Correlation between mass distributions of zinc, cadmium clusters and electronic shell structure

Abstract

Mass distributions of zinc (Zn) n + and cadmium (Cd) n + clusters have been investigated up to the cluster size n = 75. The clusters produced by the bombardment of the metals by 10 keV Xe ions have been analyzed using a single focusing mass spectrometer. The mass distributions for these metal clusters are quite similar. The ion intensity of clusters decreases with an increase of n. Superimposed on this general decrease, abundant ion currents are observed for clusters with n = 10, 18, 20, 28, 30, 32, 35, 40, 41, 46, 54, 57, 60 and 69. These numbers can be explained by a shell-closing effect of s-valence electrons which are bound in a spherically symmetric potential well of the cluster. The most probable potential is the finite square well potential with round edges.