Evaluation of parameters of intramolecular interaction from absorption and fluorescence spectra of substituted arylpolyene with poor resolved vibrational structure

The fluorescence and fluorescence excitation spectra (conjugated spectra) of new synthesized substituted arylpolyene (C6H5-[CH=CH]2-C6H4-NH2) in solid n-octane at T=4.2 K were studied. Spectra have feebly marked vibrational structure. The method of finding vibronic interaction parameters from conjugated spectra was developed. The method is based on the modeling of spectra in the form of set of vibronic bands. Each vibronic band is represented as the sum of narrow zero-phonon line and broad phonon wing. It allows carrying out the theoretical calculation of the conjugated spectra with poor resolved vibrational structure, which can be compared with the measured spectra. The vibronic interaction parameters which determine shape of the spectra can be found from comparative analysis of experimental and model spectra. This analysis allowed us to explain the deviation from the mirror symmetry between measured conjugated spectra as a joint manifestation of Franck-Condon and Herzberg-Teller interactions. The parameters of both interactions for main normal vibrations of molecule were found.