Radiative force from optical cycling on a diatomic molecule

TL;DR

This paper demonstrates a scheme for optical cycling in SrF molecules using specific electronic transitions, enabling potential laser cooling by allowing over 100,000 photon scatters through suppressed vibrational and rotational branching.

Contribution

The authors introduce a novel optical cycling scheme for SrF molecules that suppresses vibrational and rotational branching, paving the way for direct laser cooling of diatomic molecules.

Findings

Successful demonstration of optical cycling in SrF

Observation of molecular beam deflection via radiative force

Potential for over 10^5 photon scatters enabling laser cooling

Abstract

We demonstrate a scheme for optical cycling in the polar, diatomic molecule strontium monofluoride (SrF) using the $X ^2\Sigma^+\toA^2\Pi_{1/2}$ electronic transition. SrF's highly diagonal Franck-Condon factors suppress vibrational branching. We eliminate rotational branching by employing a quasi-cycling $N=1\to N^\prime=0$ type transition in conjunction with magnetic field remixing of dark Zeeman sublevels. We observe cycling fluorescence and deflection through radiative force of an SrF molecular beam using this scheme. With straightforward improvements our scheme promises to allow more than $10^5$ photon scatters, possibly enabling the direct laser cooling of SrF.