Neutralization of Li+ions scattered by (100) and (111) Cu surfaces: a localized atom-atom interaction model.

EVELINA A. GARCÍA; M. A. ROMERO; C. GONZÁLEZ; E. C. GOLDBERG

Puerto Iguazú

Simposio; XIX Latin American Symposium on Solid State Physics (SLAFES); 2008

Large and face dependent neutral fractions have been found recently in ion scattering experiments in Li+/Cu(100) and Li+/Cu(111) systems. These results for surfaces with high work functions are unexpected within the ‘traditional’ picture of a Li+ departing from a jellium surface model. In the present work the Li+/Cu(100) and Li+/Cu(111) interacting systems are described by apreviously developed bond-pair model based on the localized interactions between the projectile ion and the atoms of the surface, and on the extended features of the electronic band structure through the density matrix. By only including the resonant neutralization to the Li atom ground state we explained the face and energy dependences of the measured neutral fraction within the range of large outgoing energy values. We found that the downward shift of the Li ionization level below the Fermi level caused by the short range chemical interactions, is the main responsible of a high neutralization by the resonant mechanism. The remaining differences between theory and experiment at low energy values and the calculated distance behavior of the energy levels suggest that the first excited (Li-1s22p) and negative (Li-1s22s2) states cannot be disregarded in the ion-surface charge exchange process, and neither the presence of projected surface band gaps in the Cu(111) surface.