Competitive fragmentation and electron loss kinetics of photoactivated silver cluster anions:: Dissociation energies of Agn- (n=7-11)

The photodecomposition kinetics of silver cluster anions, Ag-n(-) (n=7-11), has been investigated. The time-resolved intensities of Ag-n(-) parent ions and Ag-n-1(-) and Ag-n-2(-) photofragment product ions are measured following excitation with visible laser radiation, 415-750 nm. The atom-loss and dimer-loss product yields and reactant cluster ion depletion are compared to elucidate the decomposition kinetics of photoexcited silver cluster anions, including electron loss channels. Both prompt, direct electron photodetachment and delayed, statistical electron emission are observed in competition with cluster fragmentation product channels for some clusters. Dissociation threshold energies are determined by fitting the measured time profiles for fragmentation products using a statistical unimolecular dissociation model. The photodissociation lifetime method for measuring cluster dissociation energies is compared with previous energy-resolved collision-induced dissociation experiments on silver cluster anions. (C) 1999 American Institute of Physics. [S0021-9606(99)00227-5].