FTIR Isotopic Study of the $\nu_1$($\sigma$) Stretching Mode of Linear CrC$_3$ Condensed in Solid Ar

Earlier gas phase investigations of chromium-carbon species using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations have shown the existence of both the \textit{C}$_{2v}$ (fan-shaped) and linear isomers of CrC$_3 $.\footnote{H.~-J.~Zhai, L.~-S.~Wang, P.~Jena, G.~L.~ Gustev, and C.~W.~Bauschlicher, Jr., \textit{J. Chem. Phys.} \underline {\textbf{120}}, 8996 (2004).} We report the first results from Fourier transform infrared (FTIR) spectroscopic studies on CrC$_3 $, produced by Nd:YAG laser ablation of carbon and chromium rods and trapping the products in solid Ar at $\sim$10 K.\footnote {S.~A.~Bates, C.~M.~L.~Rittby, and W.~R.~M.~Graham, \textit{J. Chem. Phys.} \underline{\textbf{125}}, 074506 (2006).} Extensive $^{13}$C isotopic shift measurements and predictions from DFT calculations at the B3LYP/6-311G+(3\textit{df}) level show that linear CrC$_3$ is the ground state isomer and enables the assignment of its $\nu_1$($\sigma$) fundamental at 1789.5 cm$^{- 1}$.