Interpreting the data on helium-ion scattering in metallic films

Abstract

Earlier measurements of angular distributions in the multiple scattering of a helium-ion beam with energy below 300 keV on Al yielded rather unexpected results: the ratio between the half-width of the measured angular distribution, (θ1/2)e, and that predicted with the Moliere–Bethe theory, (θ1/2)MB, proved to stay almost constant throughout the investigated energy range. At the same time, one could expect the (θ1/2)e/(θ1/2)MB value to be affected by the beam-content variation due to the charge–exchange scattering. Towards resolving this problem, we compute the interaction potentials between the Не++, Не+, and Не0 ions and the scattering atoms and reveal the electron-screening effects on the scattering process. Thereby, we explain the energy dependence of (θ1/2)e/(θ1/2)MB observed in the old and new measurements carried out at higher beam energies.