Precision Spectroscopy of 2S-nS Transitions in Atomic Hydrogen: A Determination of the Proton Charge Radius

Author

• R. G. Bullis
• W. L. Tavis
• M. R. Weiss
• Orellana O. Cisneros
• A. J. Cheeseman
• Ulrich D. Jentschura, Missouri University of Science and TechnologyFollow
• D. C. Yost

Abstract

We present absolute frequency measurements of 2S_1/2-nS_1/2 two-photon transitions with n=8, 9, and 10 in a cryogenic beam of atomic hydrogen. Each transition has been measured with a fractional uncertainty of ≈2.6x10^-12. Combining the results from this Letter and the 1S_1/2-2S_1/2 transition frequency, we extract a root-mean-square proton radius of rp=0.8433(31) fm and a Rydberg frequency of cR_∞=3 289 841 960 252.9(9.7) kHz. These are in good agreement with the CODATA 2022 recommended values.

Recommended Citation

R. G. Bullis et al., "Precision Spectroscopy of 2S-nS Transitions in Atomic Hydrogen: A Determination of the Proton Charge Radius," Physical Review Letters, vol. 136, no. 12, article no. 123001, American Physical Society, Mar 2026.

The definitive version is available at https://doi.org/10.1103/lgl2-6cb8

Department(s)

Physics

Comments

National Institute of Standards and Technology, Grant PHY-2207298

International Standard Serial Number (ISSN)

1079-7114; 0031-9007

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 American Physical Society, All rights reserved.

Publication Date

27 Mar 2026

PubMed ID

41965043