# $g$-factor of Boronlike Argon $^{40}\textrm{Ar}^{13+}$

## TL;DR

This study precisely measured the g-factor of boronlike argon ions, confirming theoretical predictions and supporting future fundamental constant determinations.

## Contribution

First high-precision measurement of the boronlike argon g-factor using a double Penning-trap setup, aligning with advanced theoretical calculations.

## Key findings

- Measured g-factor with 1.4e-9 fractional uncertainty
- Confirmed theoretical g-factor prediction within uncertainties
- Supports potential for independent fine-structure constant determination

## Abstract

We have measured the ground-state $g$-factor of boronlike argon $^{40}\textrm{Ar}^{13+}$ with a fractional uncertainty of \SI{1.4e-9}{} with a single ion in the newly developed ALPHATRAP double Penning-trap setup. The here obtained value of $g=0.663\,648\,455\,32(93)$ is in agreement with our theoretical prediction of $0.663\,648\,12(58)$. The latter is obtained accounting for quantum electrodynamics, electron correlation, and nuclear effects within the state-of-the-art theoretical methods. Our experimental result distinguishes between existing predictions that are in disagreement, and lays the foundations for an independent determination of the fine-structure constant.