Revisiting TL: Dose measurement beyond the OSL range using SAR

Abstract

We show here that isothermal TL (ITL) at 310 and 320°C can be used to extend the luminescence dating range in quartz. These signals have markedly different behaviour than the OSL signal with respect to dose response and bleaching efficiency using blue light; this suggests that the 325°C TL peak, from which these signals are likely to be derived, perhaps, consists of traps with very different optical depths and saturation characteristics. The feldspar IRSL signal (blue emission) shows significant dose under-estimation on account of fading. This problem is partly circumvented by measurements using blue ITL at 310°C. The red ITL signal at 310°C does not show dose underestimates. A firm conclusion as to whether this signal fades or not can, however, only be made with a better understanding of sensitivity changes during the red ITL measurement of the natural signal. Both blue and red ITL signals in feldspars perhaps use the same trap. The fading and/or sensitivity changes, therefore, relate to the recombination centre. On account of the high dose at which saturation appears, the ITL signal from quartz at 310 and 320°C is the best candidate for extending the dose range up to 1.4 kGy in samples from the southern Indo-Gangetic plains.