Laser-based spectroscopy of FeD: Excitations to the g ⁶Φ electronic state

Bands of the g ⁶Φ-X ⁴Δ, g ⁶Φ-A ⁴Π, g ⁶Φ-a ⁶Δ, and g ⁶Φ-b ⁶Π electronic transitions of iron monodeuteride (FeD) have been measured in laser excitation and in dispersed fluorescence. The molecules were produced both in a cold supersonic molecular jet source and in a chemical reaction between iron pentacarbonyl [Fe(CO₅)] and a microwave discharge of argon and hydrogen gases. Dispersed fluorescence from the latter source was detected at high resolution with a Fourier transform spectrometer, yielding a large number of the transitions observed. The data reveal that FeD experiences strong interstate couplings that compromise fitting of the data with traditional Hamiltonians but that the problem is less severe than in corresponding spectra of FeH. This work greatly expands the available data on FeD, which were previously characterized only through the F ⁴Δ-X ⁴Δ spectrum and pure rotational data in the ground state.