Ab initio calculation on the low-lying excited states of [formula omitted] cation including spin–orbit coupling

Abstract

Ab initio all-electron relativistic calculations of the low-lying excited states of Si2+ have been performed at MRCI+Q/AVQZ level. The calculated electronic states, including 12 doublet and 12 quartet Λ–S states, are correlated to the dissociation limit of Si(3Pg)+Si+(2Pu). Spin–orbit interaction is taken into account via the state interaction approach with the full Breit-Pauli Hamiltonian, which causes the entire 24 Λ–S states to split into 54Ω states. This is the first time that spin–orbit coupling (SOC) calculation has been performed on Si2+. The obtained potential energy curves (PECs) of Λ–S and Ω states are respectively depicted with the aid of the avoided crossing rule between the same symmetry. The spectroscopic constants of the bound Λ–S and Ω states are determined, and excellent agreements with the latest theoretical results are achieved.