The spectrum of an octahedral molecule in a degenerate electronic state: The ν6 fundamental band of jet-cooled V(CO)6

The jet-cooled FTIR spectrum of the ν6 fundamental band (C–O stretch) of vanadium hexacarbonyl, V(CO)6, is studied for the first time. The spectrum shows a very unusual structure consisting of three well-defined broad subbands, without the usual PQR structure. V(CO)6 being an open-shell system this is attributed to a dynamical F2g⊗F1u Jahn–Teller coupling which considerably complicates the analysis. A new theoretical model based on group theory and tensorial algebraic techniques is developed in this paper for the very first attempt to analyze such a rovibronic spectrum. The assumption of a negligible spin–orbit coupling is validated by the overall agreement between predicted and observed band profiles. The rovibronic Hamiltonian and dipole moment operators have been expanded in order to enable a simultaneous treatment of the four vibronic sublevels. We were able to satisfactorily reproduce the band profile and thus to give the first estimation of some rovibronic parameters for this molecule.