title: Electronic energy dissipation during scattering of vibrationally excited molecules at metal surfaces: ab initio simulations for HCl/Al(111).
abstract: In this Letter, ab initio molecular dynamics simulations based on time-dependent density functional theory for the electrons and Ehrenfest dynamics for the nuclei are reported that detail the interaction of a vibrating HCl molecule with an Al(111) substrate. The mechanism responsible for the strong electron-hole-pair (EHP)-vibrational coupling in case of highly vibrationally excited molecules is traced back to a large eigenenergy shift of the spz*-like antibonding HCl lowest unoccupied molecular orbital with the bond length. As a consequence of this mechanism, the electronic excitation spectra turn out to be highly asymmetric. The simulations suggest an explanation of how to reconcile a strong EHP-vibrational coupling in case of highly vibrationally excited molecules with the small, but clearly evident, electronic contribution to the v=0 → v=1 vibrational excitation observed experimentally during the scattering of HCl molecules at a hot Au surface by Ran et al. [Phys. Rev. Lett. 98 237601 (2007)].
authors.affiliation: Institut fur Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Grotemeyer
authors.affiliation: Institut fur Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.
authors.forename: Eckhard
authors.initials: E
authors.lastname: Pehlke