A Rotational and Hyperfine Analysis of the [14.0]2Σ+–X2Σ+Band System of Cobalt Monocarbide

Abstract

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 withTrot∼ 30 K. Low resolution laser-induced fluorescence studies showed the [14.0]2Σ+–X2Σ+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. TheX2Σ+state is best described by a Hund's case (bβS) coupling scheme, while the [14.0]2Σ+state conforms to case (bβJ). Analysis of the hyperfine parameters indicates that theX2Σ+state arises from a valence (8σ)2(3π)4(1δ)4(9σ)1electronic configuration and that the [14.0]2Σ+state originates from a (8σ)1(3π)4(1δ)4(9σ)2configuration. The vibrational levels of the [14.0]2Σ+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]2Σ+state, and effects are also observed on the Fermi contact and electric quadrupolar parameters.