We report on the realization of quantum degenerate gas mixtures of the
alkaline-earth element strontium with the alkali element rubidium. A key
ingredient of our scheme is sympathetic cooling of Rb by Sr atoms that are
continuously laser cooled on a narrow linewidth transition. This versatile
technique allows us to produce ultracold gas mixtures with a phase-space
density of up to 0.06 for both elements. By further evaporative cooling we
create double Bose-Einstein condensates of 87Rb with either 88Sr or 84Sr,
reaching more than 10^5 condensed atoms per element for the 84Sr-87Rb mixture.
These quantum gas mixtures constitute an important step towards the production
of a quantum gas of polar, open-shell RbSr molecules.Comment: 9 pages, 5 figure
Abstract.We report on our study of the free-fall expansion of a finite-temperature BoseEinstein condensed cloud of 87 Rb. The experiments are performed with a variable total number of atoms while keeping constant the number of atoms in the condensate. The results provide evidence that the BEC dynamics depends on the interaction with thermal fraction. In particular, they provide experimental evidence that thermal cloud compresses the condensate.
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