A millimeter/sub-millimeter-wave spectroscopic study of the FeCl radical (X ⁶Δ_i)

Pure rotational spectroscopy of the FeCl radical (X ⁶Δ_i) has been carried out using millimeter/sub-millimeter direct absorption techniques. The species was created by the reaction of chlorine with iron vapor. All six spin - orbit components were observed in the majority of the twenty-one rotational transitions recorded. Chlorine hyperfine structure was resolved in the Ω = 9/2 and 7/2 components, and lambda-type doubling observed in the Ω = 3/2, 1/2, and - 1/2 ladders. The data were analyzed with a ⁶Δ Hamiltonian, and rotational, fine structure, lambda-doubling, and hyperfine parameters determined. The hyperfine and lambda-doubling interactions in FeCl appear to be different from those in the FeF radical.