Application of the Quadratic Response Theory to the Screening of a Positron in an Electron Gas of Metallic Density

The screened Coulomb potential following from the quadratic response theory is modified and applied to the Kahana equation for a positron in an electron gas. Electron—electron correlations are taken into account in a local way, proposed by Shaw. For the first time within this formalism no divergence of the total annihilation rates occurs in the low density region. Self‐consistency, according to the total screening charge around the positron, is approached. The momentum dependent enhancement factors are found to be in good agreement with the experimental data.