Singlet-triplet excitation ratios in Ne III, Ar III and N II under ion impact E. Träbert, H.-P. Garnir, P.-D. Dumont and T. Bastin Eur. Phys. J. D, 15 1 (2001) 25-31 Published online: 15 July 2001 DOI: 10.1007/s100530170179