Satellite EPR resonances of the N4− radical in ultraviolet irradiated potassium azide

When EPR spectra of irradiated KN3 are recorded at low temperatures for the magnetic field in the [100] crystal direction, a nine-line spectrum is found which is attributable to the presence of N4− ion–molecules in the material. Between each pair of the lines of the N4− pattern is found a satellite line of less intensity. The literature has conflicting explanations for these lines, either ascribing them to an exchange interaction between closely neighboring N4− ion molecules or to the presence of N32− ion molecules. This paper compares predictions of the two proposals to measurements of EPR spectra for angles near the [100] direction and finds that only the exchange model is compatible with experimental results.