Electron capture and loss in the scattering of H+ from HOPG graphite

In this paper we report measurements of the positive (H+) and negative (H−) ion fractions after H+ scattering from a highly oriented pyrolytic graphite (HOPG) surface. The experimental results show that for a fixed (large) exit angle the negative fraction is almost independent of the primary ion energy, while the positive fraction increases steadily. For a fixed incident energy, the H+ and H− fractions show a complementary behavior with exit angle. A dynamical quantum mechanical calculation, based on the localized and extended features of the atom-surface interaction, allows us to understand many of the features of the experimental results.