Rotational and vibrational excitation of the N2+ (B) state in a He + N2 electron-beam plasma Original Research Article

Emissions of the first negative system of N2+ 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 N2+(B) state and the He density dependecies 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.N2)+. This channel produces the vibrational and rotational heated ions N2+(B), with the rotational temperature independent of the rotational distribution in the ground state of the N2 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 Hönl-London factors in the excitation.