide band gap insulating MgO ultrathin film on Mo(100) was chosen as substrate to minimize the electronic interaction between metal clusters and support. After MgO ultrathin film prepn. no photoemission from the Mo substrate is obsd. anymore, instead very weak 2-photon photoemission is detected possibly originating from surface or subsurface oxide defect states. Soft-landing deposition of 2% of at. monolayer equiv. of Ag3 clusters results in the disappearance also of the MgO 2-photon photoemission signal, while a strong single photon photoemission signal is detected from states located directly below the Fermi level. The theor. study of structural, electronic, and optical properties of Ag3 at 2 model sites of MgO (100), the stoichiometric MgO(100) and an FS-center defect, based on the DFT method and the embedded cluster model provides insight into the interactions between the cluster and the support which are responsible for the characteristic spectroscopic features. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The electronic structure of supported mass-selected Ag3 clusters is analyzed by joint femtosecond photoemission spectroscopy and ab initio theor. investigations. A wide band gap insulating MgO ultrathin film on Mo(100) was chosen as substrate to minimize the electronic interaction between metal clusters and support. After MgO ultrathin film prepn. no photoemission from the Mo substrate is obsd. anymore, instead very weak 2-photon photoemission is detected possibly originating from surface or subsurface oxide defect states. Soft-landing deposition of 2% of at. monolayer equiv. of Ag3 clusters results in the disappearance also of the MgO 2-photon photoemission signal, while a strong single photon photoemission signal is detected from states located directly below the Fermi level. The theor. study of structural, electronic, and optical properties of Ag3 at 2 model sites of MgO (100), the stoichiometric MgO(100) and an FS-center defect, based on the DFT method and the embedded cluster model provides insight into the interactions between the cluster and the support which are responsible for the characteristic spectroscopic features. [on SciFinder(R)] |
| 40. | Bonacic-Koutecky, V; Buergel, C; Kronik, L; Kuznetsov, A E; Mitric, R Optical properties of small silver clusters supported at MgO. Journal Article European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, 45 (3), pp. 471–476, 2007, ISSN: 1434-6060. @article{Bonacic-Koutecky2007a, title = {Optical properties of small silver clusters supported at MgO.}, author = {V Bonacic-Koutecky and C Buergel and L Kronik and A E Kuznetsov and R Mitric}, doi = {10.1140/epjd/e2007-00166-9}, issn = {1434-6060}, year = {2007}, date = {2007-01-01}, journal = {European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics}, volume = {45}, number = {3}, pages = {471--476}, publisher = {EDP Sciences}, abstract = {We present structural and optical properties of Ag clusters Agn (n = 2, 4, 6, 8) at 2 model support sites of MgO, stoichiometric MgO(100) and FS-center defect, based on d. functional theory and embedded cluster model. Our results provide the mechanism responsible for the absorption and emission patterns due to the specific interaction between the excitations within the cluster and the support site which is strongly cluster size and structure dependent. We propose Ag4 at stoichiometric site as well as Ag2, Ag4, and Ag6 at FS-center defects as good candidates for the emissive centers in the visible regime. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present structural and optical properties of Ag clusters Agn (n = 2, 4, 6, 8) at 2 model support sites of MgO, stoichiometric MgO(100) and FS-center defect, based on d. functional theory and embedded cluster model. Our results provide the mechanism responsible for the absorption and emission patterns due to the specific interaction between the excitations within the cluster and the support site which is strongly cluster size and structure dependent. We propose Ag4 at stoichiometric site as well as Ag2, Ag4, and Ag6 at FS-center defects as good candidates for the emissive centers in the visible regime. [on SciFinder(R)] |
| 39. | Stanzel, Jorg; Burmeister, Florian; Neeb, Matthias; Eberhardt, Wolfgang; Mitric, Roland; Burgel, Christian; Bonacic-Koutecky, Vlasta. Size-dependent dynamics in excited states of gold clusters: From oscillatory motion to photoinduced melting. Journal Article Journal of Chemical Physics, 127 (16), pp. 164312/1–164312/5, 2007, ISSN: 0021-9606. @article{Stanzel2007, title = {Size-dependent dynamics in excited states of gold clusters: From oscillatory motion to photoinduced melting.}, author = {Jorg Stanzel and Florian Burmeister and Matthias Neeb and Wolfgang Eberhardt and Roland Mitric and Christian Burgel and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.2795727}, issn = {0021-9606}, year = {2007}, date = {2007-01-01}, journal = {Journal of Chemical Physics}, volume = {127}, number = {16}, pages = {164312/1--164312/5}, publisher = {American Institute of Physics}, abstract = {Femtosecond time resolved photoelectron spectroscopy in combination with direct ab initio mol. dynamics "on the fly" based on d. functional theory has been used to study the relaxation dynamics of optically excited states in small mass selected anionic gold clusters (Aun-; n = 5-8). The nature of the dynamics strongly depends on the cluster size and structure. Oscillatory wavepacket motion (Au5-), a long lived excited state (Au6-), as well as photoinduced melting (Au7-,Au8-) is obsd. in real time. This illustrates nonscalable properties of excited states in clusters in the size regime, in which each atom counts. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Femtosecond time resolved photoelectron spectroscopy in combination with direct ab initio mol. dynamics "on the fly" based on d. functional theory has been used to study the relaxation dynamics of optically excited states in small mass selected anionic gold clusters (Aun-; n = 5-8). The nature of the dynamics strongly depends on the cluster size and structure. Oscillatory wavepacket motion (Au5-), a long lived excited state (Au6-), as well as photoinduced melting (Au7-,Au8-) is obsd. in real time. This illustrates nonscalable properties of excited states in clusters in the size regime, in which each atom counts. [on SciFinder(R)] |
| 38. | Mitric, Roland; Petersen, Jens; Kulesza, Alexander; Bonacic-Koutecky, Vlasta; Tabarin, Thibault; Compagnon, Isabelle; Antoine, Rodolphe; Broyer, Michel; Dugourd, Philippe. Photoabsorption and photofragmentation of isolated cationic silver cluster-tryptophan hybrid systems. Journal Article Journal of Chemical Physics, 127 (13), pp. 134301/1–134301/9, 2007, ISSN: 0021-9606. @article{Mitric2007a, title = {Photoabsorption and photofragmentation of isolated cationic silver cluster-tryptophan hybrid systems.}, author = {Roland Mitric and Jens Petersen and Alexander Kulesza and Vlasta Bonacic-Koutecky and Thibault Tabarin and Isabelle Compagnon and Rodolphe Antoine and Michel Broyer and Philippe. Dugourd}, doi = {10.1063/1.2772630}, issn = {0021-9606}, year = {2007}, date = {2007-01-01}, journal = {Journal of Chemical Physics}, volume = {127}, number = {13}, pages = {134301/1--134301/9}, publisher = {American Institute of Physics}, abstract = {The authors present a theor. study of the size and structure selective absorption properties of cationic silver cluster-tryptophan Trp-Ag+n (n = 2-5,9) hybrid systems supported by photofragmentation expts. The authors time-dependent d. functional theory calcns. provide insight into the nature of excitations in interacting nanoparticle-biomol. subunits and allow to det. characteristic spectral features as fingerprints of two different classes of structures: charge solvated and zwitterionic. Moreover, different types of charge transfer transitions have been identified. Charge transfer from $pi$ system of tryptophan to silver cluster occurs for charge solvated structures while charge transfer from silver to the NH+3 group takes place for zwitterionic structures. This has been confirmed by exptl. measured photofragmentation channels and mol. dynamics simulations. The authors findings provide fundamental insight into the structure- and size-dependent mechanism responsible for the enhanced absorption and emission in nanoparticle-biomol. hybrid systems. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a theor. study of the size and structure selective absorption properties of cationic silver cluster-tryptophan Trp-Ag+n (n = 2-5,9) hybrid systems supported by photofragmentation expts. The authors time-dependent d. functional theory calcns. provide insight into the nature of excitations in interacting nanoparticle-biomol. subunits and allow to det. characteristic spectral features as fingerprints of two different classes of structures: charge solvated and zwitterionic. Moreover, different types of charge transfer transitions have been identified. Charge transfer from $pi$ system of tryptophan to silver cluster occurs for charge solvated structures while charge transfer from silver to the NH+3 group takes place for zwitterionic structures. This has been confirmed by exptl. measured photofragmentation channels and mol. dynamics simulations. The authors findings provide fundamental insight into the structure- and size-dependent mechanism responsible for the enhanced absorption and emission in nanoparticle-biomol. hybrid systems. [on SciFinder(R)] |
| 37. | Mitric, Roland; Bonacic-Koutecky, Vlasta. Optimal control of mode-selective femtochemistry in multidimensional systems. Journal Article Physical Review A: Atomic, Molecular, and Optical Physics, 76 (3, Pt. A), pp. 031405/1–031405/4, 2007, ISSN: 1050-2947. @article{Mitric2007b, title = {Optimal control of mode-selective femtochemistry in multidimensional systems.}, author = {Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1103/PhysRevA.76.031405}, issn = {1050-2947}, year = {2007}, date = {2007-01-01}, journal = {Physical Review A: Atomic, Molecular, and Optical Physics}, volume = {76}, number = {3, Pt. A}, pages = {031405/1--031405/4}, publisher = {American Physical Society}, abstract = {We present a strategy for optimal control of the ground-state dynamics in multidimensional systems based on a combination of the semiclassical Wigner distribution approach with direct quantum chem. mol. dynamics (MD) "on the fly. " This allows one to treat all degrees of freedom without the need for precalcn. of global potential energy surfaces. We demonstrate the scope of our theor. procedure on two prototype systems representing rigid sym. mols. (Na3F) and flexible biomols. with low-frequency modes (glycine). We show that the ground-state isomerization process can be selectively driven by ultrashort laser pulses with different shapes which are characteristic of the prototype systems. Thus, our method opens perspectives for control of the functionality of biomols. Moreover, assignment of the underlying processes to pulse shapes based on MD allows one to use optimal control as a tool for anal. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a strategy for optimal control of the ground-state dynamics in multidimensional systems based on a combination of the semiclassical Wigner distribution approach with direct quantum chem. mol. dynamics (MD) "on the fly. " This allows one to treat all degrees of freedom without the need for precalcn. of global potential energy surfaces. We demonstrate the scope of our theor. procedure on two prototype systems representing rigid sym. mols. (Na3F) and flexible biomols. with low-frequency modes (glycine). We show that the ground-state isomerization process can be selectively driven by ultrashort laser pulses with different shapes which are characteristic of the prototype systems. Thus, our method opens perspectives for control of the functionality of biomols. Moreover, assignment of the underlying processes to pulse shapes based on MD allows one to use optimal control as a tool for anal. [on SciFinder(R)] |
| 36. | Mitric, Roland; Buergel, Christian; Bonacic-Koutecky, Vlasta. Reactivity-promoting criterion based on internal vibrational energy redistribution. Journal Article Proceedings of the National Academy of Sciences of the United States of America, 104 (25), pp. 10314–10317, 2007, ISSN: 0027-8424. @article{Mitric2007c, title = {Reactivity-promoting criterion based on internal vibrational energy redistribution.}, author = {Roland Mitric and Christian Buergel and Vlasta. Bonacic-Koutecky}, doi = {10.1073/pnas.0704066104}, issn = {0027-8424}, year = {2007}, date = {2007-01-01}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {104}, number = {25}, pages = {10314--10317}, publisher = {National Academy of Sciences}, abstract = {We propose to introduce intrinsic dynamical properties as a criterion for promoting reactivity of small size noble metal reactive centers relevant for heterogeneous catalysis. To illustrate the concept, collisions between Ag-6 or Au-6 clusters and mol. oxygen have been investigated with direct ab initio mol. dynamics by using DFT. We show that different nature and efficiency of internal vibrational energy redistribution (IVR) during reaction dynamics is responsible for significantly different sticking probabilities of O2 to gold and to silver clusters. In the case of Au-6 and O2 collisions, resonant IVR occurs between two subunits activating O2 and promoting subsequent oxidn. reactions. In contrast, a dissipative IVR in Ag-6 and O2 mol. prevents O2 to react with other adsorbates. These findings allow us to introduce the nature of IVR as a criterion for promoting the reactivity of noble metal clusters: Resonant IVR between reactants promotes reactivity toward adsorbates. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose to introduce intrinsic dynamical properties as a criterion for promoting reactivity of small size noble metal reactive centers relevant for heterogeneous catalysis. To illustrate the concept, collisions between Ag-6 or Au-6 clusters and mol. oxygen have been investigated with direct ab initio mol. dynamics by using DFT. We show that different nature and efficiency of internal vibrational energy redistribution (IVR) during reaction dynamics is responsible for significantly different sticking probabilities of O2 to gold and to silver clusters. In the case of Au-6 and O2 collisions, resonant IVR occurs between two subunits activating O2 and promoting subsequent oxidn. reactions. In contrast, a dissipative IVR in Ag-6 and O2 mol. prevents O2 to react with other adsorbates. These findings allow us to introduce the nature of IVR as a criterion for promoting the reactivity of noble metal clusters: Resonant IVR between reactants promotes reactivity toward adsorbates. [on SciFinder(R)] |
