The experimental data were taken from
(1) V. D. Gordon, M. C. McCarthy, A. J. Apponi, and P. Thaddeus, 2001, Astrophys. J. Suppl. Ser. 134, 311.
Please note that the distortion parameter was kept fixed to the value of the main species scaled with the square of the B ratio because of the limited data. As a consequence, predictions beyond about 40 GHz should be viewed with caution.
The dipole moment was assumed to agree with that of the main species, see e092501.cat.