Charge exchange in gas-surface collisions: Momentum transfer

A description of near-resonant charge exchange in gas-surface collisions that includes momentum transfer is presented. The surface is represented by a cluster of metal atoms. A diatomics in molecules procedure is used to obtain the surface eigenvalues and eigenfunctions. These are combined with those of the gas atom or ion to construct the interaction potentials and electronic coupling terms. These provide the input needed to solve for the nuclear and electronic motions in the common eikonal formalism which leads to a time dependent description of the event. The formalism is applied to a sodium atom scattering from a W(110) surface. The surface consists of five W atoms. The center W atom is allowed to move during the collision. Transition probabilities are presented for various two and three electronic state systems and compared to the case where the position of the center W atom remains fixed.