摘要：

Recent developments in laser and molecular beam technology have now made itpossible to produce supersonic beams of virtually any element in the periodic table.Using laser vaporization of the appropriate target, the beam source conditions maybe adjusted to produce either the cold free atoms alone, or clusters of these atomswith each other—or with another element. Since the vaporization laser heats only asmall spot on the target, extremely high local temperatures can be obtained withoutheating any other part of the apparatus; and beams of even the highest boiling element(tungsten) are readily obtained both in atomic and cluster form. The physics andchemistry of these exotic cluster species is almost completely unknown on the fundamentallevel. Even for clusters containing 100 atoms, most of these atoms lie on thesurface, and the chemical and physical properties will be predominately surfacephenomena. Initial studies of these clusters have entailed the use of one- and two- photonlaser ionization with time-of-flight mass selective detection. Using a variety offixed frequency lasers, the work function of copper clusters has been examined as afunction of cluster size in the range from 2 to 29 atoms per cluster. Considerabledetailed information has also been obtained for the electronic structure and bondlengths of a number of transition metal dimers and trimers (including Cu2, Cr2, V2,Mo2, and Cu3) through the use of high resolution laser spectroscopy with mass-selectivephotoionization detection.

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