The molecule displays internal rotation of the methyl group. The transition frequencies were summarized in
(1) H. S. P. Müller, F. Lewen, J.-C. Guillemin, and S. Schlemmer, 2026, Mol. Phys., submitted.
Besides extensive millimeter and submillimeter data from that work, microwave data up to 34 GHz and J ≤ 4 were taken from
(2) D. R. Lide Jr., and D. E. Mann, 1957, J. Chem. Phys. 27, 874.
The calculation should be sufficient for observational purposes. Transitions with calculated uncertainties exceeding 0.1 MHz should be viewed with caution.
Please note that state number 0 and 1 refer to the A and E symmetry components, respectively. This differs slightly from the standard erham notation.
The partition function refers to the complete ground vibrational state which was evaluated with g_I = 1.
The dipole moment components were determined in (2) with slight adjustment because of the OCS reference value as detailed in (1).