Coherent Dark Resonances in Atomic Barium

TL;DR

This paper reports the observation of dark resonances in atomic barium and their impact on optical cooling, providing experimental data and modeling to improve laser cooling techniques for heavy alkaline earth atoms.

Contribution

It presents the first detailed observation and modeling of dark resonances in barium, enhancing understanding of optical cooling limitations and optimization strategies.

Findings

Dark resonances affect optical cooling efficiency in barium.

Optical Bloch equations accurately model the observed phenomena.

Parameters for effective laser cooling of barium are extracted.

Abstract

The observation of dark-resonances in the two-electron atom barium and their influence on optical cooling is reported. In heavy alkali earth atoms, i.e. barium or radium, optical cooling can be achieved using n^1S_0-n^1P_1 transitions and optical repumping from the low lying n^1D_2 and n^3D_{1,2} states to which the atoms decay with a high branching ratio. The cooling and repumping transition have a common upper state. This leads to dark resonances and hence make optical cooling less inefficient. The experimental observations can be accurately modelled by the optical Bloch equations. Comparison with experimental results allows us to extract relevant parameters for effective laser cooling of barium.