Ions in Nitrogen

Abstract

${\mathrm{N}}^{+}$, ${\mathrm{N}}_2^{+}$, ${\mathrm{N}}_3^{+}$, and ${\mathrm{N}}_4^{+}$ ions have been identified in nitrogen gas by use of a mass spectrometer operated with the ion source in the pressure range from ${10}^{-3\mathrm{}}$ mm Hg to 0.6 mm Hg. Appearance potentials occur at 15.5±0.2 ev for ${\mathrm{N}}_2^{+}$, at 15.8±0.3 ev for ${\mathrm{N}}_4^{+}$, at 22.1±0.5 ev for ${\mathrm{N}}_3^{+}$, and at 24.2±0.4 ev for ${\mathrm{N}}^{+}$; ${\mathrm{N}}_3^{+}$ ions thus are formed only at much higher electron energies than ${\mathrm{N}}_2^{+}$ but still at 2 ev less energy than ${\mathrm{N}}^{+}$. It is believed that the ${\mathrm{N}}_4^{+}$ is formed by the process ${\mathrm{N}}_2^{+}$+${\mathrm{N}}_2$→${\mathrm{N}}_4^{+*}$ (excited vibrationally) and the ${\mathrm{N}}_3^{+}$ is formed by the process ${\mathrm{N}}_2^{+*}$+${\mathrm{N}}_2$→${\mathrm{N}}_3^{+}$+N, where ${\mathrm{N}}_2^{+*}$ is an excited ion. ${\mathrm{N}}_4^{+}$ and ${\mathrm{N}}_3^{+}$ currents decrease with increasing $\frac{E}{p}$ in the source, suggesting that they may be dissociated by molecular impacts. The ${\mathrm{N}}_4^{+}$ ions are considerably more readily lost than the ${\mathrm{N}}_3^{+}$ ions. Since the formation of ${\mathrm{N}}_3^{+}$ must necessarily release a nitrogen atom, this process constitutes a form of dissociation of ${\mathrm{N}}_2$ which may account for the value of the dissociation energy of 7.38 ev found by some methods.