The rotational spectrum was recorded and analyzed up to 660 GHz by
(1) L. H. Coudert, L. Margulès, T. R. Huet, R. A. Motiyenko, H. Møllendal, and J.-C. Guillemin, 2012, Astron. Astrophys. 543, Art. No. A46.
The H atom of the methyl group can occupy two different positions, out of plane and in plane. The out of plane position is doubly degenerate, and tunneling leads to a symmetric and an antisymmetric tunneling component. These are indicated by state numbers 0 and 1, respectively; 2 indicates the in plane position. Very weak c-type transitions connect the two tunneling states.
The catalog entry corresponds to the one provided in (1). The calculations should be sufficiently accurate for all observational purposes. Transitions with calculated uncertainties exceeding 0.1 MHz should be viewed with some caution.
The partition function from (1) refers to the ground vibrational state with J up to 60.
The dipole moment components were derived from the main species in (1).