An attempt is made to predict/interpret theoretically the experimentally measured values of f(D) and S(Ds)/So for composite peak 5 in TLD-100. using the Unified Interaction Model (UNIM) with identical values of the UNIM parameters for both sets of experimental data. Although an excellent fit can be obtained to the experimental f(D) data over the entire dose region where f(D) is greater than unity. i.e. from 5 Gy to several thousand Gy, a satisfactory fit to both sets of data is found to require different values for at least one of the parameters. The lack of success in fining f(D) and S(Ds)/So with the same values of all the parameters, suggests that the sensitisation anneal (particularly the duration of the anneal) may somehow change the structure (S(LC)) and/or the total number of available LCs in an unknown manner.

The optical absorption (OA) and thermoluminescence (TL) of dosimetric LiF:Mg,Ti (TLD-100) as well as nominally pure LiF single crystal have been studied as a function of irradiation dose, thermal and optical bleaching in order to investigate the role of the 4.45 eV OA band in low temperature TL. Computerised deconvolution was used to resolve the absorption spectrum into individual gaussian bands and the TL glow curve into glow peaks. Although the 4.45 eV OA band shows thermal decay characteristics similar to the 4.0 eV band its dose filling constant and optical bleaching properties suggest that it cannot be associated with the TL of composite peaks 4 or 5. Its presence in optical grade single crystal LiF further suggests that it is an intrinsic defect or possibly associated with chance impurities other than Mg, Ti.

Optical absorption (OA) dose-response of LiF:Mg,Ti (TLD-100) is studied as a function of electron energy (ionisation density) and irradiation dose. Contrary to the situation in thermoluminescence dose-response where the supralinearity is strongly energy-dependent, no dependence of the OA dose filling constants on energy is observed. This result is interpreted as indicating a lack of competitive process in the radiation absorption stage. The lack of an energy dependence of the dose filling constant also suggests that the charge carrier migration distances are sufficiently large to smear out the differences in the non-uniform distribution of ionisation events created by the impinging gamma/electron radiation of various energies.