2006 |
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| 35. | Kimble, Michele L; Moore, Nelly A; Johnson, Grant E; Castleman Jr., A W; Burgel, Christian; Mitric, Roland; Bonacic-Koutecky, Vlasta. Joint experimental and theoretical investigations of the reactivity of Au2On- and Au3nO- (n=1-5) with carbon monoxide. Journal Article Journal of Chemical Physics, 125 (20), pp. 204311/1–204311/14, 2006, ISSN: 0021-9606. @article{Kimble2006, title = {Joint experimental and theoretical investigations of the reactivity of Au2On- and Au3nO- (n=1-5) with carbon monoxide.}, author = {Michele L Kimble and Nelly A Moore and Grant E Johnson and A W {Castleman Jr.} and Christian Burgel and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.2371002}, issn = {0021-9606}, year = {2006}, date = {2006-01-01}, journal = {Journal of Chemical Physics}, volume = {125}, number = {20}, pages = {204311/1--204311/14}, publisher = {American Institute of Physics}, abstract = {The interactions between small gold oxide cluster anions, Au2,3O-n (n=1-5), and CO were investigated in a fast-flow reactor mass spectrometer, and exptl. results were verified with a guided ion beam mass spectrometer. D. functional calcns. along with mol. dynamics simulations were also utilized to explain the exptl. findings. From these studies, we show that, for the interactions between AumO-n and CO, each atom counts. With the addn. of a single gold atom, it is obsd. that assocn. of CO and replacement of O2 by CO become the dominant reaction channels as opposed to CO oxidn. We also present results that show that the oxidn. of CO takes place only in the presence of a peripheral oxygen atom. However, this condition is not always sufficient. Furthermore, the assocn. of CO onto AumO-n follows a general qual. rule based on the relationship between the energy of the cluster LUMO and the binding energy of CO. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The interactions between small gold oxide cluster anions, Au2,3O-n (n=1-5), and CO were investigated in a fast-flow reactor mass spectrometer, and exptl. results were verified with a guided ion beam mass spectrometer. D. functional calcns. along with mol. dynamics simulations were also utilized to explain the exptl. findings. From these studies, we show that, for the interactions between AumO-n and CO, each atom counts. With the addn. of a single gold atom, it is obsd. that assocn. of CO and replacement of O2 by CO become the dominant reaction channels as opposed to CO oxidn. We also present results that show that the oxidn. of CO takes place only in the presence of a peripheral oxygen atom. However, this condition is not always sufficient. Furthermore, the assocn. of CO onto AumO-n follows a general qual. rule based on the relationship between the energy of the cluster LUMO and the binding energy of CO. [on SciFinder(R)] |
| 34. | Schaefer-Bung, B; Mitric, R; Bonacic-Koutecky, V Photostabilization of the ultracold Rb2 molecule by optimal control. Journal Article Journal of Physics B: Atomic, Molecular and Optical Physics, 39 (19), pp. S1043–S1053, 2006, ISSN: 0953-4075. @article{Schaefer-Bung2006, title = {Photostabilization of the ultracold Rb2 molecule by optimal control.}, author = {B Schaefer-Bung and R Mitric and V Bonacic-Koutecky}, doi = {10.1088/0953-4075/39/19/S16}, issn = {0953-4075}, year = {2006}, date = {2006-01-01}, journal = {Journal of Physics B: Atomic, Molecular and Optical Physics}, volume = {39}, number = {19}, pages = {S1043--S1053}, publisher = {Institute of Physics Publishing}, abstract = {The authors present a theor. study of the photostabilization of the ultracold Rb2 mol. by tailored laser fields. The simulations involve the ground and two excited electronic states, taking into account spin-orbit coupling, and are based on the full quantum mech. optimal control theory. The authors demonstrate starting from a highly excited bound vibrational state that almost 100% population of the ground state $nu$ = 0 vibrational level can be achieved. The obtained optimal pulse has a long temporal and very broad spectral range. The authors results reveal the mechanism of the photostabilization process and allow the proposal of new strategies for the formation of ultracold mols. taking into account the necessary constraints for possible exptl. realization. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a theor. study of the photostabilization of the ultracold Rb2 mol. by tailored laser fields. The simulations involve the ground and two excited electronic states, taking into account spin-orbit coupling, and are based on the full quantum mech. optimal control theory. The authors demonstrate starting from a highly excited bound vibrational state that almost 100% population of the ground state $nu$ = 0 vibrational level can be achieved. The obtained optimal pulse has a long temporal and very broad spectral range. The authors results reveal the mechanism of the photostabilization process and allow the proposal of new strategies for the formation of ultracold mols. taking into account the necessary constraints for possible exptl. realization. [on SciFinder(R)] |
| 33. | Compagnon, Isabelle; Tabarin, Thibault; Antoine, Rodolphe; Broyer, Michel; Dugourd, Philippe; Mitric, Roland; Petersen, Jens; Bonacic-Koutecky, Vlasta. Journal of Chemical Physics, 125 (16), pp. 164326/1–164326/5, 2006, ISSN: 0021-9606. @article{Compagnon2006, title = {Spectroscopy of isolated, mass-selected tryptophan-Ag3 complexes: A model for photoabsorption enhancement in nanoparticle-biomolecule hybrid systems.}, author = {Isabelle Compagnon and Thibault Tabarin and Rodolphe Antoine and Michel Broyer and Philippe Dugourd and Roland Mitric and Jens Petersen and Vlasta. Bonacic-Koutecky}, doi = {10.1063/1.2357947}, issn = {0021-9606}, year = {2006}, date = {2006-01-01}, journal = {Journal of Chemical Physics}, volume = {125}, number = {16}, pages = {164326/1--164326/5}, publisher = {American Institute of Physics}, abstract = {Gas-phase studies of small metal cluster-biomol. complexes provide fundamental insights into the mechanism leading to enhanced optical absorption in nanoparticle-biomol. hybrid systems. Here the authors present, for the 1st time, a joint exptl. and theor. study of photoabsorption and photofragmentation of the Ag trimer-tryptophan cation complex ([TrptextperiodcenteredAg3]+). Binding the metal cluster to a biomol. leads to a remarkably high optical absorption as compared to the bare tryptophan or the [TrptextperiodcenteredAg]+ complex. As calcns. show this arises due to coupling between the excitations in the metallic subunit with a charge transfer excitation to the tryptophan mol. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Gas-phase studies of small metal cluster-biomol. complexes provide fundamental insights into the mechanism leading to enhanced optical absorption in nanoparticle-biomol. hybrid systems. Here the authors present, for the 1st time, a joint exptl. and theor. study of photoabsorption and photofragmentation of the Ag trimer-tryptophan cation complex ([TrptextperiodcenteredAg3]+). Binding the metal cluster to a biomol. leads to a remarkably high optical absorption as compared to the bare tryptophan or the [TrptextperiodcenteredAg]+ complex. As calcns. show this arises due to coupling between the excitations in the metallic subunit with a charge transfer excitation to the tryptophan mol. [on SciFinder(R)] |
| 32. | Springer, Andreas; Buergel, Christian; Boehrsch, Verena; Mitric, Roland; Bonacic-Koutecky, Vlasta; Linscheid, Michael W The gas-phase chemistry of cis-diammineplatinum(II) complexes: a joint experimental and theoretical study. Journal Article ChemPhysChem, 7 (8), pp. 1779–1785, 2006, ISSN: 1439-4235. @article{Springer2006, title = {The gas-phase chemistry of cis-diammineplatinum(II) complexes: a joint experimental and theoretical study.}, author = {Andreas Springer and Christian Buergel and Verena Boehrsch and Roland Mitric and Vlasta Bonacic-Koutecky and Michael W Linscheid}, doi = {10.1002/cphc.200600177}, issn = {1439-4235}, year = {2006}, date = {2006-01-01}, journal = {ChemPhysChem}, volume = {7}, number = {8}, pages = {1779--1785}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {Prior to reactions with DNA, the anticancer drug cisplatin [PtII(NH3)2Cl2] forms a series of solvolysis intermediates by successive replacement of the chloro ligands by water or hydroxyl groups. The bonding of water to PtII is weak, and it is easily substituted by donor ligands present in the soln., for example, amines or alcs. We studied such compds. using high-resoln. electrospray mass spectrometry with a linear ion trap and DFT computations. This combination allows for the first time a detailed description of the reactions initiated by the central atom of the complexes. Pos. charged cisplatin adducts with primary and secondary alcs. ([PtII(NH3)2(ROH)Cl]+) show unexpected reactions when fragmented in a linear ion trap. Either water loss is accompanied by formation of the corresponding carbene complex, or loss of the corresponding aldehyde/ketone leads to the formation of the complex [Pt(NH3)2(H2)Cl]+. Complete loss of the alc. ligand is not obsd. for kinetic reasons. A detailed investigation by DFT and mol. dynamics for the cis-platin/methanol complex [PtII(NH3)2(CH3OH)Cl]+ allowed identification of the reaction mechanisms leading to the obsd. fragmentation patterns. The initial step for both fragmentation pathways is activation of the $alpha$-CH bond and subsequent H transfer within the complex. Direct activation of the OH or CO bond is less favorable. Ligands bound to the PtII center such as the chloro ligand can directly catalyze the reaction by intermediate binding of H atoms. Upon collision activation, adducts without an $alpha$-H atom such as [Pt(NH3)2(CH3)3COHCl]+ show loss of water or the corresponding alkene. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Prior to reactions with DNA, the anticancer drug cisplatin [PtII(NH3)2Cl2] forms a series of solvolysis intermediates by successive replacement of the chloro ligands by water or hydroxyl groups. The bonding of water to PtII is weak, and it is easily substituted by donor ligands present in the soln., for example, amines or alcs. We studied such compds. using high-resoln. electrospray mass spectrometry with a linear ion trap and DFT computations. This combination allows for the first time a detailed description of the reactions initiated by the central atom of the complexes. Pos. charged cisplatin adducts with primary and secondary alcs. ([PtII(NH3)2(ROH)Cl]+) show unexpected reactions when fragmented in a linear ion trap. Either water loss is accompanied by formation of the corresponding carbene complex, or loss of the corresponding aldehyde/ketone leads to the formation of the complex [Pt(NH3)2(H2)Cl]+. Complete loss of the alc. ligand is not obsd. for kinetic reasons. A detailed investigation by DFT and mol. dynamics for the cis-platin/methanol complex [PtII(NH3)2(CH3OH)Cl]+ allowed identification of the reaction mechanisms leading to the obsd. fragmentation patterns. The initial step for both fragmentation pathways is activation of the $alpha$-CH bond and subsequent H transfer within the complex. Direct activation of the OH or CO bond is less favorable. Ligands bound to the PtII center such as the chloro ligand can directly catalyze the reaction by intermediate binding of H atoms. Upon collision activation, adducts without an $alpha$-H atom such as [Pt(NH3)2(CH3)3COHCl]+ show loss of water or the corresponding alkene. [on SciFinder(R)] |
| 31. | Mitric, Roland; Bonacic-Koutecky, Vlasta; Pittner, Jiri; Lischka, Hans. Ab initio nonadiabatic dynamics study of ultrafast radiationless decay over conical intersections illustrated on the Na3F cluster. Journal Article Journal of Chemical Physics, 125 (2), pp. 024303/1–024303/7, 2006, ISSN: 0021-9606. @article{Mitric2006, title = {Ab initio nonadiabatic dynamics study of ultrafast radiationless decay over conical intersections illustrated on the Na3F cluster.}, author = {Roland Mitric and Vlasta Bonacic-Koutecky and Jiri Pittner and Hans. Lischka}, doi = {10.1063/1.2209233}, issn = {0021-9606}, year = {2006}, date = {2006-01-01}, journal = {Journal of Chemical Physics}, volume = {125}, number = {2}, pages = {024303/1--024303/7}, publisher = {American Institute of Physics}, abstract = {The authors present a theor. approach for the ultrafast nonadiabatic dynamics based on the ab initio mol. dynamics carried out on the fly in the framework of the CI method combined with Tully's surface hopping algorithm for nonadiabatic transitions. This approach combined with Wigner distribution approach allows one to perform accurate simulations of femtosecond pump-probe spectra in the systems where radiationless transitions among electronic states take place. The authors illustrate this by theor. simulation of ultrafast processes and nonradiative relaxation in the Na3F cluster, involving 3 excited states and the ground electronic state. Also, accurate simulation of the photoionization pump-probe spectrum is in full agreement with the exptl. signal. Based on the nonadiabatic dynamics at high level of accuracy and taking into account all degrees of freedom, the nonradiative lifetime for the 1 1B1 excited state of Na3F is ∼900 fs. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a theor. approach for the ultrafast nonadiabatic dynamics based on the ab initio mol. dynamics carried out on the fly in the framework of the CI method combined with Tully's surface hopping algorithm for nonadiabatic transitions. This approach combined with Wigner distribution approach allows one to perform accurate simulations of femtosecond pump-probe spectra in the systems where radiationless transitions among electronic states take place. The authors illustrate this by theor. simulation of ultrafast processes and nonradiative relaxation in the Na3F cluster, involving 3 excited states and the ground electronic state. Also, accurate simulation of the photoionization pump-probe spectrum is in full agreement with the exptl. signal. Based on the nonadiabatic dynamics at high level of accuracy and taking into account all degrees of freedom, the nonradiative lifetime for the 1 1B1 excited state of Na3F is ∼900 fs. [on SciFinder(R)] |
