Apparent anomalous fading of thermoluminescence associated with competition with radiationless transitions

Anomalous fading of thermoluminescence (TL) is the effect of a fading which is significantly faster than what is warranted by the trapping parameters which are evaluated from the features of the TL peak in question. A previou s work suggested that in certain cases, apparent anomalous fading may be a normal fading in disguise. The idea was that, at least in some cases, radia tionless transitions into competing recombination centers may yield a very narrow peak which, while using either the curve fit technique or the differ ent peak shape method will result in very high values of effective activati on energy E and frequency factor s which, in turn, will yield an apparent l ife-time orders of magnitude higher than the real one. The question has bee n raised whether this anomaly is observable only when the peak shape method s are utilized and in particular, can the same effect occur when the broadl y used initial-rise method is applied. It is demonstrated in this work that under similar circumstances of competition, very high effective values of E and s are evaluated which result in very high life-times when the activat ion energy is evaluated by the initial-rise method. Thus, the explanation o f apparent anomalous fading as being a normal decay in disguise, is extende d to cases in which the initial-rise method is utilized for the parameter e valuation. (C) 2000 Elsevier Science Ltd. All rights reserved.