Energies and QED effects in few-electron atoms and ions

Abstract

QED corrections in few-electron atomic systems can be extracted from measured transition frequencies if the lower order nonrelativistic energies and relativistic corrections can be calculated to sufficient accuracy. This paper will particularly emphasize the region of low nuclear charge Z, where essentially exact results are available for the nonrelativistic energy and lowest-order relativistic corrections of order α2Z4. Helium and He-like ions have been particularly well studied. Spin-dependent corrections of O(α4) and O(α5 ln α) have been calculated, and work on terms of pure O(α5) is in progress. A comparison with experiment at the 1 kHz level of accuracy for the fine structure splittings of the 1s2p3PJ states will yield a significant new measurement of the fine structure constant α. Other comparisons with experiment are presented for the QED shifts in total energies. Recently, important progress has been achieved for lithium and Li-like ions, including the use of isotope shifts to measure the nuclear charge radius of the exotic neutron-rich “halo” nucleus 11Li.