Role of orientational forces in nonactivated molecular dissociation on a metal surface

Starting from a six-dimensional study of the dissociative adsorption process of H-2 on Pd(111), we show that orientational forces in the approach toward the surface determine the dissociation probability. We conclude that the nonmonotunous variation of the transition probability with energy observed in the experiments can be interpreted essentially with a two-dimensional mechanism involving only molecular translation and rotation.