State-to-state Photodissociation Dynamics of Carbonyl Sulfide: S(³P)+CO(X¹Σ⁺) Channel

The ultraviolet photolysis of carbonyl sulfide (OCS) has been studied via the time-sliced velocity map imaging at excitation wavelengths in the range of 212−250 nm. The S(³P_J=0,1,2)+CO(X¹Σ⁺) product channel was investigated from the raw images of S(³P_J=0,1,2) atoms. From the S(³P_J=0,1,2) images, product total kinetic energy release distributions and spatial angular distributions were acquired, respectively. The CO(X¹Σ⁺) product rovibrational state distributions and anisotropy parameters β values are markedly different for the three spin-orbit states of S(³P_J=0,1,2) and excitation wavelength. Based on the experimental results, we propose two possible dissociation mechanisms: the first dissociation route is 1¹A′→2¹A′→1¹A′(bent OCS)→2³A″, which yields the S(³P_J=0,1,2) atoms in association with vibrationally cold but rotationally hot CO co-products. The second dissociation pathway, which corresponds to the excited 1³A′ electronic state, produces S(³P_J=0,1,2) atoms in conjunction with the vibrationally hot and rotationally cold CO co-products.