Observation of direct vibrational excitation in collisions of H2 and D2 with a Cu(111) surface

We have observed the direct vibrational excitation (v=0'v=1) of H2 and D2 molecules colliding with a Cu(111) surface. The dependence of this process on kinetic energy is found to be similar for both molecules, resembling the function determined for dissociative chemisorption of molecules in the v=0 state. This suggests that translational-vibrational coupling is strong only when molecules closely approach the dissociation barrier. © 1992 The American Physical Society.