SiC₂ is a cyclic molecule with a fairly low barrier to linearity which is probably responsible for the large centrifugal distortion effects.
Transition frequencies from laboratory measurements and radioastronomical observations have been reported in
(1) J. Cernicharo, M. Guélin, C. Kahane, M. Bogey, C. Demuynck, and J. L. Destombes, 1991, Astron. Astrophys., 246, 213.
Additional rest frequencies from radioastronomical observations come from
(2) J. H. He, D.-V. Trung, S. Kwok, H. S. P. Müller, T. Hasegawa, T. C. Peng, and Y. C. Huang, 2008, Astrophys. J. Suppl. Ser., 177, 275.
With respect to the Aug. 2007 entry, a different parameter set was taken from the main isotopic species as starting point, see e052527.cat. This turned out to yield a better fit for the ¹³C species. The version number has been retained.
The radioastronomical lines have not been merged.
Since the data set is fairly small predictions with uncertainties larger than 1.0 MHz should be viewed with caution.
The dipole moment was assumed to agree with that of the main isotopic species, see e052527.cat.