First Corrections to Hyperfine Splitting and Lamb Shift Induced by Diagrams with Two External Photons and Second Order Radiative Insertions in the Electron Line

Abstract

Contributions to HFS and to the Lamb shift intervals of order $\alpha^2(Z\alpha)^5$ induced by graphs with two radiative photons inserted in the electron line are considered. It is demonstrated that this last gauge invariant set of diagrams which are capable of producing corrections of considered order consists of nineteen topologically different diagrams. Contributions both to HFS and Lamb shift induced by graphs containing one-loop electron self-energy as a subgraph and also by the graph containing two one-loop vertices are obtained.