Singlet—triplet absorption spectra of several carbonyl compounds

Abstract

Singlet—triplet absorption spectra of benzaldehyde, acetophenone and benzophenone have been studied in solution and the absorption curves have been presented. For comparison, the spectrum of benzoquinone has also been studied. Phosphorescence spectra of these compounds have been studied for confirmation of the triplet state. Vibrational analyses made by SIDMAN for the crystal spectrum of benzoquinone and by ANNO and SADO for the vapour spectrum have been criticized. The S′— T separation, i.e. the separation between the lowest excited singlet state and the lowest triplet state, is seen to decrease with increasing ratio, f S,T | f S,S ′, namely, an f-number of a single—triplet spectrum over an f-number of a singlet—singlet spectrum.