Low-lying electronic states of aluminum monoiodide

High-level ab initio calculations of aluminum monoiodide (AlI) molecule are performed by utilizing the multi-reference configuration interaction plus Davidson correction (MRCI+Q) method. The core-valence correlation (CV) and spin-orbit coupling (SOC) effect are considered. The adiabatic potential energy curves (PECs) of a total of 13 Λ-S states and 24Ω states are computed. The spectroscopic constants of bound states are determined, which are in accordance with the results of the available experimental and theoretical studies. The interactions between the Λ-S states are analyzed with the aid of the spin-orbit matrix elements. Finally, the transition properties including transition dipole moment (TDM), Frank-Condon factors (FCF) and radiative lifetime are obtained based on the computed PEC. Our study sheds light on the electronic structure and spectroscopy of low-lying electronic states of the AlI molecule.