The phosphorescence of benzene: Zeeman effect and microwave induced emission

Abstract

Results are given of Zeeman and microwave induced delayed phosphorescence experiments which determine the relative activities of the three zero-field spin components in the phosphorescence of benzene. The results allow one to decide which of the mechanisms proposed by Albrecht are responsible for the intensity of some of the most prominent bands in the phosphorescence spectrum. It is confirmed that vibronic coupling in the triplet manifold plays the dominant role for the phosphorescence bands that involve e _2g vibrations and it follows that the phosphorescence in these bands is almost purely out-of-plane polarized. Our results indicate that spin-orbit coupling occurs via the same mechanism as in other aromatic hydrocarbons.