PUB - Publikationen an der Universität Bielefeld

Time-resolved two-color two-photon photoemission experiments are used to investigate the electronic dynamics in highly oriented pyrolytic graphite (HOPG) and in Ag nanoparticles grown on HOPG. The multiphoton photoemission using 267 nm and 400 nm excitation is presented and discussed. For the first time the known unoccupied state on graphite 3.6 eV above the Fermi level can be identified as an image potential state. A lower limit of 60 fs is given for the lifetime of this state. The two-color experiments reveal that the carrier relaxation deduced from time-resolved experiments is influenced by feeding of the intermediate states. First results of the strongly enhanced multiphoton photoemission from Ag nanoparticles on HOPG at 400 nm wavelength are presented. This observation is explained by the excitation of the surface plasmon and its subsequent decay.