Role of Screening in Surface Ion Neutralization

Abstract

Two points in the theory of surface ion neutralization are discussed, following the lines established by Hagstrum and others. Firstly, because of the large energy $\hslash \omega$ transferred to the ejected election, the Coulomb interaction which is responsible for the process is effectively unscreened, but it is shown that the long range of the unscreened potential does not lead to any divergences in calculating the emergent current. The ejected electrons originate largely in the first one or two atomic layers of the solid, and some even originate outside it. Secondly, we summarize previous work relating the observed directional dependence to variations of the matrix element and of the transmission coefficient through the surface, and add some new ideas.