BWhat changed
Sheldon and colleagues observed that the apparent positronium 2³S₁ → 2³P₂ transition frequency changed when a free-space microwave horn was rotated, even when the spectral lines showed little measurable asymmetry. They then measured the interval in a redesigned waveguide apparatus with reduced chamber reflections, reversed microwave directions and a retroreflected excitation laser. Averaging the two directions gave 8627.94±0.30(stat)±0.91(syst) MHz, within 1.3 standard deviations of the cited QED value. These experiments established practical diagnostics for microwave-field distortions while retaining a substantial unresolved direction-dependent systematic error.
Scientific scope
Sheldon and colleagues observed that the apparent positronium 2³S₁ → 2³P₂ transition frequency changed when a free-space microwave horn was rotated, even when the spectral lines showed little measurable asymmetry. They then measured the interval in a redesigned waveguide apparatus with reduced chamber reflections, reversed microwave directions and a retroreflected excitation laser. Averaging the two directions gave 8627.94±0.30(stat)±0.91(syst) MHz, within 1.3 standard deviations of the cited QED value. These experiments established practical diagnostics for microwave-field distortions while retaining a substantial unresolved direction-dependent systematic error. The free-space spectra diagnose field-dependent line shifts and do not provide a reliable precision interval. The redesigned experiment extrapolated finite-field measurements to zero field using a Zeeman model. Its two microwave directions differed by about 1.8 MHz; half this difference was assigned as an additional systematic uncertainty, rather than independently explained or eliminated. Mode simulations reproduced MHz shifts qualitatively but not the observed horn-angle dependence. Agreement with theory is limited to the reported uncertainty and does not resolve all earlier J=0 discrepancies. The cited archived paper and the later journal version differ in wording.
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 free-space spectra diagnose field-dependent line shifts and do not provide a reliable precision interval. The redesigned experiment extrapolated finite-field measurements to zero field using a Zeeman model. Its two microwave directions differed by about 1.8 MHz; half this difference was assigned as an additional systematic uncertainty, rather than independently explained or eliminated. Mode simulations reproduced MHz shifts qualitatively but not the observed horn-angle dependence. Agreement with theory is limited to the reported uncertainty and does not resolve all earlier J=0 discrepancies. The cited archived paper and the later journal version differ in wording.
Contributors
- The named authors in the research record · SCIENCE: These are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.
- Microwave spectroscopy of positronium atoms in free space (PRA107042810)
- Precision Microwave Spectroscopy of the Positronium 2tripletS1 to2tripletP2 Interval (PRL131043001 archived formal copy)
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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