The molecule tunnels between two equivalent positions. Transitions within the tunneling states obey a- or b-type selection rules while c-type transitions connect the two tunneling states. The experimental data were taken from
(1) S. Mato, J. Cernicharo, I. Le&ocaute;n, B. A. McGuire, and E. R. Alonso, 2025, Astrophys. J. 994, Art.-No. 217.
The calculations should be sufficient for observational astronomy. Transition freqencies with calculated uncertainties larger than 0.1 MHz should be viewed with caution.
¹⁴N hyperfine splitting may matter in astronomical observations. Therefore, a separate hyperfine calculation is provided for J ≤ 20 below 50 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 components were taken from a quantum chemical calculation in (1).