Ab initio study of the low-lying electronic states of the CaO molecule

► The five lowest electronic states of Cao have been determined ab initio at a high level of accuracy. ► Large active space, core-valence correlation and configuration interaction are required. ► The multi-configurational nature of the electronic ground state is confirmed as well as its monovalent and divalent ionic nature using dipole moment analysis. ► These interacting potentials will serve for future obtention of spin-rovibronic levels.