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 ac etate dihydrate (Li-Ac . 2H(2)O:CH3COOLi . 2H(2)O) and lithium phosphate (L i-phosphate:Li3PO4) were irradiated by gamma-rays to study radicals with (E SR) in addition to magnesium lactate (Mg-lactate (CH3CH(OH)COO)(2)Mg) doped with nominal pure lithium lactate (Mg(Li)-lactate) and lithium lactate (CH 3CH(OH)COOLi) doped with Mg-lactate (Li(Mg)-lactate). A triplet spectrum wi th intensity ratio of 1:2:1 in Li-Ac . 2H(2)O was ascribed to acetate radic al which has g = 2.0031 +/- 0.0004 and hyperfine splitting of A/g beta = 2. 12+/-0.1 mT. The Li-phosphate spectrum shows splitting due to anisotropic g -factors of g(parallel to) = 2.0190+/-0.0005 and g(perpendicular to) = 1.99 74+/-0.0004. Quarter 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/g beta = 1.922+/-0.06 and 1.82 +/- 0.06 mT, respectively. The res ponse 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.2H(2)O, Li-phosphate, Mg(Li)-lactate, and LI(ME)lactate, r espectively. The lifetimes were estimated from Arrhenius plots to be approx imately 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 . 2H(2 )O cannot be estimated because of the decomposition by heating. (C) 2000 El sevier Science Ltd. All rights reserved.