Forming metastable carbon-rich anions in planetary atmospheres: the case of diacetylene Isabella Baccarelli, Francesco Sebastianelli, Bernd M. Nestmann and Franco A. Gianturco Eur. Phys. J. D, 67 5 (2013) 93 Published online: 07 May 2013 DOI: 10.1140/epjd/e2013-30741-2