Electron spin resonance of gamma‐irradiated cellulose

Abstract

AbstractIrradiation of purified cellulose with cobalt‐60 gamma rays in vacuo produces moderate yields of radicals detectable by electron spin resonance. The ESR spectrum is asymmetric, with five partially resolved peaks occupying a total region of about 50 gauss wide and a spectroscopic splitting factor near g = 2. The peaks show differing saturation behavior with increasing microwave power. Differences of crystallinity have no obvious effect on the yield or nature of the radical ESR spectrum. The presence of about 8% water during irradiation decreases the yield greatly and modifies the hyperfine structure. For dry cellulose the initial G value for radicals is near 2.8 radicals per 100 e.v. absorbed, but the concentration levels off at doses a little over 6 × 1020 e.v./g. Despite the early falling‐off in yield, the radicals in stored irradiated specimens do not decay appreciably in several days. Even upon contact with air the decay is quite slow. Thermal decay is imperfectly second‐order, fairly rapid above 120°C., and indicates several radicals of differing lifetimes.