Theory of time-resolved two-photon photoemission from a metal surface: theeffect of Coulomb interactions between electrons

The effect of Coulomb interactions between electrons on time-resolved two-p hoton photoemission from a met al surface is investigated theoretically. It is shown by nonequilibrium perturbation theory that the correlation trace (photoelectron intensity as a function of the pump-probe delay time) depend s on lifetimes of both photoexcited electrons and holes due to the effect o f Coulomb interactions. The numerical results of the correlation trace repr oduce the qualitative features of the experimental results.