Laser photodetachment studies have been performed on silver and copper cluster negative ion beams extracted from a supersonic metal cluster source. This source involves the use of laser vaporization within a pulsed nozzle to prepare the neutral cluster jet, followed by ArF excimer irradiation of the nozzle orifice as the copper clusters emerge into the expansion. Photoelectrons ejected from the aluminum nozzle by the excimer radiation are entrained in the supersonic flow and attach to the neutral copper clusters, producing negative ions which stabilize and extensively cool in the subsequent supersonic expansion. Laser photolysis of masshyphen;selected negative copper cluster ions extracted from this source reveals efficient photodetachment to produce a free electron in the absence of measurable fragmentation. The laser fluence dependence of the photodetachment process at different photon energy permits a rough experimental determination of the electron affinities of copper metal clusters as a function of cluster size for the first time.
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