Spectroscopic parameters for silacyclopropynylidene, SiC$_2$, from   extensive astronomical observations toward CW Leo (IRC +10216) with the   Herschel satellite
  A molecular line survey has been carried out toward the carbon-rich asymptotic giant branch star CW Leo employing the HIFI instrument on board of the Herschel satellite. Numerous features from 480 GHz to beyond 1100 GHz could be assigned unambiguously to the fairly floppy SiC$_2$ molecule. However, predictions from laboratory data exhibited large deviations from the observed frequencies even after some lower frequency data from this survey were incorporated into a fit. Therefore, we present a combined fit of all available laboratory data together with data from radio-astronomical observations. 
H. S. P. M\"uller, J. Cernicharo, M. Ag\'undez, L. Decin, P. Encrenaz,   J. C. Pearson, D. Teyssier, L. B. F. M. Waters
astro-ph.GA physics.atm-clus