The molecule exists in two conformers, the second one being about 1.4 kJ/mol (~170 K) higher in energy. This entry considers only the low energy conformer called A. The transition frequencies were taken from
(1) A. Insausti, E. R. Alonso, L. Kolesniková, A. Belloche, I. León, and S. Mato, 2025, Astrophys. J., 981, Art. No. 64.
Using Watson's S reduction instead of the A reduction, a fit of almost the same quality was achieved with five fewer spectroscopic parameters.
The calculation was truncated at J = 99. The calculation should be sufficiently accurate for observational purposes; caution is advised for transition frequencies with calculated uncertainties exceeding 0.2 MHz.
The ¹⁴N hyperfine splitting may be resolvable in astronomical observations. Therefore, a separate hyperfine calculation is provided up to J = 10 and up to 120 GHz. The partition function takes into account the spin-multiplicity of ¹⁴N.
The dipole moment components were determined by
(2) W. Caminati, R. Meyer, M. Oldani, and F. Scappini, 1985, J. Chem. Phys., 83, 3729.