The observed lines are from
(1) K. Kawaguchi, E. Kagi, T. Hirano, S. Takano, and S. Saito 1993, Astrophys. J. 406, L39;
and
(2) K. A. Walker and M. C. L. Gerry 1998, J. Mol. Spectrosc., 198, 40.
For transitions with N = 5 – 4 or higher, the hyperfine splitting is smaller than ca. 1 MHz for the strong hfs components. Therefore, predictions without hyperfine structure are also available.
The dipole moment is from an ab initio calculation by
(3) K. Ishii, T. Hirano, U. Nagashima, B. Weis, and K. Yamashita 1993, Astrophys. J. 410, L43.
In the meantime, the dipole moment has been determined experimentally by
(4) T. C. Steimle and R. R. Bousquet, 2001, J. Chem. Phys. 115 5203 to be 5.308 (75) D. Thus, the value used in the present calculation is lower by only about one standard deviation.