Calculation of molecular spectra. Electronic transitions, vibrational patterns and radiative lifetimes of spin-allowed and spin-forbidden transitions

Abstract

The use of large-scale configuration-interaction calculations for a purely ab initio description of the details of molecular spectra is discussed. It is shown that the theoretical tool is applicable to a large range of problems and that it produces quantitative data such as transition energies to within 0.2 eV or better independent of the wavelength region, fine-structure effects due to spin–orbit coupling, vibronic features in large-amplitude motion and radiative lifetimes of excited states on the 10^–9 to 10³ s timescale. In addition it gives insight into the electronic structure and the origin of the various processes; this is important for an understanding and the prediction of features which occur when, for example, first-row atoms in molecules are replaced by their second-row analogues, or for radiation processes in competition with intersystem crossing.