A COMPARATIVE-STUDY OF THE DISSOCIATION DYNAMICS OF ENERGETIC H2, N2 AND NO SCATTERED FROM CU(111) UNDER GLANCING ANGLES OF INCIDENCE

We have scattered fast beams of H-2, N2 and NO and their positive ions from Cu(111) under glancing angles of incidence. By directly measurin g the relative velocity v of the dissociation fragments of those molec ules which dissociatively scatter, we obtain distributions of the kine tic energy released in the H-H, N-N and N-0 internuclear coordinate as a function of the final orientation of the internuclear axis. We prop ose a dissociation mechanism involving repeated electronic excitation- relaxation cycles with the dynamics dominated in the case of H-2 by th e topography of electronically excited states, and in the case of N2 a nd NO by vibrational excitation in the exit channel of the ground stat e. This interpretation is supported by classical dynamics simulations.