Core-electron binding energies in free and supported metal clusters.

Core-electron binding energy shifts in free and supported clusters are discussed using the Born-Haber formalism. For grounded clusters this approach shows that the shift reflects the decrease in the average atomic cohesive energy of the cluster relative to that of the bulk metal. This shift is closely related to the surface-atom core level shift. For free clusters there is a second term reflecting the unit charge left on the cluster by the emission of the photoelectron. In small clusters this term results in the suppression of conduction electron screening.