Observation of a new electronic state of carbon monoxide using LIF on highly vibrationally excited CO(X 1Σ+)

UV laser-induced fluorescence studies of highly nonequilibrium, vibrationally excited CO molecules, have been employed to characterize a previously unobserved electronic state of CO, the D′ 1Σ+ state. Rotational and vibrational constants have been obtained from excitation spectra of several D′ ← X transitions and these constants have been verified from isotopic spectra (13C16O) of the same transitions. The values obtained here for the D′ 1Σ+ state are ωe=651.4±5.7 cm−1 (one σ), ωexe=20.4±2.5 cm−1, Te=89 438.4 cm−1±3.4 cm−1, Be=0.980 48 cm−1, ∝e=0.026 56 cm−1, Re=1.583 Å. The possible interactions of this newly discovered state with the A 1Π and B 1Σ+ states of CO are discussed in the context of the established electronic spectroscopy of CO.