Hannover 2003 – wissenschaftliches Programm
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Q: Quantenoptik
Q 8: Quantengase 1
Q 8.8: Vortrag
Montag, 24. März 2003, 15:45–16:00, F303
On the nature of the molecules in the JILA experiment — •Thomas Gasenzer1, Thorsten Köhler2, and Keith Burnett2 — 1Institut für Theoretische Physik, Philosophenweg 16, D-69120 Heidelberg — 2Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK
In a recent experiment at JILA [Donley et al., Nature (London) 417, 529 (2002)], large oscillations in the atom number of the condensate and “burst” fractions as well as in the sum of these have been observed, when the rubidium-85 system was exposed to rapid variations of an external magnetic field close to a Feshbach resonance. We present a microscopic theory of these oscillations [T. Köhler, T. Gasenzer, and K. Burnett, arXiv.org eprint cond-mat/0209100, Phys. Rev. A, to appear (2002)] which shows that, besides the atomic condensate, a fraction of molecules as well as a “burst” of unbound atom pairs develops. The results strongly indicate that the fraction of missing atoms in the experiment corresponds to atoms bound to diatomic molecules. We present the density profile of the molecules confined in the trap. This shows that the molecules in fact form a Bose-Einstein condensate. We discuss the nature of these extremely diffuse, loosely bound molecules and show their emergence in the Feshbach resonant system of open and closed molecular channels. The theory allows us to identify the role of these molecules in the experiment as well as to examine the viability of proposed detection schemes for the molecules. It gives a transparent account of the Ramsey-like interference mechanism which leads to the observed oscillations and enables the identification of possible optimization procedures.