New evidence for spatially correlated TC-LC mechanisms in thermoluminescence of LiF:Mg,Ti.

New experimental investigations, consistent with the spatial coupling/perturbation between the trapping centres (TC) and luminescent centres (LC) giving rise to the peaks 5 and 4 thermoluminescence (TL) of LiF:Mg,Ti are discussed: (1) The glow peak widths of peaks 2 and 3 are constant as a function of Ti concentration, while the width of peak 4 decreases with a correlated increase in the width of peak 5. The dependence of glow peak shape on Ti concentration indicates that peaks 4 and 5 arise from a TC/LC spatially correlated extended defect. (2) The increased TL intensity of peak 5a following high ionisation density HCP irradiation compared to low ionisation density gamma irradiation strongly suggests that peak 5a arises from the geminate recombination of a locally trapped e-h pair. (3) The observation that the optical bleaching conversion efficiency (CE) of peak 5a to peak 4 is measured to be 3+/-0.5 and is three orders of magnitude greater than the CE of peak 5 to peak 4, is strong evidence for the unique structure of peak 5a--trap, i.e. peak 5a is due to a TC/LC structure which has captured an e-h pair, optical ionisation of the electron leads directly to the peak 4 TC.