Hyperfine-structure-resolved laser spectroscopy of many-electron highly charged ions

TL;DR

This paper demonstrates hyperfine-structure-resolved laser spectroscopy of highly charged ions in a plasma, providing experimental validation for atomic-structure calculations and opening new avenues for fundamental physics research.

Contribution

It introduces a novel spectroscopic method using laser-induced fluorescence in an electron beam ion trap plasma for many-electron HCIs.

Findings

Successful observation of hyperfine-structures in HCIs

Validation of atomic-structure calculations for HCIs

Potential for new fundamental physics experiments

Abstract

Hyperfine-structures of highly charged ions (HCIs) are favourable spectroscopic targets for exploring fundamental physics as well as nuclear properties. Recent proposals of HCI atomic clocks highlight their importance, especially for many-electron HCIs, and they have been theoretically investigated by refining atomic-structure calculations. Nonetheless, no established spectroscopic method is currently available to verify these theoretical calculations. Here, we demonstrate hyperfine-structure-resolved laser spectroscopy of HCIs in an electron beam ion trap plasma, employing the magnetic-dipole transition in 4$d^{9}$5$s$ of $^{127}$I$^{7+}$. Ion-state manipulation by controlled electron collisions in the well-defined laboratory plasma enables laser-induced fluorescence spectroscopy of trapped HCIs. The observed spectrum of evaporatively cooled ions under the low magnetic field shows remarkable features reflecting the hyperfine-structures. The present demonstration using the combined optical and plasma approach provides a new benchmark for state-of-the-art atomic calculations of hyperfine-structures in many-electron HCIs and offers possibilities for a variety of unexploited experiments.