Precise Determination of the2s1/2−2p1/2Splitting in Very Heavy Lithiumlike Ions Utilizing Dielectronic Recombination

Abstract

The 2s(1/2)-2p(1/2) energy splittings DeltaE(L) of the lithiumlike ions 19779Au76+, 20882Pb79+, and 23892U89+ have been measured at the Experimental Storage Ring, utilizing low energy dielectronic recombination. The resonance energies in total 41 different 1s(2) 2p(1/2)nl(j(')) (n > or =20) autoionizing Rydberg states populated in the dielectronic capture process have been determined. The 2s(1/2)-->2p(1/2) excitation energies have been obtained by extrapolation of these resonance energies to the associated series limits n--> infinity. The combined analysis of the experimental data for all three ions yields DeltaE(L)=216.134(96) eV for Au76+, 230.650(81) eV for Pb79+, and 280.516(99) eV for U89+.

Nuclear-resonant electron scattering

“…For a number of heavy nuclei, the IC rates for low-lying first excited levels are substantially higher than the radiative decay rates, with the immediate consequence that NRES cross sections and resonance strengths are larger than the corresponding values for NEEC followed by the radiative decay of the nucleus. Furthermore, in storage ring experiments aiming at the observation of NEEC by detecting the recombined ions (as in the case of, e.g., dielectronic recombination experiments [36,37]) both nuclear decay channels should be taken into account. The interest for electron scattering and recombination experiments at the present and future storage ring facilities of the GSI Darmstadt [38,39] makes nuclear-resonant electron scattering in heavy highly charged ions an important issue for the experimental observation of NEEC.…”

Nuclear effects in atomic transitions

“…In a storage ring recombination setup, the free electrons for DR are provided by a co-propagating electron target or by the electron cooler used to cool the ion beam. Particularly at very low ion-electron collision energies, storage ring experiments have enabled precise determination of Lamb shifts in several highly charged ions [48]. In order to determine very precise isotope shifts, DR of an electron with very small kinetic energy, preferably less than 10 eV, is required.…”

Testing high-Z QED with SuperEBIT: An estimate of the two-loop Lamb shift based on a measurement of the – transition in

“…Our measurement was carried out on the Livermore SuperEBIT electron beam ion trap, and an accuracy of 0.015 eV was achieved. This represents almost a factor of seven improvement over the accuracy achieved by Schweppe et al (1991), who achieved an accuracy of 0.10 eV, and recently by Brandau et al (2003), who achieved an accuracy of 0.099 eV. Unlike the earlier, accelerator-based measurements, our measurement employed passive emission spectroscopy.…”