Vibronic and electron‐phonon coupling in spectra of substituted polyenes in rigid matrices

It is found that the electronic excited state 11Bu does not influence the intensity distribution in the electronic 11Ag → 21Ag transition though it is partially allowed. It is determined with the help of the electron‐vibrational interaction theory using the joint analysis of fluorescence spectra and fluorescence excitation spectra of three arylpolyenes in n‐paraffin matrices at 4.2 K. Elastic forces, binding the polyene molecules with the environment, are shown to change in the phototransition.