Vibrational excitation of N2+ ions in collisions of protons and electrons with N2 molecules

The excitation cross sections for bands of the first negative system of the N2+ ion ( Bsup(2)Σsub(u)sup(+)→Xsup(2)Σsub(g) sup(+) transitions) are measured on exsitation of N2 molecules by 0.2-10 keV protons or 0.8 keV electrons. The measurements show that the population of levels with v' = 1, 2 in the Bsup(2)Σsub(u)sup(+) state relative to the v' = 0 level of the same state increases with diminishing energy. An anomalous population of highly excited levels v' = 2, 3 of the Bsup(2)Σsub(u)sup(+) state is observed on excitation of N2 molecules by fast (v > or approximately 108 cm/sec) protons. Even at a proton energy of 10 keV for which agreement between the experiments and calculations based on the Franck-Condon theory should exist as previous studies show, the population o, the level with v' = 2 exceeds by 5 times and that of the level with v' = 3 by 150-170 times the calculated values. It is also found that the relative populations of the vibrational levels of the Bsup(2)Σsub(u)sup(+) state on excitation by 10 keV protons or by electrons are the same within the experimental errors. The regularities observed are explained within the framework of a model in which the quasimolecular behaviour of the particle system during collisions and the multichannel nature of the state excitation processes are taken into account. In the low proton energy range, E < or approximately 5 keV, the excessive population of vibrational levels of the final electron state can be ascribed to transitions via quasimolecular intermediate states of the particle system. At high proton energies, E > or approximately 10 keV, the excessive level population is explained by virtual transitions through intemediate particle system states, the transitions being taken into account in the second order in perturbation theory. In the case of excitation of the molecules by electrons it can be explained by virtual transitions through intermediate states of single molecules