Multiply negatively charged aluminium clusters - Production of Aln2- in a Penning trap N. Walsh, F. Martinez, G. Marx and L. Schweikhard Eur. Phys. J. D, 43 1-3 (2007) 241-245 Published online: 24 May 2007 DOI: 10.1140/epjd/e2007-00114-9