Radiative deflection of a BaF molecular beam from the optical cycling

TL;DR

This paper demonstrates a method for radiative deflection of BaF molecules using optical cycling, enabling potential laser cooling and slowing of the molecular beam.

Contribution

It introduces a quasi optical cycling scheme for BaF molecules and shows controlled beam deflection through radiative force, advancing molecular laser cooling techniques.

Findings

Achieved 0.8 mm beam deflection with ~150 photon scatterings

Hyperfine and Zeeman sublevels are effectively closed during cycling

Model predictions agree with experimental results

Abstract

We demonstrate a quasi optical cycling for the $X(v=0)\to A(v'=0)$ transition and a radiative force induced deflection on the buffer-gas cooled BaF molecular beam. The laser induced fluorescence enhancement with additional sidebands and a polarization modulation scheme indicates that the hyperfine states and the Zeeman sublevels are closed. The quasi optical cycling by repumping the $X(v=1)\to A(v'=0)$ leads to a $\sim$ 0.8 mm deflection of the beam via scattering $\sim$ 150 photons per molecule, in good agreement with the predictions from our multi-level rate equation model. Further improvement by closing the leakage $X(v=2)$ and $\Delta$ state allows scattering thousands of photons, and laser cooling and slowing of BaF.