Measurement of collisions between rubidium atoms and optically dark rubidium ions in trapped mixtures

Abstract

We measure the collision rate coefficient between laser cooled Rubidium (Rb) atoms in a magnetooptical trap (MOT) and optically dark Rb + ions in an overlapping Paul trap. In such a mixture, the ions are created from the MOT atoms and allowed to accumulate in the ion trap, which results in a significant reduction in the number of steady state MOT atoms. A theoretical rate equation model is developed to describe the evolution of the MOT atom number, due to ionization and ion-atom collision, and derive an expression for the ion-atom collision rate coefficient. The loss of MOT atoms is studied systematically, by sequentially switching on the various mechanisms in the experiment. Combining the measurements with the model allows the direct determination of the ion-atom collision rate coefficient. Finally the scope of the experimental technique developed here is discussed.

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 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 + .…”

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

“…Recently, a hybrid trap was developed that also incorporates an optical cavity [9]. Over the past decade, since the hybrid trap was originally proposed [10,11], both experimental [2,[4][5][6][7][8][9][12][13][14][15][16][17][18][19][20][21][22] and theoretical [23][24][25][26][27][28][29][30] interest in low-energy ion-neutral collisions has surged.…”

“…Recently, hybrid trap measurements of the total elastic and change-exchange collision rate for closed-shell, optically dark Rb+ ions on Rb (rubidium) were reported by Lee et al [17]. The fluorescence of the neutral species is used to measure the total collision rate of optically dark ions.…”