EGAS41 - Swansea University

41 st EGAS CP 72 Gdańsk 2009
Precision spectroscopy on a fast lithium ion beam for a time
dilation test
Ch. Novotny 1,∗ , D. Bing 3 , B. Botermann 1 , C. Geppert 1,4 , G. Gwinner 5 , T.W. Hänsch 2 ,
R. Holzwarth 2 , G. Huber 1 , S. Karpuk 1 , T. Kühl 4 , W. Nörtershäuser 1,4 , S. Reinhardt 2 ,
G. Saathoff 2 , D. Schwalm 3 , T. Stöhlker 4 , T. Udem 2 , A. Wolf 3
1 Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
2 Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany
3 Max-Planck-Institut für Kernphysik, D-69029 Heidelberg, Germany
4 GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany
5 University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
∗ Corresponding author: christian.novotny@uni-mainz.de
In Ives-Stilwell-type experiments, fast atomic ions containing a well-known transition are
used as moving clocks, and time dilation as well as the velocity are derived from the
simultaneous laser-spectroscopic measurements of the Doppler shifts with and against the
direction of motion. In order to accurately measure these Doppler shifts, the Doppler
broadening caused by the ions’ velocity distribution needs to be overcome. We performed
laser spectroscopy on 7 Li + ions in the 2s 3 S 1 metastable ground state at the GSI in Darmstadt.
The ions were stored in the Experimental Storage Ring (ESR) at a velocity of
0.338c, and optical-optical double resonance spectroscopy on a closed Λ-type three-level
system was performed with two laser beams propagating parallel and antiparallel, respectively,
to the ions. The used laser setup (shown in Fig. 1 left) allows for a frequency
accuracy of ∆ν/ν < 10 −9 by stabilizing the lasers to atomic and molecular references.
Analyzing the emerging fluorescence signal (Fig. 1 right) and taking all statistic and
systematic uncertainties into account, the current experiment sets an upper bound on
hypothetical deviations from the predictions of special relativity of the order 7 × 10 −8 ,
which is comparable to the so far leading experiment [1], but an improvement of this limit
by an order of magnitude seems to be feasible in future measurements.
Figure 1: Left: Experimental setup (PI: proportional-integral controller, PM: photomultiplier,
SHG: second harmonic generator, rf: radio-frequency source, FPI: Fabry-Perot interferometer).
Right: Example signal from optical-optical Λ-type spectroscopy.
References
[1] S. Reinhardt, et al., Nature Physics 3, 861-864 (2007)
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