title: Rydberg excitation of Bose-Einstein condensates.
abstract: Rydberg atoms provide a wide range of possibilities to tailor interactions in a quantum gas. Here, we report on Rydberg excitation of Bose-Einstein condensed 87Rb atoms. The Rydberg fraction was investigated for various excitation times and temperatures above and below the condensation temperature. The excitation is locally blocked by the van der Waals interaction between Rydberg atoms to a density-dependent limit. Therefore, the abrupt change of the thermal atomic density distribution to the characteristic bimodal distribution upon condensation could be observed in the Rydberg fraction. The observed features are reproduced by a simulation based on local collective Rydberg excitations.
authors.affiliation: 5. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, Stuttgart, Germany. r.heidemann@physik.uni-stuttgart.de
authors.forename: Rolf
authors.initials: R
authors.lastname: Heidemann
authors.forename: Ulrich
authors.initials: U
authors.lastname: Raitzsch
authors.forename: Vera
authors.initials: V
authors.lastname: Bendkowsky
authors.forename: Björn
authors.initials: B
authors.lastname: Butscher
authors.forename: Robert
authors.initials: R
authors.lastname: Löw
authors.forename: Tilman
authors.initials: T
authors.lastname: Pfau