Radical Formation of Lithium and Magnesium Citrates for Electron Spin Resonance Dosimetry

Abstract

Lithium citrate (Li3C6H5O7: (CH2COOLi)2C(OH)COOLi); Li-citrate) and magnesium citrate (Mg3(C6H5O7)2: Mg2(CH2COO)4Mg(C(OH)COO)Mg; Mg-citrate) were irradiated by γ-rays to study radicals with electron spin resonance (ESR). A doublet spectrum has g=2.0044 ±0.0005 and hyperfine splitting of A/gβ=2.5 ±0.2 mT in Li-citrate. Mg-citrate shows a triplet spectrum with g=2.0032 ±0.0004 and hyperfine splitting of A/gβ=2.21 ±0.18 mT. The energy level, g-factor, A/gβ and optical absorption spectra of several radicals have been calculated using software of MOPAC-V2 and Gaussian-98 based on the unrestricted Hartree-Fock: (UHF). ion 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 and Mg-citrate are six times and five times more sensitive to the γ-ray dose, 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.