Separation of quartz optically stimulated luminescence components using green (525 nm) stimulation

It is well known that estimates of total absorbed ionizing radiation dose can be made using the Optically Stimulated Luminescence (OSL) signal of natural quartz. For some quartz samples, isolation of the so-called ‘fast component’ of the OSL improves the accuracy of absorbed dose estimates. Isolation of this signal usually involves decomposing the measured OSL signal into several exponential components and the aim of this work was to improve the reliability of this procedure. The fitting of multiple (overlapping) exponential functions is a well-known ill-posed problem, where many solutions (fits) may exist (some of which are not necessarily physically meaningful) and cannot be distinguished on grounds of ‘goodness of fit’ parameters. The situation is improved as the difference between the component decay rates increases. This principal can be applied to the fitting of the ‘fast’ and ‘medium’ components of quartz OSL by making use of the known dependence of the relevant photoionization cross-sections on stimulation wavelength. Empirical data are shown to match well with theoretical predictions, suggesting that stimulation of quartz with ∼525 nm, rather than the usual ∼470 nm light, provides improved conditions for component decomposition, without reducing the overall signal decay rate to an impracticably low level.