Measurement of Linear Stark Interference in 199Hg

TL;DR

This paper measures Stark interference in $^{199}$Hg, confirming theoretical predictions and validating the experimental setup for detecting tiny EDM-like frequency shifts.

Contribution

It provides the first precise measurement of Stark interference amplitude in $^{199}$Hg, aligning with advanced theoretical models and demonstrating the apparatus's sensitivity.

Findings

Measured interference amplitude $a_{SI}$ = (5.8 ± 1.5)×10^{-9} (kV/cm)^{-1}

Confirmed theoretical predictions of relativistic many-body calculations

Validated the experimental setup's capability to detect sub-nHz frequency shifts.

Abstract

We present measurements of Stark interference in the 6$^1S_0$ $\rightarrow$ 6$^3P_1$ transition in $^{199}$Hg, a process whereby a static electric field $E$ mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to $E$-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, $a_{SI}$ = $(a_{M1} + a_{E2})$ = (5.8 $\pm$ 1.5)$\times 10^{-9}$ (kV/cm)$^{-1}$, agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the $^{199}$Hg EDM search apparatus to resolve non-trivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.