Penning-trap mass spectrometry in atomic and nuclear physics has become a well-established and reliable tool for the determination of atomic masses. In combination with short-lived radioactive nuclides it was first introduced at ISOLTRAP at the Isotope Mass Separator On-Line facility (ISOLDE) at CERN. Penning traps have found new applications in coupling to other production mechanisms, such as in-flight production and separation systems. The applications in atomic and nuclear physics range from nuclear structure studies and related precision tests of theoretical approaches to description of the strong interaction to tests of the electroweak Standard Model, quantum electrodynamics and neutrino physics, and applications in nuclear astrophysics. The success of Penning-trap mass spectrometry is due to its precision and accuracy, even for low ion intensities (i.e., low production yields), as well as its very fast measurement cycle, enabling access to short-lived isotopes. The current reach in relative mass precision goes beyond δ m/ m=10 −8 , the half-life limit is as low as a few milliseconds, and the sensitivity is on the order of one ion per minute in the trap. We provide a comprehensive overview of the techniques and applications of Penning-trap mass spectrometry in nuclear and atomic physics.
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Investigation of the fine structure of antihydrogen
At the historic Shelter Island Conference on the Foundations of Quantum Mechanics
in 1947, Willis Lamb reported an unexpected feature in the fine structure of atomic
hydrogen: a separation of the 2S1/2 and 2P1/2 states1. The observation of this separation,
now known as the Lamb shift, marked an important event in the evolution of modern
physics, inspiring others to develop the theory of quantum electrodynamics2–5.
Quantum electrodynamics also describes antimatter, but it has only recently become
possible to synthesize and trap atomic antimatter to probe its structure. Mirroring the
historical development of quantum atomic physics in the twentieth century, modern
measurements on anti-atoms represent a unique approach for testing quantum
electrodynamics and the foundational symmetries of the standard model. Here we
report measurements of the fine structure in the n = 2 states of antihydrogen, the
antimatter counterpart of the hydrogen atom. Using optical excitation of the 1S–2P
Lyman-α transitions in antihydrogen6, we determine their frequencies in a magnetic
field of 1 tesla to a precision of 16 parts per billion. Assuming the standard Zeeman and
hyperfine interactions, we infer the zero-field fine-structure splitting (2P1/2–2P3/2) in
antihydrogen. The resulting value is consistent with the predictions of quantum
electrodynamics to a precision of 2 per cent. Using our previously measured value of
the 1S–2S transition frequency6,7, we find that the classic Lamb shift in antihydrogen
(2S1/2–2P1/2 splitting at zero field) is consistent with theory at a level of 11 per cent. Our
observations represent an important step towards precision measurements of the
fine structure and the Lamb shift in the antihydrogen spectrum as tests of the charge–
parity–time symmetry8 and towards the determination of other fundamental
quantities, such as the antiproton charge radius9,10, in this antimatter system.
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- NSF-PAR ID:
- 10159547
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Nature
- Volume:
- 578
- Issue:
- 7795
- ISSN:
- 0028-0836
- Page Range / eLocation ID:
- 375 to 380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41586-020-2006-5
