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Updated: Aug 1, 2025

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
Update of Muonium 1S-2S transition frequency
Irene Cortinovis1, Ben Ohayon1, Lucas de Sousa Borges1
1Institute for Particle Physics and Astrophysics, ETH, 8093 Zurich, Switzerland.
Abstract:
We present an updated value of the Muonium 1S-2S transition frequency, highlighting contributions from different QED corrections as well as the large uncertainty in the Dirac contribution, stemming from the uncertainty of the electron to muon mass ratio. Improving the measurement of this spectral line would allow to extract a more accurate determination of fundamental constants, such as the electron to muon mass ratio or, combined with the Muonium hyperfine splitting, an independent value of the Rydberg constant. Furthermore, we report on the current status of the Mu-MASS experiment, which aims at measuring the Muonium 1S-2S transition frequency at a uncertainty level.
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