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    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/25467

    Title: Ab initio study of spin-forbidden unimolecular decomposition of carbon dioxide
    Authors: 黃德彥;Hwang, Der-yan;Mebel, Alexander A. M.
    Contributors: 淡江大學化學學系
    Date: 2000-06-01
    Issue Date: 2009-12-01
    Publisher: Elsevier
    Abstract: The results of ab initio G2(MP2), QCISD(T)/6-311+G(3df) and full valence active space CASSCF(16,12)/6-311+G(3df) calculations of the stationary points on the lowest singlet and triplet potential energy surfaces of carbon dioxide and their intersystem crossing show that spin-forbidden unimolecular decomposition of CO2 can proceed by two different mechanisms. The non-collinear channel goes through a C2v-symmetric minimum energy crossing point MSX1 in the vicinity of the bent local minimum 4 in the triplet state. Once on the triplet surface, the molecule has to overcome the barrier of 131.3 kcal/mol at transition state TS3 before yielding the products, Full-size image (<1 K). The collinear channel directly leads from CO21 to the products via linear MSX2. The barrier at MSX2, estimated as ∼135 kcal/mol, is higher than that for the non-collinear channel, but the probability of intersystem crossing for the collinear mechanism is expected to be higher than for the non-collinear channel, since the spin–orbit coupling value for MSX2 (Full-size image (<1 K)) is much higher than that for MSX1 (Full-size image (<1 K)). The two mechanisms of unimolecular decomposition of CO2 are expected to compete with each other and exhibit different mode-specific dynamics. Spin-forbidden fragmentation of CO2 is compared with the fragmentation of the isoelectronic N2O molecule. The mechanisms for the reverse Full-size image (<1 K) and Full-size image (<1 K) reactions are also discussed.
    Relation: Chemical physics 256(2), pp.169-176
    DOI: 10.1016/S0301-0104(00)00108-7
    Appears in Collections:[化學學系暨研究所] 期刊論文

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