Scattering of fast H-2 molecules from Pd surfaces: Classical trajectory simulations

Abstract

Classical trajectories simulations have been carried out for H-2 molecules at energies from a few hundred eV up to a few keV scattering under grazing incidence from Pd surfaces of distinct crystallographic orientation. Emphasis is laid on the importance of collisional dissociation mechanisms for incidence along surface semi-channels and along highly indexed directions. The initial molecule orientation is found to be decisive for the dissociation probability. Distributions of the center-of-mass energy and the angular momentum of the scattering products suggest that collisional dissociation is rotationally induced for channeling conditions, the molecule axis being initially oriented at an angle with the beam. For off-channeling incidence, collisional dissociation is vibrationally induced, the molecule axis being initially perpendicular to the surface plane.