Ab initio spectroscopic studies of AlF and AlCl molecules

In this work, we report the results from our spectroscopic study on AlF and AlCl molecules. We carry out detailed electronic structure calculations in both the molecules, including obtaining the potential energy surfaces of the [Formula: see text] ground electronic state and some of the low-lying excited electronic states belonging to [Formula: see text] and [Formula: see text] symmetries. This is followed by evaluating the spectroscopic constants and molecular properties such as electric dipole moments and electric quadrupole moments. Throughout, we employ the multi-reference configuration interaction method and work with high-quality quadruple zeta basis sets. Further, transition dipole moments between the ground electronic state and singlet excited states are also studied. The relevant vibrational parameters are computed by solving the vibrational Schrödinger equation. Subsequently, the vibrational energy spacings and transition dipole moments between the vibrational levels belonging to the same electronic states are used to evaluate the spontaneous and black-body radiation-induced transition rates, followed by computing the lifetimes. Finally, the energy differences between rotational levels belonging to different vibrational levels and within an electronic state as well as the Einstein coefficients are reported.