How the solvent affects the oscillator strengths of the intense vibronic absorption bands of polyatomic organic molecules

Abstract

An improved theoretical expression has been obtained that describes the laws that determine how universal intermolecular interactions affect the matrix elements of the transition dipole moment in polyatomic molecules. The theoretical predictions are quantitatively compared with the results of experimental studies, using as an example the intense vibronic absorption bands (oscillator strength fa=0.9-5.0) of solutions of nonpolar anthracene (in the 37 000 - 44 000 cm−1 region) and a polar dye (in the 15 000 - 22 000 cm−1 region) in various solvents. It is shown that the theory as a whole correctly describes the experimentally observed dependences in both the former and the latter cases, making it possible to conclude that nonspecific solvation processes have a relatively weak effect on the oscillator strengths of the spectral bands of interest.