The second version of Jan. 2016 was updated with highly accurate hyperfine-resolved infrared transition frequencies and with N = 1 – 0 and 2 – 1 rotational transition frequencies obtained with microwave accuracy taken from
(1) W. G. D. P. Silva, L. Schneider, U. U. Graf, H. S. P. Müller, P. Jusko, A. M. Jacob, D. Riechers, S. Schlemmer, and O. Asvany, 2026, Phys. Chem. Chem. Phys. 28, 12651.
New v = 1 – 0 infrared data with megahertz accuracies were included in the initial fit to improve the first entry from Apr. 2003. Details of the new fit as well as the data are presented in
(2) C. R. Markus, J. M. Hodges, A. J. Perry, G. S. Kocheril, H. S. P. Müller, and B. J. McCall, 2016, Astrophys. J. 817, Art. No. 138.
The N = 1 – 0 rotational transition frequencies with HFS splitting were taken from
(3) J. P. Bekooy, P. Verhoeve, W. L. Meerts, and A. Dymanus, 1985, J. Chem. Phys. 82, 3868.
The N = 13 – 12 transition frequencies with FS splitting were reported in
(4) D.-L. Liu, W.-C. Ho, and T. Oka, 1987, J. Chem. Phys. 87, 2442.
Vibration-rotation transitions up to v = 5 – 4 were also included in the fit. These were published in
(5) B. D. Rehfuss, M.-F. Jagod, L.-W. Xu, and T. Oka, 1992, J. Mol. Spectrosc. 151, 59.
The calculations should be accurate enough for observational purposes; increasing caution is advised for N > 5.
The electric dipole moment is from a quantum chemical calculation by
(6) M. Cheng, J. M. Brown, P. Rosmus, R. Linguerri, N. Komiha, and E. G. Myers, 2007, Phys. Rev. A 75, Art. No. 012502.