Transition frequencies of the lower spin-orbit component were taken from
(1) P. M. Sheridan, L. M. Ziurys, T. Hirano, 2003, Astrophys. J. 593, L141.
The spin-orbit splitting is only known from quantum-chemical calculations. Its magnitude is close to the ground state vibrational splitting. The partition function takes into account both spin-orbit components but no vibrational corrections. The predictions should be sufficiently accurate for observational purposes. The calculated dipole moment was reported by
(2) M. H. de Oliveira, H. P. Martins Filho, J. D. da Motta Neto, 2011, Int. J. Quantum Chem. 111, 1453.