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 state have been determined. Three of these possess Ω′=3, one possesses Ω′=4, and two possess Ω′=2. The Ω′=3 state with an origin near 13 168 cm−1 is likely a Δ33 state and has been assigned as the analog of the [14.0]2Σ+←X2Σ+ charge transfer transition in CoC. The Ω′=4 state is most likely a Φ43 state. Additionally, seven bands with Ω′=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 Ω=3, the ground state has been confirmed as arising from an Ω=3 state that is most likely the Ω=3 spin orbit component of a Δi3 term derived from a 1δ39σ1 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.