M Weidemüller

Universität Heidelberg, Heidelburg, Baden-Württemberg, Germany

Are you M Weidemüller?

Claim your profile

Publications (135)564.63 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We provide a comprehensive comparison of a coupled channels calculation, the asymptotic bound state model (ABM), and the multichannel quantum defect theory (MQDT). Quantitative results for $^6$Li -$^{133}$Cs are presented and compared to previously measured $^6$Li -$^{133}$Cs Feshbach resonances (FRs) [M. Repp et al., Phys. Rev. A 87 010701(R) (2013)]. We demonstrate how the accuracy of the ABM can be stepwise improved by including magnetic dipole-dipole interactions and coupling to a non-dominant virtual state. We present a MQDT calculation, where magnetic dipole-dipole and second order spin-orbit interactions are included. A frame transformation formalism is introduced, which allows the assignment of measured FRs with only three parameters. All three models achieve a total rms error of < 1G on the observed FRs. We critically compare the different models in view of the accuracy for the description of FRs and the required input parameters for the calculations.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We observe two consecutive heteronuclear Efimov resonances in an ultracold Li-Cs mixture by measuring three-body loss coefficients as a function of magnetic field near a Feshbach resonance. The first resonance is detected at a scattering length of $a_-^{(1)}=-320(10)~a_0$ corresponding to $\sim 7 $ ($\sim 3$) times the Li-Cs (Cs-Cs) van der Waals range. The second resonance appears at $5.8(1.0) a_-^{(1)}$ close to the unitarity-limited regime at the sample temperature of 450 nK. Indication of a third resonance is found in the atom loss spectra. The scaling of the resonance positions is close to the universal scaling value of 4.9 predicted for zero temperature. Deviations from universality might be caused by finite-range and temperature effects, as well as magnetic field dependent Cs-Cs interactions.
    Physical Review Letters 03/2014; 112(25). · 7.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We experimentally study the full counting statistics of few-body Rydberg aggregates excited from a quasi-one-dimensional atomic gas. We measure asymmetric excitation spectra and increased second and third order statistical moments of the Rydberg number distribution, from which we determine the average aggregate size. Estimating rates for different excitation processes we conclude that the aggregates grow sequentially around an initial grain. Direct comparison with numerical simulations confirms this conclusion and reveals the presence of liquidlike spatial correlations. Our findings demonstrate the importance of dephasing in strongly correlated Rydberg gases and introduce a way to study spatial correlations in interacting many-body quantum systems without imaging.
    Physical Review Letters 01/2014; 112(1):013002. · 7.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electronically highly excited (Rydberg) atoms experience quantum-state changing interactions similar to Förster processes found in complex molecules, offering a model system to study the nature of dipole-mediated energy transport under the influence of a controlled environment. We demonstrate a nondestructive imaging method to monitor the migration of electronic excitations with high time and spatial resolution using electromagnetically induced transparency on a background gas acting as an amplifier. The many-body dynamics of the energy transport is determined by the continuous spatial projection of the electronic quantum state under observation and features an emergent spatial scale of micrometer size induced by Rydberg-Rydberg interactions.
    Science 11/2013; · 31.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent developments in the study of ultracold Rydberg gases demand an advanced level of experimental sophistication, in which high atomic and optical densities must be combined with excellent control of external fields and sensitive Rydberg atom detection. We describe a tailored experimental system used to produce and study Rydberg-interacting atoms excited from dense ultracold atomic gases. The experiment has been optimized for fast duty cycles using a high flux cold atom source and a three beam optical dipole trap. The latter enables tuning of the atomic density and temperature over several orders of magnitude, all the way to the Bose-Einstein condensation transition. An electrode structure surrounding the atoms allows for precise control over electric fields and single-particle sensitive field ionization detection of Rydberg atoms. We review two experiments which highlight the influence of strong Rydberg--Rydberg interactions on different many-body systems. First, the Rydberg blockade effect is used to pre-structure an atomic gas prior to its spontaneous evolution into an ultracold plasma. Second, hybrid states of photons and atoms called dark-state polaritons are studied. By looking at the statistical distribution of Rydberg excited atoms we reveal correlations between dark-state polaritons. These experiments will ultimately provide a deeper understanding of many-body phenomena in strongly-interacting regimes, including the study of strongly-coupled plasmas and interfaces between atoms and light at the quantum level.
    Frontiers in Physics 09/2013;
  • Matthias Weidemüller
    Nature 06/2013; · 38.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Photoionization of laser-cooled atoms using short pulses of a high-power light-emitting diode (LED) is demonstrated. Light pulses as short as 30 ns have been realized with the simple LED driver circuit. We measure the ionization cross section of (85)Rb atoms in the first excited state, and show how this technique can be used for calibrating efficiencies of ion detector assemblies.
    The Review of scientific instruments 04/2013; 84(4):043107. · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The highly exoergic nucleophilic substitution reaction F- + CH3 I shows strikingly different reaction dynamics than substitution reactions of larger halogen anions. Over a wide range of collision energies, a large fraction of indirect scattering via a long-lived hydrogen-bonded complex is found both in crossed-beam imaging experiments and in direct chemical dynamics simulations. Our measured differential scattering cross sections show large-angle scattering and low product velocities for all collision energies, resulting from efficient transfer of the collision energy to internal energy of the CH3 F reaction product. Both findings are in strong contrast to the previously studied substitution reaction of Cl- + CH3 I [Science 2008, 319, 183] at all but the lowest collision energies, a discrepancy that was not captured in a subsequent study at only a low collision energy [J. Phys. Chem. Lett. 2010, 1, 2747]. Our direct chemical dynamics simulations at the DFT/B97-1 level of theory show that the reaction is dominated by three atomic-level mechanisms, an indirect reaction proceeding via an F- -HCH2 I hydrogen-bonded complex, a direct rebound and a direct stripping reaction. The indirect mechanism is found to contribute about half of the overall substitution reaction rate at both low and high collision energies. This large fraction of indirect scattering at high collision energy is particularly surprising, since the barrier for the F- -HCH2 I complex to form products is only 0.10 eV. Overall, experiment and simulation agree very favorably in both the scattering angle and the product internal energy distributions.
    Journal of the American Chemical Society 01/2013; · 10.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Vibrationally resolved photoionization spectra of RbHe exciplexes forming on He nanodroplets are recorded using femtosecond pump-probe spectroscopy with amplitude-shaped probe pulses. The time-evolution of the spectra reveals an exciplex formation time ∼10 ps followed by vibrational relaxation extending up to ≳ 1 ns. This points to an indirect, time-delayed desorption process of RbHe off the He surface.
