Electronic spectroscopy and electronic structure of diatomic CrC

Optical spectra of jet-cooled diatomic CrC have been recorded in the near infrared region using resonant two-photon ionization spectroscopy combined with mass-selective detection of the resulting ions. Several weak transitions have been observed, along with one relatively strong band near 842 nm. Rotational resolution and analysis of this band confirms that the ground state is of $Σ3−$ symmetry. Ab initio calculations have been performed that demonstrate that the ground state is highly multiconfigurational in nature, with a leading configuration of $1σ22σ21π41δ2$ for the ten valence electrons. From the rotational analysis of the 842 nm $Σ3−←XΣ3−$ band, the derived spectroscopic constants of the ground and excited states for $C52rC12$ are $B0″=0.65997(49)$⁠, $λ0″=6.74(24)$⁠, $γ0″=−0.066(20)$⁠, $T0=11870.7660(65)$⁠, $B′=0.60829(39)$⁠, $λ′=7.11(24)$⁠, and $γ′=0.144(17)cm−1$⁠. Here and throughout this article, $1σ$ error limits are reported in parentheses. These rotational constants may be inverted to provide the bond lengths in the ground and excited states, $r0″=1.6188(6)Å$ and $r′=1.6861(5)Å$⁠, respectively. Ab initio calculations show that the upper state is the third state of $Σ3−$ symmetry.