Model-independent measurements of the sodium magneto-optical trap's excited-state population

Abstract

We present model-independent measurements of the excited-state population of atoms in a sodium (Na) magneto-optical trap (MOT) using a hybrid ion-neutral trap composed of a MOT and a linear Paul trap (LPT). We photoionize excited Na atoms trapped in the MOT and use two independent methods to measure the resulting ions: directly by trapping them in our LPT, and indirectly by monitoring changes in MOT fluorescence. By measuring the ionization rate via these two independent methods, we have enough information to directly determine the population of MOT atoms in the excited-state. The resulting measurement reveals that there is a range of trapping-laser intensities where the excited-state population of atoms in our MOT follows the standard two-level model intensity-dependence. However, an experimentally determined effective saturation intensity must be used instead of the theoretically predicted value from the two-level model. We measured the effective saturation intensity to be $I_{\mathrm{se}}=22.9(3)\text{mW}/{\text{cm}}^2$ for the type-I Na MOT and $I_{\mathrm{se}}=48.9(7)\text{mW}/{\text{cm}}^2$ for the type-II Na MOT, approximately 1.7 and 3.6 times the theoretical estimate, respectively. Lastly, at large trapping-laser intensities, our experiment reveals a clear departure from the two-level model at a critical intensity that we believe is due to a state-mixing effect, whose critical intensity can be determined by a simple power broadening model.

arXiv comment10 pages, 8 figures

References in corpus (12)

• Laser cooling of a diatomic molecule
• Observation of Cold Collisions between Trapped Ions and Trapped Atoms
• Light-assisted ion-neutral reactive processes in the cold regime: radiative molecule formation vs. charge exchange
• Controlling chemical reactions of a single particle
• Evidence of sympathetic cooling of Na+ ions by a Na MOT in a hybrid trap
• The role of electronic excitation in cold atom-ion chemistry
• Blue-detuned magneto-optical trap
• Ion-neutral sympathetic cooling in a hybrid linear rf Paul and magneto-optical trap
• Measurement of low-energy Na^+ -- Na total collision rate in an ion--neutral hybrid trap
• Ultracold, radiative charge transfer in hybrid Yb ion - Rb atom traps
• Loading a linear Paul trap to saturation from a magneto-optical trap
• Off-resonance energy absorption in a linear Paul trap due to mass selective resonant quenching

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• Measurement of charge-exchange between Na and \ce{Ca+} in a hybrid trap