Production of Light by Collisions of 2.5–490 eV He+ with N2: NI, N2+ Second Negative, and Unresolved Emissions between 1200 and 3200 Å

The production of light in collisions between He+ and N2 has been studied at primary ion energies, E, between 2.5 and 490 eV. Strong emissions are present between 1200 and 3200 Å, and spectra have been obtained for spectral resolutions between 1.5 and 16 Å. NI emissions, N2+ second negative (2N) emissions, and strong, unresolved emissions have been found. The total cross section for producing the emission between 1200 and 3200 Å is of the order of 10−16 cm2. For E <̃ 40 eV, the cross section for producing the unresolved emissions is greater than the cross section for producing the N2+(2N) emissions. The cross section for production of the NI emissions decreases with decreasing E and vanishes near the threshold energies expected for NI emission produced by He++N2→N++N+He. With decreasing E, total cross sections for the N2+(2N) and unresolved emissions increase. Apparent populations of the vibrational levels of the N2+(2N) parent state depend differently on E; in particular, for E = 490 eV the υ′ = 1 and 2 levels are the most highly populated, and for E = 4.5 eV the υ′ = 3 and 4 levels are the most highly populated. The electronic transition moment of the C 2Σu+ → X 2Σg+ transitions, which produce the N2+(2N) emissions, varies considerably with the wavelength of the emitted light.