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;
and from
(2) Y. Kasai, K. Obi, Y. Ohshima, Y. Hirahara, Y. Endo, K. Kawaguchi, and A. Murakami, 1993, Astrophys. J. 410, L45.
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 more limited data. As a consequence, predictions beyond about 60 GHz should be viewed with caution.
The dipole moment was assumed to agree with that of the main species, see e092501.cat.