title: Precision Test of Many-Body QED in the Be+ 2p Fine Structure Doublet Using Short-Lived Isotopes.
abstract: Absolute transition frequencies of the 2s 2S{1/2}→2p2P{1/2,3/2} transitions in Be^{+} were measured for the isotopes ^{7,9-12}Be. The fine structure splitting of the 2p state and its isotope dependence are extracted and compared to results of ab initio calculations using explicitly correlated basis functions, including relativistic and quantum electrodynamics effects at the order of mα(6) and mα(7) ⁢ln α. Accuracy has been improved in both the theory and experiment by 2 orders of magnitude, and good agreement is observed. This represents one of the most accurate tests of quantum electrodynamics for many-electron systems, being insensitive to nuclear uncertainties.
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Nörtershäuser
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany.|Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Geppert
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany.|Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Krieger
authors.affiliation: Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Pachucki
authors.affiliation: Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland.|Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Puchalski
authors.affiliation: Max-Planck-Institut für Kernphysik, D-69117 Heidelberg, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Blaum
authors.affiliation: Instituut voor Kern- en Stralingsfysica, KU Leuven, B-3001 Leuven, Belgium.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Bissell
authors.affiliation: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany.
authors.forename: Nadja
authors.initials: N
authors.lastname: Frömmgen
authors.affiliation: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hammen
authors.affiliation: CERN, Physics Department, CH-1211 Geneva 23, Switzerland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kowalska
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Krämer
authors.affiliation: Max-Planck-Institut für Kernphysik, D-69117 Heidelberg, Germany.
authors.forename: Kim
authors.initials: K
authors.lastname: Kreim
authors.affiliation: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Neugart
authors.affiliation: Instituut voor Kern- en Stralingsfysica, KU Leuven, B-3001 Leuven, Belgium.
authors.forename: Gerda
authors.initials: G
authors.lastname: Neyens
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Sánchez
authors.affiliation: CERN, Physics Department, CH-1211 Geneva 23, Switzerland.
authors.forename: Deyan T
authors.initials: DT
authors.lastname: Yordanov