Evidence of sympathetic cooling of Na+ ions by a Na MOT in a hybrid trap

TL;DR

This paper provides experimental evidence that Na+ ions can be sympathetically cooled by cold Na atoms in a hybrid trap, demonstrating a general cooling method applicable to species lacking optical transitions.

Contribution

First experimental demonstration of sympathetic cooling of Na+ ions by a Na MOT in a hybrid trap system, highlighting a versatile cooling approach for optically inaccessible ions.

Findings

Na+ ions are cooled via collisions with Na atoms in a hybrid trap.

Sympathetic cooling is effective even for closed-shell ions without optical transitions.

Large scattering cross sections facilitate efficient cooling at cold temperatures.

Abstract

A hybrid ion-neutral trap provides an ideal system to study collisional dynamics between ions and neutrals. This system provides a general cooling method that can be applied to optically inaccessible species and can also potentially cool internal degrees of freedom. The long range polarization potentials ($V\propto-\alpha/r^4$) between ions and neutrals result in large scattering cross sections at cold temperatures, making the hybrid trap a favorable system for efficient sympathetic cooling of ions by collisions with neutral atoms. We present experimental evidence of sympathetic cooling in a hybrid trap of \ce{Na+} ions, which are closed shell and therefore do not have a laser induced atomic transition, by equal mass cold Na atoms in a magneto-optical trap (MOT).