Temperature-dependent EPR characteristics of quartz paramagnetic centers: Some insights for dating purposes

Abstract

EPR (electron paramagnetic resonance) spectra of quartz samples, γ-irradiated with varying absorbed doses (0–8000 Gy), were measured at different temperature levels (294–94 K). The temperature dependence of the E1′, Ge, peroxy, Al, and Ti centers was systematically investigated, and a phenomenological model was developed to theoretically explain the temperature saturation phenomenon. The experimental results indicated that the temperature dependence of different paramagnetic centers varies, primarily due to differences in the spin-lattice relaxation processes. Under the limited experimental conditions and temperature range, reliable conclusions regarding the temperature dependence of equivalent dose (DE) could not be drawn. The simulation results demonstrated that DE values obtained at higher temperatures are closer to intrinsic one, while those obtained in the temperature saturation region are questionable. Additionally, measurement recommendations to avoid signal interference were provided by comparing spectra at different temperatures and power levels. In the context of inconsistent spin-lattice relaxation times (T1) among the series aliquots, a more precise characterization of the temperature dependence of T1 is essential for further enhancing dating reliability and presents a challenge for relative quantitative EPR.