Very accurate millimeter and submillimeter transition frequencies were added with respect to the first entry from Feb. 2006. These were taken from
(1) H. S. P. Müller, A. Maeda, S. Thorwirth, F. Lewen, S. Schlemmer, I. R. Medvedev, M. Winnewisser, F. C. De Lucia, and E. Herbst, 2019, Astron. Astrophys. 621, Art. No. A143.
With respect to the Feb. 2006 entry, transition frequencies were limited to data from
(2) R. D. Brown, P. D. Godfrey, D. McNaughton, and K. Yamanouchi, 1987, Mol. Phys. 62, 1429.
Higher order distortion parameters were estimated based on interpolation between H₂C³⁴S and H₂CS values, as detailed in (1), and were kept fixed in the fit. The components of one transition of (2) were omitted from the final fit because they displayed very large residuals between observed and calculated frequencies. This entry is sufficiently accurate for all astronomical purposes. Transition frequencies with calculated uncertainties exceeding 0.2 MHz should be viewed with caution. The ³³S hyperfine structure will be resolvable for low values of J. As corresponding transition frequencies are distributed over a fairly large region the entry provides predictions with hyperfine structure throughout.
The dipole moment was assumed to agree with that of the main isotopic species, see e046509.cat.
At low temperatures, it may be necessary to discern between ortho-H₂C³³S and para-H₂C³³S. The ortho states are described by K_a odd, the para states by K_a even. The nuclear spin-weights are 3 and 1 for ortho-H₂C³³S and para-H₂C³³S, respectively. The J_KaKc = 1₁₁, F = 0.5 is the lowest ortho state. It is 10.2766 cm^–1 above ground.