Hyperfine Interactions

, 239:44 | Cite as

Single-photon laser spectroscopy of cold antiprotonic helium

  • Masaki HoriEmail author
Open Access
Part of the following topical collections:
  1. Proceedings of the 13th International Conference on Low Energy Antiproton Physics (LEAP 2018) Paris, France, 12-16 March 2018


Some laser spectroscopy experiments carried out by the Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA) collaboration to measure the single-photon transition frequencies of antiprotonic helium (\(\overline {p}\text {He}^{+}\equiv \overline {p}+\text {He}^{2+}+e^{-}\)) atoms are reviewed. The \(\overline {p}\text {He}^{+}\) were cooled to temperature T = 1.5–1.7 K by buffer-gas cooling in a cryogenic gas target, thus reducing the thermal Doppler width in the single-photon resonance lines. The antiproton-to-electron mass ratio was determined as \(M_{\overline {p}}/m_{e}= 1836.1526734(15)\) by comparisons with the results of three-body quantum electrodynamics calculations. This agreed with the known proton-to-electron mass ratio.


Antiprotonic helium CPT symmetry Exotic atoms 



Open access funding provided by Max Planck Society. We are deeply indebted to the ASACUSA collaboration and to the CERN PS and AD operation teams. We thank V.I. Korobov. This work was supported by the Max-Planck-Gesellschaft.


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Authors and Affiliations

  1. 1.Max-Planck-Institut für QuantenoptikGarchingGermany

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