Model-independent determination of nuclear charge radii from Li-like ions

TL;DR

This paper introduces a model-independent method using advanced QED theory and electron-scattering constraints to accurately determine nuclear charge radii of heavy elements from Li-like ions, validated on lead and applied to bismuth.

Contribution

It presents a novel approach combining QED calculations and scattering data to determine nuclear radii without relying on nuclear models.

Findings

Validated method on $^{208}$Pb with consistent results.

Applied approach to $^{209}$Bi, overcoming nuclear excitation complexities.

Achieved model-independent nuclear charge radius measurements.

Abstract

We demonstrate that recent advances in QED theory of Li-like ions [V. A. Yerokhin et al., Phys. Rev. A 112, 042801 (2025)] enable determinations of absolute nuclear charge radii for heavy elements. By incorporating constraints derived from electron-scattering data, we obtain radii that are independent of the assumed model of the nuclear charge distribution. Our approach is validated for $^{208}$Pb, a well-studied spherical nucleus, and is then applied to $^{209}$Bi, where low-lying nuclear excitations complicate the interpretation of muonic-atom data.