Metal ion-organic compound for high sensitive ESR dosimetry
A systematic study to find a tissue equivalent and high sensitive dosimeter material has been made to stimulate the field of ESR dosimetry. Lithium acetate dihydrate (Li-Ac.2H2O:CH3COOLi.2H2O) and lithium phosphate (Li-phosphate:Li3PO4) were irradiated by gamma-rays to study radicals with (ESR) in addition to magnesium lactate (Mg-lactate (CH3CH(OH)COO)2Mg) doped with nominal pure lithium lactate (Mg(Li)-lactate) and lithium lactate (CH3CH(OH)COOLi) doped with Mg-lactate (Li(Mg)-lactate). A triplet spectrum with intensity ratio of 1:2:1 in Li-Ac.2H2O was ascribed to acetate radical which has g = 2.0031+/-0.0004 and hyperfine splitting of A/gbeta = 2.12+/-0.1 mT. The Li-phosphate spectrum shows splitting due to anisotropic g-factors of g(parallel) = 2.0190+/-0.0005 and g(perpendicular) = 1.9974+/-0.0004. Quartet spectra with the intensity ratio of 1:3:3:1 in Mg(Li)-lactate and Li(Mg)-lactate were ascribed to lactate radicals with g-factors of 2.0032+/-0.0004 and 2.0029+/-0.0004 and the intensity ratio of 1:3:3:1 and A/gbeta = 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. The obtained number of free radicals per 100 eV (G-values) were 0.4+/-0.13, 1.02+/-0.31, 1.35+/-0.35 and 0.78+/-0 for Li-Ac.2H2O, Li-phosphate, Mg(Li)-lactate, and Li(Mg)-lactate, respectively. The lifetimes were estimated from Arrhenius plots to be approximately 2.0+/-0.6, 50.7+/-20 and 10+/-3.5 years for Li-phosphate, Mg(Li)-lactate and Li(Mg)-lactate, respectively. The lifetime for Li-Ac.2H2O cannot be estimated because of the decomposition by heating.
Hassan
GM
Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Japan. gh@ess.sci.osaka-u.ac.jp
Ikeya
M