On the role of Z centres and competing nonluminescent centres in the sensitisation and supralinearity mechanism of LiF TLD-100 phosphor

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Abstract
On the basis of a competing nonluminescent centre model, an attempt has been made to explain the dependence of supralinearity on glow-peak temperature and LET of the radiation, and enhanced TL sensitivity at elevated Tirr. Thermal annealing near 300 degrees C or 254 nm optical bleaching treatment (which are reported to result in the creation of Z3 centres) not only reduces peak 5 but also reduces peak 7 TL intensity. After a high gamma ray dose, the sample annealed at 400 degrees C for 1 h in the dark exhibits intense photo-TL at peak 5 but not at peak 7, thereby confirming that the presence of peak 10 is necessary for the formation of peak 7 and not of peak 5. All these data tend to suggest that (i) the TL peaks 7 and 10 are due to the thermal ionisation of Z2 and Z3 centres respectively, and (ii) a trap conversion between these two centres is taking place with a mechanism similar to that proposed by Nink and Kos (1976).