| 30. | Bonacic-Koutecky, Vlasta; Mitric, Roland; Werner, Ute; Woeste, Ludger; Berry, Stephen. R Ultrafast dynamics in atomic clusters: analysis and control. Journal Article Proceedings of the National Academy of Sciences of the United States of America, 103 (28), pp. 10594–10599, 2006, ISSN: 0027-8424. @article{Bonacic-Koutecky2006, title = {Ultrafast dynamics in atomic clusters: analysis and control.}, author = {Vlasta Bonacic-Koutecky and Roland Mitric and Ute Werner and Ludger Woeste and Stephen. R Berry}, doi = {10.1073/pnas.0600151103}, issn = {0027-8424}, year = {2006}, date = {2006-01-01}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {103}, number = {28}, pages = {10594--10599}, publisher = {National Academy of Sciences}, abstract = {We present a study of dynamics and ultrafast observables in the frame of pump-probe neg.-to-neutral-to-pos. ion (NeNePo) spectroscopy illustrated by the examples of bimetallic trimers Ag2Au-/Ag2Au/Ag2Au+ and silver oxides Ag3O-2/Ag3O2/Ag3O+2 in the context of cluster reactivity. First principle multistate adiabatic dynamics allows us to det. time scales of different ultrafast processes and conditions under which these processes can be exptl. obsd. Furthermore, we present a strategy for optimal pump-dump control in complex systems based on the ab initio Wigner distribution approach and apply it to tailor laser fields for selective control of the isomerization process in Na3F2. The shapes of pulses can be assigned to underlying processes, and therefore control can be used as a tool for anal. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a study of dynamics and ultrafast observables in the frame of pump-probe neg.-to-neutral-to-pos. ion (NeNePo) spectroscopy illustrated by the examples of bimetallic trimers Ag2Au-/Ag2Au/Ag2Au+ and silver oxides Ag3O-2/Ag3O2/Ag3O+2 in the context of cluster reactivity. First principle multistate adiabatic dynamics allows us to det. time scales of different ultrafast processes and conditions under which these processes can be exptl. obsd. Furthermore, we present a strategy for optimal pump-dump control in complex systems based on the ab initio Wigner distribution approach and apply it to tailor laser fields for selective control of the isomerization process in Na3F2. The shapes of pulses can be assigned to underlying processes, and therefore control can be used as a tool for anal. [on SciFinder(R)] |
| 29. | Antoine, Rodolphe; Tabarin, Thibault; Broyer, Michel; Dugourd, Philippe; Mitric, Roland; Bonacic-Koutecky, Vlasta. Optical properties of gas-phase tryptophan-silver cations: charge transfer from the indole ring to the silver atom. Journal Article ChemPhysChem, 7 (2), pp. 524–528, 2006, ISSN: 1439-4235. @article{Antoine2006, title = {Optical properties of gas-phase tryptophan-silver cations: charge transfer from the indole ring to the silver atom.}, author = {Rodolphe Antoine and Thibault Tabarin and Michel Broyer and Philippe Dugourd and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1002/cphc.200500495}, issn = {1439-4235}, year = {2006}, date = {2006-01-01}, journal = {ChemPhysChem}, volume = {7}, number = {2}, pages = {524--528}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {The authors present a joint exptl. and theor. study of the electronic excitation spectra of the tryptophan-silver complex. The photodissocn. spectrum of gas-phase [Trp-Ag]+ was measured from 215 to 330 nm using a quadrupole ion trap coupled to an optical parametric-oscillator laser. The calcd. time-dependent d. functional theory (TD-DFT) absorption spectra for different prototypes of structures are presented. Low-energy transitions that are exptl. obsd. are only calcd. for the charge-solvation (CS) structures. These transitions are a signature of the metal-$pi$ interaction in [Trp-Ag]+. The recorded spectrum is compared to a Boltzmann av. of the absorption spectrum obtained from direct mol. dynamics (MD) simulations involving simultaneous transitions to excited states based on semiempirical CI calcns. Charge transfer can be photoinduced from the indole ring to the silver atom. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors present a joint exptl. and theor. study of the electronic excitation spectra of the tryptophan-silver complex. The photodissocn. spectrum of gas-phase [Trp-Ag]+ was measured from 215 to 330 nm using a quadrupole ion trap coupled to an optical parametric-oscillator laser. The calcd. time-dependent d. functional theory (TD-DFT) absorption spectra for different prototypes of structures are presented. Low-energy transitions that are exptl. obsd. are only calcd. for the charge-solvation (CS) structures. These transitions are a signature of the metal-$pi$ interaction in [Trp-Ag]+. The recorded spectrum is compared to a Boltzmann av. of the absorption spectrum obtained from direct mol. dynamics (MD) simulations involving simultaneous transitions to excited states based on semiempirical CI calcns. Charge transfer can be photoinduced from the indole ring to the silver atom. [on SciFinder(R)] |
| 28. | Moore, Nelly A; Mitric, Roland; Justes, Dina R; Bonacic-Koutecky, Vlasta; Castleman Jr., A W Kinetic Analysis of the Reaction between (V2O5)n=1,2+ and Ethylene. Journal Article Journal of Physical Chemistry B, 110 (7), pp. 3015–3022, 2006, ISSN: 1520-6106. @article{Moore2006, title = {Kinetic Analysis of the Reaction between (V2O5)n=1,2+ and Ethylene.}, author = {Nelly A Moore and Roland Mitric and Dina R Justes and Vlasta Bonacic-Koutecky and A W {Castleman Jr.}}, doi = {10.1021/jp055652u}, issn = {1520-6106}, year = {2006}, date = {2006-01-01}, journal = {Journal of Physical Chemistry B}, volume = {110}, number = {7}, pages = {3015--3022}, publisher = {American Chemical Society}, abstract = {A systematic exptl. and theor. investigation of the influence of reactant energy on the reactivity of (V2O5)n=1,2+ clusters with ethylene (Justes, D. R.; Mitric, R.; Moore, N. A.; Bonacic-Koutecky, V.; Castleman, A. W. Jr. J. Am. Chem. Soc., 2003, 125, 6289)1 provided evidence of the rate controlling steps in the reaction. Herein, we present further exptl. and theor. evidence for our recently proposed radical cation mechanism for oxygen atom transfer from (V2O5)n=1,2+ clusters to ethylene. In particular the results of ab initio mol. dynamics simulations are found to further support the radical cation mechanism. Exptl. reaction cross sections at the zero pressure limit and rate coeffs. show that the energy dependence of the reaction cross section is in accord with the Langevin formula. Evidence is presented that ion-mol. assocn. is the rate detg. step, whereas subsequent hydrogen transfer and formation of acetaldehyde proceed without significant barriers. We propose a kinetic model for the reaction cross section that fully accounts for the exptl. findings. The model offers the prospect of elucidating the details of the general reaction mechanisms through a study of the energy dependence of the reaction cross sections. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A systematic exptl. and theor. investigation of the influence of reactant energy on the reactivity of (V2O5)n=1,2+ clusters with ethylene (Justes, D. R.; Mitric, R.; Moore, N. A.; Bonacic-Koutecky, V.; Castleman, A. W. Jr. J. Am. Chem. Soc., 2003, 125, 6289)1 provided evidence of the rate controlling steps in the reaction. Herein, we present further exptl. and theor. evidence for our recently proposed radical cation mechanism for oxygen atom transfer from (V2O5)n=1,2+ clusters to ethylene. In particular the results of ab initio mol. dynamics simulations are found to further support the radical cation mechanism. Exptl. reaction cross sections at the zero pressure limit and rate coeffs. show that the energy dependence of the reaction cross section is in accord with the Langevin formula. Evidence is presented that ion-mol. assocn. is the rate detg. step, whereas subsequent hydrogen transfer and formation of acetaldehyde proceed without significant barriers. We propose a kinetic model for the reaction cross section that fully accounts for the exptl. findings. The model offers the prospect of elucidating the details of the general reaction mechanisms through a study of the energy dependence of the reaction cross sections. [on SciFinder(R)] |
| 27. | Buergel, C; Mitric, R; Bonacic-Koutecky, V Emissive properties of silver particles at silver oxide surface defects. Journal Article Applied Physics A: Materials Science & Processing, 82 (1), pp. 117–123, 2006, ISSN: 0947-8396. @article{Buergel2006, title = {Emissive properties of silver particles at silver oxide surface defects.}, author = {C Buergel and R Mitric and V Bonacic-Koutecky}, doi = {10.1007/s00339-005-3344-8}, issn = {0947-8396}, year = {2006}, date = {2006-01-01}, journal = {Applied Physics A: Materials Science & Processing}, volume = {82}, number = {1}, pages = {117--123}, publisher = {Springer}, abstract = {The absorption and fluorescence properties of pure Ag and Ag2O model systems were explored using ab initio linear response methods in context of the obsd. fluorescence by photoactivation of thin Ag2O films. Ag clusters interacting with F-center defects created from Ag2O surfaces as well as Ag clusters interacting directly with the Ag2O surface are good candidates for emissive centers giving rise to fluorescence in the visible regime. These findings represent a starting point towards conceptual understanding of emissive Ag cluster-support properties, which might be important for the development of optical storage media with large data capacities. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The absorption and fluorescence properties of pure Ag and Ag2O model systems were explored using ab initio linear response methods in context of the obsd. fluorescence by photoactivation of thin Ag2O films. Ag clusters interacting with F-center defects created from Ag2O surfaces as well as Ag clusters interacting directly with the Ag2O surface are good candidates for emissive centers giving rise to fluorescence in the visible regime. These findings represent a starting point towards conceptual understanding of emissive Ag cluster-support properties, which might be important for the development of optical storage media with large data capacities. [on SciFinder(R)] |
| 26. | Bonacic-Koutecky, Vlasta; Mitric, Roland; Bernhardt, Thorsten M; Woeste, Ludger; Jortner, Joshua. Analysis and control of ultrafast dynamics in clusters: Theory and experiment. Journal Article Advances in Chemical Physics, 132 , pp. 179–246, 2006, ISSN: 0065-2385. @article{Bonacic-Koutecky2006a, title = {Analysis and control of ultrafast dynamics in clusters: Theory and experiment.}, author = {Vlasta Bonacic-Koutecky and Roland Mitric and Thorsten M Bernhardt and Ludger Woeste and Joshua. Jortner}, issn = {0065-2385}, year = {2006}, date = {2006-01-01}, journal = {Advances in Chemical Physics}, volume = {132}, pages = {179--246}, publisher = {John Wiley & Sons, Inc.}, abstract = {A review. The following topics are discussed: dynamics of ultrafast processes (multistate adiabatic nuclear dynamics and simulations of NeNePo signals, electronic structure, semiclassical dynamics); exptl. setup for NeNePo spectroscopy; the trimer Ag2Au; tetramers Ag4 and Au4; fragmentation of Ag2O2; scope of NeNePo spectroscopy; multistate nonadiabatic nuclear dynamics in electronically excited and ground states; photoisomerization through a conical intersection in the Na3F2 cluster; control of ultrafast processes. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A review. The following topics are discussed: dynamics of ultrafast processes (multistate adiabatic nuclear dynamics and simulations of NeNePo signals, electronic structure, semiclassical dynamics); exptl. setup for NeNePo spectroscopy; the trimer Ag2Au; tetramers Ag4 and Au4; fragmentation of Ag2O2; scope of NeNePo spectroscopy; multistate nonadiabatic nuclear dynamics in electronically excited and ground states; photoisomerization through a conical intersection in the Na3F2 cluster; control of ultrafast processes. [on SciFinder(R)] |
| 25. | Bonacic-Koutecky, V; Mitric, R; Buergel, C; Schaefer-Bung, B Cluster properties in the regime in which each atom counts. Journal Article Computational Materials Science, 35 (3), pp. 151–157, 2006, ISSN: 0927-0256. @article{Bonacic-Koutecky2006b, title = {Cluster properties in the regime in which each atom counts.}, author = {V Bonacic-Koutecky and R Mitric and C Buergel and B Schaefer-Bung}, doi = {10.1016/j.commatsci.2004.12.075}, issn = {0927-0256}, year = {2006}, date = {2006-01-01}, journal = {Computational Materials Science}, volume = {35}, number = {3}, pages = {151--157}, publisher = {Elsevier B.V.}, abstract = {In this contribution we address (A) size selective reactivity of anionic gold clusters relevant for catalysis and (B) femtochem. of metallic clusters and its control by tailored laser fields. In this connection the following results will be presented. (I) General mechanism for co-adsorption of O2 and CO based on structure-reactivity relation has been obtained using DFT method which permits to elucidate fully available exptl. results. (II) Simulation of pump-probe signals in the framework of neg.-to-neutral-to-pos. (NeNePo) spectroscopy using combination of Wigner distribution approach and MD "on the fly" allows to det. exptl. conditions under which different processes such as geometric relaxation and internal vibrational relaxation (IVR) in Ag2Au can be obsd. (III) We show that optimal control theory can be used as a tool for anal. of ultrafast processes on example of photoionization processes in NaK, since the shapes of the optimized pulses based on full quantum mech. treatment can be used to deduce the mechanisms of the processes underlying the optimal control. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this contribution we address (A) size selective reactivity of anionic gold clusters relevant for catalysis and (B) femtochem. of metallic clusters and its control by tailored laser fields. In this connection the following results will be presented. (I) General mechanism for co-adsorption of O2 and CO based on structure-reactivity relation has been obtained using DFT method which permits to elucidate fully available exptl. results. (II) Simulation of pump-probe signals in the framework of neg.-to-neutral-to-pos. (NeNePo) spectroscopy using combination of Wigner distribution approach and MD "on the fly" allows to det. exptl. conditions under which different processes such as geometric relaxation and internal vibrational relaxation (IVR) in Ag2Au can be obsd. (III) We show that optimal control theory can be used as a tool for anal. of ultrafast processes on example of photoionization processes in NaK, since the shapes of the optimized pulses based on full quantum mech. treatment can be used to deduce the mechanisms of the processes underlying the optimal control. [on SciFinder(R)] |
2005 |
