The EPR spectra near g \ 2 of a few carbonated calcium apatites, synthesized at high temperatures are studied in X-and Q-band. Solid state reactions at high temperatures were used to prepare samples with carbonate substituting for OH~(A-type) and (B-type). In the present study the experience from previous X-band PO 4 3w ork on the same samples is combined with the higher resolution of Q-band experiments, to gain further insight into the composite nature of the spectra. X-Irradiation of carbonated calcium apatites gives rise to highly composite EPR spectra, due to the presence of di †erent paramagnetic centres. Except for A-type carbonated apatite, the contribution of several types of radicals dominate the spectra. The comparison CO 3 3b etween X-and Q-band results allows us to identify the di †erent types of (hydroxyl site, phosphate CO 3 3s ite, surface), together with a smaller component. Simulations of the experimental spectra support these CO 2 ãssignments. A-type carbonated apatite spectra are dominated by one or more contributions. In order CO 2 to elucidate the composite nature of the spectra, recent hydroxyapatite single crystal results are used to simulate the spectra, again in both frequency bands. Similar simulations of tooth enamel spectra and an evaluation of A-type carbonated apatite as a model system for tooth enamel are presented.
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