Influence of surface band gaps on the lifetimes of charge transfer states

Using a first principles electronic structure method, we investigate how a band gap in the surface projected density of states of a noble metal influences the resonant tunneling lifetime of an atomic level near the surface. Comparing Li atoms outside Cu(1 1 1), where the Li 2s level is within the gap, with Cu(0 0 1), where the Li 2s level is below the gap, reveals that the lifetime of the ionization level of Li is longer on Cu(1 1 1). This difference is caused both by the decreased final state phase space for the tunneling electron on Cu(1 1 1) and by a reduction in intra-atomic hybridization in Li outside a surface whose band gap encompasses the ionization level. Our results are consistent with previous experiments and theory that predict a similar trend for the ionization level of Cs above Cu(1 1 1) and Cu(0 0 1).