Radical formation of lithium and magnesium citrates for electron spin resonance dosimetry

Lithium citrate (Li3C6H5O7: (CH2COOLi)(2)C(OH)COOLi); Li-citrate) and magne sium citrate (Mg-3(C6H5O7)(2): Mg-2(CH2COO)(4)Mg(C(OH)COQ)Mg; Mg-citrate) w ere irradiated by gamma-rays to study radicals with electron spin resonance (ESR). A doubler spectrum has g = 2.0044 +/- 0.0005 and hyperfine splittin g of A/g beta = 2.5 +/- 0.2 mT in Li-citrate, Mg-citrate shows a tripler sp ectrum with g = 2.0032 +/- 0.0004 and hyperfine splitting of A/g beta = 2.2 1 +/- 0.18 mT The energy level, g-factor, A/g beta and optical absorption s pectra of several radicals have been calculated using software of MOPAC-V2 and Gaussian-98 based on the unrestricted Hartree-Fock: (UHF). Abstraction of hydrogen from -CH2 is expected for Li-citrate, and homolytic cleavage of the OH group is expected for Mg-citrate. The powders of both Li-citrate an d Mg-citrate are six times and five times more sensitive to the gamma-ray d ose, respectively than a commercial alanine dosimeter. The numbers of free radicals per 100 eV (G-values) were 0.77 +/- 0.25 and 1.11 +/- 0.35 for Li- citrate and Mg-citrate, respectively.