Theory of time-resolved two-photon photoemission from Cu(111): effect of Coulomb interactions among electrons

The effect of Coulomb interactions among electrons on the time-resolved two -photon photoemission spectra of Cu(1 1 1) is investigated by nonequilibriu m perturbation theory. It is demonstrated that then are contributions to ph otoemission via an image state on the surface from processes involving scat tering of photoexcited electrons and holes due to Coulomb interactions. As a result, the con-elation trace (photoelectron intensity as a function of t he pump-probe delay time) is affected by the lifetimes of the electron in t he image stale, the photoexcited electron and hole. (C) 2001 Elsevier Scien ce B.V. All rights reserved.