Configuration interaction study on low-lying states of AlCl molecule

High-level ab initio calculations of the Λ-S states for aluminum monoiodide (AlCl) molecule are performed by utilizing the explicitly correlated multireference configuration interaction (MRCI-F12) method. The Davidson correction and scalar relativistic correction are investigated in the calculations. Based on the calculation by the MRCI-F12 method, the spin-orbit coupling (SOC) effect is investigated with the state-interacting technique. The adiabatic potential energy curves (PECs) of the 13 Λ-S states and 24 Ω states are calculated. The spectroscopic constants of bound states are determined, which are in accordance with the results of the available experimental and theoretical studies. Finally, the transition properties of 0⁺(2)-X0⁺, 1(1)-X0⁺, and 1(2)-X0⁺ transitions are predicted, including the transition dipole moments (TDMs), Franck-Condon factors (FCFs), and the spontaneous radiative lifetimes.