Theoretical investigation of the doublet electronic states of Sr35Cl and Sr79Br molecules

Abstract The energies of the lowest-lying doublet electronic states of Sr 35 Cl and Sr 79 Br have been calculated in the representation 2 S + 1 Λ ± (neglecting spin-orbit effects). This is the first time that ab-initio methods (MRCI+Q) based on Complete-Active-Space-Self-Consistent-Field have been employed to determine the first 11 electronic states and the permanent electric dipole moments of these molecules. The transition dipole moments (TDM) between the electronic states have been also calculated. The ground states have 2 Σ + symmetry for both molecules with an internuclear distance R e  = 2.55 A and R e  = 2.74 A for Sr 35 Cl and Sr 79 Br, respectively. Among the 11 lowest doublet electronic states predicted for each molecule, two have not yet been observed experimentally for Sr 35 Cl and five for Sr 79 Br. Potential energy curves (PECs) have been also calculated with equilibrium energies up to 37,000 cm −1 . Spectroscopic constants have been predicted, including the harmonic vibrational wave number ω e , the relative electronic energy T e referred to the ground state, the rotational constant B e , the equilibrium internuclear distance R e and the transition dipole moments calculated at the internuclear distance R e for the ground state. The calculated energies and the spectroscopic constants are in good agreement with the experimental data with a relative error less than 7% for both molecules.