QED corrections to singlet levels of the helium atom:: A complete set of effective operators to mα6 -: art. no. 062104

Using singlet S states of the helium atom as an example, precise calculation of energy levels in few-electron atoms is described. In particular, a complete set of effective operators is derived, which generates O(m alpha (6)) relativistic and radiative corrections to the Schrodinger energy. Average values of these operators can be calculated using a variational Schrodinger wave function.