Two-Electron Lamb-Shift Calculations on Heliumlike Ions

Abstract

Complete second-order calculations of the two-electron contribution to the ground-state energy of heliumlike ions are presented and compared with recent experimental results. Calculations involve relativistic many-body effects and two-electron Lamb-shift (vacuum-polarization and self-energy) contributions as well as the recently presented nonradiative QED corrections. Agreement between experimental and theoretical results verifies the many-body part of the calculation. The accuracy of the results is not high enough to test the QED part of the calculations, but an improvement by half an order of magnitude would provide an experimental test of the QED effect for heavy ions beyond the first-order Lamb shift.