Charge exchange and energy loss of particles interacting with surfaces

The charge state and energy loss of low-energy He ions scattered off a Ni(110) surface have been measured using a time-of-flight technique. A first-principles theory in combination with trajectory calculations is used to analyze both the charge-state and the energy-loss data. The neutralization of the incident He ions occurs via the Auger process. We find that the experimental results for the energy loss can only be explained when accounting for the charge exchange during the interaction and for straggling effects. The change of the charge state appears in the spectra through the asymmetry, whereas the straggling shows up as a broadening of the peak