Phase and Energy Relaxation in an Antibonding Surface State: Cs/Cu(111)

Electron dynamics induced by direct photoexcitation of the antibonding state on the Cs/Cu(111) surface are studied by interferometric time-resolved two-photon photoemission. Femtosecond resolution pump-probe correlation measurements 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 phase dynamics are nonexponential and strongly temperature dependent. The energy dependence of the antibonding state population dynamics is consistent with Cs photodesorption.