EPR of Radiation-Induced Nitrogen Centers in Hydroxyapatite: New Approaches to the Study of Electron-Nuclear Interactions

Abstract

Radiation-induced impurity nitrogen centers ( $${\text{NO}}_{3}^{{2 - }}$$ ) in nanosized powders of synthetic hydroxyapatite are studied by pulse EPR and pulse double-frequency EPR, which is named the NMR detected by electron–electron double resonance (ELDOR detected NMR, EDNMR) method. The EPR signals caused by the interaction of the electron of $${\text{NO}}_{3}^{{2 - }}$$ with the environmental nuclei (1H, 14N, and 31P) are identified, and the parameters of the hyperfine and quadrupole interactions of the electron with the 14N nuclei are determined. The possibility of using the EDNMR method in the X-band of microwave frequencies (νmw ≈ 9 GHz) at room temperature to obtain a detailed information about peculiarities of electron-nuclear interactions in hydroxyapatite is demonstrated.