Data of all four stable isotopic species have been treated in one global fit. Pure rotational transitions were considered up to v = 3 while rovibrational transitions were included up to v = 4 – 3. This restriction was made to avoid the interactions between the ground and the first excited as well as that between the first and the second excited electronic states. Predictions of v = 0 and 1 data should be affected negligibly by this restriction.
The pure rotational lines for ¹²C¹⁴N were taken from
(1) T. A. Dixon and R. C. Woods, 1977, J. Chem. Phys., 67, 3956 (N" = 0, v = 1); from
(2) D. D. Skatrud, F. C. de Lucia, G. A. Blake, and K. V. L. N. Sastry, 1983, J. Mol. Spectrosc., 99, 35 (N" = 1, 2, v = 0 – 3); from
(3) M. A. Johnson, M. L. Alexander, I. Hertel, and W. C. Lineberger, 1984, Chem. Phys. Lett., 105, 374; (N" = 0, v = 2); from
(4) E. Klisch, T. Klaus, S. P. Belov, G. Winnewisser, and E. Herbst, 1995, Astron. Astrophys., 304, L5; and from
(5) E. Klisch, PhD thesis, Cologne, 1998; (N" = 6 – 8, v = 0 – 2).
Additional v = 0, N" = 0 – 2 data (estimated accuracies mostly 5 – 10 kHz) was kindly provided by
(6) C. A. Gottlieb, 2005, private communication. As these data may be submitted for publication at some later point, this data was not merged.
The pure rotational lines for ¹³C¹⁴N, v = 0 – 3, N" = 0, 1 were taken from
(7) M. Bogey, C. Demuynck, and J. L. Destombes, 1984, Can. J. Phys., 62, 1248; and from
(8) M. Bogey, C. Demuynck, and J. L. Destombes, 1986, Chem. Phys., 102, 141.
Rotational data on ¹²C¹⁵N is available only through interstellar observation reported by
(9) A. H. Saleck, R. Simon, and G. Winnewisser, 1994, Astrophys. J., 436, 176; (v = 0, N" = 0, 1).
Infrared transitions v = 1 – 0 for all four stable isotopic species by
(10) M. Hübner, M. Castillo, P. B. Davies, and J. Röpke, 2005, Spectrochim. Acta, A 61, 57;
as well as v = 2 – 1 to 4 – 3 for ¹²C¹⁴N; reported by
(11) V. Horká, S. Civis, V. Spirko, and K. Kawaguchi, 2004, Collect. Czech. Chem. Commun., 69, 73;
were also used in the fit.
In general, lines deviating from their calculated position by more than 3 times their uncertainties have been omitted from the final fit. It should be noted that the ¹²C¹⁴N, v = 1 – 0 transition frequencies of (10) and (11) differ on the average by 0.0033 cm^–1 — the latter are higher and have been adjusted in the fit. The vibrational energies should be viewed with some caution because of this discrapancy.
Predictions for ¹³C¹⁴N beyond 1 THz should viewed with some caution even though the infrared transitions may cause them to be reliable as far as they have been provided.
NOTE: Because of the large ¹³ hyperfine splitting at low N, the ¹³ nuclear spin angular momentum was coupled to the rotational angular momentum first in Refs (7) and (8), and the electronic spin angular momentum was coupled to the resulting angular momentum subsequently. This coupling order has been reversed in the present calculation for consistency reasons and because this coupling scheme is more appropriate at higher N rotational transitions. As a consequence, the intermediate quantum numbers F₁ and F₂ from Refs. (7) and (8) usually do not agree with the J and F₁ quantum numbers in the present calculation. The values for the first and for the last quantum numbers, N and F, respectively, do agree.
The dipole moment was assumed to be the same as for the main isotopic species, see e026504.cat.
All vibrational states used in the fit have been considered for the calculation of the partition function. Contributions of the individual states are given in parentheses.