Radiative Force from Optical Cycling on a Diatomic Molecule

We demonstrate a scheme for optical cycling in the polar, diatomic molecule strontium monofluoride (SrF) using the X²Σ⁺→A²Π_1/2 electronic transition. SrF’s highly diagonal Franck-Condon factors suppress vibrational branching. We eliminate rotational branching by employing a quasicycling N=1→N^′=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 10⁵ photon scatters, possibly enabling the direct laser cooling of SrF.