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| 24. | Bonacic-Koutecky, V; Mitric, R; Buergel, C; Noack, H; Hartmann, M; Pittner, J Tailoring the chemical reactivity and optical properties of clusters by size, structures and lasers. Journal Article European Physical Journal D: Atomic, Molecular and Optical Physics, 34 (1-3), pp. 113–118, 2005, ISSN: 1434-6060. @article{Bonacic-Koutecky2005, title = {Tailoring the chemical reactivity and optical properties of clusters by size, structures and lasers.}, author = {V Bonacic-Koutecky and R Mitric and C Buergel and H Noack and M Hartmann and J Pittner}, doi = {10.1140/epjd/e2005-00098-4}, issn = {1434-6060}, year = {2005}, date = {2005-01-01}, journal = {European Physical Journal D: Atomic, Molecular and Optical Physics}, volume = {34}, number = {1-3}, pages = {113--118}, publisher = {EDP Sciences}, abstract = {Results are presented of theor. studies in 3 areas. I. Reactivity of anionic noble metal oxide clusters (Ag, Au) relevant for catalyst design: the cooperative effects are needed to activate clusters to invoke strongly size selective reactions with O2 and CO. These results obtained with DFT method elucidated fully exptl. findings. II. Stationary optical properties of Ag clusters: ab initio results on absorption spectra of small Ag clusters and on geometric relaxation of their excited states leading to the obsd. fluorescence are presented and compared with exptl. data. III. Real-time study of ultrafast processes and their control by tailored laser fields: nonstoichiometric NanFn-1 clusters are suitable prototypes to study dynamics in excited electronic states. For this purpose the combination of the Wigner distribution method and MD on the fly was used allowing to treat all degrees of freedom. Anal. of simulated pump-probe signals are shown for Na2F for which exptl. data are available. Pump-dump control of the photoisomerization in Na3F2 avoiding conical intersection will be presented using the new strategy for obtaining tailored laser fields based on the intermediate target in excited state which (if available) guarantees the controllability in the complex systems. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Results are presented of theor. studies in 3 areas. I. Reactivity of anionic noble metal oxide clusters (Ag, Au) relevant for catalyst design: the cooperative effects are needed to activate clusters to invoke strongly size selective reactions with O2 and CO. These results obtained with DFT method elucidated fully exptl. findings. II. Stationary optical properties of Ag clusters: ab initio results on absorption spectra of small Ag clusters and on geometric relaxation of their excited states leading to the obsd. fluorescence are presented and compared with exptl. data. III. Real-time study of ultrafast processes and their control by tailored laser fields: nonstoichiometric NanFn-1 clusters are suitable prototypes to study dynamics in excited electronic states. For this purpose the combination of the Wigner distribution method and MD on the fly was used allowing to treat all degrees of freedom. Anal. of simulated pump-probe signals are shown for Na2F for which exptl. data are available. Pump-dump control of the photoisomerization in Na3F2 avoiding conical intersection will be presented using the new strategy for obtaining tailored laser fields based on the intermediate target in excited state which (if available) guarantees the controllability in the complex systems. [on SciFinder(R)] |
| 23. | Bernhardt, Thorsten M; Hagen, Jan; Socaciu, Liana D; Mitric, Roland; Heidenreich, Andreas; Le Roux, Jerome ; Popolan, Denisia; Vaida, Mihai; Woeste, Ludger; Bonacic-Koutecky, Vlasta; Jortner, Joshua. Femtosecond time-resolved geometry relaxation and ultrafast intramolecular energy redistribution in Ag2Au. Journal Article ChemPhysChem, 6 (2), pp. 243–253, 2005, ISSN: 1439-4235. @article{Bernhardt2005, title = {Femtosecond time-resolved geometry relaxation and ultrafast intramolecular energy redistribution in Ag2Au.}, author = {Thorsten M Bernhardt and Jan Hagen and Liana D Socaciu and Roland Mitric and Andreas Heidenreich and Jerome {Le Roux} and Denisia Popolan and Mihai Vaida and Ludger Woeste and Vlasta Bonacic-Koutecky and Joshua. Jortner}, doi = {10.1002/cphc.200400454}, issn = {1439-4235}, year = {2005}, date = {2005-01-01}, journal = {ChemPhysChem}, volume = {6}, number = {2}, pages = {243--253}, publisher = {Wiley-VCH Verlag GmbH & Co. KGaA}, abstract = {The ultrafast dynamics of the bimetallic cluster Ag2Au is investigated by pump-probe neg. ion-to-neutral-to-pos. ion (NeNePo) spectroscopy. Prepn. of the neutral cluster in a highly nonequil. state by electron detachment from the mass-selected anion, and subsequent probing of the neutral nuclear dynamics through two-photon ionization to the cationic state, leads to strongly probe-energy-dependent transient cation-abundance signals. The origin of this pronounced time and wavelength dependence of the ionization probability on the femtosecond scale is revealed by ab initio theor. simulations of the transient spectra. Based on the anal. of underlying dynamics, two fundamental processes involving geometry relaxation from linear to triangular structure followed by ultrafast intramol. vibrational energy redistribution (IVR) have been identified and for the first time exptl. obsd. in the frame of NeNePo spectroscopy under conditions close to zero electron kinetic energy. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The ultrafast dynamics of the bimetallic cluster Ag2Au is investigated by pump-probe neg. ion-to-neutral-to-pos. ion (NeNePo) spectroscopy. Prepn. of the neutral cluster in a highly nonequil. state by electron detachment from the mass-selected anion, and subsequent probing of the neutral nuclear dynamics through two-photon ionization to the cationic state, leads to strongly probe-energy-dependent transient cation-abundance signals. The origin of this pronounced time and wavelength dependence of the ionization probability on the femtosecond scale is revealed by ab initio theor. simulations of the transient spectra. Based on the anal. of underlying dynamics, two fundamental processes involving geometry relaxation from linear to triangular structure followed by ultrafast intramol. vibrational energy redistribution (IVR) have been identified and for the first time exptl. obsd. in the frame of NeNePo spectroscopy under conditions close to zero electron kinetic energy. [on SciFinder(R)] |
| 22. | Bonacic-Koutecky, Vlasta; Mitric, Roland. Theoretical Exploration of Ultrafast Dynamics in Atomic Clusters: Analysis and Control. Journal Article Chemical Reviews (Washington, DC, United States), 105 (1), pp. 11–65, 2005, ISSN: 0009-2665. @article{Bonacic-Koutecky2005a, title = {Theoretical Exploration of Ultrafast Dynamics in Atomic Clusters: Analysis and Control.}, author = {Vlasta Bonacic-Koutecky and Roland. Mitric}, doi = {10.1021/cr0206925}, issn = {0009-2665}, year = {2005}, date = {2005-01-01}, journal = {Chemical Reviews (Washington, DC, United States)}, volume = {105}, number = {1}, pages = {11--65}, publisher = {American Chemical Society}, abstract = {A review. The authors establish the connection between developments in cluster science and femtosecond spectroscopy. This sets up requirements on the theory to introduce means for analyzing and controlling the ultrafast processes and to provide the conceptual frame for observations. For this purpose contributions from quantum chem., mol. dynamics, wave packet propagation, and theory of optical control are needed. The authors address methods for investigations of ultrafast dynamics and for simulations of femtosecond signals (fs-signals). Their applications to elemental clusters with different sizes and at. compns., allowing to analyze the underlying processes and to predict observable properties, are given. Control of ultrafast processes in clusters by tuning laser parameters or using tailored fields is discussed. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A review. The authors establish the connection between developments in cluster science and femtosecond spectroscopy. This sets up requirements on the theory to introduce means for analyzing and controlling the ultrafast processes and to provide the conceptual frame for observations. For this purpose contributions from quantum chem., mol. dynamics, wave packet propagation, and theory of optical control are needed. The authors address methods for investigations of ultrafast dynamics and for simulations of femtosecond signals (fs-signals). Their applications to elemental clusters with different sizes and at. compns., allowing to analyze the underlying processes and to predict observable properties, are given. Control of ultrafast processes in clusters by tuning laser parameters or using tailored fields is discussed. [on SciFinder(R)] |
2004 |
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| 21. | Sieber, Christoph; Buttet, Jean; Harbich, Wolfgang; Felix, Christian; Mitric, Roland; Bonacic-Koutecky, Vlasta. Isomer-specific spectroscopy of metal clusters trapped in a matrix: Ag9. Journal Article Physical Review A: Atomic, Molecular, and Optical Physics, 70 (4), pp. 041201/1–041201/4, 2004, ISSN: 1050-2947. @article{Sieber2004, title = {Isomer-specific spectroscopy of metal clusters trapped in a matrix: Ag9.}, author = {Christoph Sieber and Jean Buttet and Wolfgang Harbich and Christian Felix and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1103/PhysRevA.70.041201}, issn = {1050-2947}, year = {2004}, date = {2004-01-01}, journal = {Physical Review A: Atomic, Molecular, and Optical Physics}, volume = {70}, number = {4}, pages = {041201/1--041201/4}, publisher = {American Physical Society}, abstract = {Clusters of metal atoms at a fixed size can assume different structural arrangements, known as isomers, which may have nearly the same energy. Therefore, at given exptl. conditions distribution of these isomers can be present. While the size selection is a relatively common technique, the isomer selection is not; it is therefore more difficult to obtain information about a single isomer. We report here on isomer-specific spectroscopy of Ag9 clusters together with ab initio calcns. allowing to identify the isomer responsible for the measured excitation pattern and fluorescence. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Clusters of metal atoms at a fixed size can assume different structural arrangements, known as isomers, which may have nearly the same energy. Therefore, at given exptl. conditions distribution of these isomers can be present. While the size selection is a relatively common technique, the isomer selection is not; it is therefore more difficult to obtain information about a single isomer. We report here on isomer-specific spectroscopy of Ag9 clusters together with ab initio calcns. allowing to identify the isomer responsible for the measured excitation pattern and fluorescence. [on SciFinder(R)] |
| 20. | Heitz, M -C; Durand, G; Spiegelman, F; Meier, C; Mitric, R; Bonacic-Koutecky, V Journal of Chemical Physics, 121 (20), pp. 9906–9916, 2004, ISSN: 0021-9606. @article{Heitz2004, title = {Ultrafast excited state dynamics of the Na3F cluster: Quantum wave packet and classical trajectory calculations compared to experimental results.}, author = {M -C Heitz and G Durand and F Spiegelman and C Meier and R Mitric and V Bonacic-Koutecky}, doi = {10.1063/1.1802451}, issn = {0021-9606}, year = {2004}, date = {2004-01-01}, journal = {Journal of Chemical Physics}, volume = {121}, number = {20}, pages = {9906--9916}, publisher = {American Institute of Physics}, abstract = {Short-time, excited-state dynamics of the lowest isomer of the Na3F cluster was studied theor. to interpret the features of recent time-resolved pump-probe ionization expts. [J.M. L'Hermite, V. Blanchet, A. Le Padellec, B. Lamory, and P. Labastie, Eur. Phys. J. D 28, 361(2004)]. The authors propose an identification of the vibrational motion responsible for the oscillations in the ion signal, from quantum mech. wave packet propagations and classical trajectory calcns. The good agreement between expt. and theory allows for a clear interpretation of the detected dynamics. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Short-time, excited-state dynamics of the lowest isomer of the Na3F cluster was studied theor. to interpret the features of recent time-resolved pump-probe ionization expts. [J.M. L'Hermite, V. Blanchet, A. Le Padellec, B. Lamory, and P. Labastie, Eur. Phys. J. D 28, 361(2004)]. The authors propose an identification of the vibrational motion responsible for the oscillations in the ion signal, from quantum mech. wave packet propagations and classical trajectory calcns. The good agreement between expt. and theory allows for a clear interpretation of the detected dynamics. [on SciFinder(R)] |
| 19. | Durand, G; Heitz, M -C; Spiegelman, F; Meier, C; Mitric, R; Bonacic-Koutecky, V; Pittner, J Different approaches for the calculation of electronic excited states of nonstoichiometric alkali halide clusters: The example of Na3F. Journal Article Journal of Chemical Physics, 121 (20), pp. 9898–9905, 2004, ISSN: 0021-9606. @article{Durand2004, title = {Different approaches for the calculation of electronic excited states of nonstoichiometric alkali halide clusters: The example of Na3F.}, author = {G Durand and M -C Heitz and F Spiegelman and C Meier and R Mitric and V Bonacic-Koutecky and J Pittner}, doi = {10.1063/1.1802432}, issn = {0021-9606}, year = {2004}, date = {2004-01-01}, journal = {Journal of Chemical Physics}, volume = {121}, number = {20}, pages = {9898--9905}, publisher = {American Institute of Physics}, abstract = {The electronic structure and excited states of the Na3F cluster are investigated using different approx., but numerically efficient, computational schemes, such as a 2e hybrid quantum/classical pseudopotential model with full-CI or time-dependent d.-functional theory. Various quantities such as geometries and transition energies are compared with results previously obtained by multireference CI calcns., taken as ref. data. The potential energy surfaces of the lowest excited states are investigated and the finite-temp. absorption spectra are calcd. The good agreement with recent beam expts. [J.-M. L'Hermite et al., Eur. Phys. J. D 28, 361 (2004)] leads to the conclusion that the absorption spectrum obsd. exptl. corresponds to the lowest energy isomer which has a C2v planar rhombic geometry. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The electronic structure and excited states of the Na3F cluster are investigated using different approx., but numerically efficient, computational schemes, such as a 2e hybrid quantum/classical pseudopotential model with full-CI or time-dependent d.-functional theory. Various quantities such as geometries and transition energies are compared with results previously obtained by multireference CI calcns., taken as ref. data. The potential energy surfaces of the lowest excited states are investigated and the finite-temp. absorption spectra are calcd. The good agreement with recent beam expts. [J.-M. L'Hermite et al., Eur. Phys. J. D 28, 361 (2004)] leads to the conclusion that the absorption spectrum obsd. exptl. corresponds to the lowest energy isomer which has a C2v planar rhombic geometry. [on SciFinder(R)] |
