Measurement of the low-energyNa+−Natotal collision rate in an ion-neutral hybrid trap

Abstract

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.

Universal nonmonotonic structure in the saturation curves of magneto-optical-trap-loadedNa+ions stored in an ion-neutral hybrid trap: Prediction and observation

“…Apart from our research group [15], several other groups [16][17][18][19][20] have the necessary experimental facilities to test our predictions in the case of MOT-loaded traps, and since, as we showed, the predicted phenomenon is robust with respect to rf trap types, loading mechanisms, and temperature effects, we hope that other research groups may soon test and confirm our predictions.…”

“…For this purpose we used a MOT-loaded ion-neutral hybrid trap [15]. Figure 5 shows the results of our experiments.…”

“…In fact, we found that the shape of N s (λ) is universal, i.e., it is the same for any kind of rf trap, and shows four clearly defined dynamical regimes, which we label Regions I to IV. In this paper, based on physical arguments and detailed ab-inito molecular-dynamics simulations, we predict the qualitative shape of the universal curve N s (λ), and experimentally verify our predictions with the help of a MOT-loaded ion-neutral trap [15]. While knowledge of the steady-state ion capacity N s of rf traps in general is in itself an important fundamental problem, the results are also of practical interest in atomic physics.…”

“…For many applications (see, e.g., [15,19]) it is necessary to know N s (λ) for a given rf trap. Figure 2 shows N s (λ) as a function of loading rate λ for the same Paul trap control parameters used to generate Fig.…”

“…While knowledge of the steady-state ion capacity N s of rf traps in general is in itself an important fundamental problem, the results are also of practical interest in atomic physics. Collision-rate experiments [15][16][17][18][19][20], e.g., use the steady-state ion capacity to measure the total collision rate, because it ensures constant density, size, and temperature conditions during the measurement. This is particularly helpful when working with optically dark, closed-shell ions such as Rb + and Na + .…”