The experimental data have been taken from
(1) M. C. McCarthy, J.-U. Grabow, M. J. Travers, W. Chen, C. A. Gottlieb, and P. Thaddeus, 1999, Astrophys. J., 513, 305.
Predictions are limited to J = 50 and 200 GHz because of the available experimental data. They may be sufficiently reliable if the uncertainties do not exceed 100 kHz. Predictions with K_a ≥ 2 should be viewed with caution. ¹⁴N hyperfine structure has been considered.
The dipole moment components are from an unpublished ab initio calculation mentioned in (1).