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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.


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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.

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Correspondence to S. Sturm.

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The authors declare no competing financial interests.

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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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