Regensburg 2000 – wissenschaftliches Programm

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O: Oberflächenphysik

O 11: Postersession (Eröffnung)

O 11.128: Poster

Montag, 27. März 2000, 19:00–22:00, Bereich C

Time-Resolved Two-Photon Photoemission on Deposited Silver Clusters — •Liana Daniela Socaciu, Ulrike Busolt, Emmanuel Cottancin, Holger Röhr, Thomas Leisner, and Ludger Wöste — Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin

We use time-resolved two-photon photoemission to investigate electron and adsorbate dynamics of small mass-selected silver clusters deposited on HOPG (Highly Oriented Pyrolitic Graphite). The silver clusters are produced by sputtering, mass selected in a quadrupole mass filter and soft landed on the sample. After deposition, the sample is irradiated with two subsequent ultrashort laser pulses and the created photoelectrons are collected in a magnetic bottle type time-of*flight spectrometer, where their kinetic energy is recorded as a function of the delay-time between the two laser pulses. The experiments were performed under UHV conditions and at liquid nitrogen temperature.

The recorded photoelectron spectra for different cluster sizes are shifting along the energy axis and this shift reveals a pronounced odd-even effect, which we associate with the influence of the charge transfer between adsorbat and substrate. 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. During the annealing of the sample a sharp increase of the photoelectron yield has been observed, which is caused by the exciting of the silver nanoparticles plasmon.