Spectroscopy of laser cooling transitions in MgF

We measure the complete set of transition frequencies necessary to laser cool and trap MgF molecules. Specifically, we report the frequency of multiple low $J$ transitions of the $X^2\Sigma^+(v^{\prime\prime}=0,1) \rightarrow A^2\Pi_{1/2}(v^\prime=0)$, $X^2\Sigma^+(v^{\prime\prime}=1,2) \rightarrow A^2\Pi_{1/2}(v^\prime=1)$, and $X^2\Sigma^+(v^{\prime\prime}=1) \rightarrow B^2\Sigma^+(v^{\prime}=0)$ bands of MgF. The measured $X^2\Sigma^+(v^{\prime\prime}=1)\rightarrow B^2\Sigma^+(v^\prime=0)$ spectrum allowed the spin-rotation and hyperfine parameters of the $B^2\Sigma^+(v=0)$ state of MgF to be determined. Furthermore, we demonstrate optical cycling in MgF by pumping molecules into the $X^2\Sigma^+(v=1,2)$ states. Optical pumping enhances the spectroscopic signals of transitions originating in the $N^{\prime\prime}=1$ level of the $X^2\Sigma^+(v^{\prime\prime}=1,2)$ states.