An electron spin resonance study of radicals induced by radiation in oat (Avena sativa L.)

A detailed electron spin resonance (ESR) investigation of the spectroscopic features and kinetic behaviours over a range of temperatures of the long‐life free radicals induced in a sample of ground oat that had been irradiated with γ‐radiation is reported. Unirradiated ground oat exhibited a weak, broad single‐line ESR spectra centered at g = 2.0048 ± 0.0008. The structure of this radical is unknown and is assigned as radical III in this work. The γ‐irradiation of oats yields radical III and other radical species. Although all these species are stable at 77 K, some of them are very unstable at room temperature. A model based on three radical species (designated I, II and III) was used to describe the room temperature spectra of their decay at room and at high temperatures. Annealing studies at six different temperatures were used to determine the kinetic behaviour and activation energies of the radicals induced by radiation. A dose–response curve was also constructed and it was concluded that ground oat is potentially a good dosimetric material. The presence of an ESR signal after a storage time of 90 days was interpreted as providing an opportunity to distinguish irradiated from unirradiated oats.