Triplet state yields for benzene and benzene-d 6 in the vapour phase

Abstract

The singlet and triplet states of benzene and benzene-d₆ produced by illumination with 2537 Å light have been studied by the cis-trans isomerization of cis-butene-2 and cis-dideutero-ethylene. The triplet yields of C₆H₆ and C₆D₆ are 0.63±0.01 and 0.55±0.01 respectively and non-radiative lifetimes of 12.5 and 14.0 µsec for the triplet states may be calculated from the experimental data. Consideration of the results and the evidence provided by other work on fluorescence suggest that an internal conversion process ¹A_1gâ†�¹B_2u operates to the extent of about 10 %.