Initial sticking of O2 modeled by nonadiabatic charge transfer

The behavior of the initial sticking of the oxygen molecule on the Al(1 1 1) surface and its enhancement due to vibrational excitation of the molecule are explained within a simple diabatic model. Key parameters of the model are the workfunction for the surface and the vertical affinity of the molecule. The motion of the molecule is treated classically, in one dimension, along the diabatic potential-energy curves of O2/Al(1 1 1) (obtained by matching the van der Waals potential from a recent van der Waals density functional, to the repulsive part, based on Thomas–Fermi and density-functional theory) and O2−/Al(1 1 1)+ (image potential, saturated Jennings form in the vicinity of the surface). The characteristic S-shaped energy dependence of the sticking probability and its vibrational enhancement are accounted for.