BWhat changed
Heiss and colleagues combined pulsed two-photon positronium 1³S₁ → 2³S₁ spectroscopy with excitation of surviving 2S atoms to the 20P Rydberg state and subsequent field ionization. Time-of-flight detection supplied velocity-distribution information for joint fits of spectral profiles and Doppler shifts. Two experimental runs gave a combined interval of 1,233,607,210.5±49.6 MHz, about 40 parts per billion. The second run added an optical frequency comb and a pulse-by-pulse laser-chirp measurement.
Scientific scope
Heiss and colleagues combined pulsed two-photon positronium 1³S₁ → 2³S₁ spectroscopy with excitation of surviving 2S atoms to the 20P Rydberg state and subsequent field ionization. Time-of-flight detection supplied velocity-distribution information for joint fits of spectral profiles and Doppler shifts. Two experimental runs gave a combined interval of 1,233,607,210.5±49.6 MHz, about 40 parts per billion. The second run added an optical frequency comb and a pulse-by-pulse laser-chirp measurement. The combined uncertainty assumes uncorrelated runs and depends on the simulated emission, laser and detector distributions. A Maxwell–Boltzmann distribution fitted the measured time-of-flight data but does not establish that the emitted atoms were thermal. The first run lacked a working absolute-frequency calibration and contemporaneous chirp measurement. Per-atom Doppler correction and sub-MHz continuous-wave precision remained proposed extensions. Printed simulation conventions need clarification before independent reuse; no raw-data replay or comparison with the later formal text was performed.
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 combined uncertainty assumes uncorrelated runs and depends on the simulated emission, laser and detector distributions. A Maxwell–Boltzmann distribution fitted the measured time-of-flight data but does not establish that the emitted atoms were thermal. The first run lacked a working absolute-frequency calibration and contemporaneous chirp measurement. Per-atom Doppler correction and sub-MHz continuous-wave precision remained proposed extensions. Printed simulation conventions need clarification before independent reuse; no raw-data replay or comparison with the later formal text was performed.
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.
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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