| 18. | Bonacic-Koutecky, V; Mitric, R; Hartmann, M; Pittner, J Theoretical approach for simulation of femtosecond spectra: New strategies for optimal control of complex systems. Journal Article International Journal of Quantum Chemistry, 99 (4), pp. 408–420, 2004, ISSN: 0020-7608. @article{Bonacic-Koutecky2004, title = {Theoretical approach for simulation of femtosecond spectra: New strategies for optimal control of complex systems.}, author = {V Bonacic-Koutecky and R Mitric and M Hartmann and J Pittner}, doi = {10.1002/qua.10845}, issn = {0020-7608}, year = {2004}, date = {2004-01-01}, journal = {International Journal of Quantum Chemistry}, volume = {99}, number = {4}, pages = {408--420}, publisher = {John Wiley & Sons, Inc.}, abstract = {We present the ab initio Wigner distribution approach for simulation of femtosecond pump-probe and pump-dump signals and the new strategy for tailoring the light pulses that allow for optimal control of ultrafast processes. Our ab initio Wigner distribution approach combines the Wigner-Moyal representation of the vibronic d. matrix with the ab initio multistate adiabatic and nonadiabatic mol. dynamics "on the fly" involving ground and excited electronic states. This approach allows for accurate simulations of femtosecond signals based on analytic formulation for systems of moderate complexity taking into account all degrees of freedom. For this purpose the following items are needed: (1) temp.-dependent ground-state initial conditions; (2) an ensemble of trajectories for the investigation of the dynamics of the system either on the adiabatic electronic excited state or on both the excited and ground states through nonadiabatic coupling; and (3) either the cationic or neutral ground state for the probing step. The goal of optimal control of femtosecond processes is to tailor pump-dump pulses that drive the system via electronically excited state to the desired ground-state objective with the maximal yield. For the multidimensional systems this is possible only if the connective pathway between initial state and the objective can be ensured and the optimal pathway can be found. We show that these requirements are fulfilled by introducing the concept of the intermediate target in the excited state. Its role is to select the appropriate parts of energy surfaces at the given time delay between the two pulses, allowing us to reach optimally the objective. We illustrate the scope of our approach on nonstoichiometric halide deficient NanFn-1 clusters, which are characterized by strong ionic bonding and one excess electron. The choice of the systems has been made to det. timescales of different processes in the excited states and apply the new strategy for optimal control. This involves the bond breaking leading to (1) periodic geometric rearrangements such as in the case of Na2F or (2) nonadiabatic radiationless decay through conical intersection between the first excited state and the ground state occurring for Na3F2. In the latter case we optimize and analyze the pump and dump pulses to drive the isomerization process in the Na3F2 cluster to the second isomer by suppressing radiationless transition through conical intersection. The shaped pump-dump pulses serve as guidance for the exptl. work in progress. Population of one of the two isomers allows us to establish a mol. switch. Such bimodal type of behavior might provide a basic element for information storage. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present the ab initio Wigner distribution approach for simulation of femtosecond pump-probe and pump-dump signals and the new strategy for tailoring the light pulses that allow for optimal control of ultrafast processes. Our ab initio Wigner distribution approach combines the Wigner-Moyal representation of the vibronic d. matrix with the ab initio multistate adiabatic and nonadiabatic mol. dynamics "on the fly" involving ground and excited electronic states. This approach allows for accurate simulations of femtosecond signals based on analytic formulation for systems of moderate complexity taking into account all degrees of freedom. For this purpose the following items are needed: (1) temp.-dependent ground-state initial conditions; (2) an ensemble of trajectories for the investigation of the dynamics of the system either on the adiabatic electronic excited state or on both the excited and ground states through nonadiabatic coupling; and (3) either the cationic or neutral ground state for the probing step. The goal of optimal control of femtosecond processes is to tailor pump-dump pulses that drive the system via electronically excited state to the desired ground-state objective with the maximal yield. For the multidimensional systems this is possible only if the connective pathway between initial state and the objective can be ensured and the optimal pathway can be found. We show that these requirements are fulfilled by introducing the concept of the intermediate target in the excited state. Its role is to select the appropriate parts of energy surfaces at the given time delay between the two pulses, allowing us to reach optimally the objective. We illustrate the scope of our approach on nonstoichiometric halide deficient NanFn-1 clusters, which are characterized by strong ionic bonding and one excess electron. The choice of the systems has been made to det. timescales of different processes in the excited states and apply the new strategy for optimal control. This involves the bond breaking leading to (1) periodic geometric rearrangements such as in the case of Na2F or (2) nonadiabatic radiationless decay through conical intersection between the first excited state and the ground state occurring for Na3F2. In the latter case we optimize and analyze the pump and dump pulses to drive the isomerization process in the Na3F2 cluster to the second isomer by suppressing radiationless transition through conical intersection. The shaped pump-dump pulses serve as guidance for the exptl. work in progress. Population of one of the two isomers allows us to establish a mol. switch. Such bimodal type of behavior might provide a basic element for information storage. [on SciFinder(R)] |
| 17. | Schaefer-Bung, Boris; Mitric, Roland; Bonacic-Koutecky, Vlasta; Bartelt, Andreas; Lupulescu, Cosmin; Lindinger, Albrecht; Vajda, Stefan; Weber, Stefan M; Woeste, Ludger. Optimal Control of Ionization Processes in NaK: Comparison between Theory and Experiment. Journal Article Journal of Physical Chemistry A, 108 (19), pp. 4175–4179, 2004, ISSN: 1089-5639. @article{Schaefer-Bung2004, title = {Optimal Control of Ionization Processes in NaK: Comparison between Theory and Experiment.}, author = {Boris Schaefer-Bung and Roland Mitric and Vlasta Bonacic-Koutecky and Andreas Bartelt and Cosmin Lupulescu and Albrecht Lindinger and Stefan Vajda and Stefan M Weber and Ludger. Woeste}, doi = {10.1021/jp049153p}, issn = {1089-5639}, year = {2004}, date = {2004-01-01}, journal = {Journal of Physical Chemistry A}, volume = {108}, number = {19}, pages = {4175--4179}, publisher = {American Chemical Society}, abstract = {Agreement is reported between the shapes of tailored pulses obtained theor. and exptl. by using the optimal-control theory and the closed-loop learning technique to maximize the ionization yield in NaK. The theor. pulse shapes are robust regarding the choice of the initial guess. The authors assign the leading features of the pulse shapes to processes underlying the optimal control and reveal the mechanism which involves an electronic transition followed by a direct 2-photon process and sequential 1-photon processes at later times. The optimal control not only serves for maximizing the desired yield but also as a tool for the anal. and the identification of the responsible processes. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Agreement is reported between the shapes of tailored pulses obtained theor. and exptl. by using the optimal-control theory and the closed-loop learning technique to maximize the ionization yield in NaK. The theor. pulse shapes are robust regarding the choice of the initial guess. The authors assign the leading features of the pulse shapes to processes underlying the optimal control and reveal the mechanism which involves an electronic transition followed by a direct 2-photon process and sequential 1-photon processes at later times. The optimal control not only serves for maximizing the desired yield but also as a tool for the anal. and the identification of the responsible processes. [on SciFinder(R)] |
| 16. | Hagen, Jan; Socaciu, Liana D; Le Roux, Jerome ; Popolan, Denisia; Bernhardt, Thorsten M; Woeste, Ludger; Mitric, Roland; Noack, Holger; Bonacic-Koutecky, Vlasta. Cooperative Effects in the Activation of Molecular Oxygen by Anionic Silver Clusters. Journal Article Journal of the American Chemical Society, 126 (11), pp. 3442–3443, 2004, ISSN: 0002-7863. @article{Hagen2004, title = {Cooperative Effects in the Activation of Molecular Oxygen by Anionic Silver Clusters.}, author = {Jan Hagen and Liana D Socaciu and Jerome {Le Roux} and Denisia Popolan and Thorsten M Bernhardt and Ludger Woeste and Roland Mitric and Holger Noack and Vlasta. Bonacic-Koutecky}, doi = {10.1021/ja038948r}, issn = {0002-7863}, year = {2004}, date = {2004-01-01}, journal = {Journal of the American Chemical Society}, volume = {126}, number = {11}, pages = {3442--3443}, publisher = {American Chemical Society}, abstract = {A novel size dependence in the adsorption reaction of multiple O2 mols. onto anionic silver clusters Ag-n (n = 1-5) is revealed by gas-phase reaction studies in an rf-ion trap. Ab initio theor. modeling based on DFT method provides insight into the reaction mechanism and finds cooperative electronic and structural effects to be responsible for the size selective reactivity of Agn- clusters toward one or more O2. In particular, Ag-n clusters with odd n have paired electrons and therefore bind one O2 only weakly, but they are simultaneously activated to adsorb a strongly bound second oxygen mol. For the clusters Ag3O4- and Ag5O4-, this cooperative effect results in a superoxo-like, doubly bound O2 subunit with potentially high activity in catalytic silver cluster oxidn. processes. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } A novel size dependence in the adsorption reaction of multiple O2 mols. onto anionic silver clusters Ag-n (n = 1-5) is revealed by gas-phase reaction studies in an rf-ion trap. Ab initio theor. modeling based on DFT method provides insight into the reaction mechanism and finds cooperative electronic and structural effects to be responsible for the size selective reactivity of Agn- clusters toward one or more O2. In particular, Ag-n clusters with odd n have paired electrons and therefore bind one O2 only weakly, but they are simultaneously activated to adsorb a strongly bound second oxygen mol. For the clusters Ag3O4- and Ag5O4-, this cooperative effect results in a superoxo-like, doubly bound O2 subunit with potentially high activity in catalytic silver cluster oxidn. processes. [on SciFinder(R)] |
| 15. | Kimble, Michele L; Castleman Jr., Welford A; Mitric, Roland; Buergel, Christian; Bonacic-Koutecky, Vlasta. Reactivity of Atomic Gold Anions toward Oxygen and the Oxidation of CO: Experiment and Theory. Journal Article Journal of the American Chemical Society, 126 (8), pp. 2526–2535, 2004, ISSN: 0002-7863. @article{Kimble2004, title = {Reactivity of Atomic Gold Anions toward Oxygen and the Oxidation of CO: Experiment and Theory.}, author = {Michele L Kimble and Welford A {Castleman Jr.} and Roland Mitric and Christian Buergel and Vlasta. Bonacic-Koutecky}, doi = {10.1021/ja030544b}, issn = {0002-7863}, year = {2004}, date = {2004-01-01}, journal = {Journal of the American Chemical Society}, volume = {126}, number = {8}, pages = {2526--2535}, publisher = {American Chemical Society}, abstract = {Results for the binding of carbon monoxide and oxygen along with the oxidn. of CO in the presence of at. Au- have been obtained utilizing a fast-flow reactor mass spectrometer. In addn., d. functional calcns. have been performed to explain the exptl. findings. It was obsd. that upon oxygen addn. to the metal plasma, gold oxide species of the form AuOn-, where n = 1-3, were produced. The addn. of carbon monoxide to the preoxidized gold atom revealed that AuO- and AuO3- promote the oxidn. of CO. D. functional calcns. on structures and their energetics confirmed the exptl. findings and allowed us to propose mechanisms for the oxidn. of carbon monoxide. The reactions of CO with AuO1,3- proceed via complex formation with CO bound to the oxygen atom, followed by either cleavage of the Au-O bond or complex rearrangement to form a weakly bound CO2 unit, leading in both cases to the emanation of CO2. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Results for the binding of carbon monoxide and oxygen along with the oxidn. of CO in the presence of at. Au- have been obtained utilizing a fast-flow reactor mass spectrometer. In addn., d. functional calcns. have been performed to explain the exptl. findings. It was obsd. that upon oxygen addn. to the metal plasma, gold oxide species of the form AuOn-, where n = 1-3, were produced. The addn. of carbon monoxide to the preoxidized gold atom revealed that AuO- and AuO3- promote the oxidn. of CO. D. functional calcns. on structures and their energetics confirmed the exptl. findings and allowed us to propose mechanisms for the oxidn. of carbon monoxide. The reactions of CO with AuO1,3- proceed via complex formation with CO bound to the oxygen atom, followed by either cleavage of the Au-O bond or complex rearrangement to form a weakly bound CO2 unit, leading in both cases to the emanation of CO2. [on SciFinder(R)] |
2003 |
