State-selective single-electron capture in very slow collisions between metastable N<SUB>2</SUB><SUP>2+</SUP> ions and neutral atoms and molecules

State-selective, non-dissociative electron capture processes by very slow nitrogen dications from atoms (He, Ne and Ar) and molecules (D2, N2 and O2) has been studied experimentally at impact energies of 28 eV by means of ion translational energy spectrometry and theoretically by means of ab initio configuration interaction calculations of the potential energy curves involved in the electron capture process. Information is obtained on the principal quantal states involved in the incoming and outgoing channels; indications are obtained that the electron capture occurs primarily into electronically-excited states of N2+ and that the dynamics may involve non-Franck-Condon routes