SUPRALINEARITY AND SENSITIZATION OF THERMOLUMINESCENCE .2. INTERACTIVE TRAP SYSTEM MODEL APPLIED TO LIFMG, TI

A theoretical treatment based on a partly interactive trap system (PITS) described in an earlier paper is applied to peak 5 of LiF:Mg, Ti. The model assumes two types of thermoluminescence traps for the given glow peak: (i) supralinear response. The former are spatially associated with the luminescent recombination centres. The latter are randomly distributed and the carriers released from them during readout heating may be recaptured by the thermally disconnected deeper traps non-radiatively in addition to undergoing recombination to produce luminescence. The trap filling constant, defined as the fraction of traps filled per unit dose, is determined using the intensity growth of profile of the related optical absorption band and that of the thermoluminescence of pre-dose sensitized sample. The value of this constant is 1.16 x 10(-3)Gy-1 for peak 5. For peak 12 it is an order of magnitude lower. Fractions of the thermoluminescence trap population responsible for linear and supralinear parts of the response are determined using pre-dose sensitization. The ratio of these two populations is calculated to be 1:13. A method is suggested to determine the relative concentration of the deep traps with respect to the shallower thermoluminescence traps. This estimation is carried out by separating the supralinear part of the response curve and calculating its under response factor at low doses. The realative concentration of deep traps is seen to be dependent on the relative coefficients for trapping and recombination. The calculated parameters are backfitted into the theoretical expression and the response profile so obtained is compared with the experimental response curve. The two are found to be in good agreement.