The study of Ne2+ ions produced by electron promotion in Ne+ ion-surface scattering

Abstract

A systematic study of doubly charged Ne2+ ions scattered from Fe (1 1 0), Ni (1 0 0) and Cu3Au (1 0 0) surfaces has been performed using low energy singly charged Ne+ projectiles (≤7 keV). Scattered Ne2+ ions have been observed at projectile energies above a threshold. The Ne2+ yields scattered from the corresponding Fe, Ni and Cu atoms on the surfaces have been measured as a function of the primary ion energy under various scattering geometries. A charge exchange model is described for the formation and neutralisation of the scattered Ne2+ ions. Neutralisation of the Ne+ projectile along the incoming trajectory has also taken into account. A simple expression for the scattered Ne2+ ion yield is presented, which matches the experimental data well. The ionisation probability for Ne+ → Ne2+ or Ne0 → Ne2+ in the violent collision and the characteristic velocity vc″ for Ne2+ along the exit trajectory have been extracted by fitting the model to experimental data. For further understanding about the process involving Ne2+ ions, the inelastic energy loss associated with the scattered Ne2+ ions has also been presented and discussed.