INFLUENCE OF THE INITIAL ROTATIONAL STATE ON THE DISSOCIATION OF HYDROGEN ON COPPER

The initial sticking coefficients s0(J) of H-2 on Cu(110) is calculated as a function of initial rotational state J by means of quasi-classical trajectories and an effective medium potential-energy surface. The observed non-monotonic variation of s0(J) is accounted for qualitatively and analyzed in terms of a late energy barrier in the dissociation channel and a strong rotational anisotropy. The low-J decrease is due to decreasing ability to get the steering necessary to pass the barrier, as J grows, while the high-J increase is caused by rotational energy being fed into the reaction-coordinate motion.