Vibrational Analysis of the 3400A Triplet-Singlet Emission of Benzene

The triplet-singlet emission of benzene at 3400A in a rigid glass-solution has been obtained and measured more accurately than in previous work. An assignment is proposed accounting for all the important bands observed. The analysis of the vibrational structure indicates the presence of the 703 cm−1 b2g fundamental, showing that in the triplet-singlet transition, the triplet level combines in the same manner as a 1B1u state for electric dipole radiation. This will lead to a definite assignment of the symmetry of this triplet level when the theoretical rules for intercombinations in polyatomic molecules are derived. The analysis supports a hexagonally symmetric planar model for this triplet state.