MICROCLUSTER IOPTICAL ABSORPTION SPECTRA OF AG-MICROCLUSTERS FORMED BY MATRIX TECHNIQUES

Abstract

Silver microclusters have been prepared by co-condensation of a monoatomic silver beam with an excess of noble gas on a cooled sapphire target and investigated by optical transmission spectroscopy in the U.V.-VIS. range. Depending on the condensation parameters (i.e. temperature, gas/metal ratio, the gas admission rate and the gas itself) the condensing metal atoms can either be isolated as single atoms or as a mixture of aggregates at the surface of the growing matrix layer. The optical absorption spectra of such mixtures show several distinct absorption bands within the range 2 000-5 000 Å. The spectral features of monoatomic and diatomic silver can be clearly identified, allowing the remaining bands to be assigned to multimeric silver particles