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The general behaviour of the main UV emission during radiofluorescence (RF) in natural quartz with dose rates ranging from 10 to 500 mGy s −1 is analysed. RF emission spectra were recorded and deconvolved to extract information on the C band, which is often the main emission of quartz annealed at a temperature close to 500 °C. Our results confirmed theoretical findings, e.g., the direct proportionality of the initial RF signal of the C band with dose rate and the direct proportionality of the initial slope with the squared dose rate. Furthermore, numerical simulations employing a three-energy-level model and experimental data are in agreement. A first concept of using quartz UV-RF for dosimetric application is given based on the findings that different absorbed doses resulting from different dose rates match well into a single UV-RF decay curve. [ABSTRACT FROM AUTHOR]

An analytical solution for the behaviour of quartz radiofluorescence (RF) in the UV-band is described based on a kinetic model involving one (deep) electron trap and two kinds of recombination centres. This model has been previously used to provide a qualitative description of quartz UV-RF. The derived numerical solution of differential equations describing charge transport in quartz can successfully reproduce experimental data. Here, this set of differential equations is solved analytically by assuming a dynamic balance during the RF stimulation. The analytical results are compared with numerical solutions and experimentally derived data. With the analytical solutions a better understanding of common natural quartz UV-RF behaviour is provided, and several experimentally observed phenomena can now be explained. Furthermore the comparison of two different kinetic models shows that the characteristic decay of the UV-RF signal in preheated quartz is attributed to an increasing competition of radiative and non-radiative centres during RF. [ABSTRACT FROM AUTHOR]

A better understanding of the physical mechanisms and point defects involved in quartz's charge trapping and luminescence processes enables improving the luminescence dating and dosimetry applications relying on this mineral. Here we report on the progress in our systematic investigation of two reference quartz samples using various spectroscopic techniques [1]. One sample originates from the "Silver Sands of Morar", Scotland -- UK, and the other one from the Oligocene Fontainebleau Sandstone Formation, France. We conducted wavelength-resolved thermally stimulated luminescence (WR-TSL) measurements over an extended temperature range, from 10 K to 630 K, to point out similarities and differences between the luminescence properties of the two samples. We identified various luminescence emission bands, studied their correlation with specific TSL traps and compared the results with the data reported in the literature. We will show which emission bands previously evidenced by X-ray radioluminescence (RL) measurements are also detectable in TSL emission spectra [2]. In particular, we focus on the so-called 190 K TSL peak, which has been correlated to the [SiO4/Li]0 centres and is known to display a pre-dose-like behaviour analogously to the 110 °C peak, resulting in an enhancement of their UV emission [3]. We attempt to determine which of the previously reported UV bands, i.e., the 3.42 eV emission (C band) or the 3.73 eV one (M band), is enhanced in the pre-dose, like sensitization of the 190 K peak. Finally, we report RL measurements over the range of 10 K -- 320 K to determine the temperature dependence of the luminescence emissions and quantify the contribution of the self-trapped exciton (STE) band. The results obtained, together with the data reported on the same samples in previous works, provide a more comprehensive picture of the luminescence properties of these reference materials. The data will be discussed in relation to experimental results reported in the literature on different types of quartz. [ABSTRACT FROM AUTHOR]

The radioluminescence (RL) spectra of three types of quartz have been compared to those obtained from wavelength resolved thermally stimulated luminescence (TSL) measurements. A detailed numerical deconvolution into Gaussian components allowed to identify which of the bands are involved in either types of luminescence processes. The blue “A band” at 2.51 eV was confirmed to dominate both RL and TSL spectra in samples exposed to prolonged irradiation. The UV emission of the 110 °C TSL peak was found to be composite. Analogously to what previously reported for RL spectra, an annealing at 500 °C for 10 min induced a strong enhancement of the “C band” at 3.42 eV. This effect was particularly evident in natural and pre-irradiated quartz. A second intense UV component, the “M band” at 3.7 eV, was found to contribute to both TSL and RL spectra of samples annealed at 1000 °C for 10 min. A further broad UV emission seems to be involved only in RL emission but not in the TSL one. [ABSTRACT FROM AUTHOR]

