Radiation-induced defects in magnesium lactate as ESR dosimeter

Abstract

Magnesium lactate (Mg–lactate: (CH 3CH(OH)COO) 2Mg), magnesium lactate doped with lithium lactate (Mg(Li)–lactate) and nominal pure lithium lactate (CH 3CH(OH)COOLi) doped with Mg–lactate (Li(Mg)–lactate) were irradiated by γ-rays to study radicals for materials of radiation dosimeter with electron spin resonance (ESR). Quartet spectra were ascribed to lactate radicals in Mg–lactate and Li(Mg)–lactate with the spectroscopic splitting factors ( g-factor) of 2.0032±0.004 and 2.0029±0.004 and the intensity ratio of 1:3:3:1 due to the hyperfine coupling constants of ( A/ gβ) of 1.92±0.06 and 1.82±0.06 mT, respectively. The response to γ-ray dose and the thermal stability as well as the effect of UV-illumination have been studied to establish this material as an ESR dosimeter. The number of free radicals per 100 eV (G-value) was obtained to be 1.15±0.32, 1.35±0.35, 0.46±0.14 and 0.78±0.24 for Mg–lactate, Mg(Li)–lactate, Li–lactate and Lie(Mg)–lactate, respectively. Thermoluminescence (TL) curves gave activation energies ( E) of 0.75, 0.79 and 0.77 eV and frequency factors s (1/ ν 0) of 5×10 7, 4.5×10 7 and 8×10 7 for Mg–lactate, Mg(Li)–lactate and Li(Mg)–lactate, respectively. The lifetimes of radicals in both Mg–lactate and Mg(Li)–lactate were estimated from Arrhenius plots to be approximately 50.7±20 years, while they were 4.9±2.5 and 10±3.5 years for those of Li–lactate and Li(Mg)–lactate, respectively.