Measurement of the 2S_{1/2}-8D_{5/2} Transition in Hydrogen

Area of Science:

• Atomic physics
• Quantum mechanics
• Spectroscopy

Background:

• Precise measurements of atomic transitions are crucial for fundamental constants.
• Discrepancies in proton radius measurements persist, necessitating further investigation.
• The Rydberg constant and proton radius are key parameters in atomic physics.

Purpose of the Study:

• To measure the hydrogen 2S_{1/2}-8D_{5/2} transition frequency with high precision.
• To derive updated values for the proton radius and Rydberg constant.
• To compare the new results with established CODATA values.

Main Methods:

• Utilized a cryogenic atomic beam for high-resolution spectroscopy.
• Measured the resonance frequency of the 2S_{1/2}-8D_{5/2} transition in hydrogen.
• Combined the new data with existing 1S-2S transition measurements.

Main Results:

• The measured resonance frequency is 770649561570.9(2.0) kHz, with a relative uncertainty of 2.6×10^{-12}.
• Derived proton radius: r_{p}=0.8584(51) fm.
• Derived Rydberg constant: R_{∞}=10973731.568332(52) m^{-1}.

Conclusions:

• The derived proton radius and Rydberg constant differ from CODATA 2018 values by 3.1σ.
• This precise measurement challenges current understanding and may indicate new physics.
• Further experimental and theoretical work is needed to resolve the discrepancy.