Cluster-size dependence of electron capture and excitation cross sections in proton-Na-n collisions

We have evaluated electron capture and excitation cross sections for H+ + N a-n collisions (n = 8,20,40,92) in the impact energy range 40-500 eV. The t heoretical method includes the many-electron aspect of the problem and make s use of realistic cluster potentials obtained with density functional theo ry and a spherical jellium model. Both electron capture and excitation cros s sections increase monotonically with cluster size, but the rate of this i ncrease is much more pronounced than expected from purely geometrical consi derations. Also, capture cross sections are between one and two orders of m agnitude larger than the geometrical cross sections. For the larger systems , our results differ from recent theoretical estimates obtained at higher i mpact energies. [S1050-2947(99)08611-4].