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The ground state and 23 other low-lying singlet and triplet electronic states of the strontium mono-sulfide molecule SrS, in the 2s+1 Λ ± representation, have been examined by ab initio calculations using the computational chemistry software MOLPRO and the graphical user interface GABEDIT. The potential energy curves, in terms of the internuclear distance R, resulted from the complete active space self-consistent field (CASSCF) and multi-reference doubly and singly configuration interaction (MRDSCI) with Davidson correction (+Q) calculations. The permanent dipole moments (μ) and the spectroscopic constants (T e : the electronic energy with respect to the ground state, ω e : the harmonic frequency, R e : the equilibrium internuclear distance, B e : the rotational constant, D e : the equilibrium dissociation energy) have been investigated. The results of this work are in good agreement with the results available in literature. Moreover, for the first time, it was possible to study 20 new singlet and triplet electronic states of SrS molecule.

Using the graphical user interface GABEDIT and the computational chemistry software MOLPRO, the ab initio calculation method has been applied to explore 25 low-lying singlet and triplet electronic states, including the X1Σ+ ground state, of the calcium sulfide molecule CaS in the 2s+1Λ± representation. The multi-reference configuration interaction with Davidson correction (MRCI+Q) and the complete active space self-consistent field (CASSCF) calculations were performed to obtain the potential energy curves in terms of the internuclear distance R. The permanent dipole moments μe of these low-lying electronic states of CaS have been investigated, in addition to the corresponding spectroscopic constants (including the electronic energy with respect to the ground state Te, the equilibrium internuclear distance Re, the harmonic vibrational frequency ωe, the rotational constant Be, and the equilibrium dissociation energy De). In the present work, 19 new singlet and triplet CaS electronic states were investigated for the first time. In addition, it is noticeable that the current results and those already available in literature are in good agreement.