Open-system density-matrix approach to image-potential dynamics of electrons at Cu(100): Energy- and time-resolved two-photon photoemission spectra -art. no. 035420

Dynamical simulations of femtosecond two-photon photoemission spectra of im age potential states on a clean Cu(100) surface are presented. A realistic one-electron potential by Chulkov, Silkin, and Echenique [Surf. Sci. 437, 3 30 (1999)] is employed together with a mapped Fourier grid Hamiltonian meth od to accurately determine bound continuum, image potential, and free conti nuum states. The wave functions are used to determine the lifetimes of imag e potential states, and the dipole matrix elements for the laser pump and p robe transitions. A multistate open-system density-matrix approach is adopt ed to model the pump-probe process including energy and phase relaxation. I n contrast to previous work no scaling laws are assumed for any input param eters, a discretized continuum of final states is used to allow for final-s tate energy resolution, and image states with high quantum numbers n (up to n=15) are considered. Very good agreement between theory and experiment is obtained.