The lines were taken from
(1) S. Thorwirth, V. Lattanzi, and M. C. McCarthy, 2015, J. Mol. Spectrosc. 310, 119.
Higher order parameters were kept fixed to values from a quantum chemical calculation in (1).
Only two rotational transitions were measured. Therefore, it is difficult to judge the quality of the calculation. It should be reliable at least up to 54 GHz.
The dipole moment was taken from a quantum chemical calculation in (1).