The astronomical lines have been reported by
(1) J. R. Pardo, C. Cabezas, J. P. Fonfría, M. Agúndez, F. Tercero, P. de Vincente, M. Guélin, and J. Cernicharo, 2021, Astron. Astrophys. 652, Art. No. L13.
The transition frequencies and their uncertainties were communicated by J. Cernicharo; the frequencies differ slightly from those in the letter. He performed an additional fit with D fixed to a value from a quantum-chemical calculation. Four lines displayed rather large residuals; these lines were omitted in the present fit. The finally applied uncertainties are close to those derived from standard errors, half those communicated. Although D was still determined with large uncertainty, it was kept floated. This produces more realistic uncertainties of the calculated transition frequencies. Hyperfine splitting due to the ¹H nucleus may be resolvable for low N transitions. Calculations at lower frequencies should therefore be viewed with caution. The calculations may be quite reliable up to about 50 GHz.
The dipole moment was taken from an ab initio calculation in (1).