Magnetic-dipole transitions in highly-charged ions as a basis of ultra-precise optical clocks

TL;DR

This paper explores the potential of magnetic-dipole transitions in highly-charged ions for ultra-precise optical clocks, promising unprecedented accuracy and new ways to test fundamental constants.

Contribution

It introduces a novel approach using M1 transitions in highly-charged ions for optical clocks, achieving low systematic shifts and expanding fundamental physics tests.

Findings

Projected fractional accuracy below 10^{-20} for systematic effects.

Transitions in the optical domain enable precise probing of fundamental constants.

Low degeneracy and simple structure reduce systematic uncertainties.

Abstract

We evaluate the feasibility of using magnetic-dipole (M1) transitions in highly-charged ions as a basis of an optical atomic clockwork of exceptional accuracy. We consider a range of possibilities, including M1 transitions between clock levels of the same fine-structure and hyperfine-structure manifolds. In highly charged ions these transitions lie in the optical part of the spectra and can be probed with lasers. The most direct advantage of our proposal comes from the low degeneracy of clock levels and the simplicity of atomic structure in combination with negligible quadrupolar shift. We demonstrate that such clocks can have projected fractional accuracies below the $10^{-20}-10^{-21}$ level for all common systematic effects, such as black-body radiation, Zeeman, AC-Stark and quadrupolar shifts. Notice that usually-employed hyperfine clock transitions lie in the microwave spectral region. Our proposal moves such transitions to the optical domain. As the hyperfine transition frequencies depend on the fine-structure constant, electron-to-proton mass ratio, and nuclear magnetic moment, our proposal expands the range of experimental schemes for probing space and time variations of fundamental constants.