Theoretical Predictions and Experimental Detection of the SiC Molecule

The 0-0 band of the $d{}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}-b{}_{}{}^1{}_{}{}^{}\Pi$ electronic transition of SiC was detected near 6100 ${\mathrm{cm}}^{-1\mathrm{}}$. The SiC molecule was observed by high-resolution Fourier-transform emission spectroscopy from a composite-wall hollow cathode. Ab initio quantum chemical calculations confirm the identity of the carrier of the spectrum as SiC and the $d{}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}-b{}_{}{}^1{}_{}{}^{}\Pi$ assignment. Combination of the observed $r_0$ for SiC $b{}_{}{}^1{}_{}{}^{}\Pi$ with theoretical shifts in bond lengths from $b{}_{}{}^1{}_{}{}^{}\Pi$ to $X{}_{}{}^3{}_{}{}^{}\Pi$ gives the astrophysically important bond lengths $r_0=1.723\mathrm{}$ Å and $r_e=1.719\mathrm{}$ Å for $X{}_{}{}^3{}_{}{}^{}\Pi$ to an estimated accuracy of 0.001 Å.