Theoretical predictions and experimental detection of the SiC molecule.

Abstract

The 0-0 band of the $d^{1}\ensuremath{\Sigma}^{+}\ensuremath{-}b^{1}\ensuremath{\Pi}$ electronic transition of SiC was detected near 6100 ${\mathrm{cm}}^{\ensuremath{-}1}$. 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 $d^{1}\ensuremath{\Sigma}^{+}\ensuremath{-}b^{1}\ensuremath{\Pi}$ assignment. Combination of the observed ${r}_{0}$ for SiC $b^{1}\ensuremath{\Pi}$ with theoretical shifts in bond lengths from $b^{1}\ensuremath{\Pi}$ to $X^{3}\ensuremath{\Pi}$ gives the astrophysically important bond lengths ${r}_{0}=1.723$ \AA{} and ${r}_{e}=1.719$ \AA{} for $X^{3}\ensuremath{\Pi}$ to an estimated accuracy of 0.001 \AA{}.