The Electronic Spectrum of Jet-Cooled FeC in the Visible Region

Abstract

The iron monocarbide radical (FeC) has been produced by the reaction of laser ablated Fe atoms with CH4, and its laser-induced florescence spectrum has been recorded in the region 15 000 to 23 800 cm−1 at a resolution of 0.04 to 0.06 cm−1 under supersonic jet-cooled conditions. Rotational analyses have been carried out for about 46 vibronic bands. About 35 bands have been observed for the first time, while the other 11 bands were previously recorded at 0.2 cm−1 resolution by Balfour et al. (J. Chem. Phys.103, 4046 (1995)). The classification of the band systems has been made based on the 56Fe12C/56Fe13C isotope shifts, the dispersed fluorescence spectra, and the excited level lifetimes. The energy separation between the Ω=3, 1 spin components of the X3Δi state has been determined to be 719.56 cm−1 with an upper state rotational perturbation. In the visible spectrum, we could characterize five electronic states for which the Hund's case (a) labels are possible, namely, three 3Δ, one 3Π, and one 1Δ state. The 3Δi, state of which the 3Δ3,2,1 substates lie at 20 274, 20 455, and 20 845 cm−1, respectively, has been shown to have very irregular spin–orbit splittings due to the spin–orbit interaction with the nearby 1Δ state.