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(111) is investigated by nonequilibrium perturbation theory. It is demonstrated that there are contributions to photoemission via an image state on the surface from processes involving scattering of photoexcited electrons and holes due to Coulomb interactions. As a result, the correlation trace (photoelectron intensity as a function of the pump-probe delay time) is affected by the lifetimes of the electron in the image state, the photoexcited electron and hole.#2001 Elsevier Science B.V. All rights reserved.