LABORATORY AND ASTRONOMICAL DETECTION OF RHOMBOIDAL $SiC_{3}$

Author Institution: Harvard-Smithsonian Center for AstrophysicsThe rotational spectrum of rhomboidal $SiC_{3}$ in its $^{1}A_{1}$ 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 $SiC_{3}$ has a planar geometry with $C_{2v}$ 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 $SiC_{3}$ near 100 GHz were detected in the circumstellar envelope of the evolved carbon star IRC+10216 using the NRAO 12 meter telescope