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 ${}^1{\Sigma }^{+}$ 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 ${\Phi }_0$ 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 ${}^3{\Sigma }^{+}{,}^3\Pi$ , and ${}^1\Pi$ states of NaLi and the ${}^2{\Sigma }^{+}$ 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.