The rotational transition frequencies were mostly taken from
(1) L. Kolesniková, J. L. Alonso, C. Bermúdez, E. R. Alonso, B. Tercero, J. Cernicharo, and J.-C. Guillemin, 2016, Astron. Astrophys. 591, Art. No. A75.
Four hyperfine-free microwave transition frequencies were taken from
(2) M. Y. Fong, L. J. Johnson, and M. D. Harmony, 1974, J. Mol. Spectrosc. 53, 45.
The parameter set differs slightly from that in (1). The uncertainties from that work were slightly conservative and were adjusted. The experimental lines were not merged, but the can be inspected in the archive directory. Please note that erham sometimes mislabels transitions. Hyperfine structure splitting is not provided. It is likely very small except for some transitions having very small quantum numbers. The molecules displays commonly splitting caused by methyl internal rotation; state number 0 signals the A symmetry component, 1 the E symmetry component. Calculations with uncertainties exceeding 0.3 MHz should be viewed with substantial caution.
The dipole moment components were derived from a quantum-chemical calcultion by
(3) H. S. P. Müller, 2020, unpublished.