Li+ on (100) and (111) Cu surfaces: High neutralization to the Li ground state

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

Puerto Iguazú, Argentina

Simposio; XIX Latin American Symposium on Solid State Physics; 2008

Through a time-dependent quantum mechanical calculation we describe the resonant process that occur when alkali Li+ ions scatter off Cu(100) and Cu(111) surfaces. The neutral fractions are calculated by taking into account the correct spin degeneration. We are able to reproduce satisfactorily the very recent experimental data observed in ion scattering experiments in Li/Cu system. A high neutralization of ions is found, which it is unexpected given the low ionization potential of Li atoms. We can explain the energy-dependence of the neutral fraction by considering the behaviour of the ionization Li-2s  level energy. Our results lead to conclude that the downward shift of the Li ionization level is the main responsible of the neutralization caused by a resonant mechanism. We found a qualitative good agreement with the experimental trends at energies above 500 eV but not at lower energies. Comparison of the experimental results with time-dependent quantum mechanical calculations, leads us to suggest that other channels as neutral first excited (Li-2p) and negative states (Li-2s2) should play a role in the neutralization process in these systems.