TRANSIENT HYPERTHERMAL DIFFUSION FOLLOWING DISSOCIATIVE CHEMISORPTION - A MOLECULAR-DYNAMICS STUDY

The non-equilibrium diffusion of highly hyperthermal atoms resulting from dissociative adsorption of a diatomic molecule is investigated using molecular dynamics and an effective-medium model potential. The parameters of the potential are chosen to describe O2 On Al (111) and the simulation results are discussed in relation to recent STM measurements for this system [Brune et al., Phys. Rev. Lett. 68 (1992) 624]. The transient displacement along the surface is found to be about one order of magnitude larger than the distance to the nearest adsorption site. The traveling distance is limited mainly by the rapid randomization of the adsorbate motion, and not primarily by the rate of energy transfer to the substrate degrees of freedom.