The transition frequencies have been reported in
(1) M. Hutchinson, H. W. Kroto, and D. R. M. Walton, 1980, J. Mol. Spectrosc. 82, 394 and, more extensively, in
(2) K. M. T. Yamada, C. Degli Esposti, P. Botschwina, P. Förster, L. Bizzocchi, S. Thorwirth, and G. Winnewisser, 2004, Astron. Astrophys. 425, 767.
¹⁴N hyperfine splitting may be resolved at low values of J. However, these transitions are expected to be too weak to be observable in the ISM/CSM.
The calculation should be reliable throughout.
The partition function DOES take into account now the hyperfine splitting, but no vibrational contributions !
Vibrational correction factors for a posteriori corrections have been derived for the main isotopolog in the harmonic approximation.
The vibrational energy is from a quantum-chemical calculation in (2). The dipole moment was assumed to be the same as that of the ground vibrational state, see e075503.cat.