Delocalized electronic states in small clusters.

Photoelectron spectra of Na; , Cu; , Ag; , and Au; clusters reveal the electronic structure of these particles. The experimen-tal results are compared to the predictions of quantum chemical calculations and of the shell model. The spectra of Ag; allow for a stringent est of both approaches, because most of the observed features are assigned to s-derived orbitals and they also display much sharper features than the alkali data. A qualitative quivalence of the electronic shell model with high-level quan-tum chemical calculations in terms of the symmetries of the involved single particle orbitals is found for the delocalized states derived from the atomic s-electrons. 1