THE PURE ROTATIONAL SPECTRUM OF FEC(X(3)DELTA(I))

The pure rotational spectrum of the FeC radical (X(3) Delta(i)) has be en measured in the laboratory for the first time using millimeter/subm illimeter direct absorption techniques. FeC was created by the reactio n of iron vapor, produced in a high-temperature Broida-type oven, and methane gas under DC discharge conditions. Six rotational transitions each were recorded for the two lower spin-orbit ladders of this molecu le in the frequency range 240-484 GHz, as well as six transitions for the Omega = 3 ladder of the iron isotopomer (FeC)-Fe-54. The data were analyzed using a (3) Delta Hamiltonian, and rotational and certain sp in-orbit parameters were determined. The observation of SiC in the cir cumstellar shell of IRC + 10216 suggests that metal carbides such as F eC may be present as well.