Problems in the description of the intensities of electronic spectra of diatomic molecules in the adiabatic approximation

A review is given of the current state of research into the radiative properties of diatomic molecules. Problems that arise in the theoretical description of intensity distributions in molecular spectra are discussed, possible ways of solving these problems are examined, and progress achieved in overcoming such problems is surveyed. It is shown that it is possible to provide a reliable quantitative description of the intensity distribution in the electronic spectra of diatomic molecules by using the adiabatic Bom–Oppenheimer model, provided the appropriate “corrections” are introduced for the electron-vibration (EV) and vibration-rotation (VR) interactions. Particular attention is devoted to the current state of research into the effect of these interactions on Franck–Condon factors, and to a possible way of taking into account the VR interaction, which has not been adequately dealt with in the literature. A special section deals with possible applications of studies of radiative parameters (above all the Franck–Condon factors with allowance for molecular rotations) in the effective solution of many applied and theoretical problems in different branches of science, engineering, and technology, which are concerned with molecular transitions between EVR levels.