We describe the effect of nanoscale spatially coupled trapping centre (TC)-luminescent centre (LC) pairs on the thermoluminescence (TL) properties of LiF : Mg,Ti. It is shown that glow peak 5a (a low-temperature satellite of the major glow peak 5) arises from localized electron-hole (e-h) recombination in a TC-LC pair believed to be based on Mg 2+-Li vac trimers (the TCs) coupled to Ti(OH) n molecules (the LCs). Due to the localized nature of the e-h pair, two important properties are affected: (i) heavy charged particle (HCP) TL efficiency: the intensity of peak 5a relative to peak 5 following HCP high-ionization density irradiation is greater than that following low ionization density irradiation in a manner somewhat similar to the ionization density dependence of the yield of double-strand breaks (DSBs) induced in DNA. Our experimental measurements in a variety of HCP and fast neutron radiation fields have demonstrated that the ratio of glow peaks 5a/5 is nearly independent of particle species for the protons, deuterons and He ions investigated, is somewhat dependent on HCP energy, and is roughly 2-3 times greater than the peak 5a/5 ratio in low ionization density electron and photon fields. The intensity ratio of peak 5a/5 thus has the potential of estimating the ratio of dose deposited via high ionization density interactions compared to low ionization density interactions in a nanoscale volume without any prior knowledge of the characteristics of the radiation field, (ii) non-linear TL dose response: the relative lack of competitive processes in the localized recombination transitions leading to the TL of composite peak 5 versus the dose-dependent competitive processes in conduction band-mediated delocalized luminescence recombination leads to non-linear dose response (supralinearity) for composite peak 5 and a dependence of the supralinearity on ionization density. This behaviour is modelled in the framework of the unified interaction model (UNIM).

The influence of partial substitutions of iron in TiFe by some other 3-d transition metals on the hydrogenation characteristics of the corresponding ternary (pseudo-binary) TiFexM1−x(M=Cr, Mn, Co, Ni; 0.5≲x≲1) compounds was systematically investigated. Such substitutions result in two main effects:(i) stabilization of the monohydride β phases and (ii) reduction of hysteresis in the absorption-desorption isotherms. A linear dependence of the enthalpies of the monohydride formation on the iron concentration (i.e.x) has been obtained and accounted for by a model assuming local interactions of hydrogen with nearest-neighbor metal atoms.

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.

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The composite structure of glow peak 5 in LiF:Mg,Ti (TLD-100) has been investigated using optical bleaching by 310 nm (4 eV) light. The glow peak conversion efficiency of peak 5a (Tm = 187 degrees C) to peak 4 traps is very high at a value of 3+/-0.5 (1 SD) whereas the glow peak conversion efficiency of peak 5 (Tm = 205 degrees C) to peak 4 traps is 0.0026+/-0.0012 (1 SD). The high conversion efficiency of peak 5a to peak 4 arises from direct optical ionisation of the electron in the electron-hole pair. leaving behind a singly-trapped hole (peak 4), a direct mechanism, relatively free of competitive mechanisms. Optical ionisation of the 'singly-trapped' electron (peak 5), however, can lead to peak 4 only via multi-stage mechanisms involving charge carrier transport in the valence and conduction bands, a mechanism subject to competitive processes. The conduction/valence band competitive processes lead to the factor of one thousand decrease in the conversion efficiency of peak 5 compared to peak 5a.