SPECTRAL MEASUREMENTS OF FEW-ELECTRON URANIUM IONS PRODUCED AND TRAPPED IN A HIGH-ENERGY ELECTRON-BEAM ION-TRAP

Measurements of 2s(1/2)-2p(3/2) electric dipole and 2p(1/2)-2p(3/2) magnetic dipole and electric quadrupole transitions in U82+ through U89+ have been made with a high-resolutioon crystal spectrometer that recorded the line radiation from stationary ions produced and trapped in a high-energy electron beam ion trap. From the measurements we infer -39.21 +/- 0.23 eV for the QED contribution to the 2s(1/2)-2p(3/2) transition energy of lithiumlike U89+. A comparison between our measurements and various computations illustrates the need for continued improvements in theoretical approaches for calculating the atomic structure of ions with two or more electrons in the L shell.