The lowest triplet and singlet electronic states of the molecule SO Original Research Article

A comprehensive study of the singlet and triplet states of SO, correlating with the first two dissociation channels, is carried out using a state-averaged complete active space self-consistent field/internally contracted multireference configuration-interaction approach, and correlation-consistent polarized-valence quadruple-zeta basis sets. Potential energy curves and dipole moment functions for all states are presented. Besides providing an accurate and global description of the manifold of electronic states known to date, reliable evidence of two 1Π bound states, for which experimental evidences were reported very recently, and a discussion of the vibrational numbering problem of the transitions c 1Σ− → a 1Δ, and A′ 3Δ → X 3Σ−, for which there has been some conflict in the available experimental data, are also presented. These results are of special relevance to elucidate further experimental assignments in the electronic spectroscopy of SO.