The ratio of the single and double scattering intensities in ion scattering spectroscopy as a quantitative measure of surface structures

Abstract

The ratio R of the intensities of the single and double scattering peaks observed in Ion Scattering Spectroscopy has been determined as a function of several experimental parameters. If all particles scattered through a certain scattering angle are detected with a time of flight spectrometer or when alkali ions are used as primary particles then the absolute value of R as well as the dependence on the experimental parameters correspond with the results of several theoretical models. A simple two atom model, using the Thomas-Fermi-Molière potential, yields very satisfying results. For low index directions on the surface R is a straightforward measure for the interatomic distance of neighbour surface atoms. For high index directions surface zig-zag collisions complicate the interpretation, but the shape of the energy spectra can be understood reasonably well. When noble gas ions are used as primary particles and only the scattered ions are detected, R+ is influenced by charge exchange and neutralization processes, which complicate the interpretation, and the dependence of R+ on the experimental parameters does not agree with theoretical expectations for R.