The observed transitions were taken from
(1) K. Demyk, H. Mäder, B. Tercero, J. Cernicharo, J. Demaison, L. Margulès, M. Wegner, S. Keipert, and M. Sheng, 2007, Astron. Astrophys. 466, 255.
With respect to the entry from Apr. 2007, additional extensive data were used from
(2) C. Richard, L. Margulès, R. A. Motiyenko, and J.-C. Guillemin, 2013, Astron. Astrophys. 543, Art. No. 135.
The transitions from (1) and (2) were used as reported in (2). Higher order parameters, including two from (2), were kept fixed to those of the main isotopolog, see e055502.cat.
Please note: In the case of asymmetry doublets with splitting less than 0.1 kHz, (1) and (2) have listed only one transition. There is no effect on the spectroscopic parameters or on the predictions, except that in the merged catalog file only one transition will be flagged. Corrections had been made in the line list for (1), but not for (2) because of the extensive data.
Predictions with uncertainties exceeding 0.5 MHz should be viewed with caution. The predictions are deemed to be reliable throughout for astronomical observations.
The ¹⁴N hyperfine splitting is negligible in most instances. However, it may be resolved for low values of J. Therefore, a separate hyperfine calculation together with partition function values are provided for J' ≤ 10 and frequencies below 92 GHz. At present, the hfs parameters were taken from the main isotopic species. Deviations will be small, but maybe not always negligible.
The partition function values below refer to the ground vibrational state only. Vibrational correction factors have been derived for the main isotopolog in the harmonic approximation. Errors caused by isotopic substitution are small.
The dipole moment was assumed to agree with that of the main isotopic species:
(3) A. Krasnicki, Z. Kisiel, 2011, J. Mol. Spectrosc. 270, 83.
Some small deviations are expected to occur, but these are probably within the experimental uncertainties.