The line list was extended with respect to the first entry of June 2002 as descibed in
(1) H. S. P. Müller, A. Maeda, F. Lewen, S. Schlemmer, I. R. Medvedev, and E. Herbst, 2023, Mol. Phys., in press.
Extensive transition frequencies from the upper millimeter to the lower submillimeter region were taken from that work. Further, mostly millimeter data are from
(2) M. Winnewisser and E. Schäfer, 1980, Z. Naturforsch. 35a, 483.
J = 3 – 2 transitions are from
(3) K. Georgiou, H. W. Kroto, and B. M. Landsberg, 1979, J. Mol. Spectrosc. 77, 365.
K_a = 1 Q-branch transitions were taken from
(4) B. Bak, O. J. Nielsen, H. Svanholt, A. Holm, N. H. Toubro, A. Krantz, and J. Laureni, 1979, Acta Chem. Scand. A 33, 161.
Some higher order centrifugal distortion constants were kept fixed to values from
(5) D. McNaughton, E. G. Robertson, and L. D. Hatherley, 1996, J. Mol. Spectrosc. 175, 377.
Even though K_a = 7 lines are in the fit, their calculated positions at higher J should be viewed with some caution because of probable interaction with K_a = 4 of v₉ = 1. Transitions with even higher values of K_a are probably unreliable. Moreover, calculations above 800 GHz should also be viewed with some caution.
At low temperatures, it may be necessary to discern between ortho-H₂C₂S and para-H₂C₂S. 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-H₂C₂S and para-H₂C₂S, respectively. The J_KaKc = 1₁₁ level is the lowest ortho level. It is 9.7413 cm^–1 above ground.
The experimental dipole moment is from (2).