Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 31: Surface Chemical Reactions and Heterogeneous Catalysis I

O 31.2: Talk

Tuesday, March 27, 2007, 16:00–16:15, H38

Initial kinetic-energy and isotope dependence of electronic energy dissipation during chemisorption of H/Al(111) — Michael Lindenblatt and •Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität Kiel, 24098 Kiel

The amount of energy dissipated into electron-hole pairs during chemisorption or scattering of H-atoms at the Al(111) surface has been investigated as a function of the mass of the incoming hydrogen atom and its initial kinetic energy. The energy dissipation into electronic degrees of freedom, which occurs parallel to the energy dissipation into substrate vibrations, is evoked by electronic friction effects as well as strongly non-adiabatic effects during transfer of the local electronic spin polarization at the incoming H-atom to the substrate upon adsorption [1]. We report results from ab initio molecular dynamic simulations based on time dependent spin-density-functional theory combined with Ehrenfest dynamics for the motion of the nuclei. Essentially, the results for the energy dissipated electronically during one passage of the H-atom through the spin transition break down onto a single curve, if plotted versus the velocity of the H-atom at the spin-transition point. The respective Kohn-Sham electronic excitation spectra exhibit an asymmetry between spin-up and spin-down electrons [2], as to be expected for a delayed non-adiabatic transfer of spin polarization from the H-atom to the reservoir of substrate electrons.

[1] M.S. Mizielinski et al., J. Chem. Phys. 122, 084710 (2005).

[2] M. Lindenblatt, E. Pehlke, Phys. Rev. Lett. 97, 216101 (2006).