EFFECTS OF ROTATIONAL STATE EXCITATIONS ON THE DISSOCIATIVE ADSORPTION DYNAMICS OF D-2 CU(111)/

Recent time-of-flight experiments show a non-monotonous dependence of the dissociative adsorption/sticking probability of D-2(H-2)/Cu(111) on the initial rotational state. There is an observed decrease in the sticking probability with a slight increase in the initial rotational state quantum number j. As j is increased further, the sticking probab ility eventually increases. We show that, to account for this interest ing behaviour, there are two opposing factors working for and against the adsorption process: STEERING EFFECT and ENERGY TRANSFER EFFECT. Th e first is due to a dynamical reorientation of the molecule, and the l atter is due to the coupling of the rotational motion to the translati onal motion along the reaction path. To illustrate these two effects, we performed quantum mechanical model calculations using a variation o f the coupled-channel method, a physically realistic model potential b ased on available potential energy (hyper-) surface plots for D-2(H-2) /Cu for two different orientations-parallel and perpendicular to the s urface, and the concept of a reaction path.