Calculation of the Photoionization Cross Sections for Small Metal Clusters

Abstract

Alkali metal clusters have in a number of experiments during the last year been shown to provide good testing systems for analyzing effects of valence electron delocalization as a function of cluster size [1, 2]. A fundamental question that arises in these investigations is how the metallic character will develop and how it will depend on the geometry of the cluster, i.e. the delocalization of the valence electrons with respect to the ion cores of the cluster. Electron structure calculations treating the clusters within the framework of a Fermi gas of electrons in a spherical or deformed potential well, i.e. the jellium model, have been very successful in explaining observed magic numbers and optical response as plasma oscillations [3, 4] . Calculations within the jellium model suffer, however, from the drawback of not including the geometrical structure of the clusters as in traditional quantum chemistry methods, i.e. techniques based on the MO-LCAO approach, as the Hartree-Fock (HF), Configuration Interaction (CI) and Local Spin Density (LSD) methods. Reviews of different calculations have been given by Fantucci, Bonacic-Koutecký and Koutecký [5], and by Halicioglu and Bauschlicher [6].