Regensburg 2000 – scientific programme

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SYUO: Ultrakurzzeitdynamik an Oberflächen

SYUO 6: Poster

SYUO 6.1: Poster

Thursday, March 30, 2000, 11:00–19:00, Bereich C

Theory for ultrafast coherent and incoherent dynamics of excited electrons in noble metals — •R. Knorren, G. Bouzerar, and K.H. Bennemann — Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany

Time-resolved two-photon-photoemission (2PPE) experiments permit the study of femtosecond dynamics of excited electrons in metals. Interferometric 2PPE measurements probe both coherent and incoherent dynamics by measuring phase and energy relaxation times.

We present a theory based on the generalization of the optical Bloch equations for noble metals. The model includes the momentum dependence of electron-electron scattering rates and secondary-electron contributions to the incoherent dynamics. Energy and phase relaxation times are calculated on the same footing.

Our results clarify the coherent and incoherent contributions to the 2PPE current and their impact on the relaxation time. Experiments show an anomalous peak in the relaxation time above the threshold for d-band excitation. We determine the influence on the relaxation time of secondary electrons, in particular Auger electrons, and transport of carriers out of the detection region.