The Role of Spin–Orbit Coupling in the Double-Ionization Photoelectron Spectra of XCN2+ (X = Cl, Br, and I)

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• 作者：Soumitra Manna ; Sabyashachi Mishra
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：March 10, 2016
• 年：2016
• 卷：120
• 期：9
• 页码：1554-1561
• 全文大小：361K
• ISSN：1520-5215

文摘

The photoelectron spectra of XCN²⁺ (X = Cl, Br, and I) were calculated employing ab initio electronic structure methods with high-level electron correlation and explicit treatment of spin–orbit coupling. Twelve scalar-relativistic excited states of the dicationic systems, calculated from state-averaged CASSCF/MRCI calculations, were used as the electronic basis to evaluate spin–orbit eigenstates. While the spin–orbit effects in ClCN²⁺ are found to be negligible, the electronic spectroscopy of BrCN²⁺ and ICN²⁺ is significantly influenced by interstate spin–orbit coupling. Several electronic degeneracies are lifted, and many unexpected accidental degeneracies occurred due to the spin–orbit coupling. In particular, the spin–orbit interactions between X̃ ³Σ^––b̃ ¹Σ⁺, Ã ³Π–c̃ ¹Π, B̃ ³Δ−ã ¹Δ, and C̃ ³Σ⁺–d̃ ¹Σ^– are found to be strong in BrCN²⁺ and ICN²⁺. By careful analysis of the effect of spin–orbit coupling parameters and the spin–orbit eigenstate composition, an assignment of the hitherto unidentified experimental photoelectron bands of BrCN²⁺ and ICN²⁺ is presented.