Prompt and Delayed Fluorescence of X-Ray-Excited Anthracene Crystals

Abstract

The fluorescence of anthracene excited by x rays from a 600 keV pulsed source was investigated. An x‐ray dose of 7.6 × 1012 eV cm−3 produced a prompt fluorescence output of 1.4 × 1011photons cm−3, as well as an intense delayed fluorescence. Analysis of the time dependence of the delayed fluorescence, based on the diffusion kinetics of triplet excitons in tracks, indicated that the above dose produced 7 × 1010 singlet excitons by direct excitation ( S 0 →S n transitions) and 2.7 × 1011 short‐lived ion pairs, of which 7 × 1010 recombined to form singlet excitons and 2 × 1011 recombined to form triplet excitons. In these calculations, the value of the triplet excitondiffusion coefficient was found to be (1 ± 0.5) × 10−4 cm2 sec−1.