Stabilization of electrons on Arq+ ions after slow collisions with C-60 - art. no. 062725

We discuss hollow atom formation and stabilization of electrons on Arq+ fol lowing Arq+ + C-60 --> Ar(q-s)+ +... collisions at 3.3q keV (q = 4-18). The experimental information consists of the final projectile charge-state dis tributions f(q)(s), i.e., the relative distributions of the number of stabi lized electrons, s, and the corresponding mean values <s > = Sigma (q)(s) = (1)sf(q)(s) as functions of q. We use the classical over-the-barrier model to deduce sequences of effective principal quantum numbers and find that t he hollow atom formation is completed 3-4a(0) above the surface of the C-60 cage for all q. For q less than or equal to8 (filled L shells), the last e lectrons are transferred from delocalized outer C-60 orbitals directly to t he projectile M shell (side-feeding), while several intermediate shells are left open for larger q leading to further electron transfer at intermediat e distances and simultaneous electron emission from higher projectile shell s. At still closer distances, localized carbon K-shell electrons are transf erred directly to the argon L (q = 10 and 11) and M shells (q greater than or equal to 12). The direct transfer to the L shell of Ar10+ and Ar11+ is m anifested as significant enhancements of (s) for q = 10 and q = 11.