SiC₂ is a cyclic molecule with a fairly low barrier to linearity which is probably responsible for the large centrifugal distortion effects, especially in excited vibrational states involving excitation of v₃.
Version 3 substantially revises versions 1 from Aug. 2007 and Jan. 2008 and 2 from Aug. 2010. The parameters have been taken from
(1) H. S. P. Müller, J. Cernicharo, M. Agúndez, L. Decin, P. Encrenaz, J. C. Pearson, D. Teyssier, and L. B. F. M. Waters, 2012, J. Mol. Spectrosc., 271 50.
The observed transitions come from
(2) R. D. Suenram, F. J. Lovas, and K. Matsumura, 1989, Astrophys. J., 342, L103;
and from
(3) C. A. Gottlieb, J. M. Vrtílek, and P. Thaddeus, 1989, Astrophys. J., 343, L29.
The data from (3) display residuals between observed transition frequencies and those calculated from the spectroscopic parameters that frequently exceed the reported uncertainties. In order to account for this, the uncertainties reported in (3) have been multiplied by 1.5 as has been done in the previous entries.
In addition, extensive transition frequencies were taken from astronomical observations described in (1) and from
(4) J. Cernicharo, M. Guélin, and C. Kahane, 2000, Astron. Astrophys. Suppl., 142, 181.
Lines from (1) and (4) have not been merged.
Predictions of transitions with uncertainties larger than 1.0 and 5  MHz should be viewed with some and great caution, respectively. The largest uncertainty displayed is 999.9999 MHz.
The dipole moment was reported in (2).
NOTE: The partition function takes into account the ground vibrational state only. However, contributions of excited vibrational states to the partition function are available. These extend to v₃ =$nbsp;4 since Aug. 2015. For corrections much higher than 200 K, a list of vibrational energies is also available.