We present experiments and a theoretical model for the energy loss distribution of specularly reflected particles after slow (2-5 keV) He ions have been impinging on a Ni(110) surface under grazing incidence. The energy spectra of the backscattered particles are asymmetric with the low-energy tail falling off more slowly than the high-energy tail does.
This asymmetry is accounted for by considering charge exchange events during the interaction with the surface. The main neutralization channel for this system is the Auger-neutralization from the conduction band into the He-1s ground state. The transition rate for this process was calculated from first principles. Assuming that the ‘friction coefficient’ for the system particle-surface depends on the charge state of the particle, we calculate the energy lost by a particle during the interaction as a sum of different contributions belonging to different charge states.