ELECTRONIC SHELL STRUCTURE OF GROUP-IIIA METAL ATOMIC CLUSTERS

Ionization potentials of Aln and Inn clusters (n<80) in supercooled beams have been measured by photoionization spectroscopy. The abrupt leveling near n=5 of the initial linear increase in ionization potentials and the subsequent gradual approach to the classical metallic sphere model are consistent with a simple picture of s-p band hybridization. For n>6, there is clear evidence of electron shell filling, yet substantial deviations from shell-model predictions remain. Crystal-field effects are considered the most probable source of symmetry breaking and give insight to cluster structure. © 1990 The American Physical Society.