Understanding the high neutralization yields in collisions of keV Li + ions with copper surfaces

Abstract

Measurements of neutral atom fractions for Li+ scattered by Cu(111) and Cu(001) surfaces as a function of the exit ion energy and exit angle are reported. Large neutralization rates (between 20% and 60%) are found in all cases. A first-principles quantum-mechanical based theoretical formalism is applied to describethe time-dependent scattering process, where neutralization to the Li ground state is considered as the unique relevant charge transfer channel during the collision. The increase of the neutralization fraction as the exit energy decreases is well described by the model. The proximity of the projectile energy level to the solid Fermi level and the large extension of the ion-surface coupling interactions, affecting a large number of surface atoms, play a decisive role in explaining the experimental yields.