New measurement of the $1S-3S$ transition frequency of hydrogen: contribution to the proton charge radius puzzle

TL;DR

This paper reports a highly precise measurement of the hydrogen 1S-3S transition frequency, providing data that supports the current proton charge radius value and contributes to resolving the proton radius puzzle.

Contribution

It presents a new, highly accurate measurement of the hydrogen 1S-3S transition frequency that aligns with CODATA values, aiding the proton radius puzzle.

Findings

Proton charge radius from this measurement is 0.877(13) fm.

Measurement uncertainty is 9×10⁻¹³.

Results support the current CODATA value.

Abstract

We present a new measurement of the $1S-3S$ two-photon transition frequency of hydrogen, realized with a continuous-wave excitation laser at 205 nm on a room-temperature atomic beam, with a relative uncertainty of $9\times10^{-13}$. The proton charge radius deduced from this measurement, $r_\text{p}=0.877(13)$ fm, is in very good agreement with the current CODATA-recommended value. This result contributes to the ongoing search to solve the proton charge radius puzzle, which arose from a discrepancy between the CODATA value and a more precise determination of $r_\text{p}$ from muonic hydrogen spectroscopy.