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O: Fachverband Oberflächenphysik

O 78: Surface chemical reactions

O 78.4: Vortrag

Donnerstag, 17. März 2011, 15:45–16:00, WIL B122

Electronic energy dissipation of vibrationally excited HCl/Al(111): model study and ab initio results — •Michael Grotemeyer and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel, Germany

Molecular dynamics simulations based on time-dependent density functional theory have revealed an unexpected scaling of the dissipated energy with the mass of the nuclei in case of highly vibrationally excited HCl molecules in front of an Al(111) surface. The energy transfer from the molecular vibrations into electron-hole pair excitations is traced back to a molecular orbital which is unoccupied in the equilibrium geometry and which periodically shifts towards the Fermi level of the metal when the molecule vibrates. We suggest a simple one-dimensional tight binding model, which is capable of explaining our observations from the ab initio simulations. Our approach is similar in spirit to a recent (three-dimensional) model studied by Mizielinski and Bird [1]. Both the TDDFT simulations as well as the one-dimensional tight-binding model yield electron-hole pair excitation spectra that differ distinctly from a simple exponential decay. The dissipation mechanism essentially occurs independent of the orientation of the molecule with respect to the metal surface.

[1] M. S. Mizielinski, D.M. Bird, J. Chem. Phys, 132, 184704 (2010)