Magneto-Optical Trapping of Holmium Atoms

Abstract: We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the rare earth element Holmium. Atoms are loaded from an atomic beam source and captured in six-beam $\sigma_+ - \sigma_-$ molasses using a strong $J=15/2 \leftrightarrow J=17/2$ cycling transition at $\lambda=410.5 \rm nm$. Due to the small difference in hyperfine splittings and Land\'e $g$-factors in the lower and upper levels of the cooling transition the MOT is self-repumped without additional repump light, and deep sub-Doppler cooling is achieved with the magnetic trap turned on. We measure the leakage out of the cycling transition to metastable states and find a branching ratio $\sim 10^{-5}$ which is adequate for state resolved measurements on hyperfine encoded qubits.