Mass distributions of copper, silver and gold clusters and electronic shell structure

Abstract

Mass distribution of copper (Cu) n +, silver (Ag) n + and gold (Au) n + clusters were investigated up to cluster size n = 250. The clusters were produced by bombardment of 10 keV Xe ions and were analyzed using a sector-type mass spectrometer. The mass distributions for these metal clusters were similar. The ion intensity of clusters decreased with increasing cluster size, n. Superimposed on this general decrease, two types of anomalies were observed. One anomaly was a regular variation of ion intensity between odd and even numbers of n, where the intensity of odd- n clusters was greater than that of even- n. The other anomaly was a discontinuous variation of cluster ion intensity at peculiar numbers of n. These numbers were 3, 9, 21, 35, 41, 59, 93, 139 and ∼ 200. This behavior can be explained by a one-electron shell model in which electrons are bound in a spherically symmetric potential well.