Site-specific neutralization of slow multicharged ions incident on solid surfaces

Recent measurements of projectile neutralization during 120 degrees binary collision backscattering from Au(110) and RbI(100), performed at the ORNL Multicharged Ion Research Facility, are described. A common feature of the Au(110) and RbI(100) results is that the observed scattered charge state distributions show significant dependences on the target azimuthal orientation, even for normal or close to normal incidence conditions. The observed target azimuth dependences originate in part from the fact that for the 120 degrees backscattering geometry, quasi-binary double collisions make significant contributions to the total binary scattering collision flux. For the Au(110) target, the types of possible quasi-binary collisions vary with target azimuth because of the corrugation of the reconstructed surface and the number of layers of atoms exposed in a (110) fcc lattice. For the RbI(100) surface, quasi-binary collisions vary with azimuth because of the ordered, two-component nature of the surface even when scattering from deeper layers is blocked. Sample data for few-keV incident F, Ne, and Ar multicharged incident projectiles are presented to illustrate the underlying concepts.