Very accurate microwave data along with millimeter data were reported by
(1) S. Thorwirth, P. Theulé, C. A. Gottlieb, M. C. McCarthy, and P. Thaddeus, 2021, Astrophys. J. 662, 1309.
Additional microwave data, involving in part much higher J quantum numbers, were reported by
(2) P. Christen, A. Bauder, and H. H. Günthard, 1972, J. Mol. Spectrosc. 43, 1.
Quartic centrifugal distortion parameters were sufficient in the fit.
The calculations are sufficiently accurate for observations in cold and lukewarm sources. Transition frequencies with uncertainties exceeding 0.1 MHz should be viewed with some caution.
The dipole moment was determined by
(3) H. J. Tobler, A. Bauder, and H. H. Günthard, 1965, J. Mol. Spectrosc. 18, 239;
its value was corrected with respect to the OCS value given.