Characterization of the 1S–2S Transition in Antihydrogen
2018 · paper · Physics
Characterizes the 1S–2S laser transition in magnetically trapped antihydrogen. The line shape and resonance frequency agree with hydrogen to about 5 kilohertz, consistent with charge–parity–time invariance at a relative precision of 2 × 10⁻¹².
Checked: PDF from nature.com, fetched 4 Oct 2026. Page numbers are those of that PDF.
1 finding
Reference or label Abstract cites ref. 8 (Parthey et al., hydrogen 1S–2S measurement) for antihydrogen results: "The laser-driven 1S–2S transition was recently observed8 in antihydrogen" and "two orders of magnitude more precise than the previous determination8"; the antihydrogen observation is ref. 7 (Ahmadi et al., "Observation of the 1S–2S transition in antihydrogen").
- p. 1 Abstract
The laser-driven 1S–2S transition was recently observed8 in antihydrogen
- p. 1 Main text, first paragraph after the abstract
We previously demonstrated7 the existence of the transition in antihydrogen
- p. 4 Reference list, entries 7 and 8
Parthey, C. G. et al. Improved measurement of the hydrogen 1S–2S transition frequency.
- p. 4 Reference list, entry 8
Parthey, C. G. et al. Improved measurement of the hydrogen 1S–2S transition frequency
Judge's note: Page 1 image shows superscript 8 at both places in the abstract. The reference list on page 4 gives 7 = Ahmadi et al., Observation of the 1S–2S transition in antihydrogen, Nature 541, and 8 = Parthey et al., Improved measurement of the hydrogen 1S–2S transition frequency. The body text on the same page uses them the other way round and correctly: hydrogen "has been measured8 to a few parts in 10^15" and "We previously demonstrated7 the existence of the transition in antihydrogen". No statement in the paper makes ref. 8 an antihydrogen source. Both abstract citations should be 7. This entry covers both abstract instances (C002 is the second).
Second check: another model agreed
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4 minor (typos and the like; most checked by the judge only)
Typo Fig. 1 caption: "Cold (less that 0.5 K) anti-atoms can be trapped"; 'that' should be 'than'.
- p. 2 Fig. 1 caption
Cold (less that 0.5 K) anti-atoms
- p. 1 Body, right column
kinetic energy of less than 0.54 K
- p. 1 main text
less than 0.54 K in temperature
- p. 1 main text, first page
less than 0.54 K
Judge's note: The crop of the Fig. 1 caption on page 2 reads "less that 0.5 K", so it is not an extraction artefact. The 0.5 K against "less than 0.54 K" in the page 1 text is ordinary rounding in a caption and is not counted as a defect.
Second check: none (judge only)
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Typo Fig. 1 caption has "photo-diode are further to the right" while the Fig. 1 label reads "Photodiode" and the Methods have "photodiode that is located outside the vacuum system".
- p. 2 Fig. 1 legend
photo-diode are further to the right
- p. 6 Methods
photodiode that is located outside the vacuum
Judge's note: Page 2 image: the caption prints "photo-diode" at the start of a line (so it is not a line-break hyphen) and the label in panel a of the same figure reads "Photodiode". The Methods spelling was read from the text layer. This is a cosmetic spelling inconsistency only.
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Typo Methods: "the hyperfine splitting of the state with prin-ciple quantum number n"; should read 'principal quantum number'.
- p. 6 Methods, 'Calculation of the resonant frequency for hydrogen', text after the first equation
ciple quantum number n
- p. 6 Methods, Calculation of the resonant frequency for hydrogen
prin- ciple quantum number n
Judge's note: The crop of page 6 shows "prin-" at the line end followed by "ciple quantum number n", so the printed word is 'principle'. This is the wrong homophone for the principal quantum number.
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Typo Extended Data Fig. 1 y-axis label reads "Cummultative trapped antihydrogen atoms"; should be 'Cumulative'.
- p. 8 Extended Data Fig. 1, y-axis label
Cummultative trapped antihydrogen atoms
- p. 8 Extended Data Fig. 1 y-axis
Cummulative trapped antihydrogen atoms
Judge's note: On the page 8 image the axis label reads "Cummultative", with a double m and an extra t. Some reviewers transcribed it as 'Cummulative'; either way it is misspelled. The label is part of the figure artwork, so it is not a text-layer artefact.
Second check: none (judge only)