Abstract
Lithium oxalate (Li-oxalate: Li2C2O4) and magnesium oxalate (Mg-oxalate: MgC2O4·2H2O) were investigated by electron spin resonance (ESR) spectroscopy as new ESR dosimeter materials. The ESR spectra of Li- and Mg-oxalates irradiated by γ-rays have a singlet with a spectroscopic splitting factor (g-factor) of g=2.0043±0.0004 and are ascribed to a self-trapped hole, the oxalate radical C2O4-. A broad signal formed by high dose irradiation is considered to be due to the zero field fine structure splitting, DS2 (D/gβ\\cong0.65 mT) for the triplet state (S=1) of a dimer of C2O4- or a pair of electron and hole centers. The response to the γ-ray dose and thermal stability as well as the effect of illumination have been studied with respect to using these materials as ESR dosimeter elements. The radical formation efficiencies (G-value) for Li- and Mg-oxalates were 0.4±0.1 and 0.21±0.06 and the activation energies (E) from the Arrhenius plot were 1.16±0.24 eV and 1.28±0.26 eV, respectively. These lead to the respective lifetimes of 2.6±0.9 and 3.2±1.1 years at 25°C, which are sufficient for practical dosimetry.
Published Version
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