Production of dianionic and trianionic noble metal clusters in a Penning trap

Metal clusters, Au(n)(-), Ag(n)(-), and Cu(n)(-), from a laser vaporization source are transferred to a Penning trap and subjected to a bath of simultaneously stored electrons. After some reaction period multiply charged anionic gold, silver, and copper clusters are observed if the clusters under investigation are large enough. The cluster sizes for the onset of the formation of dianions and trianions are compared to a charged sphere model. The description of the experimental findings is largely improved if the repulsive Coulomb barrier is taken into account which prevents autodetachment of the surplus electrons on the experimental time scale of a second. (C) 2003 Elsevier B.V. All rights reserved.