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Berlin Brandenburg

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  • 1
    Language: English
    In: Physical review letters, 10 August 2018, Vol.121(6), pp.064801
    Description: Particle-beam-driven plasma wakefield acceleration (PWFA) enables various novel high-gradient techniques for powering future compact light-source and high-energy physics applications. Here, a driving particle bunch excites a wakefield response in a plasma medium, which may rapidly accelerate a trailing witness beam. In this Letter, we present the measurement of ratios of acceleration of the witness bunch to deceleration of the driver bunch, the so-called transformer ratio, significantly exceeding the fundamental theoretical and thus far experimental limit of 2 in a PWFA. An electron bunch with ramped current profile was utilized to accelerate a witness bunch with a transformer ratio of 4.6_{-0.7}^{+2.2} in a plasma with length ∼10  cm, also demonstrating stable transport of driver bunches with lengths on the order of the plasma wavelength.
    Keywords: Plasma ; Acceleration ; Deceleration ; Plasma (Physics) ; Transformers;
    ISSN: 00319007
    E-ISSN: 1079-7114
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  • 2
    In: Phys. Rev. Lett. 120, 193401 (2018)
    Description: Rydberg atoms immersed in a Bose-Einstein condensate interact with the quantum gas via electron-atom and ion-atom interaction. To suppress the typically dominant electron-neutral interaction, Rydberg states with principal quantum number up to $n = 190$ are excited from a dense and tightly trapped micron-sized condensate. This allows us to explore a regime where the Rydberg orbit exceeds the size of the atomic sample by far. In this case, a detailed lineshape analysis of the Rydberg excitation spectrum provides clear evidence for ion-atom interaction at temperatures well below a microkelvin. Our results may open up ways to enter the quantum regime of ion-atom scattering for the exploration of charged quantum impurities and associated polaron physics. Comment: 9 pages, 6 figures
    Keywords: Physics - Atomic Physics ; Condensed Matter - Quantum Gases
    ISSN: 00319007
    E-ISSN: 10797114
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  • 3
    In: Phys. Rev. Lett. 118, 223001 (2017)
    Description: We report on a novel method for photo-association of strongly polar trilobite Rydberg molecules. This exotic ultralong-range dimer, consisting of a ground-state atom bound to the Rydberg electron via electron-neutral scattering, inherits its polar character from the admixture of high angular momentum electronic orbitals. The absence of low-$L$ character hinders standard photo-association techniques. Here, we show that for suitable principal quantum numbers resonant coupling of the orbital motion with the nuclear spin of the perturber, mediated by electron-neutral scattering, hybridizes the trilobite molecular potential with the more conventional ${\rm{S}}$-type molecular state. This provides a general path to associate trilobite molecules with large electric dipole moments, as demonstrated via high-resolution spectroscopy. We find a dipole moment of 135(45) D for the trilobite state. Our results are compared to theoretical predictions based on a Fermi-model. Comment: 8 pages, 4 figures
    Keywords: Physics - Atomic Physics ; Condensed Matter - Quantum Gases
    ISSN: 10797114
    E-ISSN: 10797114
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  • 4
    In: Phys. Rev. Lett. 121, 193401 (2018)
    Description: We study the long-range interaction of a single ion with a highly excited ultracold Rydberg atom and report on the direct observation of ion-induced Rydberg excitation blockade mediated over tens of micrometer distances. Our hybrid ion-atom system is directly produced from an ultracold atomic ensemble via near-threshold photo-ionization of a single Rydberg excitation, employing a two-photon scheme which is specifically suited for generating a very low-energy ion. The ion's motion is precisely controlled by small electric fields, which allows us to analyze the blockade mechanism for a range of principal quantum numbers. Finally, we explore the capability of the ion as a high-sensitivity single-atom-based electric field sensor. The observed ion - Rydberg-atom interaction is of current interest for entanglement generation or studies of ultracold chemistry in hybrid ion-atom systems. Comment: 7 pages, 7 figures
    Keywords: Physics - Atomic Physics ; Condensed Matter - Quantum Gases
    ISSN: 00319007
    E-ISSN: 10797114
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  • 5
    In: Phys. Rev. Lett. 123, 073003 (2019)
    Description: The level structure of negative-ions near the electron detachment limit dictates the low-energy scattering of an electron with the parent neutral atom. We demonstrate that a single ultracold atom bound inside a Rydberg orbit forming an ultralong-range Rydberg molecule provides an atomic-scale system which is highly sensitive to electron-neutral scattering and thus allows for detailed insights into the underlying near-threshold anion states. Our measurements reveal the so far unobserved fine structure of the $^3P_J$ triplet of Rb$^-$ and allow us to extract parameters of the associated $p$-wave scattering resonances which deviate from previous theoretical estimates. Moreover, we observe a novel alignment mechanism for Rydberg molecules mediated by spin-orbit coupling in the negative ion. Comment: 11 pages, 6 figures
    Keywords: Physics - Atomic Physics ; Condensed Matter - Quantum Gases
    ISSN: 00319007
    E-ISSN: 10797114
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  • 6
    In: Phys. Rev. Lett. 116, 241101 (2016)
    Description: We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory. Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary files
    Keywords: Astrophysics - High Energy Astrophysical Phenomena ; Astrophysics - Instrumentation And Methods For Astrophysics ; High Energy Physics - Experiment
    ISSN: 00319007
    E-ISSN: 10797114
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