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Simulation of nonadiabatic processes on surfaces [Elektronische Ressource] / Christian Bach

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Simulation of nonadiabatic processeson surfacesChristian BachTechnische Universitat Munc henPhysik-Department T30Univ.-Prof. Dr. A. GroSimulation of nonadiabatic processeson surfacesChristian BachVollstandig er Abdruck der von der Fakultat fur Physik der Technischen UniversitatMunchen zur Erlangung des akademischen Grades einesDoktors der Naturwissenschaften (Dr. rer. nat.)genehmigten Dissertation.Vorsitzende: Univ.-Prof. Dr. K. KrischerPrufer der Dissertation: 1.Prof. Dr. A. Gro 2. Univ.-Prof. Dr. W. Brenig, em.Die Dissertation wurde am 23. Marz 2004 bei der Technischen Universitat Munc heneingereicht und durch die Fakultat fur Physik am 14. Juni 2004 angenommen. AbstractA simple one dimensional two state model for the laser induced desorption and thedesorption of NO from a NiO(100) surface are investigated. This is done by utilising amixed quantum classical algorithm derived from generalised surface hopping [1]. Thealgorithm used is a surface hopping method with optical potentials describing theelectronic excitation and de-excitation processes. The simple model is used to explorethe dependence of the desorption probability on the potential parameters. We showthat the critical parameters are the lifetime, the separation of the minima and thewidth of the excited state potential.For the NO/ NiO(100) system the electronic states taken into account are theground state and one charge transfer state.

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Published 01 January 2004
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Simulation of nonadiabatic processes
on surfaces
Christian BachTechnische Universitat Munc hen
Physik-Department T30
Univ.-Prof. Dr. A. Gro
Simulation of nonadiabatic processes
on surfaces
Christian Bach
Vollstandig er Abdruck der von der Fakultat fur Physik der Technischen Universitat
Munchen zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.
Vorsitzende: Univ.-Prof. Dr. K. Krischer
Prufer der Dissertation: 1.Prof. Dr. A. Gro
2. Univ.-Prof. Dr. W. Brenig, em.
Die Dissertation wurde am 23. Marz 2004 bei der Technischen Universitat Munc hen
eingereicht und durch die Fakultat fur Physik am 14. Juni 2004 angenommen. Abstract
A simple one dimensional two state model for the laser induced desorption and the
desorption of NO from a NiO(100) surface are investigated. This is done by utilising a
mixed quantum classical algorithm derived from generalised surface hopping [1]. The
algorithm used is a surface hopping method with optical potentials describing the
electronic excitation and de-excitation processes. The simple model is used to explore
the dependence of the desorption probability on the potential parameters. We show
that the critical parameters are the lifetime, the separation of the minima and the
width of the excited state potential.
For the NO/ NiO(100) system the electronic states taken into account are the
ground state and one charge transfer state. The corresponding forces used in the
dynamic simulation are based on two dimensional ab initio potentials, calculated by
Kluner et al. [2]. These were extended by simple models to a full description of the
desorbingmoleculetogetherwithonesurfacecoordinate. Inthesimulationstwospecies
of desorbing molecules are found, one with early and the other with late desorption
times. The second species accounts for most of the di erence in desorption yield found
when comparing the mixed quantum classical simulation to the wave packet results
in [3]. When investigating the e ect of additional degrees of freedom on the dynamics
we nd the surface oscillator to be the most decisive one, slowing down the early
desorbingmoleculesandloweringtherotationaltemperatureofthedesorbedmolecules
substantially.
iiiZusammenfassung
Durch Simulation mit einem gemischt quanten-klassischen Algorithmus wird die laser-
induzierteDesorptionvonMolekulenvoneinerFestkorperober acheuntersucht.Imers-
tenTeilderArbeitwirdeineinfacheseindimensionaleszweiZustandeModellbetrachtet
und die Abhangigkeit der Desorptionswahrscheinlickeit von den verschiedenen Modell-
parametern untersucht. Der zweite Teil ist der Desorption von NO von einer NiO(100)
Ober ache gewidmet. Ausgehend von zweidimensionalen ab initio Potentialen von T.
Kluneretal.furdenGrundzustandundeinenElektronentransferzustanderweiternwir
dasModellaufsam tlicheMolekulfreiheitsgra deundfuhren zusatzlicheinenOber ache-
noszillator ein. Der Ein uss der einzelnen Freiheitsgrade auf die Desorptionsdynamik
wird untersucht und es zeigt sich, dass die Hinzunahme des Ober ac henfreiheitsgrades
den gro ten Ein uss hat.
vAcknowledgements
First of all I would like to thank my supervisor Prof. Dr. Axel Gro for giving me the
chance to pursue my PhD in the exciting eld of surface science. I am grateful for his
invaluable support and the many things he taught me about the physics of surfaces.
I am also in debt to present and former members of the T30g and the T32 group,
Areezo Dianat, Dr. Moritz Hilf, Dr. Markus Lischka, Thomas Markert, Christian
Mosch, Ata Roudgar, Sung Sakong and Prof. Dr. Wilhelm Brenig for constant sup-
port and many interesting discussions, not all about physics.
FormakinglifeatthephysicsdepartmentaloteasierIwanttothankMrs. Liebhart-
Schilling and Mrs. Sprzagala. Many thanks also go to Dr. Herbert Muller for his
support in all computer matters.
ManythanksgotothemembersoftheSchwerpunktProgramm1093oftheDeutsche
Forschungsgemeinschaft, especially Dr. Thorsten Kluner for providing me with the ab
initiopotentialsandtheresultsofhiswavepacketsimulationsandtoProf.Dr.Helmut
Zacharias for the coordination of the Schwerpunkt and interesting discussions about
the NO/NiO system.
I would like to thank the Wilhelm und Else Heraeus-Stiftung for providing me with
nancial support for attending the DPG-Fruhj ahrstagungen in 2001, 2002 and 2003.
MostofthesupportwasprovidebytheDeutscheForschungsgemeinschaftviatheSchw-
erpunkt Programm 1093, Dynamik von Elektronentransferprozessen an Grenz achen.
I especially want to thank my parents and my brother for constant support and
encouragement during the past years.
Munc hen Christian Bach
March 2004
vii