Precision Nuclear-Spin Effects in Atoms: EFT Methods for Reducing Theory Errors

TL;DR

This paper employs effective field theory to analyze nuclear effects on atomic energy levels, demonstrating that fewer nuclear parameters influence atomic spectra than previously thought, enabling more precise tests of fundamental physics.

Contribution

The authors extend EFT methods to spinning nuclei and show that atomic energy levels depend on fewer nuclear parameters, reducing theoretical uncertainties in precision atomic physics calculations.

Findings

Nuclear properties influence atomic energies through fewer parameters than expected.

Position-space matching method improves efficiency in EFT calculations.

Nucleus-independent combinations of atomic energy differences can test fundamental physics.

Abstract

We use effective field theory to compute the influence of nuclear structure on precision calculations of atomic energy levels. As usual, the EFT's effective couplings correspond to the various nuclear properties (such as the charge radius, nuclear polarizabilities, Friar and Zemach moments {\it etc.}) that dominate its low-energy electromagnetic influence on its surroundings. By extending to spinning nuclei the arguments developed for spinless ones in {\tt arXiv:1708.09768}, we use the EFT to show -- to any fixed order in $Z\alpha$ (where $Z$ is the atomic number and $\alpha$ the fine-structure constant) and the ratio of nuclear to atomic size -- that nuclear properties actually contribute to electronic energies through fewer parameters than the number of these effective nuclear couplings naively suggests. Our result is derived using a position-space method for matching effective parameters to nuclear properties in the EFT, that more efficiently exploits the simplicity of the small-nucleus limit in atomic systems. By showing that precision calculations of atomic spectra depend on fewer nuclear uncertainties than naively expected, this observation allows the construction of many nucleus-independent combinations of atomic energy differences whose measurement can be used to test fundamental physics (such as the predictions of QED) because their theoretical uncertainties are not limited by the accuracy of nuclear calculations. We provide several simple examples of such nucleus-free predictions for Hydrogen-like atoms.