With respect to the Feb. 2006 entry, improved rest frequencies for the strongest ¹⁴N hyperfine components of the J" = 0 – 2 have been described by
(1) L. Pagani, F. Daniel, and M.-L. Dubernet, 2009, Astron. Astrophys. 494, 719.
The ¹⁴N hyperfine structure has been resolved completely for the 1 – 0 transition. The splittings have been determined in (1) with higher accuracy than the absolute positions, but not published. These data, communicated by L. Pagani, were used in the fit. Additional laboratory data was taken from
(2) L. Dore, P. Caselli, S. Beninati, T. Bourke, P. C. Myers, and G. Cazzoli, 2004, Astron. Astrophys. 413, 1177.
With respect to the Feb. 2005 entry, new submillimeter measurements were considered. They were reported by
(3) T. Amano, T. Hirao, and J. Takano, 2005, J. Mol. Spectrosc. 234, 170.
In order to extrapolate more reliably to higher values of J, a value for the sextic distortion parameter H was derived from DCN, see e028509.cat for references. The predictions are assumed to be reliable to at least 2 THz.
A separate hyperfine calculation is provided for J" ≤ 4. Note: The partition function takes into account this splitting !
The deuterium hyperfine splitting is unlikely to be resolved. Therefore, it was not considered.
The dipole moment was assumed to be the same as that of the main isotopomer, see e029506.cat.
Note: Intensities in the entry without HFS have been corrected in Aug. 2015. They were not compatible with the HFS entry and with the partition function.