O‐loss photodissociation of the OCS + ion in the low‐lying electronic states studied using multiconfiguration second‐order perturbation theory

The CASPT2 potential energy curves (PECs) for O‐loss dissociation from the X 2 Π, A 2 Π, B 2 Σ + , C 2 Σ + , 1 4 Σ − , 1 2 Σ − , and 1 4 Π states of the OCS + ion were calculated. The PEC calculations indicate that X 2 Π, 1 4 Σ − , 1 2 Σ − , and 1 4 Π correlate with CS + (X 2 Σ + ) + O( 3 P g ); A 2 Π and B 2 Σ + correlate with CS + (A 2 Π) + O( 3 P g ); and C 2 Σ + probably correlates with CS + (X 2 Σ + ) + O( 1 D g ). The CASSCF minimum energy crossing point (MECP) calculations were performed for the C 2 Σ + /1 4 Σ − , C 2 Σ + /1 4 Π, A 2 Π/1 4 Σ − , A 2 Π/1 2 Σ − , A 2 Π/1 4 Π, and B 2 Σ + /1 2 Σ − state pairs and the spin‐obit couplings were calculated at the located MECPs. A conical intersection point between the B 2 Σ + and C 2 Σ + potential energy surfaces was found at the CASSCF level. Based on our calculations, seven O‐loss predissociation processes of the C 2 Σ + state are suggested and an appearance potential value of 7.13 eV for the CS + + O product group is predicted. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011