N-2(-) Radical Anions Trapped in Bulk Polycrystalline MgO

Oxidation of magnesium nitride, Mg3N2, leads to segregated nitrogen impurities within the bulk of MgO. Electron paramagnetic resonance experiments in conjunction with quantum chemical calculations allow us to identify these paramagnetic centers as N-2(-) radical anions trapped in anion vacancies in the bulk of MgO. The characteristics of the defect center, derived from the spin Hamiltonian parameters, exhibit similarities but also some interesting differences with respect to the classical N-2(-) species in KCl a sort of prototype of molecular anions trapped in ionic crystals.