Direct observation of the hyperfine transition of ground-state positronium

T. Yamazaki, A. Miyazaki, T. Suehara, T. Namba, S. Asai, T. Kobayashi, H. Saito, I. Ogawa, T. Idehara, S. Sabchevski

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74 Citations (Scopus)


We report the first direct measurement of the hyperfine transition of the ground state positronium. The hyperfine structure between ortho-positronium and para-positronium is about 203 GHz. We develop a new optical system to accumulate about 10kW power using a gyrotron, a mode converter, and a Fabry-Pérot cavity. The hyperfine transition has been observed with a significance of 5.4 standard deviations. The transition probability is measured to be A=3.1-1.2+1.6×10 -8s -1 for the first time, which is in good agreement with the theoretical value of 3.37×10 -8s -1.

Original languageEnglish
Article number253401
JournalPhysical review letters
Issue number25
Publication statusPublished - Jun 20 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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