The second entry from May 2006 has been revised considerably. Additional infrared data involving states v₂ = 2 and 3 as well as v₃ = 1 and v₁ = 1 were included along with additional pure rotational data pertaining to v₂ = 2 and 3.
The first entry from April 2000 has been revised completely. Both v = 0 and v₂ = 1 data were treated together. Data for both vibrational states, including v₂ = 1 direct-l-type transitions up to J = 35 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 3rd 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 main improvement occured in the partition function, which 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. The frequencies are also better at higher values of J. Predictions above 6 THz should be viewed with some caution.
The dipole moment was assumed to be the same as for the main isotopic species; see e027501.cat.
The ¹⁴N hyperfine splitting can be resolved for low values of J. Therefore, a separate ¹⁴N hyperfine calculation is provided for J" ≤ 5. 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. In very cold and quiescent sources it may be warranted to consider ¹³C and ¹H hyperfine splitting in addition to that caused by the ¹⁴N nucleus. Therefore, a separate hyperfine calculation for all three nuclei is provided for J" ≤ 1. Note: the spin multiplicity g_I of 2 for the ¹³C and ¹H nuclei has not been considered in the calculation of the partition function and the upper state degeneracy g_up. Therefore, if hyperfine structure due to the ¹³C and ¹H nuclei are considered also all partition function values have to be multiplied by 4.
The partition function takes into account all vibrational states used in the fit.