Radiative force from optical cycling on magnesium monofluoride

We demonstrate radiative force deflection by using an optical cycling of the X ²Σ₁^{/2 +}−A ²Π_{1 /2} electronic transition in diatomic molecule magnesium monofluoride (MgF). For the (0,0) and (0,1) bands of the electronic transition, the Franck-Condon factors—obtained by the dispersed laser-induced fluorescence spectrum—are f₀₀=0.972 and f₀₁=0.028 , which suggests that the vibrational branching is quasiclosed. Furthermore, the dark Zeeman sublevels are destabilized by applying an external magnetic field. The cycling fluorescence is clearly observed to reveal that the molecular beam is deflected by 4.9 mm via scattering ∼200 photons per molecule. This work is encouraging toward laser cooling and magneto-optical trapping of MgF molecules.