Oxygen-associated holelike centers in calcium chlorapatite

Roufosse, A.; Stapelbroek, M. G.; Bartram, R.H.; Gilliam, O. R.

doi:10.1103/physrevb.9.855

Cited by 16 publications

(22 citation statements)

References 21 publications

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“…As mentioned in the theoretical part, a reliable identification of such centers in non-model systems is not easy because of the absence of hyperfine structure and possible confusion with other oxygen radicals. Therefore, in order to give an idea of typical g-values that can be expected in tooth enamel a priori, we quote the g-values of two similar bulk centres in chlorapatite reported by the same group (Roufosse et al, 1974): g // = 2.0031 and g ⊥ = 2.0255; g // = 2.0032 and g ⊥ = 2.0386 (both axial with respect to the c-axis). Again, the precursors are hydroxyl ions.…”

Section: Oxygen and Phosphate Radicals In Tooth Enamel Model Systemsmentioning

confidence: 99%

EPR dosimetry with tooth enamel: A review

Fattibene

Callens

2010

Applied Radiation and Isotopes

208

160

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When tooth enamel is exposed to ionizing radiation, radicals are formed that can be detected using Electron Paramagnetic Resonance (EPR) techniques. EPR dosimetry using tooth enamel is based on the (presumed) correlation between the intensity or amplitude of some of the radiation-induced signals with the dose absorbed in the enamel. In the present paper a critical review is given of this widely applied dosimetric method.The first part of the paper is quite fundamental and deals with the main properties of tooth enamel and several of its model systems (e.g., synthetic apatites). Considerable attention is also devoted to the numerous radiation-induced and native EPR signals, and the radicals responsible for them. The relevant EPR detection, identification and spectrum analysing methods are reviewed from a general point of view. Finally, the need for solid state modelling and the linearity of the dose response are investigated.The second part is devoted to the practical implementation of EPR dosimetry using enamel. It concerns the preparation of samples, specific irradiation problems, spectrum acquisition and it is described how the dosimetric signal intensity and dose can be retrieved from the EPR spectra. Special attention is paid to the energy dependence of the EPR response and to sources of uncertainties. Results of and problems encountered in international intercomparisons and epidemiological studies are also dealt with.In the final chapter the future of EPR dosimetry with tooth enamel is analysed.

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Section: Oxygen and Phosphate Radicals In Tooth Enamel Model Systemsmentioning

confidence: 99%

EPR dosimetry with tooth enamel: A review

Fattibene

Callens

2010

Applied Radiation and Isotopes

208

160

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“…§ E-mail address: yuanming.pan@usask.ca defect centers and to re-evaluate the structural models of Knottnerus et al (1972) and Roufosse et al (1974) for the two known centers.…”

Section: (Traduit Par La Rédaction)mentioning

confidence: 99%

“…They attributed this center to an O -ion arising from the removal of hydrogen from an OH -ion, and suggested that the hyperfi ne interaction is with the hydrogen of an adjacent OH -ion. Knottnerus et al (1972) and Roufosse et al (1974) both reported two oxygen-associated hole-like centers in X-irradiated fl ux-grown crystals of chlorapatite. It is noteworthy that the single-crystal EPR spectra in Roufosse et al (1974) are similar to those of their respective centers in Knottnerus et al (1972).…”

Section: Introductionmentioning

confidence: 99%

“…Knottnerus et al (1972) and Roufosse et al (1974) both reported two oxygen-associated hole-like centers in X-irradiated fl ux-grown crystals of chlorapatite. It is noteworthy that the single-crystal EPR spectra in Roufosse et al (1974) are similar to those of their respective centers in Knottnerus et al (1972). However, these two groups of investigators reported different spin-hamiltonian parameters and disagreed in the proposed structural models.…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, defect centers in the anion columns of hydroxylapatite and chlorapatite have been investigated by EPR studies (Knottnerus et al 1972, Roufosse et al 1974, Mengeot et al 1975, Pan & Fleet 2002, and references herein). For example, Mengeot et al (1975) reported a spin-½ hole-like center exhibiting hyperfi ne interaction with a hydrogen nucleus (confirmed by deuteration) in X-irradiated hydroxylapatite.…”

Section: Introductionmentioning

confidence: 99%

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Multifrequency Epr Study of Radiation-Induced Defects in Chlorapatite

Nokhrin¹,

Pan²,

Weil³

et al. 2005

The Canadian Mineralogist

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Gamma-irradiated chlorapatite, synthesized from a CaCl 2 fl ux, has been investigated by powder and single-crystal electron paramagnetic resonance (EPR) spectroscopy at X-and W-band frequencies, including in situ high-T X-band EPR. The powder EPR spectra, particularly high-T X-band spectra and high-resolution W-band spectra, reveal a new hole-like center, H(III), in addition to two previously reported hole-like centers, H(I) and H(II). Center H(III) is characterized by an electron spin ½ and hyperfi ne interaction with one 35 Cl nucleus, suggesting a structural model consisting of a hole trapped by a substitutional oxygen ion adjacent to a Cl -ion vacancy in the anion column. This discovery of center H(III) also lends support to the structural model already proposed by other authors for center H(II). Single-crystal X-band EPR spectra also disclose a new electronic center, E(I). The structure model for center E(I) includes an electron trapped at an isolated Cl -ion vacancy in the anion column, corresponding to center F E(II) in fl uorapatite and similar to the well-known F center in alkali halides.

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