Electron spin resonance (ESR) studies of CO−2 radicals in irradiated A and B-type carbonate-containing apatites

ESR spectra of irradiated carbonate-containing hydroxyapatites are complex and strongly dependent on the method of preparation of these materials. This paper describes results of our studies of the ESR spectra of irradiated A- and B-type carbonated hydroxyapatites. The most intense and stable lines in these spectra are attributed to CO−2 radicals. The ESR spectrum of A-type carbonated apatite can be predominantly due to either axial or orthorhombic CO−2 species, depending on whether the apatite was cooled in or without a CO2 flow. The B-type carbonated apatite has an ESR spectrum composed basically of signals from isotropic and orthorhombic CO−2 species. These signals are different in intensity, line width, and g-factor for samples heated for 3 h at 200, 400 and 600°C. The effect of the method of preparation of the A- and B-type carbonated apatites on the ESR spectra and the application of these materials to the ESR dating and dosimetry are discussed.