Dissociation of the OCS{sup +} ion in low-lying electronic states studied using multiconfiguration second-order perturbation theory
- College of Chemistry and Chemical Engineering, Graduate School, Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049 (China)
Complete active space self-consistent-field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with atomic natural orbital basis sets were performed to investigate the S-loss direct dissociation of the 1 {sup 2}{pi}(X {sup 2}{pi}), 2 {sup 2}{pi}(A {sup 2}{pi}), 1 {sup 2}{sigma}{sup +}(B {sup 2}{sigma}{sup +}), 1 {sup 4}{sigma}{sup -}, 1 {sup 2}{sigma}{sup -}, and 1 {sup 2}{delta} states of the OCS{sup +} ion and the predissociations of the 1 {sup 2}{pi}, 2 {sup 2}{pi}, and 1 {sup 2}{sigma}{sup +} states. Our calculations indicate that the S-loss dissociation products of the OCS{sup +} ion in the six states are the ground-state CO molecule plus the S{sup +} ion in different electronic states. The CASPT2//CASSCF potential energy curves were calculated for the S-loss dissociation from the six states. The calculations indicate that the dissociation of the 1 {sup 4}{sigma}{sup -} state leads to the CO+S{sup +} ({sup 4}S{sub u}) products representing the first dissociation limit; the dissociations of the 1 {sup 2}{pi}, 1 {sup 2}{sigma}{sup -}, and 1 {sup 2}{delta} states lead to the CO+S{sup +}({sup 2}D{sub u}) products representing the second dissociation limit; and the dissociations of the 2 {sup 2}{pi} and 1 {sup 2}{sigma}{sup +} states lead to the CO+S{sup +}({sup 2}P{sub u}) products representing the third dissociation limit. Seams of the 1 {sup 2}{pi}-1 {sup 4}{sigma}{sup -}, 2 {sup 2}{pi}-1 {sup 4}{sigma}{sup -}, 2 {sup 2}{pi}-1 {sup 2}{sigma}{sup -}, 2 {sup 2}{pi}-1 {sup 2}{delta}, and 1 {sup 2}{sigma}{sup +}-1 {sup 4}{sigma}{sup -} potential energy surface intersections were calculated at the CASPT2 level, and the minima along the seams were located. The calculations indicate that within the experimental energy range (15.07-16.0 eV) the 2 {sup 2}{pi}(A {sup 2}{pi}) state can be predissociated by 1 {sup 4}{sigma}{sup -} forming the S{sup +}({sup 4}S{sub u}) ion and can undergo internal conversion to 1 {sup 2}{pi} followed by the direct dissociation of 1 {sup 2}{pi} forming S{sup +}({sup 2}D{sub u}) and that within the experimental energy range (16.04-16.54 eV) the 1 {sup 2}{sigma}{sup +}(B {sup 2}{sigma}{sup +}) state can be predissociated by 1 {sup 4}{sigma}{sup -} forming the S{sup +}({sup 4}S{sub u}) ion and can undergo internal conversion to 2 {sup 2}{pi} followed by the predissociation of 2 {sup 2}{pi} by 1 {sup 2}{sigma}{sup -} and 1 {sup 2}{delta} forming the S{sup +}({sup 2}D{sub u}) ion. These indications are in line with the experimental fact that both the {sup 4}S{sub u} and {sup 2}D{sub u} states of the S{sup +} ion can be formed from the 2 {sup 2}{pi} and 1 {sup 2}{sigma}{sup +} states of the OCS{sup +} ion.
- OSTI ID:
- 20864278
- Journal Information:
- Journal of Chemical Physics, Vol. 125, Issue 5; Other Information: DOI: 10.1063/1.2222357; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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