Extensive ab initio calculation on low-lying excited states of SiN⁺ cation including spin-orbit coupling

Abstract

Electronic structures and transition properties of the SiN⁺ molecule are investigated by performing ab initio calculations based on scalar relativistic multireference configuration interaction (MRCI) method plus Davidson correction (+Q). The potential energy curves (PECs) for the 22 Λ-S electronic states of the SiN⁺ are obtained. The spectroscopic constants of the bound states are determined, where good agreements with the available spectroscopic data are achieved. Spin-orbit coupling (SOC) effect is introduced via the state interaction approach with the full Breit-Pauli Hamiltonian operator for the state X³ Σ ⁻, a ³ Π, ⁵ Σ ⁻ and ⁵ Π. This is the first time that SOC calculation has been carried out on the SiN⁺. The four states split into 15 Ω states after the consideration of the SOC effect. The SOC effect, leading to some avoided crossings, is found to be substantial for the SiN⁺. Moreover, the transition dipole moments (TDMs) and Franck-Condon factors are derived. Finally, the corresponding radiative lifetimes of the a ³ Π ₁ state are evaluated.

Graphical abstract