Deposition of Lead Clusters on Cold Silver and Photoemission by Synchrotron Radiation

Abstract

Lead clusters grown in a pulsed arc cluster ion source (PACIS) are deposited under UHV conditions on LN2-cooled polycristalline silver targets. Photoemission experiments with light from the synchrotron BESSY serve to investigate the electronic level structure of the clusters. The Pb 5d core levels clearly shift with the cluster size, yielding — for small clusters with below about 100 atoms each — a shift of — 0.33 eV relative to the bulk value. The same maximum shift is obtained in the case of atom deposition. Born-Haber cycles and the equivalent core approximation are used to explain the observed shifts.