Influence of the nonresonant processes in the dynamics of the image-potential states of Cu(100) and Ag(100)

Abstract

We will concentrate on the peculiar role played by the nonresonant processes resulting from the existence of an initial distribution of bulk states on the two-photon photoemission spectroscopy of Cu(100) and Ag(100) surfaces. In contrast to previous studies on the Cu(111) surface where the process is initiated from an intrinsic surface state, here the transitions occur between the initially occupied bulk band states located below the energetic gap and the image-potential states because there is no intrinsic surface state for this type of surface orientation. We will show that the initial distribution of bulk states plays an important role in the evolution of the image-potential states and cannot be reduced to a single state as previously described. The resulting nonresonant processes can strongly affect the magnitude of the resonance structure of the photoemission spectrum with respect to the predictions obtained on the basis of the sole resonant process.