ESR on the hydroxyl ion vacancies in the apatites

Heating biological apatites and synthetic apatites in the stream of inert gas saturated with heavy water vapor, introduces OD ions which substitute for the hydroxyl (OH) ions and partially for the OH vacancies, depending on the heating time and the gas flow rate. This has been verified by ESR and partially by IR. Deuteration gives no serious alterations of the a-axis dimension or of the PO4 bands in the IR spectra. These findings have been interpreted as suggesting that the OH ions diffuse out and the OD ions diffuse in through specific pathways, and the diffusing ions interact permanently with none of the other ions in the apatite structure. Heating in dry inert gas results in the formation of hydroxyl ion vacancies. The ESR spectra of these samples in the g = 2.06 region have been interpreted in terms of O-2 and O-. The shortening of the a-axis dimension in this case has been accounted for based on the loss of structurally incorporated H2O and the loss of the OH ions on the hexad axis.