Rotational transition frequencies are from
(1) W. H. Kirchhoff, 1968, J. Am. Chem. Soc. 91, 2437;
and from
(2) A. dal Borgo, G. di Lonardo, F. Scappini, and A. Trombetti, 1979, Chem. Phys. Lett. 63, 115.
¹⁴N quadrupole parameters were derived from two very accurate MW transitions reported by
(3) N. Heineking and M. C. L. Gerry, 1993, J. Mol. Spectrosc. 158, 62.
Ground state combination differences were derived from
(4) L. Puskar, E. G. Robertson, and D. McNaughton, 2006, J. Mol. Spectrosc. 240, 244.
We are grateful to the last two authors for communicating the GSCDs. Nuclear spin-rotation parameters were kept fixed to values from a quantum-chemical calculation by
(5) H. S. P. Müller, 2023, unpublished.
The calculated spectrum was truncated at J = 40 and at 400 GHz. Nevertheless, it is accurate enough for searches in cold environments and may be sufficient for searchesd in luke-warm sources. Frequencies with calculated uncertainties exceeding 0.2 MHz should be viewed with caution.
¹⁴N hyperfine splitting may matter in astronomical observations. Therefore, a separate hyperfine calculation is provided for J ≤ 10 below 200 GHz and with somewhat lowered intensity cut-offs. NOTE: The partition function takes into account the spin multiplicity of the ¹⁴N nucleus !
The dipole moment was determined accurately in (1).