The 846 nm A? ???u ? ??? band system of jet-cooled V?

The 846 nm band system of jet-cooled 5?V2 has been recorded using resonant two-photon ionization spectroscopy, and is assigned as the A ? 3?u- +X ??g- band system. Both the ?'= 1u? ?" = 1g and ?'= Ou+ ??? = 0g+ subbands of the O-O band have been rotationally resolved and analyzed. Although the transition could, in principle, correspond to a rr?g ?rru or ?*u ? ?g excitation, it is assigned as a ?*u ? ?g excitation. Either of the other two possibilities makes it difficult to rationalize the small reduction in bond length which accompanies the excitation [re (X 3?g-) = 1.77 ?, r?(A? 3?u-) = 1.756 ?]. In addition, the second order spin-orbit splitting of the ground X 3?g- state is reanalyzed to predict the existence of a ??g+ state, arising from the same s??gd?gdrr4ud??g electronic configuration as the X 3?g- ground state, at an energy about 182 1 cm-? above the ground state. This allows a state previously observed in an electronic resonance Raman effect 1860 cm-? above the ground state to be positively identified as the s??gd??gdrr?ud??g, ??g+ state, which is responsible for the anomalous spin-orbit splitting in the ground X ??g- state. A similar analysis of the spin-orbit splitting of the A? ??u- state, predicts the location of the s??gd??gdrr?ud?g?*u?, ??u+ state at 13 426 cm-? above the V? X ??g-(0g+) ground state.