Photoluminescence, thermally stimulated luminescence and electron paramagnetic resonance studies of U⁶⁺ doped BaSO₄

Abstract

U⁶⁺ doped BaSO₄ samples were synthesized by precipitation route. PL, TL and EPR investigations of γ and self α irradiated samples were carried out. PL spectra of these samples give structured broad band peaking around 518 nm with five vibronic bands centred around 498·4, 516·0, 533·7, 554·0 and 575·1 nm, respectively and the average frequency of symmetric stretching of O=U=O in the ground electronic state was found to be 674 cm⁻¹. Trap level spectroscopic studies of U doped BaSO₄ give glow peaks at 411, 488 and 512 K, respectively and their spectral characteristics are typical of UO$_{2}^{2+}$ emission. EPR studies of γ-irradiated U⁶⁺:BaSO₄ sample have shown the presence of sulphoxy centred radicals like SO$_{4}^{-}$ and SO$_{3}^{-}$ in addition to OH^•, O$_{3}^{-}$ and SH²⁻. TSL peaks at 411 and 488 K were correlated with thermal destruction of SO$_{4}^{-}$ and SO$_{3}^{-}$ radicals.