Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 2: Clusters I: Metal Clusters (joint session A and MO)
MO 2.8: Vortrag
Montag, 2. April 2001, 17:30–17:45, H1012
Ultraviolet photoelectron spectroscopy of Si4− to Si1000− — •Gert Wrigge, Margarita Astruc Hoffmann, Bernd von Issendorff, and Hellmut Haberland — Fakultät für Physik, Universität Freiburg, H. Herderstr. 3, 79104 Freiburg, Germany
We have measured UV (hν = 6.4 eV) photoelectron spectra of cold (T≃100 K) mass-selected silicon cluster anions in a very broad size range (n = 4 to 1000). The clusters were produced in a magnetron sputter gas aggregation source, size-selected by a tandem reflectron time-of-flight mass spectrometer, and irradiated by an excimer laser in the interaction region of a magnetic bottle type photoelectron spectrometer. For Sin− with n≤50 the spectra exhibit rich structures. The spectra of larger clusters show only a gradual onset at the detachment threshold. No trace of a bandgap has been found even for clusters with more than 1000 atoms. The additional electron of the negatively charged clusters thus probably occupies a low lying surface state and not the cluster equivalence of the bulk conduction band. Currently the measurements are repeated with hydrogen passivated silicon clusters.
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