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The influence of annealing on the lifetime and luminescence intensity has been studied in quartz annealed at 873, 1073, 1173, and 1273 K and in unannealed quartz. Luminescence was stimulated by pulsed green (525 nm) light. Luminescence intensity increased as a function of temperature from 293 K to a peak at 373 K, and decreased thereafter to 473 K, the maximum temperature in the investigations. Luminescence lifetimes from both unannealed quartz and samples annealed at 873 K for up to 5 min were constant at about 40 micros below 373 K. Lifetimes decreased strictly monotonically with temperature in samples annealed above 873 K. Values of the activation energy for thermal assistance accounting for the increase in luminescence intensity, and of thermal quenching describing the decrease of luminescence intensity and luminescence lifetimes are presented.

Conventional and phototransferred thermoluminescence of crystalline synthetic quartz implanted with 70 keV Ar ions at fluences in the range 1 × 1014–5 × 1015 ions/cm2is reported. The glow curves, recorded at 5°C/s from beta-irradiated samples of similar mass, show a prominent peak between 100°C and 120°C. The thermoluminescence intensity of all implanted samples was greater than that of the unimplanted one. The increase in sensitivity is attributed to a corresponding increase in the concentration of point defects, as a result of the implantation, which act as electron traps or recombination centres. Kinetic analysis carried out using the peak shape, whole glow-peak and curve-fitting methods produced values of the activation energy, frequency factor and order of kinetics that are generally independent of implantation fluence. This result suggests that implantation did not necessarily affect the nature of the electron traps. With respect to phototransferred thermoluminescence, it was observed that it only appeared in the sample implanted at the highest fluence of 5 × 1015 ions/cm2. This may be so because the concentration of deep traps produced as a result of implantation at low fluence is too low to give rise to phototransferred thermoluminescence. The intensity of the phototransferred thermoluminescence goes through a peak with illumination time. We attribute this behaviour to the relative concentration of holes at recombination centres and phototransferred electrons at shallow traps. [ABSTRACT FROM PUBLISHER]

The experimental separation of overlapping peaks is a common practical concern in thermoluminescence experiments. In this regard, we have investigated the use of isothermal heating as a method for separating closely collocated peaks for kinetic analysis. The method has been developed and applied on a sample of synthetic quartz in which the thermoluminescence intensity is not reproducible in successive measurements on the same aliquot. Preparatory experiments performed to establish a suitable combination of temperature and heating time are described in detail. A comparative analysis of results from conventional thermal cleaning with those from isothermal cleaning, done as a means to assess the effectiveness of the latter, has shown isothermal heating to be a reliable method of separating closely collocated glow-peaks. The method is conveniently applied in combination with a new technique for kinetic analysis based on the use of the temperature-dependence of the area under an isothermal decay-curve. Isothermal heating was also applied to separate collocated peaks in europium-doped orthosilicate (Sr2SiO4:Eu2+), a luminophor, and in carbon-doped aluminium oxide (α-Al2O3:C), a dosemeter. The set studied in Sr2SiO4:Eu2+, unlike in the quartz, consists of peaks where the intensity of the lower-temperature one is greater than subsequent ones at higher temperature. On the other hand, the example investigated in α-Al2O3:C is similar except that the dominant peak subsumes the lower intensity secondary peak to the extent that they appear as one. [ABSTRACT FROM AUTHOR]

The influence of irradiation dose on luminescence lifetimes has been studied in suites of natural quartz from Brazil, Nigeria and South Korea. The lifetimes were evaluated from time-resolved luminescence spectra measured from quartz pulse-stimulated at 470 nm and detected between 360 and 380 nm. The effect of irradiation varied between materials, decreasing with dose in the Brazilian quartz, independent of dose in the samples from South Korea, and increasing with dose in the quartz from Nigeria. The dose-related effects are accounted for with reference to an energy band scheme for quartz in which the luminescence lifetime is associated with a primary radiative recombination centre at which most capture of holes produced during irradiation and associated hole re-trapping takes place. The measurements on the effect of irradiation dose on luminescence lifetimes were augmented by investigations concerned with the influence of measurement temperature between 20 and 200°C on luminescence lifetimes in the same materials. It was observed that the luminescence lifetimes decrease continuously with temperature of stimulation and in a manner suggestive of increased thermal quenching of the corresponding luminescence. However, better consistency with the Mott-Seitz configurational coordinate model of thermal quenching is only apparent at temperatures greater than 120°C. The discrepancy is attributed to the model used to derive the formulae for luminescence lifetimes in which any re-trapping of stimulated charge is assumed negligible. However, it is argued that if re-trapping were in fact not negligible then the decrease of luminescence lifetimes with measurement temperature would be evidence of the progressive reduction of the re-trapping as the measurement temperature were increased with the overall effect being the monotonic decrease in luminescence lifetimes as observed. [ABSTRACT FROM AUTHOR]