SCATTERING OF ATOMS BY SURFACES WITHIN A MOLECULAR-ORBITAL APPROACH

We perform a simple model calculation of the charge exchange probability for atoms scattered by surfaces. We analyze processes involving low energy atoms and large scattering angles in which the kinematics of the atom-surface collision can be accurately described by a classical two-body collision picture. The inelastic effects due to the interaction of the electrons of the atom and the solid are treated within a localized description based on a cluster calculation. The dynamical wave function is expanded in a set of molecular orbitals and the classical atom velocity is allowed to adjust self-consistently to potential energies and transition amplitudes variations along its trajectory, in which a rigid wall approximation is used to fix the turning point. Our results show an oscillatory ion-velocity dependence of the ionization probability, which is due to the double transit of the scattered particle through the interaction region. This suggests a possible explanation of the observed behavior in the scattering of He ions by metal surfaces.