Dynamical studies of the interaction of D2 with a Cu(111) surface

Abstract

We have used molecular beam techniques to study the dynamics of adsorption and desorption in the D2/Cu(111) system. We have determined the adsorption probability S0 for beams with kinetic energies Ei up to 0.85 eV, vibrational temperatures up to 2100 K, and incidence angles from 0° to 60°. At a surface temperature Ts of 120 K, S0 increases from below 10−6 to 0.34 over the range studied. A detailed analysis provides estimated adsorption functions for each vibrational state. Angular distributions for desorption with Ts in the range 370–800 K are strongly peaked and symmetric about the surface normal in every case. These distributions are well described by a cos12 θf distribution at 600 K, being slightly narrower at 400 K and slightly broader at 800 K. Calculations using the principle of detailed balance to calculate these angular distributions based on the dependence of the adsorption probability on incidence energy and angle are not in perfect agreement with observations. In fact, we find that desorption measurements made over a range of surface temperatures cannot be adequately accounted for by any single function of the sticking probability on the incidence energy and angle. Rather, it is found necessary to allow this function to vary slightly with surface temperature.