Nuclear Charge Radii of ^{10,11}B.

Area of Science:

• Atomic Physics
• Nuclear Physics
• Quantum Chemistry

Background:

• Precise determination of nuclear charge radii is essential for understanding nuclear structure.
• Previous measurements for light elements like boron have limitations in accuracy.
• Five-electron systems offer a unique platform to test nuclear models.

Purpose of the Study:

• To perform the first laser spectroscopic determination of the nuclear charge radius change in a five-electron system.
• To accurately measure the isotope shift in boron atoms.
• To benchmark advanced ab initio nuclear structure calculations.

Main Methods:

• High-accuracy ab initio mass-shift calculations.
• High-precision laser spectroscopy of the 2s²2p ²P₁/₂→2s²3s ²S₁/₂ transition in boron.
• Analysis of isotope shifts for stable boron isotopes (¹⁰B and ¹¹B).

Main Results:

• Achieved orders of magnitude increase in accuracy for isotope shift measurements in boron.
• Determined the difference in mean-square charge radius: ⟨r_{c}^{2}⟩¹¹-⟨r_{c}^{2}⟩¹⁰ = -0.49(12) fm².
• Provided quantitative benchmarks for no-core shell model and Green's function Monte Carlo calculations.

Conclusions:

• The measured charge radius difference is qualitatively explained by potential cluster structures in boron nuclei.
• The results validate new ab initio nuclear structure calculation methods.
• This work lays the foundation for future laser spectroscopic studies of exotic nuclei like ⁸B.