Knowledge Bank

A vibration of the $C6H$ (hexatriynyl) radical has been identified for the first time at $1953.4cm-1$ in the Fourier transform infrared spectrum of the vacuum ultraviolet photolysis products of acetylene and 1,3-butadiene trapped in Ar at 10 K. The spectra for various D and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C$ isotopomers of $C6H$ produced from isotopically substituted precursors have been observed. The complex, overlapping spectra resulting from partial $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C$ substitutions have been fitted using force constant adjustment calculations, and confirm the assignment of the new band as a C=C stretching fundamental of $C6H$, for which a rotational spectrum has been observed in a stellar {atmosphere}$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ and in the {laboratory}$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$.