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<export-example>
  <doc>
    <id>571</id>
    <completedYear>2001</completedYear>
    <publishedYear>2001</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>714</pageFirst>
    <pageLast>739</pageLast>
    <pageNumber/>
    <edition/>
    <issue>6</issue>
    <volume>84</volume>
    <type>article</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>2014-07-03</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Theoretical exploration of ultrafast spectroscopy of small clusters</title>
    <abstract language="eng">The central issue in femtosecond (fs) time resolved spectroscopy of clusters is the investigation of geometric relaxation and internal vibrational redistribution (IVR) after optical excitation in a nonequilibrium configuration of nuclei by laser photoelectron excitation, and corresponding time delayed probing by multiphoton-ionization. For this purpose, we have developed multistate ab initio molecular dynamics involving adiabatic ground and excited electronic states, as well as nonadiabatic coupling between them, using the time evolution of initial thermal ensemble in Wigner representation. The combination of ab initio quantum chemical methods, used for the adiabatic and nonadiabatic molecular dynamics “on the fly,” and the Wigner distribution approach for the description of the motion of the nuclei allowed us the accurate determination of pump-probe and pump-dump signals also under temperature dependent initial conditions. The connection between simulated pump-probe signals and the underlying dynamics of nuclei involving adiabatic electronic ground states has been first established for the example of the Agequation image/Ag3/Agequation image systems, and compared with experimental negative-to-neutral-to-positive NeNePo pump-probe signals. Our simulations reproduced the experimental NeNePo results and determined, in addition to the timescales of geometric relaxation, the conditions under which the resonant or dissipative IVR, as well as vibrational coherence, should be found in the experimental pump-probe signals. This can be realized in the zero electron kinetic energy NeNePo-ZEKE experiments, which are in progress. The above combination of methods has been recently extended to the analysis of the timescales as well as of the dynamics in excited electronic states of the nonstoichiometric NanFn−1 (n=2–4) clusters with the single excess valence electron. Our approach allows the simulation of femtosecond NeExPo-pump-probe and NeExNe-pump-dump signals, based on an analytic formulation which utilizes temperature dependent ground state initial conditions of neutral system (Ne); an ensemble of trajectories carried out either on the adiabatic electronic excited state (Ex), or on both the excited and the ground states through nonadiabatic coupling in connection with the fewest switching hopping algorithm for the investigation of the dynamics of the system; and either the cationic (Po) or the neutral ground state (Ne) for the probing step. The choice of the systems has been made in order to determine the timescales of processes involving (1) fast geometric relaxation leaving the bonding frame intact versus IVR, as during the adiabatic dynamics in the first excited state of Na4F3, being the smallest prototype of F-colored centers in the bulk; and (2) the photo-isomerization process through the conical intersection during nonadiabatic dynamics due to the long amplitude motion, as in the Na3F2 cluster after breaking of one metallic and one ionic bond, representing the first example of a five atomic cluster in the gas phase exhibiting conical intersection between the ground and the first excited state. In both cases, full complexity of the problem has been considered taking into account all degrees of freedom. The investigated systems represent important test cases for providing the conceptual framework of ultrafast dynamics in finite systems.</abstract>
    <parentTitle language="eng">International Journal of Quantum Chemistry</parentTitle>
    <identifier type="urn">urn:nbn:de:0298-opus4-5712</identifier>
    <enrichment key="PeerReviewed">Keine Angabe - No details</enrichment>
    <enrichment key="LinkProfileA">https://www.srh-berlin.de/hochschule/hochschulteam/hartmann-michael/</enrichment>
    <author>Vlasta Bonačić-Koutecký</author>
    <author>Michael Hartmann</author>
    <author>Jiřı́ Pittner</author>
    <author>Huub van Dam</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Quantum chemistry</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Ultrafast spectroscopy</value>
    </subject>
    <collection role="jel" number="Y">Miscellaneous Categories</collection>
    <thesisPublisher>SRH Berlin University of Applied Sciences</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-srh/files/571/Theoretical_Exploration_of_Ultrafast.pdf</file>
  </doc>
  <doc>
    <id>552</id>
    <completedYear>2001</completedYear>
    <publishedYear>2001</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>8892</pageFirst>
    <pageLast>8905</pageLast>
    <pageNumber/>
    <edition/>
    <issue>39</issue>
    <volume>105</volume>
    <type>article</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>2014-07-01</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">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</title>
    <abstract language="eng">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.</abstract>
    <parentTitle language="eng">Journal of Physical Chemistry A</parentTitle>
    <note>Volltext aus urheberrechtlichen Gründen nicht verfügbar.&#13;
Fulltext due to copyright not available.</note>
    <enrichment key="PeerReviewed">Keine Angabe - No details</enrichment>
    <enrichment key="LinkProfileA">https://www.srh-berlin.de/hochschule/hochschulteam/hartmann-michael/</enrichment>
    <author>Roland Mitrić</author>
    <author>Michael Hartmann</author>
    <author>B. Stanca</author>
    <author>Vlasta Bonačić-Koutecký</author>
    <author>P. Fantucci</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Physical chemistry</value>
    </subject>
    <collection role="jel" number="Y">Miscellaneous Categories</collection>
    <thesisPublisher>SRH Berlin University of Applied Sciences</thesisPublisher>
  </doc>
</export-example>
