Image-potential state lifetimes in Ar/Cu(1 0 0)

Time-resolved two-photon photoemission experiments performed on the Cu(1 0 0) surface with one or several layers of argon reveal image state lifetimes unusually long compared with those obtained for the clean surface. The interaction of the image state electron with the metal surface is thus dramatically altered by the adsorbed layers, which induce a decrease in the overlap between the image state wave function and the bulk states. We report a calculation of the n=1, 2 image-potential state lifetimes in the Ar/Cu(1 0 0) system, obtained within the GW approximation of many-body theory. Image state wave functions are calculated from a one-dimensional model potential which describes the surface band structure and incorporates the modified interaction in the adlayer region. Results obtained from this model are in fairly good agreement with the experimental data.