On the adsorption and desorption of H2 at metal surfaces

Recent technological developments have made possible measurements of the distribution of internal levels of molecules desorbing from a hot surface. Such measurements provide new information concerning the desorption process and the potential energy surface (PES) that governs it. Associative, or re-combinative desorption is of particular interest because the distributions of internal levels reflect the manner in which the molecular bond is formed as the desorbing species leaves the surface. As the simplest associative desorption systems, H₂ and D₂ adsorbing on and desorbing from metal surfaces deserve special attention and serve as prototypes for systems with a more complex chemistry. In this note I review briefly from the theoretical point of view some features of the interaction of H₂ with metals and their relevance to associative adsorption and dissociative sticking.