ESR studies on the effect of lignin and gases on UV photodegradation of cellulose

Aspen wood pulp and aspen dioxane‐lignin were irradiated by ultraviolet light under vacuum employing a special technique for uniform irradiation of the powdered samples. Examination of the effect of various gases and lignin contents of the pulps on the ESR spectra showed that the spin concentration was reduced by oxygen and lignin content, while atomic hydrogen reduced it to zero. The width and shape of the line were unaffected by oxygen, while lignin content reduced the width. A resolution for the hyperfine component of the spectrum yields an average distance of 1.3 Å between the free spin at C‐5 and the protons at C‐6 of the cellulose.