The Spin-orbit Coupling Study Of Diatomic Molecular Ions

Spin-orbit coupling is a kind of relativistic effects, which are basic matter foratom and molecular physics. There is significant important in computing spin-orbitcoupling for comprehending and understanding photochemistry reaction,photosynthesis, activity for photobiology of druggery, and noctilucence and so on.With the development of computer hardware and advancing of model corepotential(MCP), the people are capable of studying accurately relatively thespin-orbit coupling.By using Multi-Configuration Quasi-Degeneate Perturbation Theory(MCQDPT)and Gamess-US procedure under model core potential, The splitting of ground statesfor molecular ions(N₂⁺,P₂⁺,As₂⁺,Sb₂⁺,O₂⁺,S₂⁺,Se₂⁺,Te₂⁺,O₂^-,S₂^-,Se₂^-,Te₂^-, F₂⁺, Vl₂⁺ and Br₂⁺) and carbide (CF and CCl) of the five,six and sevenmain group under the spin-orbit coupling have been studied in the thesis, andcoupling value of these splitting have been obtained. It is found that the couplingsPlitting value increases with the increasing molecular weight. For example,O₂⁺ (194.677cm^-1)＜S₂⁺ (463.990cm^-1)＜Se₂⁺(1524.685cm^-1)＜Te₂⁺ (2524.072cm^-1) inthe same group, and P₂⁺ (208.500cm^-1)＜S₂⁺ (463.990cm^-1)＜Cl₂⁺(665.956cm^-1) in thesame period, respectively. By the comparison of coupling splitting value and experimental results, it isconcluded that this coupling scheme are accurate for the lighter molecules andimprecise for molecular ions (As₂⁺,Sb₂⁺,Se₂⁺,Te₂⁺,Se₂^-,Te₂^-,Br₂⁺) of the fourand five periods. The reason as follows: (1) the (∧,∑) coupling scheme is taken forall molecular ions in this paper, but the (J, J) coupling scheme is exact all the morefor weighter molecular; (2) The error are brought by dissatisfactory MCP parametersand valence basis sets; (3) The error are brought due to have no whole considerScalar relativistic effect (Mass-velocity effect and Darwin effect).Firstly, the equilibrium geometry and ground electronic state for the nonsplittedground state of all molecular ions are obtained from directly optimizing calculationwith MCSCF method. Secondly, potential energy curves for splitting electronic statehave been calculated under spin-orbit coupling with basis set MCP-TZP (two andthree period) or MCP-DZP (four and five period). Finally, based on the generalprinciples of Atomic and Moleular Reaction Statics and Molecular Potential function,we have studied the force constants and spectrum data of the new splitting electricstate under spin-orbit coupling. The Murrell-Sorbie potential energy function andspectrum data of these electronic state for the first time in our calculation, and theyare in agreement with the experiment value.