Interaction of Li+ with a Au(1 0 0) surface

Results of a study of Li+ neutralisation on Au(1 0 0) are presented and compared with an earlier study of neutralisation on Au(1 1 1), where anomalously high neutralisation had been tentatively related to the existence of the L-bandgap and occupied surface state. Neutralisation probability on Au(1 0 0) has a similar magnitude to that on Au(1 1 1) and a similar incident energy dependence, though the electronic structure is different. These results for surfaces with high workfunctions are very unexpected, since significantly smaller values may be expected in a “traditional” picture of a Li+ ion departing from the surface. We can account for the relatively large value of the neutral fraction by considering that the Li(2s) level lies below the Fermi level at short atom–surface separations as this has been shown to be the case for the Cu surface by Goldberg et al. This allows electron capture at small distances and the surviving neutrals account well for the behaviour of the neutral fraction at energies above 500 eV but not at lower energies. This could be due to various reasons including intermediate Li− formation and non-adiabatic effects.