ELECTRON-DISTRIBUTION AND COLLECTIVE RESONANCES IN SODIUM CLUSTERS

Electron distribution and collective resonances of sodium metallic clu sters, with the inhomogeneous jellium model, are studied by means of t he Thomas-Fermi statistical method with a Wood-Saxon charge distributi on for positive charge background and the sum-rule formalism. The dens ity distribution of the valence electrons has been calculated for smal l sodium clusters and the ''redshift'' effect of collective resonances is found in agreement with the experimental results. The characterist ic electronic shell effects of sodium clusters are found, which cannot be obtained by using homogeneous jellium model. The collective resona nces in medium sized sodium clusters are predicted and the ''redshift' ' effect decreases as cluster size increases.