Free radicals in the photolysis and radiolysis of polymers:: IV.: Radicals in γ- and UV-irradiated wood and lignin

Free radicals formed in the radiolysis and photolysis of wood and lignin were studied using X-band and D-band EPR measurements. It was found that singlet spectra at g approximate to 2, which appeared upon the low-temperature (77 K) gamma- and UV irradiation of wood and lignin, or singlets detected in a posteffect on heating the irradiated samples belong to radicals having conjugated carbon-carbon bonds. Formyl radicals in gamma-irradiated wood and peroxide radicals in gamma- and UV-irradiated wood were detected for the first time using EPR spectra. The radiation-chemical and quantum yields of radical formation reactions were determined. In wood at 77 K, G(R) approximate to 3.2 1/100 eV and phi(R) approximate to 2 x 10(-3).