Photodissociation study of CO 2 on the formation of state-correlated CO(X 1 Σ + , v) with O( 3 P 2 ) photoproducts in the low energy band centered at 148 nm

The spin-forbidden O( P ) + CO(X Σ , v) channel formed from the photodissociation of CO in the low energy band centered at 148 nm is investigated by using the time-sliced velocity-mapped ion imaging technique. The vibrational-resolved images of the O( P ) photoproducts measured in the photolysis wavelength range of 144.62-150.45 nm are analyzed to give the total kinetic energy releases (TKER) spectra, CO(X Σ ) vibrational state distributions, and anisotropy parameters (β). The TKER spectra reveal the formation of correlated CO(X Σ ) with well resolved v = 0-10 (or 11) vibrational bands. Several high vibrational bands that were observed in the low TKER region for each studied photolysis wavelength exhibit a bimodal structure. The CO(X Σ , v) vibrational distributions all present inverted characteristics, and the most populated vibrational state changes from a low vibrational state to a relatively higher vibrational state with a change in the photolysis wavelength from 150.45 to 144.62 nm. However, the vibrational-state specific β-values for different photolysis wavelengths present a similar variation trend. The measured β-values show a significant bulge at the higher vibrational levels, in addition to the overall slow decreasing trend. The observed bimodal structures with mutational β-values for the high vibrational excited state CO( Σ ) photoproducts suggest the existence of more than one nonadiabatic pathway with different anisotropies in the formation of O( P ) + CO(X Σ , v) photoproducts across the low energy band.