Very accurate microwave data were obtained in the course of an observational study by
(1) R. Fuentetaja, C. Cabezas, M. Agúndez, B. Tercero, N. Marcelino, P. de Vicente, and J. Cernicharo, 2026, Astron. Astrophys. 706, Art. No. L10.
The transition frequencies are from astronomical observations of oblate paired R-branch transitions with 15 ≤ J ≤ 24 and J – 5 ≤ K_c ≤ J. Calculated transition frequencies should be reliable for oblate paired R-branch transitions with J – 5 ≤ K_c ≤ J. These are unresolved quartets of lines having the same J and K_c. Calculations of barely resolved quartets may be sufficiently accurate as well, all other transition frequecies should be viewed with great caution. The calculation was truncated at J = 50 and 52 GHz.
The dipole moment components are from a quantum-chemical calculation in (1).