Negative ion formation by proton reflection from a molybdenum surface at a shallow incidence angle

Proton beams at 0.3, 0.5 and 1 keV energies were injected onto a Mo surface at shallow incidence angle, and the angle- and energy-resolved intensity distributions of reflected negative/positive ions were measured. The negative to positive intensity ratio increased as the incident angle and the reflected angle became shallower and the incident energy became lower. A numerical simulation calculation, Atomic Collision in Amorphous Target (ACAT), has been carried out to get the angular distribution of total reflection particle flux. Experimentally measured angular distributions of reflected H- ion intensity showed maxima at smaller angles than the calculated results, indicating that the negative ion formation has a maximum at v⊥ of 0.03 - 0.04 atomic unit.