Laboratory microwave data were published by
(1) M. J. Travers, M. C. McCarthy, C. A. Gottlieb, and P. Thaddeus, 1997, Astrophys. J. 483, L135.
Additional microwave data were contributed from astronomical obervarions by
(2) J. Cernicharo, M. Agúndez, C. Cabezas, B. Tercero, N. Marcelino, J. R. Pardo, and P. de Vicente, 2021, Astron. Astrophys. 649, Art. No. L15.
Some distortion parameters were estimated.
The calculations were truncated at J = 25, K_a = 2, and at 180 GHz. The calculations should be sufficient for observations of cold and dense clouds. Transition frequencies with K_a = 2 or with calculated uncertainties exceeding 0.15 MHz should be viewed with caution.
The dipole moment is from a quantum-chemical calculation in (1).