The time and wavelength response of phototransferred thermoluminescence in natural and synthetic quartz

Phototransferred thermoluminescence (PTTL) properties from several types of crystalline quartz are presented. Several of the PTTL peaks display an increase, followed by a decrease, but not necessarily to zero. The data can be satisfactorily explained by a model which includes the recombination of electrons and holes during illumination, and two types of recombination center. Consideration of the rate equations describing the phototransfer of charge from deep traps to shallow traps, along with the wavelength dependence of the photoionization cross-section, leads to the realization that increasing the illumination intensity or decreasing the wavelength will have the same effect on the PTTL response. The wavelength dependence of the PTTL effect can be obtained by taking the initial slope of the PTTL-vs-illumination-time curve as a function of wavelength. Using this procedure reveals that only one source trap is emptying over the wavelength range of green light stimulation, but additional traps become active as the wavelength decreases. Over the whole wavelength range used three traps are active, with optical threshold energies of 2.37, 2.84 and 3.77 eV. (C) 1997 Elsevier Science Ltd.