    The Journal of Chemical Physics 12/2012; 137(24):244307. · 3.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Interfacing light and matter at the quantum level is at the heart of modern atomic and optical physics and enables new quantum technologies involving the manipulation of single photons and atoms. A prototypical atom-light interface is electromagnetically induced transparency, in which quantum interference gives rise to hybrid states of photons and atoms called dark-state polaritons. We have observed individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states. Strong long-range interactions between Rydberg atoms give rise to an effective interaction blockade for dark-state polaritons, which results in large optical nonlinearities and modified polariton number statistics. The observed statistical fluctuations drop well below the quantum noise limit indicating that photon correlations modified by the strong interactions have a significant back-action on the Rydberg atom statistics.
    Physical Review Letters 11/2012; 110(20). · 7.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a scheme to embed molecular anions in a gas of ultracold rubidium atoms as a route towards the preparation of cold molecular ions by collisional cooling with ultracold atoms. Associative detachment as an important loss process in collisions between OH- molecules and rubidium atoms is studied. The density distribution of trapped negative ions in the multipole radiofrequency trap is measured by photodetachment tomography, which allows us to derive absolute rate coefficients for the process. We define a regime where translational and internal cooling of molecular ions embedded into the ultracold atomic cloud can be achieved.
    Physical Review A 11/2012; 86:043438. · 3.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on the observation of nineteen interspecies Feshbach resonances in an optically trapped ultracold Bose-Fermi mixture of ^{133}Cs and ^{6}Li in the two energetically lowest spin states. We assign the resonances to s- and p-wave molecular channels by a coupled-channels calculation, resulting in an accurate determination of LiCs ground state potentials. Fits of the resonance position based on the undressed Asymptotic Bound State model do not provide the same level of accuracy as the coupled-channels calculation. Several broad s-wave resonances provide prospects to create fermionic LiCs molecules with a large dipole moment via Feshbach association followed by stimulated Raman passage. Two of the s-wave resonances overlap with a zero crossing of the Cs scattering length which offers prospects for the investigation of polarons in an ultracold Li-Cs mixture.
    Physical Review A 11/2012; · 3.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. Under continuous laser coupling we create a Rydberg ensemble in the strong blockade regime, which at longer times undergoes an ionization avalanche. By combining optical imaging and ion detection, we access the full information on the dynamical evolution of the system, including the rapid increase in the number of ions and a sudden depletion of the Rydberg and ground state densities. Rydberg-Rydberg interactions are observed to strongly affect the dynamics of plasma formation. Using a coupled rate-equation model to describe our data, we extract the average energy of electrons trapped in the plasma, and an effective cross-section for ionizing collisions between Rydberg atoms and atoms in low-lying states. Our results suggest that the initial correlations of the Rydberg ensemble should persist through the avalanche. This would provide the means to overcome disorder-induced-heating, and offer a route to enter new strongly-coupled regimes.
    Physical Review Letters 09/2012; 110(4). · 7.73 Impact Factor
  • Chemical Reviews 08/2012; 112(9):4890-927. · 41.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on a compact and transportable apparatus that consists of a cold atomic target at the center of a high resolution recoil ion momentum spectrometer. Cold rubidium atoms serve as a target which can be operated in three different modes: in continuous mode, consisting of a cold atom beam generated by a two-dimensional magneto-optical trap, in normal mode in which the atoms from the beam are trapped in a three-dimensional magneto-optical trap (3D MOT), and in high density mode in which the 3D MOT is operated in dark spontaneous optical trap configuration. The targets are characterized using photoionization.
    The Review of scientific instruments 07/2012; 83(7):073112. · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We propose a new all-optical method to image individual Rydberg atoms embedded within dense gases of ground state atoms. The scheme exploits interaction-induced shifts on highly polarizable excited states of probe atoms, which can be spatially resolved via an electromagnetically induced transparency resonance. Using a realistic model, we show that it is possible to image individual Rydberg atoms with enhanced sensitivity and high resolution despite photon-shot noise and atomic density fluctuations. This new imaging scheme could be extended to other impurities such as ions, and is ideally suited to equilibrium and dynamical studies of complex many-body phenomena involving strongly interacting particles. As an example we study blockade effects and correlations in the distribution of Rydberg atoms optically excited from a dense gas.
    Physical Review Letters 01/2012; 108(1):013002. · 7.73 Impact Factor
  • Olivier Dulieu, Roman Krems, Matthias Weidemüller, Stefan Willitsch
    [Show abstract] [Hide abstract]
    ABSTRACT: A graphical abstract is available for this content
    Physical Chemistry Chemical Physics 11/2011; 13(42):18703-4. · 3.83 Impact Factor
  • Source
    J Deiglmayr, M. Repp, O. Dulieu, R Wester, M Weidemüller
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the rovibrational population redistribution of polar molecules in the electronic ground state induced by spontaneous emission and blackbody radiation. As a model system we use optically trapped LiCs molecules formed by photoassociation in an ultracold two-species gas. The population dynamics of vibrational and rotational states is modeled using an ab-initio electric dipole moment function and experimental potential energy curves. Comparison with the evolution of the v"=3 electronic ground state yields good qualitative agreement. The analysis provides important input to assess applications of ultracold LiCs molecules in quantum simulation and ultracold chemistry.
    The European Physical Journal D 11/2011; 65:99. · 1.51 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we consider the effects of strong dipole–dipole interactions on three-level interference phenomena such as coherent population trapping and electromagnetically induced transparency. Experiments are performed on laser cooled rubidium atoms and the results compared to a many-body theory based on either a reduced many-body density matrix expansion or Monte Carlo simulations of many-body rate equations. We show that these approaches permit quantitative predictions of the experimentally observed excitation and transmission spectra. Based on the calculations, we moreover predict a universal scaling of the nonlinear response of cold Rydberg gases.
    Journal of Physics B Atomic Molecular and Optical Physics 09/2011; 44(18):184018. · 2.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present a wavelength sensor setup for monochromatic visible light, based on the double-layer photo diode WS-7.56. Employing high-precision electronics and automatic compensation of different error sources, we achieve a measurement accuracy of ±0.025 nm with a resolution below 0.01 nm. The described apparatus is particularly suited for the determination of small laser frequency deviations in atomic physics experiments. Various design issues as well as error sources and diode characteristics are discussed.
    The Review of scientific instruments 09/2011; 82(9):093111. · 1.52 Impact Factor

