The Dunham fit was described in
(1) O. Asvany, C. R. Markus, K. Nagamori, H. Kohguchi, J. Furuta, K. Kobayashi, S. Schlemmer, and S. Thorwirth, 2021, Astrophys. J. 910, Art. No. 15.
The rotational data are from that work, the rovibrational data were taken from
(2) M. Gruebele, M. Polak, G. A. Blake, and R. J. Saykally, 1986, J. Chem. Phys. 85, 6276.
The ground state dipole moment was taken from a quantum-chemical calculation by
(3) K. A. Peterson, R. C. Woods, P. Rosmus, and H.-J. Werner, 1990, J. Chem. Phys. 93, 1889.
Transition frequencies should be fairly reliable up to about 500 GHz. Please note: There are presently no experimental data for this isotopolog. The breakdown of the Born-Oppenheimer approximation had to be neglected for this substitution. This leads to a small, but likely not negligible, error in B. The hyperfine splitting is slightly different from that of the main isotopolog, but this effect is probably smaller than that caused by the neglect of the breakdown of the Born-Oppenheimer approximation.
The partition function takes excited vibrational states into account.