Abstract
Accurate measurements of different transition frequencies between atomic levels of the electronic and hyperfine structure over time are used to investigate temporal variations of the fine structure constant and the proton-to-electron mass ratio . We measure the frequency of the electric octupole () transition in against two caesium fountain clocks as with an improved fractional uncertainty of . This transition frequency shows a strong sensitivity to changes of . Together with a number of previous and recent measurements of the electric quadrupole transition in and with data from other elements, a least-squares analysis yields and , confirming a previous limit on and providing the most stringent limit on from laboratory experiments.
- Received 16 July 2014
DOI:https://doi.org/10.1103/PhysRevLett.113.210802
© 2014 American Physical Society
Viewpoint
Time Trials for Fundamental Constants
Published 17 November 2014
Single-ion clocks yield new limits on how much the proton-to-electron mass ratio and the fine structure constant change over time.
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