Observation of electronic and geometric shell structures of small silver clusters - Electron impact ionization/dissociation of size selected silver clusters

Singly charged silver clusters Ag-n(+) in the size range n = 17 to n = 78 h ave been captured and stored in a Penning trap, size selected and subjected to an electron beam which leads to further ionization as well, as dissocia tion. The resulting abundance spectra of doubly and triply charged clusters show several features: (1) A critical size for the production of doubly ch arged clusters which can be understood in terms of the decay pathways as pr eviously investigated by collision induced dissociation, (2) an odd-even al ternation in the abundance of singly and doubly charged clusters which inve rses sign with change of charge state, (3) prominent signals for particular doubly and triply charged species that indicate both electronic and geomet ric influences on the clusters' stability.