The [FA]0 center was detected in monocrystals by using electron paramagnetic resonance methods. This center consisted of an anion vacancy with a localized electron and a monovalent substitutional impurity replacing an adjacent Zn2+ ion. The impurity was assumed to be a Li+ ion in the case of ZnO, and a Cu+ ion in the case of ZnS. The spin Hamiltonian parameters of the [FA]0 center in ZnO at 60K were g|| = 1.9951, g = 1.9956, A|| = 2.36MHz and A = 2.75MHz. In ZnS at 30K, the corresponding values were g|| = g = 2.0017, A|| = 4.06MHz and A = 3.67MHz. A thermally stimulated ionic process occurred in ZnO at 530 to 650K, and in ZnS at 720 to 820K. In the first stage of this process, the anion vacancies of the normal lattice detected as F+ centers disappeared. In the second stage, the destruction of [FA]0 centers occurred.

EPR of [FA]0 Centres in Zinc Chalcogenides. Tarkpea, K., Ots, A., Nikitenko, V.: Journal of the Physics and Chemistry of Solids, 1994, 55[11], 1353-6