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Positronium fine-structure spectroscopy and diagnosis of asymmetric resonance lines

Contribution grade

Atomic and fundamental physics / positronium microwave spectroscopy · Source-reported experimental result or reusable measurement method

Reference score42,000Provisional editorial estimate of this exact contribution; its grade is assessed separately.

What changed

Gurung and colleagues used laser-prepared metastable positronium, microwave transitions and annihilation-time detection to study the n=2 fine structure. Their 2021 analysis reported 18,501.02±0.57(stat)±0.323(syst) MHz for the 2³S₁ → 2³P₀ interval, approximately 4.2 standard deviations above its cited QED prediction under that error budget. The J=1 and J=2 spectra revealed asymmetric lines. A subsequent model by Akopyan and colleagues showed that frequency-dependent microwave reflections could produce shifts of several MHz, including shifts of apparently symmetric lines, exposing a systematic uncertainty beyond the earlier budget.

Scientific scope

Gurung and colleagues used laser-prepared metastable positronium, microwave transitions and annihilation-time detection to study the n=2 fine structure. Their 2021 analysis reported 18,501.02±0.57(stat)±0.323(syst) MHz for the 2³S₁ → 2³P₀ interval, approximately 4.2 standard deviations above its cited QED prediction under that error budget. The J=1 and J=2 spectra revealed asymmetric lines. A subsequent model by Akopyan and colleagues showed that frequency-dependent microwave reflections could produce shifts of several MHz, including shifts of apparently symmetric lines, exposing a systematic uncertainty beyond the earlier budget. The reported frequencies depend on line-shape assumptions, magnetic-field extrapolation, laser alignment and electric-field and Doppler estimates. The detailed experiment added recoil Doppler uncertainty omitted in 2020 without changing its central value. Subsequent numerical modeling suggested a conservative reflection-related uncertainty of about 4 MHz; this is a model estimate, not a measured correction or a verified probability distribution. Unmodeled chamber elements prevent direct correction of the original data. The earlier 4.2-standard-deviation comparison therefore does not establish a surviving anomaly, new force or failure of QED. Asymmetric J=1 and J=2 fit centres are diagnostics, not reliable precise intervals. The modeled quantum-interference channels were too small to explain the MHz effects; other unmodeled mechanisms and later experimental comparisons remain open.

Evidence

The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The reported frequencies depend on line-shape assumptions, magnetic-field extrapolation, laser alignment and electric-field and Doppler estimates. The detailed experiment added recoil Doppler uncertainty omitted in 2020 without changing its central value. Subsequent numerical modeling suggested a conservative reflection-related uncertainty of about 4 MHz; this is a model estimate, not a measured correction or a verified probability distribution. Unmodeled chamber elements prevent direct correction of the original data. The earlier 4.2-standard-deviation comparison therefore does not establish a surviving anomaly, new force or failure of QED. Asymmetric J=1 and J=2 fit centres are diagnostics, not reliable precise intervals. The modeled quantum-interference channels were too small to explain the MHz effects; other unmodeled mechanisms and later experimental comparisons remain open.

Contributors

Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.

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