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SYCF: Symposium Cluster und Fullerene

SYCF 9: Cluster an Oberfl
ächen

SYCF 9.3: Vortrag

Freitag, 19. März 1999, 12:00–12:15, PA1

Investigation of Silver Cluster Deposited on HOPG using Time-Resolved Two-Photon Photoemission — •Liana Socaciu, Ulrike Busolt, Emmanuel Cottancin, Holger Röhr, Thomas Leisner, and Ludger Wöste — Insitut für Experimentalphysik, Freie Universität Berlin

Time-resolved two-photon photoemission has been used to study the dynamics of size-selected silver clusters deposited onto HOPG (Highly Oriented Pyrolytic Graphite). This technique allows to study the lifetime of electronically excited states of cluster-surface complexes. The clusters are produced in a sputtering ion source, mass selected in a quadrupole mass filter, and soft landed with a low coverage on HOPG surface under UHV conditions at liquid nitrogen temperature. After deposition, the sample is irradiated with two subsequent ultrashort laser pulses. The photoelectrons, which are created by two-photon photoemission, are collected in a magnetic bottle type time-of flight spectrometer, where their kinetic energy distribution is recorded as a function of the delay-time between the laser pulses. For a fixed delay-time between the two laser pulses the kinetic energy of the emitted photoelectrons has been recorded as a function of the substrate temperature. As the size dependence of the photoelectrons mean kinetic energy reveals a pronounced odd-even effect, we conclude that the deposited clusters retained their size and identity on the sample. By slow annealing of the sample, information about the stability of the clusters and their interaction with the substrate can be obtained.