The v₅ = 1 experimental frequencies have been reported by
(1) P. D. Mallinson and R. L. de Zafra, 1978, Mol. Phys. 36, 827; and by
(2) S. Thorwirth, H. S. P. Müller, and G. Winnewisser, 2001, Phys. Chem. Chem. Phys. 3, 1236.
The v₇ = 3 state is about 5.0 cm^–1 lower than v₅ = 1; this energy difference has been derived from values of strongly interacting J communicated by A. Fayt. One set of spectroscopic parameters is compatible with these results, but it has an uncertainty of ±1 in J.
Strong interactions occur between v₅ = 1 and v₇ = 3 for l = 1 / l = 3 near J = 24; for l = 1^f in both states near J = 58; and for l = 1^e near J = 66. The l = 1^e substate is the one occuring generally at lower frequencies. A few J around the strongly interacting levels predictions of transitions within the corresponding substate are not reliable at the moment.
No experimental lines have been reported for v₇ = 3 in the literatur to date. Therefore, spectroscopic parameters for this state have been estimated. Some higher order parameters for v₅ = 1 have been estimated, too. The interaction terms have been taken from the HCC¹³CN species, see (2) and e052526.cat. The present parameter set differs slightly from the one in (2). Because of the limited data set, predictions for v₅ = 1 are reliable up to 300 GHz at most while predictions for v₇ = 3 should be viewed with caution throughout.
The state numbers 0 and 1 designate v₅ = 1 and v₇ = 3, respectively.
The ¹⁴N hyperfine splitting has not been considered in the present entry. Note: The partition function does not include vibrational contributions. However, information on vibrational contributions to the partition function is available.
The dipole moments were assumed to be the same as for the main species, v₅ = 1 / v₇ = 3, see e051508.cat.