Publication Stats

3k Citations
564.63 Total Impact Points


  • 2009–2014
    • Universität Heidelberg
      • • Institute of Physics
      • • Institute of Physical Chemistry
      Heidelburg, Baden-Württemberg, Germany
    • Universität Ulm
      • Institute for Quantum Information
      Ulm, Baden-Württemberg, Germany
  • 2004–2011
    • University of Freiburg
      • Department of Microsystems Engineering (IMTEK)
      Freiburg, Lower Saxony, Germany
  • 2005–2010
    • University of São Paulo
      • • Instituto de Física (IF) (São Paulo)
      • • Instituto de Física de São Carlos (IFSC)
      São Paulo, Estado de Sao Paulo, Brazil
  • 2007
    • University Hospital München
      München, Bavaria, Germany
  • 1995–2007
    • Max Planck Institute of Quantum Optics
      Arching, Bavaria, Germany
  • 1998–2004
    • Max Planck Institute for Nuclear Physics
      Heidelburg, Baden-Württemberg, Germany
    • Ludwig-Maximilian-University of Munich
      München, Bavaria, Germany
  • 2003
    • University of Innsbruck
      • Institut für Experimentalphysik
      Innsbruck, Tyrol, Austria
  • 1997
    • Universität Hamburg
      • Institut für Laserphysik
      Hamburg, Hamburg, Germany
  • 1996
    • University of Amsterdam
      Amsterdamo, North Holland, Netherlands