TY - JOUR A1 - Hartmann, Michael A1 - Heidenreich, Andreas A1 - Pittner, Jiřı́ A1 - Bonačić-Koutecký, Vlasta A1 - Jortner, Joshua T1 - Ultrafast Dynamics of Small Clusters on the Time Scale of Nuclear Motion JF - The Journal of Physical Chemistry A N2 - We present a theoretical study of the multistate dynamics of the Ag3-/Ag3/Ag3+ system on the time scale of nuclear motion, as explored by femtosecond pump−probe negative ion-to neutral-to positive ion (NENEPO) spectroscopy. The dynamics of the Ag3 cluster initiated from its linear transition state involves configurational relaxation, intracluster collision, and onset of IVR, resonant and dissipative IVR and vibrational equilibration, whose time scales were determined. Our analysis reveals that theory is essential for the elucidation of the rich dynamic information regarding geometrical change, completion of IVR, and vibrational coherence effects in the NENEPO femtosecond signals. KW - Physical chemistry KW - Nuclear motion Y1 - 1998 N1 - Volltext aus urheberrechtlichen Gründen nicht verfügbar. Fulltext due to copyright not available. VL - 102 IS - 23 SP - 4069 EP - 4074 ER - TY - JOUR A1 - Bonačić-Koutecký, Vlasta A1 - Pittner, Jiřı́ A1 - Pou-Amérigo, Rosendo A1 - Hartmann, Michael T1 - Ab-initio study of structural and optical properties of nonstoichiometric alkalimetal- oxides JF - Zeitschrift für Physik D N2 - Structural and optical properties of nonstoichiometric LinO and NanO (n = 3, 4) clusters containing one and two excess electrons are studied using ab-initio methods accounting for electron correlation. We show that calculated absorption patterns are excellent fingerprints of structural and bonding properties. The optical response of Li4O and Na4O clusters with the most stable tetrahedral type structures is characterized by a common feature, that is the appearance of a dominant intense transition in infrared regime although excess of electrons are not localized, as it is the case for small alkali-halide clusters, with cuboid corner vacancy (surface F-center in finite systems). KW - Inorganic Chemistry KW - Physical chemistry Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0298-opus4-5748 VL - 40 IS - 1 SP - 445 EP - 447 ER - TY - JOUR A1 - Hartmann, Michael T1 - Non equilibrium Green's function approach to nonadiabetic molecular dynamics JF - Journal of Physical Chemistry A N2 - Keine Angabe - No details KW - Molecular Dynamics KW - Physical chemistry Y1 - 2002 N1 - Volltext aus urheberrechtlichen Gründen nicht verfügbar. Fulltext due to copyright not available. VL - 106 SP - Keine Angabe - No details EP - Keine Angabe - No details ER - TY - JOUR A1 - Mitrić, Roland A1 - Hartmann, Michael A1 - Stanca, B. A1 - Bonačić-Koutecký, Vlasta A1 - Fantucci, P. T1 - 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 JF - Journal of Physical Chemistry A N2 - Ultrafast ground state nuclear dynamics of small coinage metal clusters is theoretically explored in the framework of negative ion to neutral to positive ion (NeNePo) femtosecond pump−probe spectroscopy with the aim to determine the scope and perspective of this technique. This approach involves the preparation 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 calculations 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 molecular dynamics (MD) “on the fly” in the framework of gradient-corrected DFT for the propagation of an ensemble of classical trajectories and involves the average 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 minimum corresponding to an energetically high-lying isomer with the structure related to the initial anionic structure. Capture of the nuclei within the local minimum 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 minima 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 analysis of pump−probe signals and underlying dynamics, this contribution provides information about conditions under which structural properties of gas-phase clusters (global and local minima) and isomerization processes can be observed 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. KW - Physical chemistry Y1 - 2001 N1 - Volltext aus urheberrechtlichen Gründen nicht verfügbar. Fulltext due to copyright not available. VL - 105 IS - 39 SP - 8892 EP - 8905 ER -