Low-Resolution Analysis of Vibrational—Electronic Circular Dichroism Spectra

Abstract

Application of the approximations for the Born—Oppenheimer adiabatic wavefunctions, harmonic nuclear motions, and a perturbation of transition moment linear in the normal coordinates lead to general expressions which characterize position, bandwidth, and skewness of absorption and circular dichroism bands of nondegenerate electronic states. Such quantities are particularly useful when the spectra show little or no discernible vibronic structure and define in some cases parameters for a Gaussian description of the spectra. With introduction of additional assumptions which are commonly supposed in vibrational analysis in spectroscopy, the origins of the different terms in the final formulas for the mean frequency, bandwidth, and skewness can be discussed. The expressions obtained relate in a significant way the observed spectra to fundamental constants of the absorbing molecules.