  When low-energy He ions are scattered from a Ge surface, the fraction of
positive ions exhibits characteristic oscillations as a function of ion energy.
These oscillations are caused by quasi-resonant neutralization (qRN), a process
which can be observed for materials with a narrow band nearly resonant with the
unperturbed He-1s level. In the present manuscript, we employ recently
developed theoretical methods to extract quantitative information on the
efficiency of qRN. Our evaluation reveals that qRN is a highly efficient
process leading to ion fractions two orders of magnitude lower than in systems
for which neutralization is only due to Auger processes.
