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ClusterTrap has been designed to investigate properties of atomic clusters in the gas phase with particular emphasis on the dependence on the cluster size and charge state. The combination of cluster source, Penning trap and time-of-flight mass spectrometry allows a variety of experimental schemes including collision-induced dissociation, photo-dissociation, further ionization by electron impact, and electron attachment. Due to the storage capability of the trap extended-delay reaction experiments can be performed. Several recent modifications have resulted in an improved setup. In particular, an electrostatic quadrupole deflector allows the coupling of several sources or detectors to the Penning trap. Furthermore, a linear radio-frequency quadrupole trap has been added for accumulation and ion bunching and by switching the potential of a drift tube the kinetic energy of the cluster ions can be adjusted on their way towards or from the Penning trap. Recently, experiments on multiply negatively charged clusters have been resumed. [ABSTRACT FROM AUTHOR]

Earlier experiments [Eur. Phys. J. D 43, 241 (2007)] investigating the production of aluminium cluster dianions have been extended to larger cluster sizes for the purpose of producing higher charge states. Polyanions are produced using the “electron-bath technique" which involves the exposure of monoanionic clusters to a bath of low-energy secondary electrons. In this contribution the production of Aln 3- is investigated as a function of cluster size. Relative trianion yields (number of trianions produced relative to the number of precursor anions) were observed to increase from a few percent up to 55% within ~30 cluster sizes. The observed appearance size (n = 103) is in reasonable agreement with the predictions of classical models. [ABSTRACT FROM AUTHOR]