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O: Oberflächenphysik

O 20: Oberflächenreaktionen I

O 20.7: Vortrag

Dienstag, 9. März 2004, 12:45–13:00, H45

Mixed quantum classical simulation of DIET processes — •Christian Bach and Axel Groß — Physik-Department T30, Technische Universität München, 85747 Garching

We present a mixed quantum-classical method for the simulation of laser-induced desorption processes at surfaces. In this method, the nuclear motion is described classically while the electrons are treated quantum mechanically while taking the feedback between nuclei and electrons is into account self-consistently. The computational efficiency of this method allows a more realistic multi-dimensional treatment of the desorption processes. We have applied this method to the laser-induced desorption of NO from NiO(100) using a two-state two-dimensional potential energy surface derived from ab initio quantum chemistry calculations; we have extended this potential energy surface to seven dimensions employing a physically reasonable model potential. We focus on the velocity, rotational and vibrational distributions of the desorbing NO molecules and compare our results to the experiment and wave packet simulations. Furthermore, we added a surface oscillator to model the energy transfer to the substrate. Including recoil processes in the simulation has a decisive influence on the desorption dynamics, as far as the velocity and rotational distribution is concerned. In particular, the bimodality in the velocity distribution observed in low dimensions and in the experiment disappears in a high-dimensional treatment.