Formation of negative halogen ions in grazing scattering from an Al(111) surface: Multielectron effects

Results of a joint theoretical and experimental study on the formation of F^-, Cl^-, and I^- ions in grazing scattering from an Al(111) surface are presented. The negative-ion fractions in the scattered beam are studied over a wide range of collision energies. We observe a pronounced dependence of the negative-ion yield on the collision velocity component parallel to the surface, a signature of the kinematically induced projectile-surface charge-transfer process. Based on a theoretical treatment with the coupled angular mode method, we demonstrate the importance of the multielectron-multistate aspect of the charge-transfer problem originating from the presence of the six equivalent electrons on the outer p shell of negative ions. In the case of the I^--ion formation, the spin-orbit interaction in the I atom has to be taken into account.