2Σ+ and 2Π states of LiF−

Large and diffuse molecular orbital basis sets have been used to study the electronic states of LiF− arising from the Li+F− asymptotes. The 2Σ+ ground state is bound relative to LiF(X 1Σ+) by 0.33 eV, in agreement with previous calculations. The excited 2Σ+ and 2Π states, which arise from the Li(2P)+F−(1S) asymptote, also remain bound relative to the ground state of LiF as the internuclear distance decreases from 20 to 5a0; however, the corresponding 6σ and 2π orbitals change drastically from a 2p orbital localized on the Li atom to very diffuse ’’dipole’’ states. At R = 2.988a0, the 2 2Σ+ state of LiF− has a binding energy of at least 4.2 meV relative to the neutral molecule. We found no evidence of shape resonances in the electron-scattering continuum of LiF(X 1Σ+), in contrast to previous results obtained with limited basis sets.