# Lifetimes and g-factors of the HFS states in H-like and Li-like bismuth

## TL;DR

This paper reports precise measurements of hyperfine splittings, lifetimes, and g-factors in highly charged bismuth ions, providing critical data for testing quantum electrodynamics in extreme fields.

## Contribution

First experimental determination of the lifetime of the upper HFS state in lithium-like bismuth, expanding understanding of hyperfine interactions in highly charged ions.

## Key findings

- Measured hyperfine splittings in Bi$^{82+}$ and Bi$^{80+}$
- Determined g-factors of bound electrons in both charge states
- First measurement of HFS state lifetime in Li-like bismuth

## Abstract

The LIBELLE experiment performed at the experimental storage ring (ESR) at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, has successfully determined the ground state hyperfine (HFS) splittings in hydrogen-like ($^{209}\rm{Bi}^{82+}$) and lithium-like ($^{209}\rm{Bi}^{80+}$) bismuth. The study of HFS transitions in highly charged ions enables precision tests of QED in extreme electric and magnetic fields otherwise not attainable in laboratory experiments. Besides the transition wavelengths the time resolved detection of fluorescence photons following the excitation of the ions by a pulsed laser system also allows to extract lifetimes of the upper HFS levels and g-factors of the bound 1s and 2s electrons for both charge states. While the lifetime of the upper HFS state in $^{209}\rm{Bi}^{82+}$ has already been measured in earlier experiments, an experimental value for lifetime of this state in $^{209}\rm{Bi}^{80+}$ is reported for the first time in this work.