Laser cooling of a natural isotope mixture of Yb+ stored in an RF trap

We demonstrate laser cooling of Yb⁺, produced by ionization of a natural isotope mixture, stored in an RF trap. One of the three major even isotopes was directly laser cooled and other isotopes were simultaneously trapped as a result of sympathetic cooling. It was possible to carry out laser cooling to the temperature at which the cloud-to-crystal phase transition occurs for ¹⁷⁴Yb⁺ , as observed in the case where enriched isotopes are used. We observed sudden drops of fluorescence owing to pumping to the ² F_7/2 state in the case of a small number of trapped Yb ⁺ ions