Theoretical calculations on the NaS and NaS⁺ radicals: electronic structure, spectroscopy and spin-orbit couplings

Abstract

We used an ab initio methodology for the computation of the potential energy curves of the lowest electronic states of NaS and NaS⁺ diatomics. Using these highly correlated wavefunctions, we calculated their spin-orbit couplings. The X²Π and the A²Σ⁺ electronic states of NaS are found to possess deep potential wells. The upper bound electronic states have either shallow potential wells located in the molecular region or potentials of ∼ 1 eV depth located for large NaS distances. For NaS⁺, our calculations reveal the existence of shallow potentials for all states correlating to the four lowest dissociation limits. Using our potentials, we calculated an accurate set of spectroscopic constants for NaS and NaS⁺. Most of the data relative to the electronic excited states represent predictions. The spin-orbit induced predissociation of NaS(A²Σ⁺ is discussed. Finally, our cationic potentials and the NaS(X²Π) potential were used for the prediction of the single ionization spectrum of NaS.