State-selected rubidium-87 molecules were created at rest in a dilute Bose-Einstein condensate of rubidium-87 atoms with coherent free-bound stimulated Raman transitions. The transition rate exhibited a resonance line shape with an extremely narrow width as small as 1.5 kilohertz. The precise shape and position of the resonance are sensitive to the mean-field interactions between the molecules and the atomic condensate. As a result, we were able to measure the molecule-condensate interactions. This method allows molecular binding energies to be determined with unprecedented accuracy and is of interest as a mechanism for the generation of a molecular Bose-Einstein condensate.
We analyze the dynamics of a dilute, trapped Bose-condensed atomic gas coupled to a diatomic molecular Bose gas by coherent Raman transitions. This system is shown to result in a new type of "superchemistry," in which giant collective oscillations between the atomic and the molecular gas can occur. The phenomenon is caused by stimulated emission of bosonic atoms or molecules into their condensate phases.
The process of stimulated Raman adiabatic passage ͑STIRAP͒ provides a possible route for the generation of a coherent molecular Bose-Einstein condensate ͑BEC͒ from an atomic BEC. We analyze this process in a three-dimensional mean-field theory, including atom-atom interactions and nonresonant intermediate levels. We find that the process is feasible, but at larger Rabi frequencies than anticipated from a crude single-mode lossless analysis, due to two-photon dephasing caused by the atomic interactions. We then identify optimal strategies in STIRAP allowing one to maintain high conversion efficiencies with smaller Rabi frequencies and under experimentally less demanding conditions.
We report experimental evidence of Sisyphus cooling in atoms with a 1 S 0 ground state. Since Jϭ0, any cooling mechanism which requires multiple sublevels can only occur in the isotopes which have nuclear spin I 0. Ytterbium has seven stable isotopes and offers a unique system in which we can study cooling on F ϭ0→1 (168,170,172,174,176 Yb), Fϭ1/2→3/2 (171 Yb), and Fϭ5/2→7/2 (173 Yb), depending on the selection of isotope. We have trapped each of the seven stable isotopes of ytterbium in a magneto-optical trap ͑MOT͒ using the strong 1 S 0-1 P 1 transition, and transferred them into a second MOT which uses the much narrower 1 S 0-3 P 1 intercombination transition. We have measured the temperature of isotopes 171 Yb, 173 Yb, and 174 Yb in the 1 S 0-3 P 1 MOT, as a function of the intensity and detuning of the trapping laser. The temperature of 174 Yb was found to increase more rapidly with intensity than predicted by Doppler cooling theory, in agreement with earlier work on alkaline-earth atoms. In the odd isotopes the temperature was found to decrease with increasing angular momentum, as observed in earlier experiments and three-dimensional simulations.
We have observed Bose-Einstein condensation of large numbers of 87 Rb atoms in a magnetic time-averaged orbiting potential ͑TOP͒ trap. Over 1.5ϫ10 9 atoms are captured in the trap and evaporatively cooled to produce condensates containing up to 2ϫ10 5 atoms. We discuss special considerations relating to the production of large Bose-Einstein condensates in a TOP trap, and present measurements of the condensate fraction for this case.
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