TL and XF spectra in pure and Co-doped NaCl above room temperature

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Cobalt impurities in low concentration occupy substitutional sites in NaCl crystal as divalent cations and produce strong charge transfer absorption band at 193 nm. Z centres are not formed in the crystal because of electron trapping nature of the impurity ion. Only two TL glow peaks appear in both pure and Co-doped NaCl, the high temperature glow peak being much stronger than the low temperature one. Interstitials are preferentially stabilised at vacancy pairs and dimers created during irradiation than in existing free or associated cation vacancies. The low temperature glow peak is due to thermal destruction of Cl - 3 ions stabilised at free cation vacancies and the high temperature one to those at vacancy pairs and dimers. The impurity doped crystal has the same emissions as in pure NaCl together with another related to cobalt ion. These emissions arise from the decay of STE formed due to tunneling recombination of electron centres with Cl - 2 ions and the different emissions are due to perturbations of STE by different type of defects. The perturbed STE emission occur on the long wavelength side of π polarised STE emission in NaCl while it occurs on the short wavelength side in KCl. Interstitials have lower mobility in NaCl than in KCl.