Shell structure of small indium clusters below N≈200 atoms

Abstract

Neutral indium cluster In N ( N≤200) are laser photoionized near threshold and analyzed by time-of-flight mass spectrometry. Strong shell effects are observed in cluster mass spectra. For In N clusters below N=125, individual ionization potentials are deduced. They are compared with theoretical predictions calculated within the framework of the spherical-jellium model. The agreement is qualitatively quite good and the observed shell effects correspond to the successive major electronic shell closures. Deviations from electronic shell model predictions are much less important for indium clusters than for aluminum ones. A tentative explanation of this difference is given.