Radium Ion Optical Clock

C. A. Holliman, M. Fan, A. Contractor, S. M. Brewer, and A. M. Jayich

Phys. Rev. Lett. 128, 033202 – Published 20 January 2022

Abstract

We report the first operation of a ${Ra}^{+}$ optical clock, a promising high-performance clock candidate. The clock uses a single trapped ${}^{226}{Ra}^{+}$ ion and operates on the $7 s {}^{2}{S_{1 / 2}} \to 6 d {}^{2}{D_{5 / 2}}$ electric quadrupole transition. By self-referencing three pairs of symmetric Zeeman transitions, we demonstrate a frequency instability of $1.1 \times 10^{- 13} / \sqrt{τ}$ , where $τ$ is the averaging time in seconds. The total systematic uncertainty is evaluated to be $Δ ν / ν = 9 \times 10^{- 16}$ . Using the clock, we realize the first measurement of the ratio of the $D_{5 / 2}$ state to the $S_{1 / 2}$ state Landé $g$ -factors: $g_{D} / g_{S} = 0.598 805 3 (11)$ . A ${Ra}^{+}$ optical clock could improve limits on the time variation of the fine structure constant, $\dot{α} / α$ , in an optical frequency comparison. The ion also has several features that make it a suitable system for a transportable optical clock.

Received 6 October 2021
Accepted 15 December 2021

DOI:https://doi.org/10.1103/PhysRevLett.128.033202

Physics Subject Headings (PhySH)

Atomic, optical & lattice clocks

Atomic, Molecular & Optical

Authors & Affiliations

C. A. Holliman¹, M. Fan¹, A. Contractor¹, S. M. Brewer², and A. M. Jayich^1,*

¹Department of Physics, University of California, Santa Barbara, California 93106, USA
²Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA