The millimeter-wave spectrum and rest frequencies FEF (X(6)Delta(i))

The pure rotational spectrum of the FeF radical (X(6) Delta(i)) has been measured in the laboratory using millimeter/submillimeter direct absorption techniques. FeF was created by the reaction of iron vapor, produced in a high-temperature Broida-type oven, and F-2. Eleven rotational transitions in the frequency range 121-374 GHz were recorded in all six spin-orbit components. Lambda-type doubling was resolved in the Ohm = 3/2, 1/2, and -1/2 sublevels, and hyperfine structure, arising from the fluorine nuclear spin, was observed in all spin-orbit ladders. The data were successfully analyzed using a (6) Delta Hamiltonian and rotational, spin-orbit, spin-spin, lambda-doubling, and hyperfine parameters were determined. The observation of AlF in the circumstellar shell of IRC+10216 suggests that other fluoride molecules such as FeF may be present in this object.