Two-photon frequency comb spectroscopy of atomic hydrogen

Abstract

We have performed two-photon ultraviolet direct frequency comb spectroscopy on the 1S-3S transition in atomic hydrogen to illuminate the so-called proton radius puzzle and to demonstrate the potential of this method. The proton radius puzzle is a significant discrepancy between data obtained with muonic hydrogen and regular atomic hydrogen that could not be explained within the framework of quantum electrodynamics. By combining our result [f1S-3S = 2,922,743,278,665.79(72) kilohertz] with a previous measurement of the 1S-2S transition frequency, we obtained new values for the Rydberg constant [R∞ = 10,973,731.568226(38) per meter] and the proton charge radius [rp = 0.8482(38) femtometers]. This result favors the muonic value over the world-average data as presented by the most recent published CODATA 2014 adjustment.

Laser spectroscopy of light muonic atoms and the nuclear charge radii

“…At the same time various experimental activities were initiated ranging from spectroscopy of hydrogen atoms, hydrogen molecules, electron and muon scattering, laser spectroscopy of Muonium and Rydberg atoms. Recently, several of these experimental efforts produced new results: all of them but one in excellent agreement with the proton radius value as extracted from muonic hydrogen and in some tension with previous hydrogen and electron-scattering results [29][30][31][32][33].…”

“…Using the precise value of the proton radius from muonic hydrogen its relative uncertainty is decreased to 8 × 10 −13 , which is the most precise value for a fundamental constant. [29]) seems to favor the larger radius, more recent measurements from hydrogen spectroscopy H(2S-4P) (Garching 2017 [30]), H(2S-2P) (Toronto 2019 [31]), and H(1S-3S) (Garching 2020 [32]) as well as a low-Q 2 e-p scattering experiment by the PRad Collaboration [33] favor the smaller radius. CODATA has now accepted the smaller radius.…”

Frequenzkamm‐Spektroskopie am Wasserstoffatom

“…Mit neuen Experimenten am atomaren Wasserstoff am Max‐Planck‐Institut für Quantenoptik in Garching haben wir einen Frequenzkamm für die Zweiphotonenspektroskopie genutzt [1]. Die Linien des Frequenzkamms tragen dabei allesamt zur Anregung der Atome bei.…”

Dual-comb Photothermal Spectroscopy

“…Optical frequency combs (OFCs) have significantly promoted the development of many research fields in the past decades such as time and frequency metrology [1,2], attosecond science [3], optical communication [4] and precision spectroscopy [5,6]. This light source presents an optical spectrum composed of a set of evenly spaced and phase-coherent laser lines.…”