Trajectory dependencies of charge neutralization in keV ion/surface scattering

We have measured the charged fraction of scattered Ne during the 1700 scattering of kilovolt Ne+ by a two-dimensional lattice of arsenic atoms grown on a Si(111) surface template. We found that the charged fraction increases with the incident energy to reach values above 0.25 which is significantly higher than that for He+ scattered from As. The charged fraction is not sensitive to the azimuthal direction of incidence, but it is strongly dependent on the elevation angle with respect to the sample surface. We found that the collisions between the Ne+ ions and the As atoms are not purely atomic in nature. Our result directly indicates the importance of the delocalized valence band electrons in the charge exchange process. (author)