Screened radiative corrections from hyperfine-split dielectronic resonances in lithiumlike scandium

Area of Science:

• Atomic physics
• Quantum mechanics
• Spectroscopy

Background:

• Dielectronic recombination is a key process in atomic physics, influencing plasma properties.
• Accurate term energies are crucial for understanding atomic structure and validating theoretical models.
• Scandium (Sc18+) provides a valuable test case for atomic structure calculations due to its intermediate Z.

Purpose of the Study:

• To precisely determine term energies of dielectronic-recombination Rydberg resonances for Sc18+.
• To achieve high absolute accuracy in energy measurements below 0.07 eV.
• To investigate the influence of few-body effects and hyperfine structure on the spectrum.

Main Methods:

• Utilizing electron collision spectroscopy within an ion storage ring.
• Employing the twin-electron-beam technique for enhanced precision.
• Using a cryogenic photocathode to improve spectral resolution.

Main Results:

• Term energies for Sc18+ dielectronic-recombination resonances were determined with absolute accuracies below 0.0002 eV.
• The lithiumlike 2s_{1/2}-2p_{3/2} transition energy for Z=21 was measured to 4.6 ppm.
• Hyperfine structure features of the 2s state were resolved in the dielectronic-recombination spectrum.

Conclusions:

• The experimental results provide highly accurate data for Sc18+ atomic structure.
• The findings offer a stringent test for theoretical calculations, including few-body and relativistic effects.
• Resolved hyperfine structure demonstrates the capability of the technique to probe subtle atomic details.