Testing quantum electrodynamics in extreme fields using helium-like uranium

Area of Science:

• Atomic Physics
• Quantum Electrodynamics (QED)
• High-Energy Physics

Background:

• Quantum electrodynamics (QED) is the leading theory of light-matter interaction, extensively tested in low-field regimes.
• Studies in high-Z (high nuclear charge) ions and strong electromagnetic fields probe non-perturbative QED regimes, which are experimentally challenging.
• Existing experimental data for strong-field QED effects in heavy ions are limited, with theoretical predictions being only partially validated.

Purpose of the Study:

• To experimentally investigate higher-order QED effects and electron-electron interactions in the high-Z regime.
• To achieve precise measurements of atomic transitions in highly charged heavy ions.
• To provide a benchmark for state-of-the-art theoretical calculations in strong-field QED.

Main Methods:

• Utilized a multi-reference method employing Doppler-tuned X-ray emission.
• Experimentally studied stored relativistic uranium ions with varying charge states.
• Measured the 1s_1/22p_3/2 J=2 → 1s_1/22s_1/2 J=1 intrashell transition energy in U⁹⁰⁺.

Main Results:

• Achieved a highly accurate measurement (37 ppm) of the intrashell transition energy in the two-electron uranium ion (U⁹⁰⁺).
• Successfully disentangled and separately tested one-electron higher-order QED effects and electron-electron interaction terms.
• The experimental results allowed discrimination between different theoretical approaches in the strong-field domain.

Conclusions:

• The study presents a significant experimental advancement in testing QED in the non-perturbative, strong-field regime.
• The precise measurements serve as a critical benchmark for theoretical QED calculations involving heavy, highly charged ions.
• This work opens new avenues for exploring fundamental physics in extreme electromagnetic environments.