Ultrafast coherent control of electric currents at metal surfaces

摘要: We report the development of an experimental technique to measure dynamics electrical currents on the femtosecond timescale. The combines methods coherent control with time- and angle-resolved photoelectron spectroscopy. Direct snapshots momentum distribution excited electrons as function of time are then determined by photoelectron In this way we gain information on generation and decay ultrashort current pulses in unprecedented detail. particular, allows observation of elastic electron scattering terms incoherent population space. have applied optical detection scheme so-called image-potential states which represent a prototype two-dimensional electronic surface states. Electrons these states bound perpendicular metal Coulombic image potential whereas they can move almost freely parallel to surface. For (n=1) state Cu(100) find decay 10 fs due electron scattering steps defects.