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.