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, T m , the new method uses the total half width w= Tz-T1, where Tl and Tz 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=2kT",(1.26 T m/w-1) where k is Boltzmann's constant. The frequency factor is found for this case to be s=[2tJ(1.26 T",/w-1)/(e2T m)] exp(2.52Tm/w) where tJ 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 secondorder 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 m~thod for distinguishing between first-and second-order peaks is also discussed.

A Three-stage Thermal Stimulation of Thermoluminescence (Tl)

“…From the obtained peak shapes, different parameters are calculated such as symmetry factors, activation energies and frequency factors. These parameters are calculated using different formulae proposed by Chen (1969). These are the following formulae used:…”

Низкотемпературная люминесценция и термостимулированная люминесценция монокристаллов BeO : Mg

“…В наших измерениях для обоих кристаллов было получено µ g ≈ 0.42, что соответствует кинетике первого порядка [42]. Для этого случая энергия активации E может быть определена по формуле [43,44] Четыре сравнительно малоинтенсивных пика ТСЛ при 161.5, 188, 216 и 236 K наблюдаются как в BeO, так и в BeO : Mg, однако при переходе к BeO : Mg интенсивность этих пиков возрастает в несколько раз: ×3 (236 K), ×5.9 (216 K), ×24 (188 K) и ×32.5 (161.5 K). Все четыре малоинтенсивных пика ТСЛ являются частично-пере-крывающимися и мало пригодными для определения их термоактивационных параметров.…”

Thermally-Induced Depolarization Current Spectra of NaCl:Ni2+Crystals

“…The activation energy E was determined by methods employing the shape parameters of this band, according to [12]: c ω = 2.52 and 3.54; b ω , = 1.0 and 1.0 for the first-and second-order kinetics, respectively. An empirical way to deal with intermediate cases is a "general order" kinetics which satisfactorily explains the occurence of various symmetry factors μ= δ/ω.…”