Quantum electrodynamical corrections to the fine structure of helium

Order α⁶mc² corrections to the fine structure splitting of the deepest triplet P state (2³P_0,1,2) of the He⁴ atom have been investigated. The investigation is based on the covariant Bethe-Salpeter equation including external potential to take account of the nuclear Coulomb field. All order α⁶mc² corrections which arise from Feynman diagrams involving the exchange of one, two, and three photons, as well as radiative corrections to the electron magnetic moment have been found. The results are presented in a form suitable for computerized numerical evaluation.