Radiationless Processes in Fluorobenzene

Abstract

The triplet yield of fluorobenzene is studied by the biacetyl emission method. The effect of biacetyl pressure indicates a short triplet lifetime of 130 nsec for fluorobenzene in the gaseous phase. The absence of phosphorescence even in a solid matrix at low temperature is explained by a radiationless process from the triplet state of fluorobenzene. A weak sensitized emission from the first excited singlet state of biacetyl suggests that singlet–singlet energy transfer must be involved. Addition of cis‐2‐butene quenches the sensitized emission from the triplet state of biacetyl. The triplet yield of fluorobenzene results in a reasonable value of 1.03 for the sum of triplet and singlet yields on excitation at the 0–0 band.