The transition frequencies were summarized by
(1) O. Desyatnyk, L. Pszczółkowski, S. Thorwirth, T. M. Krygowski, and Z. Kisiel, 2005, Phys. Chem. Chem. Phys. 7, 1708.
The data set contained additional data from
(2) R. K. Kakar, E. A. Rinehart, C. R. Quade, and T. Kojima, 1970, J. Chem. Phys. 52, 3803;
these data were used in the fit, but not merged because of the large uncertainties. The parameter set differs slightly from the one in (1).
Predictions with uncertainties larger than 0.2 MHz should be viewed with caution. This is probably not of importance for astronomical observations.
The dipole moment was derived in (1).