Elastic and inelastic processes in the scattering of positive ions of H and He from LiF

Abstract

A theoretical calculation that allows for a fairly complete description of the charge-exchange and surface electronic excitation processes occurring in the H+ and He+ scattering by ionic surfaces is presented. The interaction parameters required to describe the collisional process are calculated by using a model Hamiltonian that has proved to provide a systematic good description of the properties like binding energy, equilibrium distance, and vibrational frequency of several dimers and atom-surface systems. The formalism is applied to the comparative study of the scattering of H+ and He+ by the fluorine atom of a LiF surface. The ion survival probabilities by elastic and inelastic processes are calculated, and the general trends of the experimental findings are reproduced. Very satisfactory results concerning the electron-hole pair excitations in the He+ scattering are obtained when the charge fluctuation on the active F site is considered. The role of the surface core states is found to be decisive for the e−h pair excitation by He+ scattering, and for the neutralization of H+ projectiles.