Spin-orbit coupling in the ground and low-lying excited states of HF+ and HF-

Abstract

Electronic structure and spectroscopic properties Be, ωe, ωexe, αe, Te of ground state and the low-lying excited states of HF+ and HF- molecular ions were investigated within scalar relativistic multireference configuration interaction with single and double excitations framework using the GAMESS-US program package. All potential energy curves (PECs) were calculated using the relativistic complete active space self-consistent field/spin-orbit multi-configuration quasi-degenerate perturbation theory (CASSCF/SO-MCQDPT). The curves are all fitted to the analytical potential energy function (APEF), from which accurate spectroscopic constants are derived. The spin-orbit splitting was also been studied, the split value of X\(^{2}{\rm \Pi}\) state of HF+ is determined to be 288.38 cm-1. The calculated properties are in good agreement with the available experimental value. Spectroscopic constants of the ground states of HF- that have never been observed in experiment are obtained. These curves provide an interpretation of the known experimental observations on this system and suggest a number of further experiments which possible provide a critical test of this data.