Predictions of stable Yb^-in the P^o_1/2state: the importance of spin-orbit coupling

Density functional theory calculations on Yb- using the Hartree-Fock system and the analogous Dirac-Hartree-Fock methods predict that Yb- is stable in the Po1/2 state. The electron affinity obtained after the correlation energy functionals used are calibrated against Ca- and Lu is 21 mHartree (4327 meV). The calculations indicate that the Po3/2 state is unlikely to be bound due to spin-orbit coupling reducing its binding energy.