IFIS - LITORAL   24734
INSTITUTO DE FISICA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Image potential state influence on charge exchange in Li+-metal surafce collisions
F. BONETTO; EVELINA A. GARCÍA; E. C. GOLDBERG
Congreso; Congreso Internacional de Metalurgia y Materiales (SAM-CONAMET/IBEROMAT 2014); 2014
The energy dependence of the neutral fraction of ions scattered by metal surfaces is observed to be affected by the presence of energy gaps and surface states in their surface band structure. The effect is more dramatic when the ion energy level remains close to the surface Fermi level of the surface, as it occurs in the scattering of Li positive ions by Cu and noble metal surfaces. We have incorporated the interaction of the ion state with the bulk- and surface-like states within an extended Anderson model and by using an ab initio calculation of the Hamiltonian terms. In this form we found that the increase of the neutral fraction at low projectile energies is explained solely by the presence of energy gaps in the case of Cu(111) while the bonding interaction with the first image potential state is also important in the Cu(100), Ag(100) and Ag(111) surfaces. When compared to experimental data, the introduction of image potential states clearly improves the calculation in all cases. This constitutes an evident step up in the description of charge transfer during ion-metal surface collisions. A better description of the experimental neutralizations vs. energy dependence is obtained after orthogonalization of Li2s and image state wave functions. However, no significant differences in the magnitude of neutral fractions are found. Main changes introduced by the image potential state in the neutralization rates are totally defined in the last part of the outgoing trajectory (ion-surface distance larger than 9 a.u.).