%0 Journal Article
%T Precision Test of Many-Body QED in the Be$^+$ $2p$ Fine Structure Doublet Using Short-Lived Isotopes
%A Wilfried N£¿rtersh£¿user
%A Christopher Geppert
%A Andreas Krieger
%A Krzysztof Pachucki
%A Mariusz Puchalski
%A Klaus Blaum
%A Mark L. Bissell
%A Nadja Fr£¿mmgen
%A Michael Hammen
%A Magdalena Kowalska
%A J£¿rg Kr£¿mer
%A Kim Kreim
%A Rainer Neugart
%A Gerda Neyens
%A Rodolfo S¨¢nchez
%A Deyan T. Yordanov
%J Physics
%D 2015
%I arXiv
%R 10.1103/PhysRevLett.115.033002
%X Absolute transition frequencies of the $2s\; ^2{\rm S}_{1/2} \rightarrow 2p\;^2\mathrm{P}_{1/2,3/2}$ 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 \textit{ab initio} calculations using explicitly correlated basis functions, including relativistic and quantum electrodynamics effects at the order of $m \alpha^6$ and $m \alpha^7 \ln \alpha$. 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.
%U http://arxiv.org/abs/1507.03830v1