Many-body theory applied to negative ions

The quasiparticle orbital for the valence electron in a negative ion having one electron outside closed shells is determined from the Dyson equation. The authors replace the proper self-energy in the Dyson equation by an approximation derived from second-order many-body perturbation theory. Solving the resulting equation for the 4d 10 5s state of the negative palladium ion they obtain a value of 0.525 eV for the electron affinity, compared with the measured value 0.558+or-0.008 eV; for the 4s 2 4p state of the calcium negative ion the authors obtain an affinity 0.056 eV, compared with the measured value 0.043+or-0.007 eV; for the strontium negative ion the authors predict a 5s 2 5p state having an affinity 0.093 eV; and for the barium negative ion they predict a 6s 2 6p state with affinity 0.192 eV.