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 previous 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, radiationless transitions into competing recombination centers may yield a very narrow peak which, while using either the curve fit technique or the different peak shape method will result in very high values of effective activation energy E and frequency factor s which, in turn, will yield an apparent life-time orders of magnitude higher than the real one. The question has been raised whether this anomaly is observable only when the peak shape methods are utilized and in particular, can the same effect occur when the broadly 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 activation energy is evaluated by the initial-rise method. Thus, the explanation of apparent anomalous fading as being a normal decay in disguise, is extended to cases in which the initial-rise method is utilized for the parameter evaluation. (C) 2000 Elsevier Science Ltd. All rights reserved.