ELECTRON-EMISSION SPECTRA IN AUGER PROCESSES NEAR METAL-SURFACES

In this article, the theory for the Auger transition rate of slow ions interacting With free-electron like metal surfaces reported previousl y is improved and applied to the calculation of the spectrum of the el ectrons emitted in the Auger neutralization process. The theory shows that the derivative of the spectrum reflects the probability that meta l excitations of a given energy are produced in the process. This prob ability depends crucially on the distance between ion and surface. It is shown that for large and intermediate distances the energy transfer red to the metal in the neutralization process is predominantly used t o excite surface plasmons bulk plasmons are seen in the spectrum only for short distances. Using a simple model for the metal surface, the d erivative of the electron emission spectrum is calculated for three mo del ions simulating He+, Ne+ and Ar+ scattered off Al. The calculation s can reproduce the experimental result for Ne+ and the case of Ar+ ca lls for a better description of the metal surface. (C) 1997 Elsevier S cience B.V.