State-to-state photodissociation dynamics of OCS: The S( 3 P) + CO(X 1 Σ + ) Channel

The ultraviolet photolysis of carbonyl sulfide (OCS) has been studied via the time-sliced velocity map imaging at excitation wavelength in range of 212-250 nm.The S( 3 P J=0,1,2 ) + CO(X 1 Σ + ) product channel was investigated from the raw images of S( 3 P J=0,1,2 ) atoms. From the S( 3 P J=0,1,2 ) images, the product total kinetic energy release (TKER) distributions and spatial angular distributions were acquired, respectively.The CO(X 1 Σ + ) product rovibrational state distributions and β values are markedly different for the three spin-orbit states of S( 3 P J=0,1,2 ) and excitation wavelength. Based on the experimental results, we propose two possible dissociation mechanism: the first dissociation route is 1 1 A→2 1 A→1 1 A(bent OCS)→2 3 A, then yields the S( 3 P 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 1 3 A′ electronic state, produces the S( 3 P J=0,1,2 ) atoms in conjunction with the vibrationally hot and rotationally cold CO co-products.