Rotational analysis of the |$3_0^1 $|$31$ band of the |$\tilde A{}^6\Sigma ^ + \leftarrow \tilde X{}^6\Sigma ^ + $|$Ã6Σ+←X̃6Σ+$ system of CrCCH

The spectrum of chromium acetylide, CrCCH, has been investigated in the near-infrared region (10 500–14 500 cm⁻¹) and an intense band system is observed. The |$3_0^1 $|$301$ band of this system has been investigated at high resolution (0.025 cm⁻¹) and this system is identified as the |$\tilde A{}^{\rm 6}{\rm \Sigma }^ + \leftarrow \tilde X{}^{\rm 6}{\rm \Sigma }^ + $|$Ã6Σ+←X̃6Σ+$ system, analogous to the near IR spectra of the CrH, CrF, and CrCl molecules. Among the many unidentified lines, we have assigned 341 lines belonging to 43 of the 54 allowed branches. Using combination differences, the rotational constants of the ground state have been determined. Computational results on the ground state are also reported, along with a comparison to other monoligated monovalent chromium compounds.