Rotational and vibrational excitation of the N-2(+)(B) state in a He+N-2 electron-beam plasma

Emissions of the first negative system of N-2(+) have been studied in a He + N2(<5%) mixture activated by a 10-keV electron beam. Flow in the free jet core was used as a gas target. Analysis of both the internal energy distributions in the N-2(+) (B) state and the He density dependencies of the excitation rates have revealed three excitation mechanisms. One of them is the excitation by atomic ions He+ going through the formation of long-living collisional complexes (He...N-2)(+). This channel produces the vibrational and rotational heated ions N-2(+)(B), with the rotational temperature independent of the rotational distribution in the ground state of the N-2 molecule before excitation. This temperature is estimated as T=(900 +/- 60) K. The other excitation channels are evidently Franck-Condon processes with the population of vibrational levels according to Franck-Condon factors and with the rotational transition probabilities close to those governed by Honl-London factors in the excitation.