The Mechanism of the Scintillation from a Benzene Solution of p-Terphenyl

Abstract

The luminescence from a benzene solution containing p-terphenyl induced by γ-ray irradiation has been compared with that induced by UV irradiation at 2500 Å in the presence of various quenchers. The quenching efficiencies of electron and positive ion scavengers (SF6, N2O, CO2 and NH3) were found to be greater for the γ-ray excitation than for the UV excitation, while 1,3-butadiene, which is known as a quencher for excited benzene, (1B2u), showed almost the same efficiency for both modes of excitation. These results suggest that, even in a benzene solution, a series of ionic reactions is partly responsible for the formation of the scintillating state of p-terphenyl, and that the apparent quenching effect of ion scavengers is mainly due to their interference in the formation of the excited state of the benzene which is produced by the recombination reaction between the benzene cation and an electron. It was estimated that more than 30% of the excited state of benzene is formed by the recombination reaction.