Electron Spin Resonance Spectrum of N2− Trapped in KCl, KBr, and KI

The EPR spectra attributable to N₂⁻ trapped in KCl, KBr, and KI have been observed between 2° and 20°K. The N₂⁻ impurity occupies a negative‐ion vacancy and is oriented so that the equilibrium direction of the N–N bond is a 〈110〉 direction of the crystal. The principal $g$ factors of N₂⁻ are characteristic of a ²Π_1/2 ground state, and the nodal plane of the $\pi$ orbital is a {100} plane of the crystal. In KI, N₂⁻ appears to be undergoing a libratory motion, which is, however, confined to this {100} plane. The ¹⁴N hyperfine structure, which is perfectly resolved in KCl:N₂⁻, is used to determine the atomic parameters ${\mathrm{〈r}}^{\text{−3}}{〉}_s$ and ${\text{(8π\hspace{0.17em}/\hspace{0.17em}3)ψ}}^2\text{(0)}$ .