INTERPLAY BETWEEN COLLECTIVE AND SINGLE ELECTROEXCITATIONS IN LARGE METAL-CLUSTERS

Collective and single electron excitations of large metal clusters sup ported on transparent substrates are investigated. The applied experim ental techniques include extinction spectroscopy and laser induced dis sociation accompanied by the ejection of individual atoms. The optical spectra depend on the electromagnetic far field and reflect collectiv e electron excitations of the conduction electrons, i.e. surface plasm ons. Dissociation, however, is correlated to repulsive single electron energy levels. The characteristics of these localized excitations ind icate a strong influence of collective excitations. In particular, it is found that nonlocal optical effects are important. In this picture surface plasmons catalytically enhance the number of single electron e xcitations and therefore of the metal atoms ejected as a result of the absorption of visible light. Results will be presented, which illustr ate this interplay between collective and single electron excitations.