Vibronic coupling, fluorescence analysis

Vibrational analysis of the benzene phosphorescence bands indicates that the radiative activity is induced predominantly by e2g vibrations [155, 156]. A weak but observable activity of b2g vibrations has also been found [156, 155, 157]. By introducing spin-orbit- and vibronic coupling through second order perturbation theory Albrecht [158] showed that the vibronic interaction within the triplet manifold is responsible for the larger part of the phosphorescence intensity. This also follows from comparison of the vibrational structure in phosphorescence and fluorescence spectra [159]. The benzene phosphorescence spectrum in rigid glasses [155] reveals a dominant vibronic activity of... 

The principal modes of vibration of the anthracene molecule, active in absorption and in fluorescence, have been given in ref. 58. This subsection is intended to provide a consistent analysis of the whole structure of the crystal absorption (reflectivity) and to discuss its shape in terms of vibron-two-particle states and collective couplings and of the spectral and dynamical (relaxation) effects to which they give rise. These active vibration modes are here summarized in decreased order of strength ... 

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