Scattering by alkali adsorbates as a decay mechanism for image potential states on Cu surfaces

A theoretical study of the electron dynamics in image potential states on Cu(1 1 1) and Cu(1 0 0) surfaces with alkali adsorbates is presented. It is shown that scattering of the image potential state electron by the adsorbates yields a sizable contribution to the decay of the image state population. Even for extremely low coverages (1 adsorbate atom per 1000 surface atoms) the decay rates due to the adsorbate induced scattering might be comparable to the decay rates due to the electron–electron interactions. We demonstrate that the inter-band transitions to other 2D continua of image or surface states is an efficient decay channel close to the Γ point.