Electron impact ionization/dissociation of size selected gold cluster cations

Singly charged gold clusters, Au⁺_n in the size range n = 12 to 72 have been captured and stored in a Penning trap, size selected and subjected to an electron beam. This interaction leads to further ionization as well as dissociation. The resulting abundance spectra of doubly and triply charged clusters show (a) a lower size limit for the production of multiply charged clusters from an ensemble of hot precursors, which can be understood in terms of the respective decay pathways, (b) an odd/even alternation of singly and doubly charged clusters in the size range below n = 30, which inverses sign with change of charge state, and (c) magic numbers, i.e. prominent signals for particular cluster sizes, which can be identified as closed electronic shells. In contrast to similar experiments on silver clusters and in spite of the well-known ligand-stabilized species, there is no indication of a particularly stable charge-state-independent cluster size of n = 55.