Isothermal Decay of Peak V in the PTTL of LiF(TLD-100)

Abstract

Abstract Recent controversy about the order of kinetics of peak V in the TL of LiF TLD-100 centres on whether the departure from a single exponential behaviour of the 165 oC isothermal decay (ID) is due to the peak V decay, this peak not following first order kinetics, or to some remaining peak IV, not completely removed by the pretreatment employed. Results obtained for the isothermal decay of peak V detected in the TLD-100 photo-transferred thermoluminescence (PTTL) glow curve are presented. The PTTL curve is very convenient for this kind of measurement, as it is known that peak IV is not excited by UV light, so that the ID recorded at 165 oC can be unambiguously associated with peak V, free from possible interference coming from peak IV when the the direct TL emissions are employed for the ID measurements. The results obtained confirm the intrinsic complexity of the 165 oC decay found previously, showing the existence of a weak rapid initial stage. As in the case of the ID for TL, this initial stage is erased by adequate thermal treatment, producing the purely exponential decay typical of first order kinetics. The origin of the perturbing rapid initial component is discussed in the light of the differences found between ID recorded for TL or PTTL emissions.