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High-precision measurement of the atomic mass of the electron


The quest for the value of the electron’s atomic mass has been the subject of continuing efforts over the past few decades1,2,3,4. Among the seemingly fundamental constants that parameterize the Standard Model of physics5 and which are thus responsible for its predictive power, the electron mass me is prominent, being responsible for the structure and properties of atoms and molecules. It is closely linked to other fundamental constants, such as the Rydberg constant R and the fine-structure constant α (ref. 6). However, the low mass of the electron considerably complicates its precise determination. Here we combine a very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics. The precision of the resulting value for the atomic mass of the electron surpasses the current literature value of the Committee on Data for Science and Technology (CODATA6) by a factor of 13. This result lays the foundation for future fundamental physics experiments7,8 and precision tests of the Standard Model9,10,11.

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Figure 1: The triple Penning-trap setup used in this Letter.
Figure 2: The magnitude of the relevant theoretical contributions to the bound electron g-factor in 12C5+.
Figure 3: Axial dip signal of a single 12C5+ ion, used to determine the axial frequency.
Figure 4: History of electron mass measurements.


  1. 1

    Farnham, D. L., Van Dyck, R. S., Jr & Schwinberg, P. B. Determination of the electron's atomic mass and the proton/electron mass ratio. Phys. Rev. Lett. 75, 3598–3601 (1995)

    CAS  ADS  Article  Google Scholar 

  2. 2

    Gräff, G., Kalinowsky, H. & Traut, J. A direct determination of the proton electron mass ratio. Z. Phys. A 297, 35–39 (1980)

    ADS  Article  Google Scholar 

  3. 3

    Beier, T. et al. New determination of the electron’s mass. Phys. Rev. Lett. 88, 011603 (2001)

    ADS  Article  Google Scholar 

  4. 4

    Hori, M. et al. Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio. Nature 475, 484–488 (2011)

    CAS  Article  Google Scholar 

  5. 5

    Cottingham, W. N. &. Greenwood, D. A. An Introduction to the Standard Model of Particle Physics (Cambridge Univ. Press, 2007)

  6. 6

    Mohr, P. J., Taylor, B. N. & Newell, D. B. CODATA recommended values of the fundamental physical constants: 2010. Rev. Mod. Phys. 84, 1527–1605 (2012)

    CAS  ADS  Article  Google Scholar 

  7. 7

    Shabaev, V. M. et al. g-Factor of heavy ions: a new access to the fine structure constant. Phys. Rev. Lett. 96, 253002 (2006)

    CAS  ADS  Article  Google Scholar 

  8. 8

    Shabaev, V. M. et al. g-Factor of high-Z lithiumlike ions. Phys. Rev. A 65, 062104 (2002)

    ADS  Article  Google Scholar 

  9. 9

    Hanneke, D., Fogwell, S. & Gabrielse, G. New measurement of the electron magnetic moment and the fine structure constant. Phys. Rev. Lett. 100, 120801 (2008)

    CAS  ADS  Article  Google Scholar 

  10. 10

    Aoyama, T., Hayakawa, M., Kinoshita, T. & Nio, M. Tenth-order QED contribution to the electron g − 2 and an improved value of the fine structure constant. Phys. Rev. Lett. 109, 111807 (2012)

    ADS  Article  Google Scholar 

  11. 11

    Bœhm, C. & Silk, J. A new test for dark matter particles of low mass. Phys. Lett. B 661, 287–289 (2008)

    ADS  Article  Google Scholar 

  12. 12

    Häffner, H. et al. High-accuracy measurement of the magnetic moment anomaly of the electron. Phys. Rev. Lett. 85, 5308–5311 (2000)

    ADS  Article  Google Scholar 

  13. 13

    Verdú, J. et al. Electronic g factor of hydrogenlike oxygen 16O7+. Phys. Rev. Lett. 92, 093002 (2004)

    ADS  Article  Google Scholar 

  14. 14

    Pachucki, K., Czarnecki, A., Jentschura, U. D. & Yerokhin, V. A. Complete two-loop correction to the bound-electron g factor. Phys. Rev. A 72, 022108 (2005)

