Illustrative examples doped alkali halides and silica glasses

5 Illustrative examples doped alkali halides and silica glasses 

The results obtained in these computer simulations of the hopping reactions were applied in [86] to the Vk centre recombination in KCl-Tl stimulated by step-like temperature increase. As it is clearly seen from Fig. 4.15, taking directly into accounthop lengths (A = ao/(2 /2) 2.2 A to be compared with ro 1 A of the electron Tl centre) permits us to obtain a much better agreement with the experimental data than the standard continuous diffusion approximation (curves 1 and 3, respectively). 

As it was shown above, the static kinetics of tunnelling luminescence is much simpler than the diffusion-controlled kinetics. The static tunnelling luminescence intensity often obeys the empirical Becquerel s law [87] I t) oc t ° , where the distinctive decay parameter a = —d ogI i)/ d ogt) is defined by the spatial distribution of defects only, usually considered to be either the isolated pairs of spatially well-correlated dissimilar defects (low dose irradiation) or the random mixture of dissimilar defects (high doses and/or high temperatures) [88]. Moreover, in the case of pairwise distribution, the partial lightsum method has been presented [88-91] in order to restorate the defect initial spatial distribution /(r) within geminate pairs -see equation (4.2.1) and below. What we have discussed here are the tran- 

The influence of excitation temperature on the the a-value parameter for tunnelling luminescence kinetics is described in [94]. 

It has first been observed by Tale and Gailitis [51] that after a sudden temperature chemge the tunnelling luminescence increase is delayed due to an inertial diffusive motion of defects the relevant theory was developed quite recently [55] and discussed above. On the other hand, when the defects are again frozen, a partial lightsum method can be used demonstrating clearly [95] that the concentration of close dissimilar defects has been enriched due to their preceding diffusive approach. 

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