Effect of a surface Al adatom on the resonant charge transfer between an H− ion and an Al(1 1 1) surface

This paper presents an investigation of how the charge transfer between an H− ion and an Al surface is influenced by the presence of a point defect on the surface. We consider the case of a single Al adatom on an Al(1 1 1) metal surface, and we study the resonant charge transfer process when the projectile is in the vicinity of the adatom. The adatom-induced electron potential is calculated using a density functional method. The coupled angular mode method is used to determine the shift and broadening of the H− level. The results show that the Al adatom introduces an attractive potential which, at large H−-metal distances, causes a downward shift of the H− level and an increase of its width. At close distances, the calculation also shows a strong coupling between the H− ion level and the Al(3p) and Al(3s) resonances located on the adatom. A diabatic modeling including the effect of the mixing of the projectile and adatom levels is developed which allows the discussion of the non-adiabatic transitions between projectile and adatom-localised levels when the H− passes through the region near the adatom.