    ADS  Article  Google Scholar 

  15. 15

    Breit, G. The magnetic moment of the electron. Nature 122, 649 (1928)

    CAS  ADS  Article  Google Scholar 

  16. 16

    Beier, T. The g j factor of a bound electron and the hyperfine structure. Phys. Rep. 339, 79–213 (2000)

    CAS  ADS  Article  Google Scholar 

  17. 17

    Yerokhin, V. A., Indelicato, P. & Shabaev, V. M. Evaluation of the self-energy correction to the g factor of S states in H-like ions. Phys. Rev. A 69, 052503 (2004)

    ADS  Article  Google Scholar 

  18. 18

    Sturm, S. et al. g-factor measurement of hydrogenlike 28Si13+ as a challenge to QED calculations. Phys. Rev. A 87 (3),. 030501 (2013)

    ADS  Article  Google Scholar 

  19. 19

    Sturm, S. et al. g Factor of hydrogenlike 28Si13+. Phys. Rev. Lett. 107, 023002 (2011)

    CAS  ADS  Article  Google Scholar 

  20. 20

    Gabrielse, G. Why is sideband mass spectrometry possible with ions in a Penning trap? Phys. Rev. Lett. 102, 172501 (2009)

    CAS  ADS  Article  Google Scholar 

  21. 21

    Sturm, S., Wagner, A., Schabinger, B. & Blaum, K. Phase-sensitive cyclotron frequency measurements at ultralow energies. Phys. Rev. Lett. 107, 143003 (2011)

    ADS  Article  Google Scholar 

  22. 22

    Cornell, E. A. et al. Single-ion cyclotron resonance measurement of M(CO+)/M(N2+). Phys. Rev. Lett. 63, 1674–1677 (1989)

    CAS  ADS  Article  Google Scholar 

  23. 23

    Dehmelt, H. Continuous Stern-Gerlach effect: principle and idealized apparatus. Proc. Natl Acad. Sci. USA 83, 2291–2294 (1986)

    CAS  ADS  Article  Google Scholar 

  24. 24

    Brown, L. S. & Gabrielse, G. Geonium theory: physics of a single electron or ion in a Penning trap. Rev. Mod. Phys. 58, 233–311 (1986)

    CAS  ADS  Article  Google Scholar 

  25. 25

    Kramida, A. Atomic Energy Levels and Spectra Bibliographic Database (version 2.0). (Physical Measurement Laboratory, Quantum Measurement Division, NIST)

  26. 26

    Bouchendira, R., Cladé, P., Gouellati-Khélifa, S., Nez, F. & Biraben, F. New determination of the fine structure constant and test of the quantum electrodynamics. Phys. Rev. Lett. 106, 080801 (2011)

    ADS  Article  Google Scholar 

  27. 27

    Mount, B. J., Redshaw, M. & Myers, E. G. Atomic masses of 6Li, 23Na, 39,41K, 85,87Rb and 133Cs. Phys. Rev. A 82, 042513 (2010)

    ADS  Article  Google Scholar 

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This work was supported by the Max Planck Society, the EU (ERC grant number 290870; MEFUCO), the IMPRS-QD, GSI and the Helmholtz Alliance HA216/EMMI.

Author information




S.S., F.K. and A.W. performed the experiment. S.S. and F.K. performed the data analysis. J.Z. performed the QED calculations. S.S., F.K., K.B., J.Z. and Z.H. prepared the manuscript. S.S. and F.K. prepared the experimental part of the Supplementary Information. J.Z. and Z.H. prepared the theoretical part of the Supplementary Information. All authors discussed the results and contributed to the manuscript at all stages.

Corresponding author

Correspondence to S. Sturm.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary text and Data, Supplementary Figures 1-2, Supplementary Tables 1-2 and Supplementary References. (PDF 494 kb)

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Sturm, S., Köhler, F., Zatorski, J. et al. High-precision measurement of the atomic mass of the electron. Nature 506, 467–470 (2014).

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