Measurement of the dissociation energies of anionic silver clusters (Ag-n(-), n = 2-11) by collision-induced dissociation

The energy-resolved collision-induced dissociation method is applied to mea sure the fragmentation patterns, cross sections, and dissociation energies of small anionic silver clusters (Ag-n(-), n = 2 - 11). The main reaction c hannels are found to be loss of atom and loss of dimer, with dimer loss fav ored for odd n values. The dissociation energies for the loss of atom, D-0( Ag-n-1(-) - Ag), show strong even-odd alternation. Threshold models that ac count for collisional activation efficiency, kinetic shifts, and competitiv e shifts are employed to obtain dissociation energies. A critical examinati on of the models is performed using a thermochemical cycle comparing sequen tial atom loss with dimer loss. (C) 1999 American Institute of Physics. [S0 021-9606(99)01211-8].