ELECTRONIC-STRUCTURE OF SUPPORTED MASS-SELECTED TRANSITION-METAL CLUSTERS - A PHOTOEMISSION-STUDY

Pt clusters are produced by bombarding a platinum target with a Xe+ beam which is provided by a cold reflex discharge ion source (CORDIS). The ionized clusters are mass selected by a quadrupole mass spectrometer and guided to the substrate by an RF-mode-only quadrupole. The substrate, held at low temperatures (20, 110 K), is in the center of the analysis chamber of a specifically designed photoelectron spectrometer (VSW) allowing in-situ characterization of the soft-landed clusters. Photoemission spectra, taken on submonolayer quantities of mass-selected monodispersed Pt clusters (Pt1, Pt2, Pt3 and Pt10) supported on Ag films, indicate the formation of spin-orbit split Pt5d virtual bound states at small particle sizes. This observation points to the validity of the single-impurity model of Friedel and Anderson in a quasi-two-dimensional dilute alloy system.