Collisional Cooling of Light Ions by Cotrapped Heavy Atoms

We experimentally demonstrate cooling of trapped ions by collisions with cotrapped, higher-mass neutral atoms. It is shown that the lighter K-39(+) ions, created by ionizing K-39 atoms in a magneto-optical trap (MOT), when trapped in an ion trap and subsequently allowed to cool by collisions with ultracold, heavier Rb-85 atoms in a MOT, exhibit a longer trap lifetime than without the localized Rb-85 MOT atoms. A similar cooling of trapped Rb-85(+) ions by ultracold Cs-133 atoms in aMOT is also demonstrated in a different experimental configuration to validate this mechanism of ion cooling by localized and centered ultracold neutral atoms. Our results suggest that the cooling of ions by localized cold atoms holds for any mass ratio, thereby enabling studies on a wider class of atom-ion systems irrespective of their masses.