Comparisons between thoery and experiment in two electron systems

Abstract

We shall report on several recent measurements of the wavelengths of the 1s2s 3S 1 - 1s2p 3P 0,2 transitions in helium-like ions of nuclear charge Z = 8−26 at several laboratories, including Argonne, Notre Dame, Oxford, Lyon, Berkeley and Lund. The precision of some of these measurements is sufficient to test the QED contributions to these transition energies to a few parts per thousand. Our theoretical understanding of such transitions will also be summarized. We show that a first-order screening correction to the one-electron Lamb shift gives close agreement between theory and all experiments for the two-electron system. It also provides agreement at a similar level of precision with a recent experimental Lamb-shift measurement in one-electron chlorine. We present a calculation of the 1 s2 p 3 P(J = 1−2) fine-structure splitting in helium-like flourine which is in much closer agreement with recent measurements than previous calculations.