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| 14. | Hrenar, T; Mitric, R; Meic, Z; Meier, H; Stalmach, U Vibrational spectra and DFT calculations of PPV-oligomers. Journal Article Journal of Molecular Structure, 661-662 , pp. 33–40, 2003, ISSN: 0022-2860. @article{Hrenar2003, title = {Vibrational spectra and DFT calculations of PPV-oligomers.}, author = {T Hrenar and R Mitric and Z Meic and H Meier and U Stalmach}, doi = {10.1016/S0022-2860(03)00526-X}, issn = {0022-2860}, year = {2003}, date = {2003-01-01}, journal = {Journal of Molecular Structure}, volume = {661-662}, pages = {33--40}, publisher = {Elsevier Science B.V.}, abstract = {The first two members of the p-phenylenevinylene-oligomer family (i.e. 1,4-distyrylbenzene and 4,4'-distyrylstilbene) were synthesized and their IR and Raman spectra recorded and empirically assigned. Mol. geometries were optimized for the planar point group (C2h) by the d. functional theory (DFT) method using the B3LYP functional and 6-31G* basis set. Calcns. of vibrational spectra, including intensities, were carried out subsequently using the DFT method with the same basis set and linear scaling was applied. Calcd. vibrational wavenumbers are in a fair agreement with our own exptl. spectra. In order to explore changes in vibrational dynamics that are obtained with the extension of the chain, differences in potential energy distribution of normal modes are investigated and discussed. It was shown that B3LYP functional well describes the mentioned differences in IR and Raman spectra and presents a sound basis for a more thorough research. The results are compared with those of trans-stilbene, a mol. structurally most closely related to the members of the p-phenylenevinylenes family. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The first two members of the p-phenylenevinylene-oligomer family (i.e. 1,4-distyrylbenzene and 4,4'-distyrylstilbene) were synthesized and their IR and Raman spectra recorded and empirically assigned. Mol. geometries were optimized for the planar point group (C2h) by the d. functional theory (DFT) method using the B3LYP functional and 6-31G* basis set. Calcns. of vibrational spectra, including intensities, were carried out subsequently using the DFT method with the same basis set and linear scaling was applied. Calcd. vibrational wavenumbers are in a fair agreement with our own exptl. spectra. In order to explore changes in vibrational dynamics that are obtained with the extension of the chain, differences in potential energy distribution of normal modes are investigated and discussed. It was shown that B3LYP functional well describes the mentioned differences in IR and Raman spectra and presents a sound basis for a more thorough research. The results are compared with those of trans-stilbene, a mol. structurally most closely related to the members of the p-phenylenevinylenes family. [on SciFinder(R)] |
| 13. | Fielicke, Andre; Mitric, Roland; Meijer, Gerard; Bonacic-Koutecky, Vlasta; Von Helden, Gert. The Structures of Vanadium Oxide Cluster-Ethene Complexes. A Combined IR Multiple Photon Dissociation Spectroscopy and DFT Calculation Study. Journal Article Journal of the American Chemical Society, 125 (51), pp. 15716–15717, 2003, ISSN: 0002-7863. @article{Fielicke2003, title = {The Structures of Vanadium Oxide Cluster-Ethene Complexes. A Combined IR Multiple Photon Dissociation Spectroscopy and DFT Calculation Study.}, author = {Andre Fielicke and Roland Mitric and Gerard Meijer and Vlasta Bonacic-Koutecky and Gert. {Von Helden}}, doi = {10.1021/ja036264d}, issn = {0002-7863}, year = {2003}, date = {2003-01-01}, journal = {Journal of the American Chemical Society}, volume = {125}, number = {51}, pages = {15716--15717}, publisher = {American Chemical Society}, abstract = {IR spectra of complexes of small vanadium oxide clusters with ethene are detd. using IR multiple photon dissocn. (IR-MPD) spectroscopy in the range of 550-1850 cm-1. The structures of the complexes have been identified by comparison of the exptl. spectra with the harmonic vibrational frequencies and corresponding IR intensities of possible isomers calcd. with DFT methods. It was found that the ethene mol. binds directly to a vanadium atom in the cluster, although this it is not in all cases the most stable arrangement. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } IR spectra of complexes of small vanadium oxide clusters with ethene are detd. using IR multiple photon dissocn. (IR-MPD) spectroscopy in the range of 550-1850 cm-1. The structures of the complexes have been identified by comparison of the exptl. spectra with the harmonic vibrational frequencies and corresponding IR intensities of possible isomers calcd. with DFT methods. It was found that the ethene mol. binds directly to a vanadium atom in the cluster, although this it is not in all cases the most stable arrangement. [on SciFinder(R)] |
| 12. | Justes, D R; Castleman Jr., A W; Mitric, R; Bonacic-Koutecky, V V2O5+ reaction with C2H4: Theoretical considerations of experimental findings. Journal Article European Physical Journal D: Atomic, Molecular and Optical Physics, 24 (1-3), pp. 331–334, 2003, ISSN: 1434-6060. @article{Justes2003, title = {V2O5+ reaction with C2H4: Theoretical considerations of experimental findings.}, author = {D R Justes and A W {Castleman Jr.} and R Mitric and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2003-00123-8}, issn = {1434-6060}, year = {2003}, date = {2003-01-01}, journal = {European Physical Journal D: Atomic, Molecular and Optical Physics}, volume = {24}, number = {1-3}, pages = {331--334}, publisher = {EDP Sciences}, abstract = {D. functional calcns. have been performed for the V2O5+ reactions towards ethylene considering at. and mol. oxygen loss, oxygen transfer and assocn. reactions. The oxygen transfer channel to ethylene is energetically favorable in contrast to the oxygen loss. This is in agreement with the exptl. results which show that V2O5+ does not lose at. oxygen during the collision induced dissocn. at thermal energies. A radical cation mechanism based on structure-reactivity relation of V2O5+ cluster is proposed to explain oxygen transfer channel indicating that this reaction in size selective. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } D. functional calcns. have been performed for the V2O5+ reactions towards ethylene considering at. and mol. oxygen loss, oxygen transfer and assocn. reactions. The oxygen transfer channel to ethylene is energetically favorable in contrast to the oxygen loss. This is in agreement with the exptl. results which show that V2O5+ does not lose at. oxygen during the collision induced dissocn. at thermal energies. A radical cation mechanism based on structure-reactivity relation of V2O5+ cluster is proposed to explain oxygen transfer channel indicating that this reaction in size selective. [on SciFinder(R)] |
| 11. | Mitric, R; Hartmann, M; Pittner, J; Bonacic-Koutecky, V New strategy for optimal control of femtosecond pump-dump processes applicable to systems of moderate complexity. Journal Article European Physical Journal D: Atomic, Molecular and Optical Physics, 24 (1-3), pp. 177–180, 2003, ISSN: 1434-6060. @article{Mitric2003a, title = {New strategy for optimal control of femtosecond pump-dump processes applicable to systems of moderate complexity.}, author = {R Mitric and M Hartmann and J Pittner and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2003-00122-9}, issn = {1434-6060}, year = {2003}, date = {2003-01-01}, journal = {European Physical Journal D: Atomic, Molecular and Optical Physics}, volume = {24}, number = {1-3}, pages = {177--180}, publisher = {EDP Sciences}, abstract = {New pump-dump optimal control strategy applicable to the systems of moderate complexity has been developed which allows to drive the system to the desired objective in the ground state via electronically excited state. The strategy is based on the concept of the intermediate target in the excited state whose role is to select appropriate Franck-Condon window at a given time delay between pump and dump pulses in order to reach optimally the objective. The concept was applied on the isomerization process in Na3F2 employing our ab initio Wigner distribution approach. The pump and dump pulses have been found which suppress the radiationless transition through the conical intersection and drive the system via electronically excited state to the second isomer in the ground state with the maximal yield. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } New pump-dump optimal control strategy applicable to the systems of moderate complexity has been developed which allows to drive the system to the desired objective in the ground state via electronically excited state. The strategy is based on the concept of the intermediate target in the excited state whose role is to select appropriate Franck-Condon window at a given time delay between pump and dump pulses in order to reach optimally the objective. The concept was applied on the isomerization process in Na3F2 employing our ab initio Wigner distribution approach. The pump and dump pulses have been found which suppress the radiationless transition through the conical intersection and drive the system via electronically excited state to the second isomer in the ground state with the maximal yield. [on SciFinder(R)] |
| 10. | Chekmarev, S F; Mitric, R; Bonacic-Koutecky, V Kinetics and equilibrium of small metallic clusters: Ab initio confinement molecular dynamics study of Au4. Journal Article European Physical Journal D: Atomic, Molecular and Optical Physics, 24 (1-3), pp. 45–48, 2003, ISSN: 1434-6060. @article{Chekmarev2003, title = {Kinetics and equilibrium of small metallic clusters: Ab initio confinement molecular dynamics study of Au4.}, author = {S F Chekmarev and R Mitric and V Bonacic-Koutecky}, doi = {10.1140/epjd/e2003-00153-2}, issn = {1434-6060}, year = {2003}, date = {2003-01-01}, journal = {European Physical Journal D: Atomic, Molecular and Optical Physics}, volume = {24}, number = {1-3}, pages = {45--48}, publisher = {EDP Sciences}, abstract = {The ab initio mol. dynamics (AIMD) is combined with the heuristic, successive confinement method of surveying a potential energy surface (PES), thereby offering a framework for the simulation study of kinetics and equil. properties of metallic clusters. This approach is applied to the study of Au4, a cluster possessing a simple but specific PES, which consists of very shallow and deep basins and due to this presents a challenge to the conventional AIMD methods. Among other things, the probabilities of the transitions between isomers have been found, and on this basis, both the time-dependent and equil. populations of the isomers have been calcd. for the conditions typical of the NeNePo expts. in the femtosecond pump-probe spectroscopy. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The ab initio mol. dynamics (AIMD) is combined with the heuristic, successive confinement method of surveying a potential energy surface (PES), thereby offering a framework for the simulation study of kinetics and equil. properties of metallic clusters. This approach is applied to the study of Au4, a cluster possessing a simple but specific PES, which consists of very shallow and deep basins and due to this presents a challenge to the conventional AIMD methods. Among other things, the probabilities of the transitions between isomers have been found, and on this basis, both the time-dependent and equil. populations of the isomers have been calcd. for the conditions typical of the NeNePo expts. in the femtosecond pump-probe spectroscopy. [on SciFinder(R)] |
| 9. | Mitric, R; Buergel, C; Burda, J; Bonacic-Koutecky, V; Fantucci, P Structural properties and reactivity of bimetallic silver-gold clusters. Journal Article European Physical Journal D: Atomic, Molecular and Optical Physics, 24 (1-3), pp. 41–44, 2003, ISSN: 1434-6060. @article{Mitric2003b, title = {Structural properties and reactivity of bimetallic silver-gold clusters.}, author = {R Mitric and C Buergel and J Burda and V Bonacic-Koutecky and P Fantucci}, doi = {10.1140/epjd/e2003-00124-7}, issn = {1434-6060}, year = {2003}, date = {2003-01-01}, journal = {European Physical Journal D: Atomic, Molecular and Optical Physics}, volume = {24}, number = {1-3}, pages = {41--44}, publisher = {EDP Sciences}, abstract = {Bimetallic silver-gold clusters are well suited to study changes in metallic vs. "ionic" properties involving charge transfer as a function of the size and the compn. We present structures, ionization potentials (IP) and vertical detachment energies (VDE) for neutral and charged bimetallic AunAgm (2 ≤ (n + m) ≤ 5) clusters obtained from d. functional level of theory. In the stable structures of these clusters Au atoms assume positions which favor charge transfer from Ag atoms. In clusters with equal nos. of hetero atoms (n = m = 1 - 4) heteronuclear bonding is preferred to homonuclear bonding, giving rise to large values of ionization potentials. For larger clusters (n = m = 5, 10) stable structures do not favor neither hetero bonding nor segregation into the single components, although they exhibit more metallic than ionic features. This remains valid also for Au8Ag12 cluster characterized by strong charge transfer to gold subunit. The influence of doping of pure gold clusters with silver atoms on VDE and IP values is discussed in context of their reactivity towards O2 and CO mols. As a starting point we consider reactivity towards CO and O2 mols. on the example of AgAu- dimer. The results show that the catalytic cycle can be fulfilled. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Bimetallic silver-gold clusters are well suited to study changes in metallic vs. "ionic" properties involving charge transfer as a function of the size and the compn. We present structures, ionization potentials (IP) and vertical detachment energies (VDE) for neutral and charged bimetallic AunAgm (2 ≤ (n + m) ≤ 5) clusters obtained from d. functional level of theory. In the stable structures of these clusters Au atoms assume positions which favor charge transfer from Ag atoms. In clusters with equal nos. of hetero atoms (n = m = 1 - 4) heteronuclear bonding is preferred to homonuclear bonding, giving rise to large values of ionization potentials. For larger clusters (n = m = 5, 10) stable structures do not favor neither hetero bonding nor segregation into the single components, although they exhibit more metallic than ionic features. This remains valid also for Au8Ag12 cluster characterized by strong charge transfer to gold subunit. The influence of doping of pure gold clusters with silver atoms on VDE and IP values is discussed in context of their reactivity towards O2 and CO mols. As a starting point we consider reactivity towards CO and O2 mols. on the example of AgAu- dimer. The results show that the catalytic cycle can be fulfilled. [on SciFinder(R)] |
