High resolution laser induced fluorescence spectroscopy of the [18.8] ³Φ _i,-X ³Φ _i (0,0) band of cobalt monofluoride

The fine and hyperfine interaction parameters in the [18.8] ³Φ (v=0) and X ³Φ (v=0) states of cobalt monofluoride, CoF, have been determined from an analysis of high-resolution laser induced fluorescence spectra of the [18.8] ³Φ ₃- X ³Φ ₃ and [18.8] ³Φ ₄-X ³O ₄ band systems. The previously reported pure rotational transitions of the X ³Φ ₄(v=0) state [T. Okabayashi and M. Tanimoto, J. Mol. Spectrosc. 221, 149 (2003)] were included in the data set. The hyperfine parameters for ⁵⁹Co (I=7/2) and ¹⁹F (I=1/2) have been interpreted using atomic data together with a proposed molecular orbital description for the [18.8] ³Φ _i and X ³Φ _i states. A comparison of the hyperfine parameters in the X ³Φ state of cobalt monohydride, CoH, with those of the X ³Φ state of CoF reveals that the bonding in the two molecules is significantly different. It is shown that, in a situation where the Ω substates of a multiplet degenerate electronic state are analyzed separately, the Fermi contact parameter b can be determined with fair accuracy from the apparent centrifugal distortion of the hyperfine structure.