Identification of paramagnetic radicals in g-irradiated natural diatomite minerals by electron paramagnetic resonance

In this study, gamma-irradiated natural diatomite minerals were investigated by electron paramagnetic resonance (EPR) spectroscopy at ambient temperature. The paramagnetic radicals produced by g-irradiation in natural diatomite minerals at ambient temperature were attributed to C_H3; _PO2 4 , _ COK2 ; organic (probably, humic or fluvic acid), _SOK2 and _SOK3 free radicals. These centers were found to be perfectly observable at below 20 mW microwave power. The g values of all the paramagnetic centers were obtained, and some of their a values were reported. The results were found to be consistent with the existing literature data and theoretical predictions for similar paramagnetic centers. q 2004 Elsevier B.V. All rights reserved