State-to-state photodissociation dynamics of CO around 108 nm: the O(S) atom channel

State-to-state photodissociation of carbon dioxide (CO 2 ) via the 3p 1 Π u Rydberg state was investigated by the time-sliced velocity map ion imaging technique (TSVMI) using a tunable vacuum ultraviolet free electron laser (VUV FEL) source. Raw images of the O( 1 S) products resulting from the O( 1 S) + CO(X 1 Σ + ) channel were acquired at the photolysis wavelengths between 107.37 and 108.84 nm. From the vibrational resolved O( 1 S) images, the product total kinetic energy releases and the vibrational state distributions of the CO(X 1 Σ + ) co-products were obtained, respectively. It is found that vibrationally excited CO co-products populate at as high as v = 6 or 7 while peaking at v = 1 and v = 4, and most of the individual vibrational peaks present a bimodal rotational structure. Furthermore, the angular distributions at all studied photolysis wavelengths have also been determined. The associated vibrational-state specific anisotropy parameters ( β ) exhibit a photolysis wavelength-dependent feature, in which the β -values observed at 108.01 nm and 108.27 nm are more positive than those at 107.37 nm and 107.52 nm, while the β -values have almost isotropic behaviour at 108.84 nm. These experimental results indicate that the initially prepared CO 2 molecules around 108 nm should decay to the 4 1 A′ state via non-adiabatic coupling, and dissociate in the 4 1 A′ state to produce O( 1 S) + CO(X 1 Σ + ) products with different dissociation time scales. We report here the state-to-state photodissociation dynamical characteristics of the O( 1 S) + CO(X 1 Σ + ) channel at a series of photolysis wavelengths from 107.37 to 108.84 nm.