Effect of impact-parameter-dependent electronic energy loss on reflected-ion spectra

Conventional theory and computation of the slowing-down of ions and associated radiation effects relies on a scheme proposed by Lindhard and Scharff, in which electronic energy losses enter as a friction force. We study limitations of this scheme, when the dependence of electronic losses on the impact parameter in individual atomic collisions is taken into account. We study this feature on the projected range - where it is found to be insignificant - and on reflected-ion spectra where major changes are observed, dependent on ion energy and ion-target combination. Most sensitive are the position of the peak in the reflected-energy spectrum as well as the behavior near the maximum energy loss. Systems studied include He-Ag, Ne-Ag, B-Si and D-Pt.