Large neutral fractions in collisions of Li+ with a highly oriented pyrolytic graphite surface:: Resonant and Auger mechanisms

We report measurements of neutral atom fractions for Li+ scattered by a highly oriented pyrolytic graphite surface as a function of the incident ion energy and exit angle. We found an unexpected large neutralization probability that increases with both energy and exit angle. Based on a dynamical quantum calculation of the scattering process that accounts for the extended features of the surface and the localized nature of the atom-atom interactions, we propose that the resonant neutralization to the Li ground state is a relevant mechanism in this collision. However, to understand the whole process including the angular dependence, and taking into account the Li energy-level variations, we conclude that other mechanisms such as Auger neutralization to the ground state and resonant neutralization to excited states should also be considered.