The electronic spectrum of vanadium monoxide across the visible: New bands and new insight.

Resonance enhanced multiphoton ionization spectra of vanadium monoxide (VO) have been measured in the 16 000–23 300 cm^-1 region. A series of intense peaks, identified as the VO C ⁴Σ^- (v^′)-X ⁴Σ^- (v^″=0) progression, has been recorded up to v^′=7 and vibrational and rotational parameters have been extracted by simulation of the rotationally resolved spectra. Additional weak transitions in the spectrum are assigned to the 2 ²Π-X ⁴Σ^- spin-forbidden band system allowing the first direct determination of a spin-orbit coupling constant within the doublet spin manifold of VO. Together, the spectra provide absolute energies for several doublet electronic states with respect to the X ⁴Σ^- ground state. A further vibronic progression observed at 22 000 cm^-1 is assigned as a second spin-forbidden excitation from the X ⁴Σ^- ground state to a ²Π state which has not previously been characterized. [ABSTRACT FROM AUTHOR]