H2 dissociation dynamics on an alloy surface -: controlling the dynamics via orientation

We demonstrate how we could influence the H, dissociation dynamics through the H-H bond orientation (with respect to the surface) dependence of the potential energy (hyper-) surface (PES), by considering the interaction of H, with an alloy surface (e.g., an ordered Cu3Pt(1 1 1)). Our preliminary results show that by changing the dependence of the PES on the H-H orientation (e.g., such that preference for H-H orientation perpendicular to the surface over intermediate H-H orientations between perpendicular and parallel occurs), not only did we observe a general increase in dissociation probability of H-2, we also observe an increase in the dissociation probability of cartwheel-like rotating H-2, relative to helicopter-like rotating H-2. Depending on the initial state of the impinging H-2 (initial rotational state and incidence energy), we also observed that the dissociation probability of cartwheel-like rotating H-2 becomes even greater than the dissociation probabilities for rotating H-2 with orientations intermediate between cartwheel-like and helicoptering H-2. Based on these results, we suggest how further information regarding the orientation dependence of the PES could be obtained experimentally. (C) 2001 Elsevier Science B.V. All rights reserved.