title: Probing an Electron Scattering Resonance using Rydberg Molecules within a Dense and Ultracold Gas.
abstract: We present spectroscopy of a single Rydberg atom excited within a Bose-Einstein condensate. We not only observe the density shift as discovered by Amaldi and Segrè in 1934, but a line shape that changes with the principal quantum number n. The line broadening depends precisely on the interaction potential energy curves of the Rydberg electron with the neutral atom perturbers. In particular, we show the relevance of the triplet p-wave shape resonance in the e^{-}-Rb(5S) scattering, which significantly modifies the interaction potential. With a peak density of 5.5×10^{14}  cm^{-3}, and therefore an interparticle spacing of 1300 a_{0} within a Bose-Einstein condensate, the potential energy curves can be probed at these Rydberg ion-neutral atom separations. We present a simple microscopic model for the spectroscopic line shape by treating the atoms overlapped with the Rydberg orbit as zero-velocity, uncorrelated, pointlike particles, with binding energies associated with their ion-neutral separation, and good agreement is found.
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schlagmüller
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Tara Cubel
authors.initials: TC
authors.lastname: Liebisch
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Huan
authors.initials: H
authors.lastname: Nguyen
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Graham
authors.initials: G
authors.lastname: Lochead
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Engel
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Böttcher
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Karl M
authors.initials: KM
authors.lastname: Westphal
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Kathrin S
authors.initials: KS
authors.lastname: Kleinbach
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Löw
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hofferberth
authors.affiliation: 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Pfau
authors.affiliation: Department of Physics and Astronomy, Purdue University, 47907 West Lafayette, Indiana, USA.
authors.forename: Jesús
authors.initials: J
authors.lastname: Pérez-Ríos
authors.affiliation: Department of Physics and Astronomy, Purdue University, 47907 West Lafayette, Indiana, USA.
authors.forename: Chris H
authors.initials: CH
authors.lastname: Greene
mesh_terms: D003080:Cold Temperature; D004583:Electrons; D004601:Elementary Particles; D005740:Gases / Q000737:chemistry*; D008962:Models, Theoretical; D011789:Quantum Theory; D012542:Scattering, Radiation; D013057:Spectrum Analysis / Q000379:methods*; D013816:Thermodynamics
chemical_list: D005740:Gases