On the Calculation of Activation Energies and Frequency Factors from Glow Curves

Abstract

A new method for calculating activation energies and frequency factors from thermoluminescence and thermally stimulated current peaks is described. The validity of this method, as well as of most of the other known ones, is examined for a broad range of energies and frequency factors by the use of a computer. A combination of theoretical and empirical-computational analysis is used to give corrected formulas for some of the previous methods, while only empirical corrections are given for some others. Apart from the maximum temperature, Tm, the new method uses the total half width ω=T2−T1, where T1 and T2 are the half-intensity temperatures on the low- and high-temperature side of the peak, respectively. For a first-order peak with a frequency factor independent of temperature, the activation energy is given by E=2kTm(1.26 Tm/ω−1) where k is Boltzmann's constant. The frequency factor is found for this case to be s=[2β(1.26 Tm/ω−1)/(e2Tm)] exp(2.52Tm/ω) where β is the (linear) heating rate and e is 2.718. For the case where pre-exponential factors depend on temperature as some power function and for second-order glow peaks, similar formulas are developed for the calculation of activation energies. The relative advantages of the various methods are discussed both from the theoretical and experimental points of view. The method for distinguishing between first- and second-order peaks is also discussed.