Abstract

The recent development of a general source to produce gas phase metal clusters using laser vaporization combined with mass selective detection techniques has enabled new studies of the fundamental chemical and physical properties of clusters as a function of their size. In our laboratory we have developed and applied a variety of experimental techniques to measure ionization thresholds, magnetic moments, and gas phase reactivities of metal clusters. We now report the first observation of infrared laser-induced dissociation (IR-LID) of metal cluster-adsorbate complexes in a molecular beam. Specifically, using a high-power pulsed CO₂ laser as the infrared source, we have measured the IR-LID spectrum for the iron clusters containing chemisorbed methanol as a function of the number of iron atoms for a known number of chemisorbed molecules. For clusters which have chemisorbed only one methanol, strong IR adsorption is observed near 985 and 1075 cm^-1, adsorptions presently assigned to the C-O stretch of chemisorbed methoxy radical and bridging hydrogen, respectively, i.e., the methanol is dissociatively chemisorbed. Both the feasibility and potential utility of IR-LID for characterizing metal cluster-adsorbate interactions have been demonstrated. The method is generally applicable to any cluster or cluster-adsorbate system dependent only on the availability of appropriate high-power IR laser sources.

© 1986 Optical Society of America