ExoMol molecular line lists. XLIV. SiO

This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the A^1^{Pi} and E^1^{Sigma}^+^ electronic states. Strong perturbations to the A^1^{PI} band system are accurately modelled through the treatment of 6 dark electronic states: C^1^{Sigma}^-^, D^1^{Delta}, a^3^{Sigma}^+^, b^3^{PI}, e^3^{Sigma}^-^ and d^3^{Delta}.

Along with the X^1^{Sigma}^+^ ground state, these 9 electronic states were used to build a comprehensive spectroscopic model of SiO using a combination of empirical and ab initio curves, including the potential energy (PE), spin-orbit (SO), electronic angular momentum (EAM) and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction (MRCI) level of theory, were refined by fitting their analytical representations to 2617 experimentally derived SiO energy levels determined from 97 vibronic bands belonging to the X-X, E-X and A-X electronic systems through the MARVEL procedure. 112 observed forbidden transitions from the C-X, D-X, e-X, and d-X bands were assigned using our predictions, and these could be fed back into the MARVEL procedure.