Abstract

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom’s stature lies in its simplicity and in the accuracy with which its spectrum can be measured1 and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and—by comparison with measurements on its antimatter counterpart, antihydrogen—the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state2,3 of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped4,5,6 in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

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References

  1. 1.

    Nobel lecture: Passion for precision. Rev. Mod. Phys. 78, 1297–1309 (2006)

  2. 2.

    , , , & RF spectroscopy of trapped neutral atoms. Phys. Rev. Lett. 61, 2431–2434 (1988)

  3. 3.

    et al. Towards antihydrogen confinement with the ALPHA antihydrogen trap. Hyperfine Interact. 172, 81–89 (2006)

  4. 4.

    et al. Trapped antihydrogen. Nature 468, 673–676 (2010)

  5. 5.

    et al. Confinement of antihydrogen for 1,000 seconds. Nature Phys. 7, 558–564 (2011)

  6. 6.

    et al. Search for trapped antihydrogen. Phys. Lett. B 695, 95–104 (2011)

  7. 7.

    Cooling neutral atoms in a magnetic trap for precision spectroscopy. Phys. Rev. Lett. 51, 1336–1339 (1983)

  8. 8.

    et al. A magnetic trap for antihydrogen confinement. Nucl. Instrum. Meth. A 566, 746–756 (2006)

  9. 9.

    The antiproton decelerator: AD. Hyperfine Inter. 109, 43–52 (1997)

  10. 10.

    et al. The ALPHA detector: module production and assembly. J. Instrum. 7, C01051 (2012)

  11. 11.

    & Homogeneity of results in testing samples from Poisson series. Biometrika 31, 313–323 (1939)

  12. 12.

    et al. Magnetic resonance studies of gaseous atomic hydrogen at low temperatures. Phys. Rev. Lett. 42, 1042–1045 (1979)

  13. 13.

    Nobel lecture: experiments with an isolated subatomic particle at rest. Rev. Mod. Phys. 62, 525–530 (1990)

  14. 14.

    et al. Evaporative cooling of antiprotons to cryogenic temperatures. Phys. Rev. Lett. 105, 013003 (2010)

  15. 15.

    et al. Autoresonant excitation of antiproton plasmas. Phys. Rev. Lett. 106, 025002 (2011)

  16. 16.

    , , , & Low-order modes as diagnostics of spheroidal non-neutral plasmas. Phys. Rev. Lett. 72, 352–355 (1994)

  17. 17.

    et al. Antihydrogen annihilation reconstruction with the ALPHA silicon detector. Nucl. Instrum. Meth. A (submitted).

  18. 18.

    Random forests. Mach. Learn. 45, 5–32 (2001)

  19. 19.

    StatPatternRecognition: a C++ package for statistical analysis of high energy physics data. Preprint at (2005)

  20. 20.

    Optimization of signal significance by bagging decision trees. Preprint at (2005)

  21. 21.

    Sensitivity of searches for new signals and its optimization. In Proc. PHYSTAT2003: Statistical Problems in Particle Physics, Astrophysics, and Cosmology 79–83 Preprint at (2003)

Download references

Acknowledgements

This work was supported by CNPq, FINEP/RENAFAE (Brazil), ISF (Israel), MEXT (Japan), FNU (Denmark), VR (Sweden), NSERC, NRC/TRIUMF, AITF, FQRNT (Canada), DOE, NSF (USA), EPSRC, the Royal Society and the Leverhulme Trust (UK). We thank them for their generous support. We are grateful to the AD team (T. Eriksson, P. Belochitskii, B. Dupuy, L. Bojtar, C. Oliveira, B. Lefort and G. Tranquille) for the delivery of a high-quality antiproton beam. We thank the following individuals for help: M. Harrison, J. Escallier, A. Marone, M. Anerella, A. Ghosh, B. Parker, G. Ganetis, J. Thornhill, D.Wells, D. Seddon, F. Butin, H. Brueker, K. Dahlerup-Pedersen, J. Mourao, T. Fowler, S. Russenschuck, R. De Oliveira, N. Wauquier, J. Hansen, M. Polini, J. M. Geisser, L. Deparis, P. Frichot, J. M. Malzacker, A. Briswalter, P. Moyret, S. Mathot, G. Favre, J. P. Brachet, P. Mésenge, S. Sgobba, A. Cherif, J. Bremer, J. Casas-Cubillos, N. Vauthier, G. Perinic, O. Pirotte, A. Perin, G. Perinic, B. Vullierme, D. Delkaris, N. Veillet, K. Barth, R. Consentino, S. Guido, L. Stewart, M. Malabaila, A. Mongelluzzo, P. Chiggiato, G. Willering, E. Mahner, A. Froton, C. Lasseur, F. Hahn, E. Søndergaard, F. Mikkelsen, W. Carlisle, A. Charman, J. Keller, P. Amaudruz, D. Bishop, R. Bula, K. Langton, P. Vincent, S. Chan, D. Rowbotham, P. Bennet, B. Evans, J.-P. Martin, P. Kowalski, A. Read, T. Willis, J. Kivell, H. Thomas, W. Lai, L. Wasilenko, C. Kolbeck, H. Malik, P. Genoa, L. Posada, R. Funakoshi, M. Okeane, S. Carey and N. Evetts. We thank former collaborators M. J. Jenkins, G. B. Andresen, R. Hydomako, S. Chapman, A. Povilus, R. Hayano, L. V. Jørgensen and Y. Yamazaki. We are grateful to the CERN Summer Student Program for funding the participation of undergraduate students (C.Ø.R. and S.C.N.) in our experiment.

