Establishing a nearly closed cycling transition in a polyatomic molecule

We study optical cycling in the polar free radical calcium monohydroxide (CaOH) and establish an experimental path towards scattering $\sim$$10^4$ photons. report rovibronic branching ratio measurements with precision at $\sim10^{-4}$ level observe weak symmetry-forbidden decays to bending modes non-zero vibrational angular momentum. Calculations are excellent agreement these predict additional decay pathways. Additionally, we perform high-resolution spectroscopy of $\widetilde{\text{X}}\,^2\Sigma^+(12^00)$ $\widetilde{\text{X}}\,^2\Sigma^+(12^20)$ hybrid states CaOH. These advances a radiative slowing, 3D magneto-optical trapping, sub-Doppler cooling