ELECTRON SPIN RESONANCE SPECTRA OF PEROXY RADICALS TRAPPED IN A GAMMA-IRRADIATED SINGLE CRYSTAL OF TRIFLUOROACETAMIDE

It was found from the electron spin resonance spectra that the ·CF2CONH2 radical trapped in γ-irradiated trifluoroacetamide reacts with atmospheric oxygen to give the peroxy radical, ·OOCF2CONH2. The esr spectra of the peroxy radicals showed a remarkable change with the observation temperature. The g tensors at 77 and 300°K were determined by analysis of the spectra of single crystals to be g1 = 2.0022, g2 = 2.0074, g3 = 2.0384 at 77°K and g1 = 2.0210, g2 = 2.0182, g3 = 2.0082 at 300°K. The decrease of the anisotropy of the g tensor at 300°K was well interpreted in terms of the partial averaging of the g tensor due to the internal rotation around the C-O bond. In addition, from the principal directions of the g tensors at both temperatures, the geometrical structure of the peroxy radical was approximately determined, by comparison with the principal direction of the hyperfine tensor of the α-fluorine atom of the ·CF2CONH2 radical trapped in the crystal together with the peroxy radicals.