Theoretical study of the spin–orbit coupled molecular states of the Mg–He dimer

Abstract

The primary objective of this study is to conduct precise ab initio calculations of the spin–orbit interaction between Mg and He atoms. Our investigation centers on identifying the first low-lying electronic states of the Mg–He molecule through high-level theoretical methods such as CCSD(T) and RCCSD(T) and SA-CASSCF/MRCI, while also integrating Davidson and BSSE corrections to refine our findings further. Additionally, we employ the state-interacting method to comprehensively account for the influence of spin–orbit coupling (SO) on molecular states. We carefully characterize the potential energy curves (PECs) of these molecular states by deriving crucial spectroscopic parameters including R_e, D_e, B_e and T_e, which are then compared against data from prior studies. Moreover, our analysis extends to evaluating vibrational levels, radiative lifetimes, and transition dipole moments (TDMs), offering a comprehensive understanding of the system's dynamics. Notably, we locate the positions of satellite features within the absorption spectra of brown and white dwarfs. To validate the precision and reliability of our findings, extensive comparisons are made with both theoretical predictions and experimental observations, ensuring robustness and accuracy in our conclusions.