Ionic Processes in γ-Irradiated Organic Solids: Recombination Luminescence

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Abstract
Several aromatic hydrocarbons, ketones, and amines phosphoresced when their γ‐irradiated dilute solutions in 3‐methyl pentane were exposed to near‐infrared light at 77°K or were warmed slightly. Triphenylamine (TPA) was examined in some detail. Optical absorption spectroscopy provides evidence for color centers tentatively identified as TPA+, TPA−, as well as solvent‐trapped electrons (e−). Formation of TPA+ is attributed to transfer of the electron vacancy in the molecular matrix. Infrared bleaching of (e−) and TPA−‐induced phosphorescence of TPA with corresponding decrease of TPA+. Addition of organic halide (e− trap) decreased TPA− and (e−), and ethanol (hole trap) decreased TPA+; both decreased phosphorescence which is attributed to ion recombination.