Spectroscopy of CrF: Rotational analysis of theB 6Π–X 6Σ+ bandsystem in the 1.2 μm region

The B  6Π–X  6Σ+ band system of the CrF radical has been recorded in emission with FTS techniques in the region between 6965 and 9240 cm−1, using a resolution of 0.025 cm−1. A rotational analysis including the (0,0), (1,1), (1,0), (0,1) and (1,2) bands of this system has been carried out, and a set of molecular parameters has been derived for the B  6Π state. The present analysis has also resulted in substantially better determined values for the λ and γ parameters of the X  6Σ+ ground state. An improved set of molecular parameters has been derived for the previously analyzed, heavily perturbed A  6Σ+ state. The present analysis gives strong support for the interpretation that the local perturbations in the v=0–3 levels of A  6Σ+ are due to interactions with the vibrational levels v=3–6 of the B  6Π state. Earlier suggestions involving a low‐lying 4Π state as the dominating perturber of the A  6Σ+ state must now be considered as erroneous. A previously suggested interpretation of the 7400 cm−1 band as being possibly due to a quartet transition has also been shown to be in error. The derived first order spin‐orbit parameter value of B  6Π [A=47.0382(18) cm−1] and the equilibrium bond distances of X  6Σ+ [1.7839 A], A  6Σ+ [1.8919 A], and B  6Π [1.8277 A] have been discussed, and it has been proposed that the 9σ (Cr4s–4p ) molecular orbital of CrF is slightly bonding, while 4π (Cr3dπ) is nonbonding and 10σ (Cr3dσ) antibonding.