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• 1
Article
Language: English
In: Applied Physics Letters, 09 April 2012, Vol.100(15)
Description: The controlled movement of magnetic beads trapped on a surface in the moving inhomogeneous stray fields of moving domain walls between artificial domains of exchange bias layer systems has been applied for mixing of two aqueous fluids in a microfluidic device of small volume. The mixing of the two fluids can be considerably accelerated by transporting full rows of beads and use them as micro stirrers. The mixing speed in the current experiment is tripled in the first 6 min of mixing as compared to normal diffusion even for ratios of 250 between container height and bead diameter.
Keywords: Device Physics
ISSN: 0003-6951
E-ISSN: 1077-3118
Source: © 2012 American Institute of Physics (AIP)〈img src=http://exlibris-pub.s3.amazonaws.com/AIP_edited.gif style="vertical-align:middle;margin-left:7px"〉
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• 2
Article
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
Article
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
Article
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
Article
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
Article
In: Phys. Rev. D 93, 122005 (2016)
Description: The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal. Comment: Replaced with published version. Added journal reference and DOI
Keywords: Astrophysics - High Energy Astrophysical Phenomena ; Astrophysics - Instrumentation And Methods For Astrophysics
ISSN: 24700010
E-ISSN: 24700029
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• 7
Article
In: Phys. Rev. D 91, 092008 (2015)
Description: Neutrinos in the cosmic ray flux with energies near 1 EeV and above are detectable with the Surface Detector array of the Pierre Auger Observatory. We report here on searches through Auger data from 1 January 2004 until 20 June 2013. No neutrino candidates were found, yielding a limit to the diffuse flux of ultra-high energy neutrinos that challenges the Waxman-Bahcall bound predictions. Neutrino identification is attempted using the broad time-structure of the signals expected in the SD stations, and is efficiently done for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for "Earth-skimming" neutrino interactions in the case of tau neutrinos. In this paper the searches for downward-going neutrinos in the zenith angle bins $60^\circ-75^\circ$ and $75^\circ-90^\circ$ as well as for upward-going neutrinos, are combined to give a single limit. The $90\%$ C.L. single-flavor limit to the diffuse flux of ultra-high energy neutrinos with an $E^{-2}$ spectrum in the energy range $1.0 \times 10^{17}$ eV - $2.5 \times 10^{19}$ eV is $E_\nu^2 dN_\nu/dE_\nu 〈 6.4 \times 10^{-9}~ {\rm GeV~ cm^{-2}~ s^{-1}~ sr^{-1}}$. Comment: Replaced with published version. Added journal reference and DOI
Keywords: Astrophysics - High Energy Astrophysical Phenomena
ISSN: 15507998
E-ISSN: 15502368
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• 8
Article
In: JCAP 08 (2015) 049
Description: A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV. Comment: Replaced with published version. Added journal reference and DOI
Keywords: Astrophysics - High Energy Astrophysical Phenomena ; High Energy Physics - Experiment
ISSN: 14757516
E-ISSN: 14757516
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• 9
Article
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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• 10
Article
Language: English
In: Journal of High Energy Physics, 2012, Vol.2012(11), pp.1-31
Description: The ALICE experiment at the LHC has studied J/ ψ production at mid-rapidity in pp collisions at $\sqrt{s}=7$ TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5 . 6 nb −1 . The fraction of J/ ψ from the decay of long-lived beauty hadrons was determined for J/ ψ candidates with transverse momentum p t 〉 1 . 3 GeV/ c and rapidity | y | 〈 0 . 9. The cross section for prompt J/ ψ mesons, i.e. directly produced J/ ψ and prompt decays of heavier charmonium states such as the ψ (2S) and χ c resonances, is σ prompt J/ ψ ( p t 〉 1 . 3 GeV /c, | y | 〈 0 . 9) = 8 . 3 ± 0 . 8 (stat . ) ± 1 . 1 (syst . ) $_{-1.4}^{+1.5 }$ (syst . pol . ) μ b. The cross section for the production of b-hadrons decaying to J/ ψ with p t 〉 1 . 3 GeV/ c and | y | 〈 0 . 9 is ${\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}}$ ( p t 〉 1.3 GeV/ c , | y | 〈 0.9) = 1.46 ± 0.38 (stat.) $_{-0.32}^{+0.26 }$ (syst.) μ b. The results are compared to QCD model predictions. The shape of the p t and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the $\mathrm{b}\overline{\mathrm{b}}$ pair total cross section and d σ/ d y at mid-rapidity.
Keywords: Hadron-Hadron Scattering
E-ISSN: 1029-8479
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