Luminescence from 2,3-Dimethylbutane Containing Toluene in the Solid Phase at 77°K during γ-Irradiation

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Abstract
The luminescence from 2,3-dimethylbutane(2,3DMB) containing toluene in the solid phase has been measured at 77°K during γ-irradiation. The emission consists of fluorescence and phosphorescence from toluene. Since the emission becomes zero upon the removal of a γ-ray source, it cannot be due to a post-irradiation effect. It is concluded from the dependency of the intensity on the concentration of toluene that the luminescence is due to an intermolecular energy transfer from 2,3DMB to toluene during γ-irradiation. ESR studies of γ-irradiated 2,3DMB containing toluene have also been undertaken at 77°K in order to obtain some information on the intermolecular energy transfer. The toluene anion is formed in the γ-irradiated 2,3DMB containing toluene. The dimer cation of toluene is formed in the γ-irradiated 2,3DMB containing toluene and an electron scavenger. The luminescence from toluene in the 2,3DMB matrix decreases upon the pre-irradiation of the sample at 77°K. When the pre-irradiated sample is illuminated by the light from a tungsten lamp to photobleach the toluene anion, the luminescence during γ-irradiation is recovered. Since the intensity of the luminescence does not correspond at all to the amount of toluene anions, the luminescence from toluene in the 2,3DMB matrix during γ-irradiation must not be due to a neutralization reaction between a toluene anion and a migrating hole. It is suggested that the migration of energy from the irradiated 2,3DMB to toluene may occur via an excitation transfer reaction.