Theoretical analysis of the relation between H-2 dissociation and reflection on Pd surfaces

We study the scattering of H-2 (v=0, J=0) molecules by the Pd(110) surface using classical trajectory methods. We show that the dissociative adsorption probability barely depends on incidence angle (total energy scaling) up to an impact energy of 200 meV. This is the consequence of a loss of memory of the initial incidence angle, mostly due to dynamic trapping, which also reflects itself in a cosinelike angular distribution of reflected molecules. Consequently, a cosinelike distribution can be the result of a subpicosecond process that involves neither energy dissipation to the surface nor transient thermal accommodation. (C) 2004 American Institute of Physics.