A rotational and hyperfine analysis of the [14.0](2)Sigma(+)-X(2)Sigma(+) band system of cobalt monocarbide

The cobalt monocarbide molecule has been produced by laser ablation of a cobalt rod in the presence of 1.5% methanol in a helium carrier gas. The mixture was expanded into a vacuum, yielding a free jet with T-rot similar to 30 K. Low resolution laser-induced fluorescence studies showed the [14.0](2) Sigma(+) - X(2) Sigma(+) band system as a long vibrational progression between 500 and 720 nm. Several vibrational bands were analyzed at high resolution; least squares fitting of the data led to the determination of rotational and hyperfine constants for both states. The X(2) Sigma(+) state is best described by a Hund's case (b(beta S)) coupling scheme, while the [14.0](2) Sigma(+) state conforms to case (b(beta J)). Analysis of the hyperfine parameters indicates that the X(2) Sigma(+) state arises from a valence (8 sigma)(2)(3 pi)(4)(1 delta)(4)(9 sigma)(1) electronic configuration and that the [14.0](2) Sigma(+) state originates from a (8 sigma)(1)(3 pi)(4)(1 delta)(4)(9 sigma)(2) configuration. The vibrational levels of the [14.0](2) Sigma(+) state appear to be perturbed by other nearby states; this is reflected in unusual distortions in the spin-rotation parameters from one vibrational level to the next. The effects of the perturbations are also observed in the sign and magnitude of the hyperfine dipolar interaction parameters of the [14.0](2) Sigma(+) state, and effects are also observed on the Fermi contact and electric quadrupolar parameters. (C) 1997 Academic Press, Inc.