Author information

Author notes

    • D. M. Silveira

    Present address: Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil.

Affiliations

  1. Department of Physics and Astronomy, York University, Toronto, Ontario, M3J 1P3, Canada

    • C. Amole
    • , A. Capra
    •  & S. Menary
  2. Department of Physics, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada

    • M. D. Ashkezari
    •  & M. E. Hayden
  3. Department of Physics, University of California, Berkeley, California 94720-7300, USA

    • M. Baquero-Ruiz
    • , J. Fajans
    • , A. Little
    • , C. So
    •  & J. S. Wurtele
  4. Department of Physics, Swansea University, Swansea SA2 8PP, UK

    • W. Bertsche
    • , M. Charlton
    • , A. Deller
    • , S. Eriksson
    • , A. J. Humphries
    • , C. A. Isaac
    • , N. Madsen
    • , S. C. Napoli
    • , C. R. Shields
    •  & D. P. van der Werf
  5. School of Physics and Astronomy, University of Manchester, M13 9PL Manchester, UK

    • W. Bertsche
  6. The Cockcroft Institute, WA4 4AD Warrington, UK

    • W. Bertsche
  7. Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark

    • P. D. Bowe
    • , J. S. Hangst
    •  & C. Ø. Rasmussen
  8. CERN, Department PH, CH-1211 Geneva 23, Switzerland

    • E. Butler
  9. Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil

    • C. L. Cesar
  10. Department of Physics, Auburn University, Auburn, Alabama 36849-5311, USA

    • P. H. Donnan
    •  & F. Robicheaux
  11. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

    • J. Fajans
    •  & J. S. Wurtele
  12. Department of Physics and Astronomy, University of Calgary, Calgary, Alberta T2N 1N4, Canada

    • T. Friesen
    • , M. C. Fujiwara
    •  & R. I. Thompson
  13. TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada

    • M. C. Fujiwara
    • , D. R. Gill
    • , L. Kurchaninov
    • , K. Olchanski
    • , A. Olin
    •  & S. Stracka
  14. Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada

    • A. Gutierrez
    •  & W. N. Hardy
  15. The Canadian Institute of Advanced Research, Toronto M5G-1Z8, Canada

    • W. N. Hardy
  16. Department of Physics, Stockholm University, SE-10691, Stockholm, Sweden

    • S. Jonsell
  17. Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK

    • J. T. K. McKenna
    • , P. Nolan
    •  & P. Pusa
  18. Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 3P6, Canada

    • A. Olin
  19. Department of Physics, NRCN-Nuclear Research Center Negev, Beer Sheva, IL-84190, Israel

    • E. Sarid
  20. Atomic Physics Laboratory, RIKEN, Saitama 351-0198, Japan

    • D. M. Silveira

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Contributions

W.B., P.D.B., J.F., M.C.F., J.S.H., N.M. and D.M.S. conceived, designed and constructed the central ALPHA apparatus and participated in all aspects of the experimental and physics programme. The microwave hardware was designed and fabricated by M.D.A., E.B., W.N.H. and M.E.H., who also participated in all aspects of the experimental programme. T.F. developed the electron cyclotron resonance diagnostic and participated actively in all aspects of the experimental programme. S.S. developed the alternative event analysis and participated actively in the experimental and analysis efforts. C.A., M.B.-R., A.C., A.G., A.J.H., J.T.K.M., E.S. and C.S. participated actively in the experimental runs, data taking, on- and offline analysis, and maintenance and modification of the apparatus. D.R.G. and A.O. contributed to all aspects of the detector systems and participated actively in the experimental shift work and analysis efforts. M.C. designed and built the positron accumulator and participated in the experimental shift work, the physics planning effort, and the strategic direction of the experiment. D.P.v.d.W. designed and built the positron accumulator, contributed to the magnetic design of the atom trap, and participated in the experimental programme. F.R., with help from P.H.D., performed the spin-flip simulations reported in this paper and supported the design and experimental programme with simulations and calculations. P.N. led the design of the ALPHA silicon detector. P.P. was responsible for implementing the silicon detector at CERN and participated in the experimental and analysis programme. A.D., C.A.I., C.Ø.R., S.C.N., A.L. and C.R.S. contributed to the experimental shift work. S.J. and J.S.W. contributed theoretical support in the form of atomic or plasma physics calculations and simulations and contributed to the experimental shift work. C.L.C., S.E., S.M. and R.I.T. participated in the experimental programme and the physics planning effort. L.K. and K.O. provided offsite support for detector electronics and database management systems, respectively, and contributed to the experimental shift work. E.B., J.S.H. and M.E.H. wrote the initial manuscript, which was edited, improved and approved by the entire collaboration.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to J. S. Hangst or M. E. Hayden.

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https://doi.org/10.1038/nature10942

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