We present measurements of the total elastic and resonant charge-exchange ion-atom collision rate coefficient jtia of cold sodium (Na) with optically dark low-energy Na+ ions in a hybrid ion-neutral trap. To determine ka, we measured the trap loading and loss rates from both a Na magneto-optical trap (MOT) and a linear radio-frequency quadra pole Paul trap. We found the total rate coefficient to be 7.4 ± 1.9 x 10~8 cm3/s for the type-I Na MOT immersed within an «140-K ion cloud and 1.10 ± 0.25 x 10"7 cm3/s for the type-II Na MOT within an « 1070-K ion cloud. Our measurements show excellent agreement with previously reported theoretical fully quantal ah initio calculations. In the process of determining the total rate coefficient, we demonstrate that a MOT can be used to probe an optically dark ion cloud's spatial distribution within a hybrid trap.

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A hybrid ion-neutral trap provides an ideal system to study collisional dynamics between ions and neutral atoms. This system provides a general cooling method that can be applied to species that do not have optically accessible transitions, and can also potentially cool internal degrees of freedom. The long range polarization potentials (V ∝ −α/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 of trapped Na + ions, which are closed shell and therefore do not have a laser induced atomic transition from the ground state, by equal mass cold Na atoms in a magneto-optical trap (MOT).

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Long range polarization forces between ions and neutral atoms result in large elastic scattering cross sections, e.g., ∼ 10 6 a.u. for Na-Na + or Na-Ca + at cold and ultracold temperatures. This suggests that a hybrid ion-neutral trap should offer a general means for significant sympathetic cooling of atomic or molecular ions. We present simion 7.0 simulation results concerning the advantages and limitations of sympathetic cooling within a hybrid trap apparatus consisting of a linear rf Paul trap concentric with a Na magneto-optical trap (MOT). This paper explores the impact of various heating mechanisms on the hybrid system and how parameters related to the MOT, Paul trap, number of ions, and ion species affect the efficiency of the sympathetic cooling.

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