Eur. Phys. J. D 43, 241-245 (2007)
https://doi.org/10.1140/epjd/e2007-00114-9

Multiply negatively charged aluminium clusters

Production of Al_n^2- in a Penning trap

Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17487 Greifswald, Germany

Corresponding author: ^a lschweik@physik.uni-greifswald.de

Received: 11 August 2006
Revised: 25 October 2006
Published online: 24 May 2007

Abstract

The first observation of gas-phase aluminium dianions, Al_n^2-, is reported. Singly negatively charged aluminium clusters are converted to dianions by exposure to low-energy electrons in a Penning trap. Attachment of such secondary electrons to the monoanions leads to the formation of dianionic clusters, as earlier observed for the noble metals, copper, silver and gold. The present work extends the `electron-bath technique' to the trivalent aluminium. The observation of Al_n^2- as a function of cluster size is compared to estimates of the second electron affinities of Al_n as given by a combination of first electron affinities and the charged conducting-sphere model. This simple approach is found to describe the appearance size (size of smallest Al_n^2- observed) very well.