The second entry from May 2006 has been revised considerably.
Additional infrared data involving states v_{2} = 2
and 3 as well as v_{3} = 1 and v_{1} = 1
were included along with additional pure rotational data
pertaining to v_{2} = 2 and 3.
The first entry from April 2000 has been revised completely.
Both v = 0 and v_{2} = 1 data were
treated together. Data for both vibrational states, including
v_{2} = 1 directltype 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 directltype transitions 6 ≤ J ≤ 15
were published in
(4) M. Winnewisser and J. Vogt,
1978, Z. Naturforsch. 33a, 1323.
The 3rd entry also employs v_{2} = 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 ^{14}N hyperfine splitting can be resolved for low values
of J. Therefore, a separate
^{14}N hyperfine calculation is provided for
J" ≤ 5. Note:
the spin multiplicity g_{I} of 3 for
the ^{14}N 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 ^{13}C and ^{1}H hyperfine splitting
in addition to that caused by the ^{14}N 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
^{13}C and ^{1}H 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 ^{13}C and
^{1}H 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.