| 8. | Wallace, William T; Wyrwas, Richard B; Whetten, Robert L; Mitric, Roland; Bonacic-Koutecky, Vlasta. Oxygen Adsorption on Hydrated Gold Cluster Anions: Experiment and Theory. Journal Article Journal of the American Chemical Society, 125 (27), pp. 8408–8414, 2003, ISSN: 0002-7863. @article{Wallace2003, title = {Oxygen Adsorption on Hydrated Gold Cluster Anions: Experiment and Theory.}, author = {William T Wallace and Richard B Wyrwas and Robert L Whetten and Roland Mitric and Vlasta. Bonacic-Koutecky}, doi = {10.1021/ja034905z}, issn = {0002-7863}, year = {2003}, date = {2003-01-01}, journal = {Journal of the American Chemical Society}, volume = {125}, number = {27}, pages = {8408--8414}, publisher = {American Chemical Society}, abstract = {The discovery that supported gold clusters act as highly efficient catalysts for low-temp. oxidn. reactions has led to a great deal of work aimed at understanding the origins of the catalytic activity. Several studies have shown that the presence of trace moisture is required for the catalysts to function. Using near-atm. pressure flow reactor techniques, we have studied humidity and temp. effects on the reactivity of gas-phase gold cluster anions with O2. Near room temp., the humid source produces abundant gold-hydroxy cluster anions, AuNOH-, and these have a reversed O2 adsorption activity: nonreactive bare gold clusters become active when in the form AuNOH-, while active bare clusters are inactive when -OH is bound. The binding energies for the stable structures obtained from d. functional calcns. confirm fully these findings. Moreover, the theory provides evidence that electron-transfer induced by the binding of a OH group enhances the reactivity toward mol. oxygen for odd anionic gold clusters and suppresses the reactivity for the even ones. The temp. dependence of O2 addn. to Au3OH- and Au-4 indicates deviations from equil. control at temps. below room temp. The effects of humidity on gold cluster adsorption activity support the conclusion drawn for the mechanism of O2 adsorption on "dry" gold cluster anions and provides insight into the possible role of water in the enhanced activity of supported gold cluster catalysts. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The discovery that supported gold clusters act as highly efficient catalysts for low-temp. oxidn. reactions has led to a great deal of work aimed at understanding the origins of the catalytic activity. Several studies have shown that the presence of trace moisture is required for the catalysts to function. Using near-atm. pressure flow reactor techniques, we have studied humidity and temp. effects on the reactivity of gas-phase gold cluster anions with O2. Near room temp., the humid source produces abundant gold-hydroxy cluster anions, AuNOH-, and these have a reversed O2 adsorption activity: nonreactive bare gold clusters become active when in the form AuNOH-, while active bare clusters are inactive when -OH is bound. The binding energies for the stable structures obtained from d. functional calcns. confirm fully these findings. Moreover, the theory provides evidence that electron-transfer induced by the binding of a OH group enhances the reactivity toward mol. oxygen for odd anionic gold clusters and suppresses the reactivity for the even ones. The temp. dependence of O2 addn. to Au3OH- and Au-4 indicates deviations from equil. control at temps. below room temp. The effects of humidity on gold cluster adsorption activity support the conclusion drawn for the mechanism of O2 adsorption on "dry" gold cluster anions and provides insight into the possible role of water in the enhanced activity of supported gold cluster catalysts. [on SciFinder(R)] |
| 7. | Justes, Dina R; Mitric, Roland; Moore, Nelly A; Bonacic-Koutecky, Vlasta; Castleman Jr., Welford A Theoretical and Experimental Consideration of the Reactions between VxOy+ and Ethylene. Journal Article Journal of the American Chemical Society, 125 (20), pp. 6289–6299, 2003, ISSN: 0002-7863. @article{Justes2003a, title = {Theoretical and Experimental Consideration of the Reactions between VxOy+ and Ethylene.}, author = {Dina R Justes and Roland Mitric and Nelly A Moore and Vlasta Bonacic-Koutecky and Welford A {Castleman Jr.}}, doi = {10.1021/ja021349k}, issn = {0002-7863}, year = {2003}, date = {2003-01-01}, journal = {Journal of the American Chemical Society}, volume = {125}, number = {20}, pages = {6289--6299}, publisher = {American Chemical Society}, abstract = {We present joint theor. and exptl. results which provide evidence for the selectivity of VxOy+ clusters in reactions toward ethylene due to the charge and different oxidn. states of vanadium for different cluster sizes. D. functional calcns. were performed on the reactions between VxOy+ and ethylene, allowing us to identify the structure-reactivity relationship and to corroborate the exptl. results obtained by Castleman and co-workers (Zemski, K. A.; Justes, D. R.; Castleman, A. W., Jr. J. Phys. Chem. A 2001, 105, 10237). The lowest-energy structures for the V2O2-6+ and V4O8-10+ clusters and the V2O3-6+-C2H4 and V4O10+-C2H4 complexes, as well as the energetics for reactions between ethylene and V2O4-6+ and V4O10+ are presented here. The oxygen transfer reaction pathway was detd. to be the most energetically favorable one available to V2O5+ and V4O10+ via a radical-cation mechanism. The assocn. and replacement reaction pathways were found to be the optimal channels for V2O4+ and V2O6+, resp. These results are in agreement with the exptl. results reported previously. Expts. were also conducted for the reactions between V2O5+ and ethylene to include an energetic anal. at increasing pressures. It was found that the addn. of energy depleted the prodn. of V2O4+, confirming that a more involved reaction rather than a collisional process is responsible for the obsd. phenomenon. In this contribution we show that investigation of reactions involving gas-phase cationic vanadium oxide clusters with small hydrocarbons is suitable for the identification of reactive centers responsible for selectivity in heterogeneous catalysis. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present joint theor. and exptl. results which provide evidence for the selectivity of VxOy+ clusters in reactions toward ethylene due to the charge and different oxidn. states of vanadium for different cluster sizes. D. functional calcns. were performed on the reactions between VxOy+ and ethylene, allowing us to identify the structure-reactivity relationship and to corroborate the exptl. results obtained by Castleman and co-workers (Zemski, K. A.; Justes, D. R.; Castleman, A. W., Jr. J. Phys. Chem. A 2001, 105, 10237). The lowest-energy structures for the V2O2-6+ and V4O8-10+ clusters and the V2O3-6+-C2H4 and V4O10+-C2H4 complexes, as well as the energetics for reactions between ethylene and V2O4-6+ and V4O10+ are presented here. The oxygen transfer reaction pathway was detd. to be the most energetically favorable one available to V2O5+ and V4O10+ via a radical-cation mechanism. The assocn. and replacement reaction pathways were found to be the optimal channels for V2O4+ and V2O6+, resp. These results are in agreement with the exptl. results reported previously. Expts. were also conducted for the reactions between V2O5+ and ethylene to include an energetic anal. at increasing pressures. It was found that the addn. of energy depleted the prodn. of V2O4+, confirming that a more involved reaction rather than a collisional process is responsible for the obsd. phenomenon. In this contribution we show that investigation of reactions involving gas-phase cationic vanadium oxide clusters with small hydrocarbons is suitable for the identification of reactive centers responsible for selectivity in heterogeneous catalysis. [on SciFinder(R)] |
2002 |
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| 6. | Meic, Zlatko; Hrenar, Tomica; Mitric, Roland. Dependence of calculated vibrational dynamics in trans-stilbene on the choice of DFT functionals. Journal Article Glasnik na Hemicarite i Tehnolozite na Makedonija, 21 (2), pp. 161–164, 2002, ISSN: 0350-0136. @article{Meic2002, title = {Dependence of calculated vibrational dynamics in trans-stilbene on the choice of DFT functionals.}, author = {Zlatko Meic and Tomica Hrenar and Roland. Mitric}, issn = {0350-0136}, year = {2002}, date = {2002-01-01}, journal = {Glasnik na Hemicarite i Tehnolozite na Makedonija}, volume = {21}, number = {2}, pages = {161--164}, publisher = {Sojuz na Hemicarite i Tehnolozite na Makedonija}, abstract = {Normal coordinate calcns. for the ground electronic state (S0) of trans-stilbene were performed. Two different d. functionals methods were used (B3LYP and B3PW91 with 6-31G* basis sets) in order to theor. investigate how functionals affect potential energy distribution of normal modes. Mols. were optimized within the C2 point group symmetry and subsequent calcns. of IR and Raman vibrational spectra were carried out. Vibrational patterns of selected modes are compared and discussed. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Normal coordinate calcns. for the ground electronic state (S0) of trans-stilbene were performed. Two different d. functionals methods were used (B3LYP and B3PW91 with 6-31G* basis sets) in order to theor. investigate how functionals affect potential energy distribution of normal modes. Mols. were optimized within the C2 point group symmetry and subsequent calcns. of IR and Raman vibrational spectra were carried out. Vibrational patterns of selected modes are compared and discussed. [on SciFinder(R)] |
| 5. | Mitric, Roland; Hartmann, Michael; Pittner, Jiri; Bonacic-Koutecky, Vlasta. New strategy for optimal control of femtosecond pump-dump processes. Journal Article Journal of Physical Chemistry A, 106 (44), pp. 10477–10481, 2002, ISSN: 1089-5639. @article{Mitric2002, title = {New strategy for optimal control of femtosecond pump-dump processes.}, author = {Roland Mitric and Michael Hartmann and Jiri Pittner and Vlasta. Bonacic-Koutecky}, doi = {10.1021/jp021754y}, issn = {1089-5639}, year = {2002}, date = {2002-01-01}, journal = {Journal of Physical Chemistry A}, volume = {106}, number = {44}, pages = {10477--10481}, publisher = {American Chemical Society}, abstract = {The authors propose a new strategy for optimal control with tailored pump-dump pulses which drive a system of moderate complexity via electronically excited states to a desired objective in the ground state with a maximal yield. It is based on the concept of the intermediate target in the excited state which selects the appropriate Franck-Condon window at a given time delay between the two pulses mandatory for reaching optimally the objective. The existence of the intermediate target ensures the connective pathway between the initial state and the objective in the ground state, necessary for the controllability of multidimensional systems involving two electronic states. The authors show the scope of this concept by optimizing and analyzing the pump and dump pulses for driving the isomerization process in the Na3F2 cluster to the second isomer by suppressing radiationless transition through the conical intersection between the first excited and the ground state. This has been realized by employing ab initio Wigner distribution approach. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors propose a new strategy for optimal control with tailored pump-dump pulses which drive a system of moderate complexity via electronically excited states to a desired objective in the ground state with a maximal yield. It is based on the concept of the intermediate target in the excited state which selects the appropriate Franck-Condon window at a given time delay between the two pulses mandatory for reaching optimally the objective. The existence of the intermediate target ensures the connective pathway between the initial state and the objective in the ground state, necessary for the controllability of multidimensional systems involving two electronic states. The authors show the scope of this concept by optimizing and analyzing the pump and dump pulses for driving the isomerization process in the Na3F2 cluster to the second isomer by suppressing radiationless transition through the conical intersection between the first excited and the ground state. This has been realized by employing ab initio Wigner distribution approach. [on SciFinder(R)] |
| 4. | Bonacic-Koutecky, Vlasta; Burda, Jaroslav; Mitric, Roland; Ge, Maofa; Zampella, Giuseppe; Fantucci, Piercarlo. Journal of Chemical Physics, 117 (7), pp. 3120–3131, 2002, ISSN: 0021-9606. @article{Bonacic-Koutecky2002, title = {Density functional study of structural and electronic properties of bimetallic silver-gold clusters: Comparison with pure gold and silver clusters.}, author = {Vlasta Bonacic-Koutecky and Jaroslav Burda and Roland Mitric and Maofa Ge and Giuseppe Zampella and Piercarlo. Fantucci}, doi = {10.1063/1.1492800}, issn = {0021-9606}, year = {2002}, date = {2002-01-01}, journal = {Journal of Chemical Physics}, volume = {117}, number = {7}, pages = {3120--3131}, publisher = {American Institute of Physics}, abstract = {Bimetallic silver-gold clusters offer an excellent opportunity to study changes in metallic vs. "ionic" properties involving charge transfer as a function of the size and the compn., particularly when compared to pure silver and gold clusters. We have detd. structures, ionization potentials, and vertical detachment energies (VDEs) for neutral and charged bimetallic AgmAun [3≤(m + n)≤5] clusters. Calcd. VDE values compare well with available exptl. data. In the stable structures of these clusters Au atoms assume positions which favor the charge transfer from Ag atoms. Heteronuclear bonding is usually preferred to homonuclear bonding in clusters with equal nos. of hetero atoms. In fact, stable structures of neutral Ag2Au2, Ag3Au3, and Ag4Au4 clusters are characterized by the max. no. of hetero bonds and peripheral positions of Au atoms. Bimetallic tetramer as well as hexamer are planar and have common structural properties with corresponding one-component systems, while Ag4Au4 and Ag8 have 3D forms in contrast to Au8 which assumes planar structure. At the d. functional level of theory we have shown that this is due to participation of d electrons in bonding of pure Aun clusters while s electrons dominate bonding in pure Agm as well as in bimetallic clusters. In fact, Aun clusters remain planar for larger sizes than Agm and AgnAun clusters. Segregation between two components in bimetallic systems is not favorable, as shown in the example of Ag5Au5 cluster. The structures of bimetallic clusters with 20 atoms Ag10Au10 and Ag12Au8 are characterized by neg. charged Au subunits embedded in Ag environment. In the latter case, the shape of Au8 is related to a pentagonal bipyramid capped by one atom and contains three exposed neg. charged Au atoms. They might be suitable for activating reactions relevant to catalysis. According to our findings the charge transfer in bimetallic clusters is responsible for formation of neg. charged gold subunits which are expected to be reactive, a situation similar to that of gold clusters supported on metal oxides. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Bimetallic silver-gold clusters offer an excellent opportunity to study changes in metallic vs. "ionic" properties involving charge transfer as a function of the size and the compn., particularly when compared to pure silver and gold clusters. We have detd. structures, ionization potentials, and vertical detachment energies (VDEs) for neutral and charged bimetallic AgmAun [3≤(m + n)≤5] clusters. Calcd. VDE values compare well with available exptl. data. In the stable structures of these clusters Au atoms assume positions which favor the charge transfer from Ag atoms. Heteronuclear bonding is usually preferred to homonuclear bonding in clusters with equal nos. of hetero atoms. In fact, stable structures of neutral Ag2Au2, Ag3Au3, and Ag4Au4 clusters are characterized by the max. no. of hetero bonds and peripheral positions of Au atoms. Bimetallic tetramer as well as hexamer are planar and have common structural properties with corresponding one-component systems, while Ag4Au4 and Ag8 have 3D forms in contrast to Au8 which assumes planar structure. At the d. functional level of theory we have shown that this is due to participation of d electrons in bonding of pure Aun clusters while s electrons dominate bonding in pure Agm as well as in bimetallic clusters. In fact, Aun clusters remain planar for larger sizes than Agm and AgnAun clusters. Segregation between two components in bimetallic systems is not favorable, as shown in the example of Ag5Au5 cluster. The structures of bimetallic clusters with 20 atoms Ag10Au10 and Ag12Au8 are characterized by neg. charged Au subunits embedded in Ag environment. In the latter case, the shape of Au8 is related to a pentagonal bipyramid capped by one atom and contains three exposed neg. charged Au atoms. They might be suitable for activating reactions relevant to catalysis. According to our findings the charge transfer in bimetallic clusters is responsible for formation of neg. charged gold subunits which are expected to be reactive, a situation similar to that of gold clusters supported on metal oxides. [on SciFinder(R)] |
