Optical spectroscopy of jet-cooled FeC between 12,000 and 18,100 cm(-1)

Iron monocarbide has been investigated between 12 000 and 18 100 cm(-1) in a supersonic expansion by resonant two-photon ionization spectroscopy. Six new electronic states have been identified for which origins relative to the ground stale have been determined. Three of these possess Omega' = 3, one possesses Omega' = 4, and two possess Omega' = 2. The Omega' = 3 state with an origin near 13 168 cm(-1) is likely a (3) Delta(3) state and has been assigned as the analog of the [14.0](2) Sigma(+) <-- X-2 Sigma(+) charge transfer transition in CoC. The Omega' = 4 state is most likely a (3) Phi(4) state. Additionally, seven bands with Omega' = 2 have been observed that have proven impossible to systematically group by electronic state. Because every transition rotationally resolved in this study possesses a lower state with Omega = 3, the ground state has been confirmed as arising from an Omega = 3 state that is most likely the Omega = 3 spin orbit component elf a (3) Delta(i) term derived from a 1 delta(3)9 sigma(1) configuration. The ionization energy (IE) of FeC has been determined as 7.74+/-0.09 eV by varying the wavelength of the ionization photon. When combined with the known IE of Fe and the bond energy of FeC+, the bond energy of FeC is calculated to be 3.9+/-0.3 eV. Presentation of the results is accompanied by an analysis of the bonding in FeC from a molecular orbital standpoint. (C) 1997 American Institute of Physics. [S0021-9606(97)2746-3].