Düsseldorf 2007 – scientific programme
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A: Fachverband Atomphysik
A 7: Ultracold Plasmas and Rydberg Dynamics (jointly with Q)
A 7.2: Fachvortrag
Tuesday, March 20, 2007, 11:00–11:30, 5M
Rydberg excitation in the strong blockade regime: from thermal cloud to BEC — •Vera Bendkowsky1, Rolf Heidemann1, Ulrich Raitzsch1, Björn Butscher1, Helmar Bender1, Robert Löw1, Luis Santos2, and Tilman Pfau1 — 15. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — 2Institut für Theoretische Physik, Universität Hannover, Appelstraße 2, 30167 Hannover
The van der Waals interaction of Rydberg atoms can - depending on the atomic density and the excitation strength - lead to a supression of Rydberg excitation in a cloud of ground state atoms. In this blockade regime the atomic sample can be considered as consisting of many blockade spheres with N ground state atoms within a sphere but only one excited Rydberg atom.
In our experiments we excite magnetically trapped Rubidium atoms at temperatures between a few µK and BEC to the 43S state. In the thermal cloud we observe saturation in the Rydberg excitation for a large range of densities and Rabi frequencies Ω0. As expected for coherent collective excitation of any mesoscopic system the initial excitation rate is proportional to √NΩ0. The scaling of the saturation value is investigated with respect to N and Ω0.
Furthermore we present first results on Rydberg excitation in a BEC. The measurements show a clear signature of Rydberg excitation within the BEC. The results are compared with a mean field calculation for the quantum dynamics above and below Tc.