Evidence for classical star orbit in largeAlNclusters

Abstract

Mass spectra of ${\mathrm{Al}}_{\mathit{N}}$ clusters produced by a laser vaporization source have been recorded via standard time-of-flight spectroscopic methods. Regular signal oscillations are observed in the size range N=200–900 when low-power near-threshold ionization is performed. This striking feature, which is a manifestation of the electronic shell structure of the aluminum clusters, is analyzed with the semiclassical theory of single-particle level density. The oscillation frequency is found to be well explained by the classical star orbit contribution.