Effect of nonadiabaticity on the vibronic spectra of molecules

Abstract

The adiabatic approximation is one of the most important approximations in the theory of vibronic spectra of molecules. The applicability of the adiabatic approximation is confirmed by the good agreement of the theoretical calculations of the energies and intensities of vibronic transitions in polyatomic molecules [i]. However, frequently such calculations, especially calculations of transition intensities in large polyatomic molecules [2-5], lead to a distorted picture of the energy distribution in the spectrum of the molecule; this might be related to a shortcoming of the adiabatic model, which does not take into account the effect of the nonadiabatic mixing of different vibronic states.