A magneto-optical trap of silver and potassium atoms

We demonstrate a dual magneto-optical trap of ¹⁰⁹Ag and ³⁹K. For silver, a decreasing-field Zeeman slower loads a MOT of 1.5×10⁸ atoms at a temperature of 0.74(5) mK, with laser cooling occurring primarily on the D₂ line of 4d¹⁰5s\; ²S1/2→ 5p\; ²P3/2 at 328 nm. We create a novel Ag "dark spot MOT," where shelving the atoms in a dark state enhances the captured atom number by a factor of two and the lifetime by a factor of four. For potassium, we obtain 2×10⁸ trapped atoms, and further cooling on the D₁ transition via grey molasses results in a cloud of 1.2× 10⁸ atoms at 7(1) $μ$K. We observe evidence of photoionization loss of the K MOT in the presence of Ag laser-cooling light, with implications for optimal dual species loading strategies. Our results on Ag point to simple and general laser cooling strategies for other coinage metals (Au, Cu). Furthermore, this work lays the foundation for the production of alkali-coinage metal degenerate quantum mixtures and highly polar molecules.