Knowledge Bank

The rotational spectrum of rhomboidal $SiC3$ in its $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A1$ electronic ground state was measured in a laboratory discharge of silane and acetylene by Fourier transform microwave spectroscopy and direct absorption millimeter wave spectroscopy. A full structure derived from observations of isotopically substituted species shows that $SiC3$ has a planar geometry with $C2v$ symmetry that consists of atoms in the shape of a distorted four-member ring and a transannular carbon-carbon bond. Following the laboratory detection, seven rotational transitions of $SiC3$ near 100 GHz were detected in the circumstellar envelope of the evolved carbon star IRC+10216 using the NRAO 12 meter telescope.