Magneto-optical trapping of holmium atoms

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 σ₊ - σ₋ molasses using a strong J=15/2 ↔ J=17/2 cycling transition at λ=410.5 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 ~ 10⁻⁵ which is adequate for state resolved measurements on hyperfine encoded qubits.