The rotational transition frequencies were reported by
(1) R. D. Suenram, F. J. Lovas, G. T. Fraser, and K. Matsumura, 1990, J. Chem. Phys. 92, 4724;
and, much more extensively, by
(2) J. Hoeft and T. Törring, 1993, Chem. Phys. Lett. 215, 367.
Also used in the fit were extensive radiofrequency measurements from
(3) W. J. Childs, O. Poulsen, and T. C. Steimle, 1987, J. Chem. Phys. 88, 598.
At low to moderate quantum numbers, the hyperfine splitting is larger or about as large as the fine structure splitting. Therefore, the coupling scheme employed was: S + I = G, N + G = F; in agreement with references mentioned above.
Predictions should be reliable up to about 700 GHz.
Vibrational contributions have been considered in the calculation of the partition function. Values for the ground state are given in parentheses.
The dipole moment was taken from (1).