Collisional cooling of light ions by cotrapped heavy atoms

Abstract

We experimentally demonstrate cooling of trapped ions by collisions with cotrapped, higher-mass neutral atoms. It is shown that the lighter 39K+ ions, created by ionizing 39K atoms in a magneto-optical trap (MOT), when trapped in an ion trap and subsequently allowed to cool by collisions with ultracold, heavier 85Rb atoms in a MOT, exhibit a longer trap lifetime than without the localized 85Rb MOT atoms. A similar cooling of trapped 85Rb+ ions by ultracold 133Cs atoms in a MOT 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.