EPR study of radicals produced by Gamma-irradiation in marine mollusc (Venus sp.) fossils

In this study, gamma-irradiated marine mollusc (Venus sp.) fossils were investigated by electron paramagnetic resonance (EPR) at ambient temperature. Powder X-ray diffraction technique indicates that the Venus sp. fossils were made mainly of CaCO₃. Before γ -irradiation, the EPR lines of the powder of fossil samples showed the existence of Mn²⁺ (I = 5/2, 100% natural abundance) ions with g_av = 2.0055 and A_av = 9.4 mT. γ -Irradiation-induced additional defects in Venus sp. fossil were attributed to axial ĊO₃^- (g⊥ = 2.0171, g// = 2.0048), orthorhombic ĊO₂^- (g_x = 2.0030, g_z = 2.0018, g_y = 1.9973, g_av = 2.0007), freely rotating ĊO₂^- (g_iso = 2.0007), isotropic ṠO₂^- (g = 2.0057), axial ṠO₃ ^- (g⊥ = 2.0036, g // = 2.0024) and isotropic ṠO ₃^- (g = 2.0032) free radicals. The g-values of these free radicals were compared with the literature data belonging to similar defects.