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 2Π1/2 ground state, and the nodal plane of the π 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 〈r−3〉s and (8π / 3)ψ2(0).