Theoretical Study of the Σ+1, 3Σ+, 3Π, 1Π States of NaLi and the Σ+2 State of NaLi+

Ab initio calculations have been performed for the NaLi molecule at a series of internuclear distances. The Hartree–Fock and extended Hartree–Fock optimized valence configuration (OVC) approximations of Das and Wahl are compared for the Σ+1 ground-state potential curve. In each approximation, the NaLi molecule is found to be bound relative to the separated atoms. The OVC wavefunctions are tabulated as a function of internuclear distance and contour diagrams of the total density for the OVC wavefunction and of the difference densities between the ground-state molecular OVC wavefunction and the atomic and molecular Hartree–Fock wavefunctions are given. The OVC calculations are compared with a further approximation in which Φ0 is frozen to be the Hartree–Fock configuration at each internuclear distance. The comparison suggests that a better approximation would be one in which only the core orbitals are frozen at the Hartree–Fock level and all valence and correlating orbitals optimized to self-consistency. In addition, potential curves for the Σ+3, 3Π, and Π1 states of NaLi and the Σ+2 state of NaLi+ have been computed in the Hartree–Fock approximation. Expectation values of various one-electron operators for all states at each internuclear distance and spectroscopic constants obtained by Dunham analysis of all bound-state potential curves are also reported.