Transition frequencies were taken from
(1) T. Sakaizumi, F. Katoh, O. Ohashi, and I. Yamaguchi, 1993, J. Mol. Spectrosc. 159, 112;
and from
(2) M. C. McCarthy, K. L. K. Lee, P. B. Carroll, J. P. Porterfield, P. B. Changala, J. H. Thorpe, and J. F. Stanton, 2020, J. Phys. Chem. A 124, 5170.
The uncertainties in (2) were conservative and were adjusted from 2 to 1 kHz. Initial estimates of the quartic distortion parameters were taken from an B3LYP quantum-chemical calculation by
(3) H. S. P. Müller, 2021, unpublished.
With respect to the first entry of Nov. 2021, additional transition frequencies were added from astronomical observations by
(4) J. Cernicharo, R. Fuentetaja, M. Agúndez, R. I. Kaiser, Cabezas, N. Marcelino, B. Tercero, J. R. Pardo, and P. de Vicente, 2022, Astron. Astrophys., in press.
One transition frequency with large residual was omitted from the line list. The data set is still somewhat limited. The calculations were therefore truncated at 200 GHz and at J = 60. The calculations should be sufficient for searches in cold and luke warm environments. Transition frequencies with calculated uncertainties exceeding 0.1 MHz should be viewed with caution. Some caution is also advised for transitions with J larger than 30.
Spin-statistical weight ratios of 9 : 7 for levels with K_a being odd and even, respectively, have been taken into account.
The dipole moment is from (1).