5.5 eV optical absorption, supralinearity, and sensitization of thermoluminescence in LiF TLD-100

Abstract

The concept of competition-during-heating as a mechanism for TL supralinearity and sensitization in TLD-100 is re-examined. It is demonstrated that with this model it is not necessary that the competing traps be removed by radiation in order for supralinearity to be obtained. Furthermore, the arguments for and against the proposal that the precursors to the 5.5 eV centers are the required competing centers are reviewed. It is shown that those experiments which are cited as arguments against this proposal have other interpretations different from those published so far. These new interpretations are consistent with the original view that the 5.5 eV centers’ precursors are indeed competitors to the main TL process. MgOH centers are also likely competitors in samples with substantial OH contents.

Investigation of the optical absorption characteristics of slow-cooled LiF:Mg,Ti (TLD-100)

“…Previous studies in rapidly cooled material (McKeever, 1990 andIssa et al, 2001) have measured values between 1.0 and 1.35 Â 10 À3 Gy À1 and 0.9 Â 10 À3 Gy À1 respectively in good agreement with these measurements. It is important to note that the maximum value of the experimentally measured supralinearity of peak 5, f(D) max ¼ 3-4, occurs at a dose level of approximately 300 Gy, whereas at this dose level, the TCs have reached only w20% of full occupation.…”

Kinetic modeling of optical absorption dose response in TLD-100

“…In this paper and for demonstrative purposes we have employed the effective values obtained from first-order kinetics. (McKeever, 1990)-both centers are believed to be electron traps. The experimentally measured dose response of these bands can be described as linear/exponentially saturating with quite similar dose filling constants of 1.5 × 10 −3 and 4 × 10 −4 Gy −1 , respectively.…”

Delocalized recombination kinetic modelling of the LiF : Mg,Ti glow peak 5 thermoluminescence system

“…(i) Linear/exponentially saturating optical absorption (OA) dose response resulting in values of the experimentally observed TC and CC dose filling constants. Peak 5 has been identified with the 4.0 eV OA band believed to arise from Mg-Li vac trimers (coupled to Ti(OH) n ) [16][17][18] with an experimentally measured dose filling constant of value β TC =∼ 10 −3 Gy −1 [17]. The 5.45 eV OA band has been attributed to a (Mg 2+ − F + e − ) structure (Z 3 centre) and has been associated with the recombination stage competitor to peak 5 traps [16,18].…”