Very accurate microwave data were obtained in the course of an observational study by
(1) A. M. Burkhardt, K. L. K. Lee, P. B. Changala, C. N. Shingledecker, I. R. Cooke, R. A. Loomis, H. Wei, S. B. Charnley, E. Herbst, M. C. McCarthy, and B. A. McGuire, 2021, Astrophys. J. Lett. 913, Art. No. L18.
Line and parameter files were kindly provided by the first author. The uncertainties appear to be better than 2σ and were thus adjusted to 1 kHz. A moderate number of less accurate microwave transition frequencies with slightly higher J and K_a were reported by
(2) W. Caminati, 1993, J. Chem. Soc. Faraday Trans. 89, 4153.
Small deviations exist, but are possibly not significant. Therefore, these data were omitted.
The calculations were truncated at J = 40 and at 120 GHz. Transition frequencies with J > 30 or K_a > 10 should be viewed with caution.
The dipole moment was determined in (2).