Lifetime of singlet oxygen in liquid solution

Abstract

A laser photolysis system has been used to obtain unimolecular rate constants for the decay of singlet oxygen in liquid solution. The decay constants were derived from a kinetic analysis of the disappearance of an oxidizable acceptor, diphenylisobenzofuran, which reacts with singlet oxygen produced by energy transfer from several electronically excited sensitizers. The singlet oxygen decay constant obtained is independent, within experimental error, of the sensitizer employed and direct excitation of aromatic hydrocarbons is shown to give the most reliable values. The lifetime of singlet oxygen, which shows no temperature dependence in the range 0–23°C, was measured using four different solvents and the values obtained varied from 5 µs (methanol) to 12 µs (benzene).