Electron Paramagnetic Resonance and Optical Absorption Studies of Radiation-Induced Radicals in Naphthalene Single Crystals

Abstract

Optical absorption and electron paramagnetic resonance (EPR) of naphthalene single crystals irradiated with X-rays or electrons at liquid nitrogen temperature have been studied. The vibronic structures of the optical absorption bands at 539, 632, and 710 nm have been analyzed. It is shown that each of the species associated with these absorption bands has another transition in the visible or ultraviolet region, and it is concluded that they are cyclohexadienyl-type radicals. The change of the EPR spectrum at room temperature of a specimen irradiated at liquid nitrogen temperature was analyzed and it was found that the broad EPR doublet, which has been ascribed to the naphthyl radical, decays according to the first reaction kinetics with the time constant of 11 hours at room temperature.