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Phase-Variation Ramsey Spectroscopy of the 23S1→23P2 Interval in Positronium

D. M. Newson and D. B. Cassidy

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Phys. Rev. Lett. 136, 033001 – Published 22 January, 2026

DOI: https://doi.org/10.1103/f2m8-5zxj

Abstract

The 2 S31→2 P23 interval (ν2) in positronium has been measured using a phase-variation separated oscillatory fields technique. A beam of positronium atoms in the 2 S13 state was passed through two spatially separated coherent microwave fields tuned close to the ν2 resonance frequency (8626.71±0.08  MHz), and the surviving beam fraction was recorded as a function of the relative phase between the fields. The resonance frequency was obtained from the frequency dependence of the phase of the interference signal without scanning over the full spectral line shape of the transition. We obtain ν2=8626.39±1.17stat±0.80sys  MHz, which is in agreement with QED theory.

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Phys. Rev. Lett. 136, 033001– Published 22 January, 2026
  • Received 7 October 2025
  • Accepted 2 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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