Laser-based spectroscopy of iron monohydride (FeH): Transitions involving the I4Φ electronic state.

We have discovered a new electronic state in iron monohydride, which we have assigned as I4Φ. The molecule was created in a chemical reaction between Fe(CO)5 and products from a microwave discharge of Ar + H2. We excited the I4Φ state with laser light of wavelength 507-520 nm, which produced strong red fluorescence to the C4Φ state. The I4Φ state also fluoresces to the A4Π, X4Δ, and a6Δ states and to an unknown set of levels that likely belong to the v = 1 level of the A4Π state, although this assignment is tentative. There is also evidence of a perturbation in the I4Φ state caused by another unknown electronic state.