Ions in Nitrogen

N⁺, N₂⁺, N₃⁺, and N₄⁺ ions have been identified in nitrogen gas by use of a mass spectrometer operated with the ion source in the pressure range from 10^-3 mm Hg to 0.6 mm Hg. Appearance potentials occur at 15.5±{}0.2 ev for N₂⁺, at 15.8±{}0.3 ev for N₄⁺, at 22.1±{}0.5 ev for N₃⁺, and at 24.2±{}0.4 ev for N⁺; N₃⁺ ions thus are formed only at much higher electron energies than N₂⁺ but still at 2 ev less energy than N⁺. It is believed that the N₄⁺ is formed by the process N₂⁺+N₂{→}N₄+* (excited vibrationally) and the N₃⁺ is formed by the process N₂+*+N₂{→}N₃⁺+N, where N₂+* is an excited ion. N₄⁺ and N₃⁺ currents decrease with increasing E/p in the source, suggesting that they may be dissociated by molecular impacts. The N₄⁺ ions are considerably more readily lost than the N₃⁺ ions. Since the formation of N₃⁺ must necessarily release a nitrogen atom, this process constitutes a form of dissociation of N₂ which may account for the value of the dissociation energy of 7.38 ev found by some methods.