Order \alpha^4 R_{\infty} corrections to positronium P levels

Abstract

The order ${\alpha }^4{R}_{\infty }$ corrections to positronium $P$ levels are found. The calculation is reduced to the ordinary perturbation theory for the nonrelativistic Schrödinger equation. The perturbation operators have the Breit-type structure and are obtained by calculating on-mass-shell diagrams. Found energy corrections constitute numerically $\delta E(2^1{P}_1)=0.06$ MHz, $\delta E(2^3{P}_2)=0.08$ MHz, $\delta E(2^3{P}_1)=0.025$ MHz, $\delta E(2^3{P}_2)=-0.58$ MHz.

Comments: LaTeX, 15 pages, BudkerINP-93-80