Theoretical analysis of emission spectra of electronic transitions of molecules in dense media

The purpose of this paper is to investigate the nature of band shapes of emission spectra and their relation to the rate of nonradiative processes. Two cases are discussed, one in which the Franck-Condon principle applies and the other in which the electronic transition is symmetry-forbidden but vibronic-allowed. The moment relations of emission spectra have been derived and their applications demonstrated.The vibrational structuring in emission spectra is discussed and empirical equations for calculation of the shapes of vibrational bands are derived. It is found that from the shapes of vibrational bands one can obtain the information of intermolecular vibration and from the areas under vibrational bands one can determine the Franck-Condon factors of intramolecular vibration.