2001 |
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| 3. | Bonacic-Koutecky, Vlasta; Veyret, Vincent; Mitric, Roland. Ab initio study of the absorption spectra of Agn (n=5-8) clusters. Journal Article Journal of Chemical Physics, 115 (22), pp. 10450–10460, 2001, ISSN: 0021-9606. @article{Bonacic-Koutecky2001, title = {Ab initio study of the absorption spectra of Agn (n=5-8) clusters.}, author = {Vlasta Bonacic-Koutecky and Vincent Veyret and Roland. Mitric}, doi = {10.1063/1.1415077}, issn = {0021-9606}, year = {2001}, date = {2001-01-01}, journal = {Journal of Chemical Physics}, volume = {115}, number = {22}, pages = {10450--10460}, publisher = {American Institute of Physics}, abstract = {The absorption spectra of Ag5-8 were detd. in the framework of the linear response equation-of-motion coupled cluster method and related techniques employing 11-electron relativistic effective core potential. In these treatments electron correlation effects for 11 electrons per atom are included, providing an accurate description of excited states of Ag clusters. The calcns. of transition energies and oscillator strengths were carried out in a large energy interval for the stable structures and for the isomeric forms higher in energy. This allowed one to study the influence of structural properties on the spectroscopic patterns and to det. the role of d-electrons. Inclusion of d-electrons in the correlation treatment is mandatory to obtain accurate values for transition energies, but the excitations of s-electrons are primarily responsible for the spectroscopic patterns. They are characterized by the interference phenomena known in mol. spectroscopy which lead to a small no. of intense and a large no. of weak resonances. The calcd. absorption spectra for the stable structures provide accurate predictions of the optical response properties in the gas phase and at the zero temp. Since for neutral Ag clusters the exptl. data in the gas phase are not yet available, the authors also calcd. spectra for deformed structures which model the influence of the environment such as rare-gas atoms, solid Ar-matrix or He-droplet. Comparison of results with available exptl. data permits one to identify structural properties responsible for the recorded spectral features. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } The absorption spectra of Ag5-8 were detd. in the framework of the linear response equation-of-motion coupled cluster method and related techniques employing 11-electron relativistic effective core potential. In these treatments electron correlation effects for 11 electrons per atom are included, providing an accurate description of excited states of Ag clusters. The calcns. of transition energies and oscillator strengths were carried out in a large energy interval for the stable structures and for the isomeric forms higher in energy. This allowed one to study the influence of structural properties on the spectroscopic patterns and to det. the role of d-electrons. Inclusion of d-electrons in the correlation treatment is mandatory to obtain accurate values for transition energies, but the excitations of s-electrons are primarily responsible for the spectroscopic patterns. They are characterized by the interference phenomena known in mol. spectroscopy which lead to a small no. of intense and a large no. of weak resonances. The calcd. absorption spectra for the stable structures provide accurate predictions of the optical response properties in the gas phase and at the zero temp. Since for neutral Ag clusters the exptl. data in the gas phase are not yet available, the authors also calcd. spectra for deformed structures which model the influence of the environment such as rare-gas atoms, solid Ar-matrix or He-droplet. Comparison of results with available exptl. data permits one to identify structural properties responsible for the recorded spectral features. [on SciFinder(R)] |
| 2. | Hartmann, M; Mitric, R; Stanca, B; Bonacic-Koutecky, V Theoretical investigation of the ultrafast NeNePo spectroscopy of Au4 and Ag4 Clusters. Journal Article European Physical Journal D: Atomic, Molecular and Optical Physics, 16 (1-3), pp. 151–155, 2001, ISSN: 1434-6060. @article{Hartmann2001, title = {Theoretical investigation of the ultrafast NeNePo spectroscopy of Au4 and Ag4 Clusters.}, author = {M Hartmann and R Mitric and B Stanca and V Bonacic-Koutecky}, doi = {10.1007/s100530170080}, issn = {1434-6060}, year = {2001}, date = {2001-01-01}, journal = {European Physical Journal D: Atomic, Molecular and Optical Physics}, volume = {16}, number = {1-3}, pages = {151--155}, publisher = {Springer-Verlag}, abstract = {Ultrafast ground state nuclear dynamics of Au4 and Ag4 is theor. explored in the framework of neg. ion - to neutral - to pos. ion (NeNePo) pump-probe spectroscopy based on the ab initio Wigner distribution approach. This involves the prepn. of a nonequil. neutral ensemble by pump induced photodetachment of a thermal anionic ground state distribution, gradient cor. DFT classical trajectory simulations on the fly on the neutral ground state, and detection of the relaxation process of the ensemble in the cationic ground state by a time-delayed probe pulse. In Au4, the initially prepd. linear structure is close to a local min. of the neutral state giving rise to characteristic vibrations in the signals for probe wavelength near the initial Franck-Condon transition. A timescale of ∼1 ps for the structural relaxation towards the stable rhombic D2h neutral isomer was detd. by the increase of the signal for probe wavelength in vicinity of the vertical ionization energy of the rhombic structure. In contrast, the relaxation dynamics in Ag4 was characterized by normal mode vibrations since both the initially prepd. anionic ground state and the neutral ground state have rhombic min. geometries. Thus, time-resolved oscillations of pump-probe signals are fingerprints of structural behavior which can be used exptl. for the identification of particular isomers in the framework of NeNePo spectroscopy. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ultrafast ground state nuclear dynamics of Au4 and Ag4 is theor. explored in the framework of neg. ion - to neutral - to pos. ion (NeNePo) pump-probe spectroscopy based on the ab initio Wigner distribution approach. This involves the prepn. of a nonequil. neutral ensemble by pump induced photodetachment of a thermal anionic ground state distribution, gradient cor. DFT classical trajectory simulations on the fly on the neutral ground state, and detection of the relaxation process of the ensemble in the cationic ground state by a time-delayed probe pulse. In Au4, the initially prepd. linear structure is close to a local min. of the neutral state giving rise to characteristic vibrations in the signals for probe wavelength near the initial Franck-Condon transition. A timescale of ∼1 ps for the structural relaxation towards the stable rhombic D2h neutral isomer was detd. by the increase of the signal for probe wavelength in vicinity of the vertical ionization energy of the rhombic structure. In contrast, the relaxation dynamics in Ag4 was characterized by normal mode vibrations since both the initially prepd. anionic ground state and the neutral ground state have rhombic min. geometries. Thus, time-resolved oscillations of pump-probe signals are fingerprints of structural behavior which can be used exptl. for the identification of particular isomers in the framework of NeNePo spectroscopy. [on SciFinder(R)] |
| 1. | Mitric, R; Hartmann, M; Stanca, B; Bonacic-Koutecky, V; Fantucci, P Journal of Physical Chemistry A, 105 (39), pp. 8892–8905, 2001, ISSN: 1089-5639. @article{Mitric2001, title = {Ab Initio Adiabatic Dynamics Combined with Wigner Distribution Approach to Femtosecond Pump-Probe Negative Ion to Neutral to Positive Ion (NeNePo) Spectroscopy of Ag2Au, Ag4, and Au4 Clusters.}, author = {R Mitric and M Hartmann and B Stanca and V Bonacic-Koutecky and P Fantucci}, doi = {10.1021/jp011759f}, issn = {1089-5639}, year = {2001}, date = {2001-01-01}, journal = {Journal of Physical Chemistry A}, volume = {105}, number = {39}, pages = {8892--8905}, publisher = {American Chemical Society}, abstract = {Ultrafast ground state nuclear dynamics of small coinage metal clusters is theor. explored in the framework of neg. ion to neutral to pos. ion (NeNePo) femtosecond pump-probe spectroscopy with the aim to det. the scope and perspective of this technique. This approach involves the prepn. of an initial ensemble in the anionic ground state of the cluster, one-photon detachment by the pump pulse, the propagation of the system on the neutral electronic ground state, and detection via the cationic ground state by a time-delayed ionizing probe pulse. The calcns. of the NeNePo-ZEKE signals under the condition of zero kinetic energy electrons are based on the combination of the Wigner distribution approach and ab initio mol. dynamics (MD) "on the fly" in the framework of gradient-cor. DFT for the propagation of an ensemble of classical trajectories and involves the av. over the entire phase space. We have chosen examples of Ag2Au and Au4 to investigate time scales and the character of isomerization processes that are influenced by a local min. corresponding to an energetically high-lying isomer with the structure related to the initial anionic structure. Capture of the nuclei within the local min. takes place with dephased (Ag2Au) or nondephased (Au4) vibrational relaxation. Structural relaxations leading to isomerization processes are in both cases of delocalized nature and take place after 1 ps. In contrast, the Ag4 cluster represents an example for which isomerization processes do not occur, since rhombic structures with slightly different bond lengths are global min. of the anionic and neutral ground states. Therefore, the relaxation dynamics is characterized by regular oscillations, which serve as fingerprints of structural properties. On the basis of the anal. of pump-probe signals and underlying dynamics, this contribution provides information about conditions under which structural properties of gas-phase clusters (global and local min.) and isomerization processes can be obsd. in the framework of the NeNePo-ZEKE type of spectroscopy. The latter is important in the context of applicability of this technique to the investigation of cluster reactivity. [on SciFinder(R)]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ultrafast ground state nuclear dynamics of small coinage metal clusters is theor. explored in the framework of neg. ion to neutral to pos. ion (NeNePo) femtosecond pump-probe spectroscopy with the aim to det. the scope and perspective of this technique. This approach involves the prepn. of an initial ensemble in the anionic ground state of the cluster, one-photon detachment by the pump pulse, the propagation of the system on the neutral electronic ground state, and detection via the cationic ground state by a time-delayed ionizing probe pulse. The calcns. of the NeNePo-ZEKE signals under the condition of zero kinetic energy electrons are based on the combination of the Wigner distribution approach and ab initio mol. dynamics (MD) "on the fly" in the framework of gradient-cor. DFT for the propagation of an ensemble of classical trajectories and involves the av. over the entire phase space. We have chosen examples of Ag2Au and Au4 to investigate time scales and the character of isomerization processes that are influenced by a local min. corresponding to an energetically high-lying isomer with the structure related to the initial anionic structure. Capture of the nuclei within the local min. takes place with dephased (Ag2Au) or nondephased (Au4) vibrational relaxation. Structural relaxations leading to isomerization processes are in both cases of delocalized nature and take place after 1 ps. In contrast, the Ag4 cluster represents an example for which isomerization processes do not occur, since rhombic structures with slightly different bond lengths are global min. of the anionic and neutral ground states. Therefore, the relaxation dynamics is characterized by regular oscillations, which serve as fingerprints of structural properties. On the basis of the anal. of pump-probe signals and underlying dynamics, this contribution provides information about conditions under which structural properties of gas-phase clusters (global and local min.) and isomerization processes can be obsd. in the framework of the NeNePo-ZEKE type of spectroscopy. The latter is important in the context of applicability of this technique to the investigation of cluster reactivity. [on SciFinder(R)] |