Please note that the identities of the exited states are not known. They have been numbered from low energies to higher energies. These two states are interacting strongely with each other.
The transition frequencies were taken from
(1) D. J. Tyree, T. W. Chapman, I. R. Medvedev, Z. Kisiel, 2022, J. Mol. Spectrosc. 390, Art. No. 111706.
There appear to be perturbations in v₅ and possibly v₄ from states outside this dyade. As a consequence, a moderate number of lines with larger residuals was omitted. The omitted lines and the parameter set differs from that in (1). The calculations should be accurate enough for all observational purposes. Transition frequencies with J up to 30 should be largely fine, should be viewed with at least some caution between 31 and 40, and with great caution above that.
The partition function considers the ground vibrational state only. Vibrational correction factors have been derived. Please do note the caveats ! Spin-statistical weights of the ratio 13 : 11 were omitted as they are close to 1 : 1. In v₄, K_a + K_c even and odd would carry the weights of 13 and 11, respectively, while it would be reversed for v₅.
The ground state dipole moment was determined in
(2) R. D. Brown, P. D. Godfrey, and J. Storey, 1975, J. Mol. Spectrosc. 58, 445.