The data from a laboratory study and from astronomical observations were summarized in
(1) R. Fuentetaja, C. Cabezas, Y. Endo, M. Agúndez, B. Tercero, N. Marcelino, P. de Vicente, and J. Cernicharo, 2024, Astron. Astrophys. 688, Art. No. L29.
The ¹⁴N quadrupole coupling parameter was taken from HNC₃
(2) Y. Hirahara, Y. Ohshima, Y. Endo, 1993, Astrophys. J. 403, L83.
The calculations should be accurate enough for all observations. Transition frequencies with calculated uncertainties larger than 0.1 MHz should be viewed with caution.
¹⁴N hyperfine splitting may matter in astronomical observations. Therefore, a separate hyperfine calculation is provided for J' ≤ 10 below 28 GHz. NOTE: The partition function does take into account the spin multiplicity of the ¹⁴N nucleus !
The dipole moment is from a quantum chemical calculation in (1).