Laser Cooling at Resonance

TL;DR

This paper demonstrates experimentally that lithium atoms can be laser cooled at resonance, and provides a comprehensive theoretical model including atomic structure and polarization effects, supported by Monte Carlo simulations.

Contribution

It introduces a detailed model for 3-D laser cooling at resonance in lithium atoms, incorporating all Zeeman sub-levels and polarization effects, validated by experimental data.

Findings

Laser cooling achieved at exact resonance with lithium atoms.

Good agreement between theoretical model and experimental results.

Coherent processes are crucial for understanding the cooling mechanism.

Abstract

We show experimentally that 3-D laser cooling of lithium atoms is achieved when the laser light is tuned exactly to resonance with the atomic transition. For a theoretical description of this surprising phenomenon we resolve to a full model which takes into account both the entire atomic structure and the laser light polarization. Here we build such a model for $^7$Li atoms cooled on the $D_{2}$-line in a $\sigma^+-\sigma^-$ laser configuration. We take all 24 Zeeman sub-levels into account and obtain good agreement with the experimental data. Moreover, by means of Monte-Carlo simulations we show that coherent processes play an important role in showing consistency between the theory and the experimental results.