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A: Fachverband Atomphysik
A 25: Posters: Precision spectroscopy of atoms and ions
A 25.10: Poster
Thursday, March 13, 2008, 16:30–18:30, Poster C3
Two-electron QED contributions to the ground state binding energy in He-like Kr ions — •Paul H. Mokler1, José R. Crespo López-Urrutia1, Fred J. Currell2,3, Nobuyuki Nakamura3, Shunsuke Ohtani3, Hiro Tawara1, Joachim Ullrich1, and Hiroyuki Watanabe3 — 1Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany — 2Queen's University, Belfast BT7 1NN, Northern Ireland, U.K. — 3University of Electro-Communications, Chofu, Tokyo 182-0021, Japan
The two-electron QED contributions to the ground state binding energy of He-like Kr(34+) ions has been determined in two independent experiments performed with electron beam ion traps (EBIT) in Heidelberg (HD) and Tokyo (BT, Belfast-Tokyo collaboration). X-rays arising from radiative recombination (RR) of free electrons to the ground state of initially bare Kr(36+) and hydrogen-like Kr(35+) ions were observed as a function of the interacting electron energy. The K edge absorption by thin Eu and W foils provided fixed photon energy references used to measure the difference in binding energy, ΔE-2e, between the H- and He-like Kr ions (35+ and 34+, respectively). The two independent measurements agree well, yielding a final result of ΔE-2e = 641.8 (+/-1.7) eV. This value confirms recent theoretical results totally based on rigorous QED calculations. Its accuracy is just of the order required to access screened radiative QED contributions.