Electronic effects in the production of small dianionic gold clusters by electron attachment on to stored Aun-, n=12-28

Single charged gold clusters Au-n(-), 12 less than or equal to n less than or equal to 28, are stored in a Penning trap, size selected and transformed into dianions, Au-n(2-) by the application of an electron beam. At the onset of dianion production, that is that range of cluster sizes n where the smallest doubly charged clusters are observed, the measured intensity ratio of the dianions to their precursors is not a continuous function of cluster size. Instead, there is a strong odd-even effect and a comparatively intense signal of Au-18(2-). The observed structures are very reminiscent of similar phenomena in the abundance spectra of metal clusters as observed by Knight et al. (1984, Phys. Rev. Lett., 52, 2141), which gave rise to the electronic shell structure interpretation and the further development of the jellium model as applied to metal clusters.