Photodissociation of metal cluster ions. Dissociation energies and optical spectroscopy

Abstract

Dissociation energies and optical absorption spectra of metal clusters have been measured from photodissociation studies with a tunable dye laser. The dissociation energies of aluminium clusters with up to 17 atoms have been determined from measurements of the dissociation rates of photoexcited clusters. The dissociation energies show an overall increase with cluster size but there are large oscillations around the electronic shell closings. The measured dissociation energies are in poor agreement with the results of a number of recent theoretical calculations, all of which underestimate the binding energies. Optical absorption spectra have been recorded for copper clusters by photodissociation. The spectrum for Cu⁺₄ contains ten electronic transitions, most of which show vibrational fine structure. Some of the transitions can be correlated with an interband transition in bulk copper, suggesting that the incipient band structure of the bulk is apparent even in a cluster containing as few as four atoms.