Phase and energy relaxation in an antibonding surface state: Cs/Cu(111)

Electron dynamics induced by direct photoexcitation of the antibonding stat e on the Cs/Cu(111) surface are studied by interferometric time-resolved tw o-photon photoemission. Femtosecond resolution pump-probe correlation measu rements indicate phase and energy decay, respectively, on 15 and 50 fs time scales for the Cs antibonding state at 33 K. Both the polarization and pha se dynamics are nonexponential and strongly temperature dependent. The ener gy dependence of the antibonding state population dynamics is consistent wi th Cs photodesorption.