Color centers in irradiated durene crystals

The optical absorption spectra of γ-irradiated durene single crystals at 77 K are measured using light polarized along the a-, b-, and c'-axes of crystals. In the shorter wavelength region five strong absorption bands are detected. At longer wavelength weak bands at 489 nm with well desolved vibrational structures and relatively broad weak bands at 570 nm are observed. On illumination with a mercury lamp the 322, 331, 340, 349, 528, and 570 nm bands are found to decay-out completely and the 335, 411 and 489 nm bands to remain unchanged. By comparing the spectra with the absorption of cyclohexadienyl and benzyl radicals, the absorption bands which are optically bleached are assigned to the methyl cyclohexadienyl radical and the ones being unchanged are attributed to the methyl benzyl radical. An emission obtained by exciting the 489 nm absorption system, is also detected. This emission is attributed to that of the methyl benzyl radical. (author)