Radiation-induced defects in magnesium lactate as ESR dosimeter

Magnesium lactate (Mg-lactate: (CH3CH(OH)COO)(2)Mg), magnesium lactate doped with lithium lactate (Mg(Li)-lactate) and nominal pure lithium lactate (CH3CH(OH)COOLi) doped with Mg-lactate (Li(Mg)-lactate) were irradiated by gamma-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/g beta) of 1.92 +/- 0.06 and 1.82 +/- 0.06 mT, respectively. The response to gamma-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/nu(0)) of 5 x 10(7), 4.5 x 10(7) and 8 x 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. (C) 1999 Elsevier Science Ltd. All rights reserved.