For Ama + , three structureless bands are observed in the total spectrum (in the energy range up to 6 eV), with the major contributions stemming from D 2 , D 8 , and D 9 (Fig. ). Notably, none of the ten transitions exhibit vibronic fine structure. This is in contrast to Ada + , for which some transitions show the fine structure (Fig. ). Also the Ada-CN + absorption spectrum shows fine structure (see Fig. and the discussion below). Unfortunately, no experimental optical spectrum has been reported for Ama + (unlike Ada + and Ada-CN + ); therefore, a comparison with experiment for Ama + is so far not possible.