P. S. Mazumdar

On the determination of activation energy in thermoluminescence by the initial rise method

Expressions are derived which estimate the systematic error involved in the determination of the activation energy by the initial rise method. It has been shown that the general belief that the initial rise method does not depend on the order of kinetics is rather a misconception if one takes the value of E thus determined in a quantitative sense. The applicability of these expressions has not only been discussed but also tested for some experimental peaks.

The determination of activation energy from the shape of a thermoluminescence peak

A new set of expressions have been derived to evaluate the thermal activation energy, E, of a thermoluminescence (TL) peak. The order of kinetics, b, of the peak may be first order (b=1), second order (b=2) or general order for which the authors have taken b=1.5 as an example. The derived expressions involve temperatures at which the intensity of the peak is 1/2, 2/3, 4/5 of the maximum and/or the peak temperature (Tm). The selection of these points is based on the fact that the upper half of the peak is free from interference of the satellite peaks. The applicability of these expressions has been checked by applying them to some typical experimental TL peaks. The value of E determined by using these new sets of expressions is in good agreement with that found by curve fitting.

A critical appraisal of methods of various heating rates for the determination of the activation energy of a thermoluminescence peak

An attempt has been made to find out precisely the errors involved in the determination of the activation energy (E) of a thermoluminescence (TL) peak by using the different variants of method of various heating rates, namely, those due to Hoogenstraaten (1958), Chen and Winer (1970), and Dussel and Bube (1967). It has been found that for all practical purposes the Chen-Winer and Hoogenstraaten methods can be considered to be independent of the order of kinetics of the TL process. Finally, the applicability of the findings has been tested experimentally by considering a non-first-order TL peak. The results suggest that the theoretical errors in all the cases are less than the experimental ones and hence these methods can be safely used for all types of TL peaks irrespective of their order of kinetics.

Computerized glow curve deconvolution: the case of LiF TLD-100

It has been accepted by a large number of workers that the glow curve of LiF TLD-100 can be described by thermoluminescence (TL) peaks following the Randall-Wilkins (RW) equation, even though the model fails to explain a number of experimental facts. A further simplification of the model is the Podgorsak-Moran-Cameron (PMC) approximation which is also in use. This paper points out the limitation of the PMC approximation in deconvoluting glow curves of LiF TLD-100.

The determination of the trapping parameters of a thermoluminescence peak by using the Kirsh method

In this paper we analyse the suitability of a method proposed by Kirsh for the determination of the trapping parameters, namely the order of kinetics, activation energy and frequency factor, of a thermoluminescence (TL) peak by applying it both to numerically generated TL peaks and to an experimental TL peak of NaCl:I irradiated with 2.04 kGy of -rays. It is found that the method can be used irrespective of the order of kinetics. It is also shown that the method proposed by Rasheedy ( 8 (1996) 1291 and 29 (1996) 1340) is a special case of the Kirsh method.

On the determination of the activation energy of a thermoluminescence peak by the two-heating-rates method

Precise estimation of the systematic error involved in the determination of the activation energy of a non-first-order thermoluminescence (TL) peak by using the two-heating-rates method of Booth (which is strictly valid for a first-order peak) has been made. A new method analogous to the Booth (1954) method is proposed, which involves both the peak temperature and peak intensity. The systematic errors involved in both these methods are found to be within the experimental error which one generally encounters in the analysis of TL. The applicability of these findings has been tested by considering a second-order TL peak of limestone.

Determination of the activation energy of a thermally stimulated luminescence peak for the case of a temperature-dependent frequency factor

The accuracy of the initial rise (IR) method and the variable heating rate (VHR) method when the frequency factor depends on temperature as Ta (with -2<or=a<or=2) for the case of a general order thermally stimulated luminescence (TSL) peak is discussed. It has been shown previously that for most practical cases the resulting maximum error in the determination of the activation energy E by the IR method and the VHR methods is about 10%. These methods can therefore be considered as independent from the order of kinetics even if the frequency factor is temperature dependent. A crucial point observed is that for a=2 both the IR and VHR methods overestimate E, whereas for a=-2 they underestimate this value.

Evaluation of temperature integral for temperature dependent frequency factors

The general method of evaluating the temperature integral for temperature dependent frequency factors have been considered. The values of the temperature integral as evaluated by the present method are in excellent agreement with those obtained numerically.ZusammenfassungEs wurde eine allgemeine Methode zur Auswertung des Temperaturintegrales für temperaturabhängige Frequenzfaktoren betrachtet. Die Werte für die Temperaturintegrale nach vorliegender Methode stehen in ausgezeichneter Übereinstimmung mit den numerisch erhaltenen Werten.

On the mixed order kinetics of the thermoluminescence glow peak

The shape factor of a thermoluminescence (TL) glow peak following mixed order (MO) kinetics has been reinvestigated. A modification of the existing equation of MO kinetics to include the filling factor , where is the initial concentration of trapped electrons and N is the concentration of the electron trap sites) has been proposed. The shifting of peak temperature for a MO kinetics peak with the change of filling factor and hence the irradiation dose absorbed by the sample is reported. A new set of expressions for the evaluation of the activation energy of a TL peak in the light of MO kinetics is presented. The applicability of the MO kinetics model is reported by fitting both the numerically simulated glow peak and the experimentally observed peak of -irradiated NaCl:I and x-irradiated BeO.

On the peak shape method for the determination of activation energy in TSL and TSC

A critical appraisal of the peak shape method for the determination of activation energy in thermally stimulated luminescence (TSL) and thermally stimulated conductivity (TSC) has been made.