Narrow-line-mediated Sisyphus cooling in the ³P₂ metastable state of strontium

We demonstrate narrow-line-mediated Sisyphus cooling of magnetically trapped strontium (Sr) in the 5s5p\,³P₂ state. A 641 nm standing-wave, blue-detuned from the 5s4d\,³D₃\,→$ $\,5p4d\,³F₄$ transition, creates a dissipative optical lattice in the $³D₃$ state. By combining Doppler cooling and Sisyphus cooling on the $5s5p\,³P₂\,→ 5s4d\,³D₃ transition at 2.92 $μ$m, we observed efficient cooling of magnetically trapped atoms. By optically pumping the atoms to the 5s5p\,³P₀ state, we facilitate continuous outcoupling via a moving optical lattice with two fold improvement in atom number. Our scheme applies to next-generation quantum sensors using continuous ultracold atomic beams.