Theoretical investigation of the molecular structure and transition dipole moments of the NaK+ low lying electronic states

The electronic structure and the spectroscopic constants of the low lying electronic states of the NaK+ ionic molecule have been determined through using an ab initio approach involving a non-empirical pseudopotential for the Na and K cores and core valence correlation correction. The potential energy of nearly 26 electronic states of 2Σ+, 2Π, and 2Δ symmetries has been calculated up to their dissociation limit Na(4d) + K+ and Na+ + K(6s). Their spectroscopic constants (Re, De, Te, ωe, ωeχe, and Be) are derived and compared with the few available theoretical studies. A good agreement has been found for the ground state and few excited states with previous works. New potential energy curves were presented, for the first time, for the higher excited states. Numerous avoided crossing between electronic states of 2Σ+, 2Π symmetries have been localized and analyzed. Their existences are related to the charge transfer between the two ionic molecules Na+K and NaK+. Furthermore, we have determined the transition dipole moments for several states and analyzed the avoided crossings related to charge transfer between alkaline atoms.