New Corrections of Order ${\alpha }^6$ to $s$-Levels of Two-Body Systems

Abstract

New corrections to the energy of $S$-levels of positronium of order $m{\alpha }^6$ which are as large as several hundred kilohertz are obtained. A new recoil correction of order $\alpha (Z\alpha {)}^5(m/M)m$ to the Lamb shift in hydrogen is calculated. This correction turns out to be too small from the phenomenological point of view.

Comments: 9 pages, LaTeX, 2 figures; Subtraction procedure is improved in the new version, two of the numerical results have changed