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Theoretical approach to the lyoluminescence of alkali halides

Journal of Luminescence
Publication Date
DOI: 10.1016/s0022-2313(97)00108-7
  • Lyoluminescence
  • Aqualuminescence
  • Alkali Halides
  • Colour Centres


Abstract When previously irradiated halide crystals are dissolved into a solvent like water, the radiative recombination of hydrated electrons with the holes on the surface of the crystallites, gives rise to the light emission. The intensity of lyoluminescence (LL) emission depends on different parameters and it can be expressed as I = ηβγαn FN 0 (β − α) { exp(−αt) − exp(−βt)} , where η is the probability of radiative recombination, β the rate constant for the recombination of hydrated electrons with holes, γ the factor correlating the number of hydrated electrons and the number of dissolved F-centres, α the rate of dissolution of solute in the solvent, n F the density of F-centres, N 0 the initial number of the molecules of solute, and t the time of dissolution. The equation shows that the LL intensity should initially increase with time, attain an optimum value and then it should decrease exponentially with time. As α increases with temperature, an increase in the value of I with temperature is expected. However, at higher temperature thermal bleaching takes place, and consequently the LL intensity should be maximum at a particular temperature. The LL intensity initially increases and then tends to attain a saturation value for higher mass of the solute added into the solvent. A good qualitative correlation is found between the experimental and theoretical results.

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