A Hunt for Highly Charged Ions as Ultra-stable Optical Clock Candidates: Art of the energy level-crossing approach

TL;DR

This paper explores highly charged ions with specific electron configurations as promising candidates for ultra-stable optical atomic clocks, analyzing their energy level-crossings, sensitivities, and shifts to evaluate their suitability.

Contribution

It introduces a novel energy level-crossing approach to identify HCIs suitable for ultra-stable optical clocks and assesses their sensitivities and shifts for precision measurements.

Findings

Some HCIs have quality factors up to 10^{18}

Identified HCIs with fractional uncertainties below 10^{-19}

HCIs are highly sensitive to variations in fundamental constants

Abstract

We examine energy level-crossings of fine-structure (FS) levels in the heavier highly charged ions (HCIs) with $d^6$ and $d^8$ configurations. From the analysis, we find that some of these HCIs are tailor-made for atomic clocks with quality factors ranging from $10^{16}$ to $10^{18}$ and fractional uncertainties below $10^{-19}$ level. Many of them are also realized to be highly sensitive to the observation of temporal variation of FS constant ($\alpha$) and testing violation of local Lorentz symmetry invariance (LLI). To probe variations of $\alpha$ and LLI, we have determined their corresponding sensitivity coefficients in the investigated HCIs. Similarly, we have estimated orders of magnitudes of the Zeeman, Stark, black-body radiation and electric quadrupole shifts of the clock transitions of the considered HCIs in order to demonstrate them as the potential candidates for atomic clocks.