Observation of electronic and geometric shell structures of small silver clusters

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