Optical Trapping of a Polyatomic Molecule in an $\mathrm{\ell }$-Type Parity Doublet State

We report optical trapping of a polyatomic molecule, calcium monohydroxide (CaOH). CaOH molecules from a magneto-optical trap are sub-Doppler laser cooled to $20(3)\mu \text{K}$ in free space and loaded into an optical dipole trap. We attain an in-trap molecule number density of $3(1)\times {10}^9{\text{cm}}^{-3}$ at a temperature of $57(8)\mu$K. Trapped CaOH molecules are optically pumped into an excited vibrational bending mode, whose $\mathrm{\ell }$-type parity doublet structure is a potential resource for a wide range of proposed quantum science applications with polyatomic molecules. We measure the spontaneous, radiative lifetime of this bending mode state to be $\sim$$0.7\text{ s}$.