Quartz is an extremely diffused natural luminescence dosimeter. Thanks to the presence of traps and luminescence centres, its TSL and OSL (Thermally and Optically Stimulated Luminescence) properties have been extensively exploited. Quartz is then used for archaeological and geological dating and is one of the most useful materials for accident dosimetry. Many luminescence emissions are known to be present in the OSL and TSL of quartz. Three main emission bands are always reported, as the red, blue and UV bands, centred at around 650, 470, and 360–380nm, respectively. Although the assignment of the luminescence emissions to specific defect centres in quartz is still undefined, a thorough analysis of the radioluminescence emissions and their response to irradiation and thermal treatments turned out to be very useful in understanding many features. Specifically, the presence of the same emission bands in natural and synthetic quartz and their dependence on the presence of extrinsic impurities is a common characteristic. The main impurities involve Al ions substituting Si ones and charge compensated by nearby either alkali ions, H+, or a hole. The emission spectra dynamics evidenced in our experiment confirm the role of Al-related centres in the luminescence properties of quartz. From the measurements presented in this paper the composite nature of the “blue” emission is confirmed. Two bands labelled as A at 2.5eV and B at 2.8eV contribute to the emission in this region, their behaviour being different as a function of irradiation. More complex is the picture in the UV region, where, besides the already detected C and D bands at 3.4eV and 3.9eV, respectively, two further emissions have been detected at 3.1eV and 3.7eV. Despite both the 3.4eV and the 3.7eV bands are shown to be affected by thermal treatments, the annealing temperature dependence of their intensity is markedly different. In fact, whereas the C band intensity, at 3.4eV, increases after annealing at 500°C followed by a decrease at higher temperatures, the 3.7eV intensity is strongly enhanced by annealing at temperature above 700°C and reaches its highest value after annealing at around 1000°C. In the light of these results a number of already known features of quartz emissions should be reconsidered. [ABSTRACT FROM AUTHOR]

Further developments in luminescence dating, dosimetry and temperature-sensing require a deep understanding of luminescence processes and their driving parameters. Natural quartz is one of the most widely used minerals for these purposes. Still, poor reproducibility of results often hampers comparability and credibility from findings in the literature. We identified the lack of suitable natural reference samples as a pivotal problem impeding significant progression. Ideally, basic investigations involve several laboratories working on well-characterised reference quartz samples with different characteristics. Investigations should include multiple complementing methods to analyse luminescence properties and mineralogical and geochemical composition. Here, we present such a multi-technique luminescence comparison of two natural quartz samples. Next to the recently introduced Fontainebleau (FB) reference quartz, we propose another reference sample derived from the 'Silver Sands of Morar' (lab code 'MR'; Scotland, UK). Our experiments confirm that both quartz samples behave fundamentally different in terms of signal composition and sensitivity. The comparative characterisation of both samples targeted electron traps via thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques and luminescence centres via radioluminescence and time-resolved OSL spectrometry. In summary, we conclude that all observed differences are likely the results of divergent defect concentrations rather than variances in defects' composition (nature). The measurement data of our study are accessible open-access for inspection by others. • Multi-technique luminescence characteristics of two reference natural quartz samples. • Fundamental differences in emission of quartz due to divergent defect concentrations. • First attempt to propose an archive of reference samples for luminescence production. • Full luminescence measurement data accessible open-access for inspection. [ABSTRACT FROM AUTHOR]

In this work we studied the thermal stability of the 110 °C TSL peak of quartz in both natural and synthetic samples. We compared it with the thermal stability of the [GeO 4 ]- paramagnetic signal with EPR. Our findings show that both these signals decay at the same rate, however, the rate is significantly different between samples. In particular, a couple of samples, a pegmatitic one and a fired synthetic one, showed a drastically increased decay time of both the TSL peak and the EPR signal well beyond the expected experimental fluctuations. The decay time of these two samples differs by almost by a factor two with respect to the average value of all the other samples. • Different quartz samples show different lifetimes for the 110 °C TSL peak. • Different quartz samples show different lifetimes for the [GeO 4 ]- signal. • The differences observed are consistent between the two different techniques. • The consistency is a new proof of the 110 °C TSL peak and the [GeO 4 ]- correlation. [ABSTRACT FROM AUTHOR]

The role of hydrogen in the formation and modification of defects in quartz is well known, but still to be clarified is its involvement in trapping and recombination properties of quartz on which its dating characteristics are based. In this work, we studied the thermal stabilities of EPR signals in natural pegmatitic quartz using an X-band spectrometer. We also observed at least two previously unreported EPR signals in quartz, one of them possessing a hydrogen hyperfine structure with large coupling constant. Its thermal stability is intermediate between the well-known [GeO 4 ]- and [GeO 4 /Li+]0 centres, while the other newly reported signals possess a thermal stability comparable to the latter. The sample has been further studied with a Q-band spectrometer to enhance the resolution of the spectrum. This allowed to confirm, without having to fit or simulate the overlapped signals, the g-factors reported in the literature for Ge related centres, which are strongly overlapped in the X-band. We performed simulations to extrapolate the g-factors and coupling constants of the observed components. We carried out pulse annealing experiments to determine the trap depth of the centres originating such signals. The hydrogen related centre signal has been simulated with the g-tensor's main components being g 1 = 2.0007, g 2 = 1.9974 and g 3 = 1.9929, with coupling constants A 1 = 233 MHz, A 2 = 235 MHz and A 3 = 239 MHz, and trap depth of 1.14 eV. • EPR signals of different Ge centres dominates at different doses. • A new EPR signal assigned to a H related centre has been observed. • New, still unassigned, EPR lines have been observed. • The thermal stability of each signal has been characterized via pulse annealing. [ABSTRACT FROM AUTHOR]