Studies of first-stage F-centre production in alkali halides doped with strontium |
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Authors: | JN Marat-Mendes JD Comins |
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Institution: | Department of Physics, University of the Witwatersrand, Johannesburg, South Africa |
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Abstract: | KBr crystals doped with strontium have been X-irradiated at 293 K. The reduction in single impurity-vacancy dipole concentration has been measured using I.T.C. techniques and is found to be proportional to and in quite close numerical agreement with F-centre growth in both first and second stage F-centre production, this being in agreement with previous results in KCl(Sr). The growth of the absorption band peaking at 263 nm was studied and was found to be proportional to F-centre growth during the earlier stages of colouration, indicating that the responsible centres are a major complement of the F-centres. Ionic conductivity experiments show little agreement between the decay of conductivity and the growth of F-centres during X-irradiation of KCl(Sr) crystals at 293 K.A model is developed in which interstitials are trapped at impurity-vacancy dipoles and in which the two stages of F-centre production is the result of dynamic processes involving modifications of the excitonic mechanism or of back reactions. |
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