Rotational effects in the dissociative adsorption of H2 on Cu(111)

Abstract

Experimental studies show that the dissociation probability of H₂ molecules impinging on a Cu(111) surface is strongly affected by the initial rotational state. Increasing the angular momentum slightly suppresses the dissociation at low J, but strongly enhances it at high J. We show that this is due to two competing effects; one is essentially orientational, and results in the decrease in dissociation probability, while the increased dissociation is due to the transfer of energy from the rotational coordinates into the reaction coordinate (R–T transfer). Quantum-mechanical wavepacket calculations are used to illustrate these effects, focussing in particular on the close connection between R–T and vibrational–translational (V–T) coupling.