Rovibrational and, as far as published, rotational data involving states v₂ = 0 to 3 as well as v₃ = 1 and v₁ = 1 were used in the fit.
Data for v = 0 and v₂ = 1, including direct-l-type transitions up to J = 35 for v₂ = 1, were reported in
(1) U. Fuchs, S. Brünken, G. W. Fuchs, S. Thorwirth, V. Ahrens, F. Lewen, S. Urban, T. Giesen, and G. Winnewisser, 2004, Z. Naturforsch. 59a, 861.
Additional v = 0 data come from
(2) G. Cazzoli and C. Puzzarini, 2005, J. Mol. Spectrosc. 233, 280;
and from
(3) F. Maiwald, F. Lewen, V. Ahrens, M. Beaky, R. Gendriesch, A. N. Koroliev, A. A. Negirev, D. G. Paveljev, B. Vohwinkel, and G. Winnewisser 2000, J. Mol. Spectrosc. 202, 166.
Further direct-l-type transitions 6 ≤ J ≤ 15 were published in
(4) M. Winnewisser and J. Vogt, 1978, Z. Naturforsch. 33a, 1323.
The 2nd entry also employs v₂ = 2 and 3 rotational data from
(5) J. Preusser and A. G. Maki, 1993, J. Mol. Spectrosc. 162, 484.
The fit also takes into account the very extensive infrared data between the various vibrational states from
(6) A. G. Maki, G. C. Mellau, S. Klee, M. Winnewisser, and W. Quapp, 2000, J. Mol. Spectrosc. 202, 67.
The partition function is essentially converged at 300 K and probably still good up to about 500 K. The rotational part is well converged up to 1000 K. Even though no pure rotational transition frequencies have been published, predictions with calculated uncertainties below 6 THz should be viewed only with slight caution. Greater caution is advised at higher frequencies.
The dipole moment was assumed to be the same as for the main isotopic species; see e027509.cat.
Note: the spin multiplicity g_I of 3 for the ¹⁴N nucleus has been considered in the calculation of the partition function and the upper state degeneracy g_up.
The partition function takes into account all vibrational states used in the fit.