A COMPARISON OF QUANTUM AND CLASSICAL DYNAMICS OF H-2 DISSOCIATION ONCU(111)

A quantitative comparison of the results from quantum and classical co mputations of the dissociation of H-2 on the ab initio Cu(111) surface is presented. In order to initiate a detailed comparison of the class ical and quantum methods, we chose to investigate motion on the vibrat ionally adiabatic ground state. This subtracts from the problem the la rgest quantum degree of freedom with the consequence that broadly spea king, quantum and classical results for the dissociation as a function of initial rotational state and incidence angle agree well. One featu re arising from the calculations is that for the first time we have sh own how the quantized nature of motion near the transition state affec ts experimental observables. We demonstrate that hitherto neglected st ructure in dissociation probabilities may be traced to quantized hinde red rotational and translational motion. An additional consequence of the quantization is a pronounced J-dependent broadening in the dissoci ation probabilities when plotted as a function of the translational en ergy which should be experimentally observable.