Linear Stark Shifts to Measure the Fr Weak Nuclear Charge with Small Atom Samples

TL;DR

This paper proposes a method to measure the weak nuclear charge in francium atoms by observing linear Stark shifts induced by a circularly polarized laser, enabling experiments with small atom samples.

Contribution

It introduces a novel approach using parity-violating energy shifts in alkali atoms dressed with laser light to measure the weak nuclear charge Q_W.

Findings

A predicted measurable energy shift of ~100 μHz at specific conditions.

A feasible experimental setup with ~10^4 francium atoms.

A calibration procedure for accurate Q_W measurement.

Abstract

We study the chirality of ground-state alkali atoms in E and B fields, dressed with a circularly-polarized laser beam close-detuned from an E-field-assisted forbidden transition, such as 7S-8S in Fr. We predict a parity violating energy shift of their sublevels, linear in E, and the weak nuclear charge Q_W$. A dressing beam of 10 kW/cm$^2$ at 506 nm produces a shift of $\sim100 \mu$Hz at E=100 V/cm, B $\gtrsim$30 mG. It should be observable with $\sim 10^4$ Fr atoms confined in an optical dipole trap. We discuss optimal conditions, parameter reversals and a calibration procedure to measure $Q_W$.