THE KINETICS OF PEAK 5 IN LIF-NG,TI-DOSE DEPENDENCE OF THE THERMOLUMINESCENCE ISOTHERMAL DECAY AT 165-DEGREES-C

The question of the order of kinetics of the thermoluminescence (TL) o f peak 5 in LiF:Mg,Ti has been subject to considerable controversy. Re cently, we have shown that peak shape analysis of post-irradiation ann ealed LiF:Mg,Ti (TLD-100) at 165 degrees C leads to non-first-order ki netics, reaching a value as high as 1.72 +/- 0.07 following a 165 degr ees C 30 min post-irradiation anneal. When no post-irradiation anneal is applied, peak shape analysis almost always yields first-order behav iour. Isothermal decay data are equally ambiguous. To begin to resolve this discrepancy (at least at the experimental level) we have studied the isothermal decay of peak 5 at 165 degrees C (presumably cleansed of the low-temperature peaks 2-4 by a 165 degrees C 15 min post-irradi ation anneal). The isothermal decay was initiated at four dose levels of 10, 100, 300 and 1000 Gy, and these decays were not even vaguely si milar. The initial rate of decay at 10(3) GY was at least five times g reater than at 10 Gy and the decays were clearly non-exponential. Our data are not consistent with first-order decay (b = 1) and lead to b = 1.82 +/- 0.18 using general-order (GO) model analysis.