EA Cornell

University of Colorado at Boulder, Boulder, Colorado, United States

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Publications (191)630.19 Total impact

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    ABSTRACT: Boltzmann noticed that his transport equation predicts special cases in which gases never reach thermal equilibrium. One example is the monopole breathe mode of atoms confined in a perfectly isotropic three-dimensional (3D) harmonic potential. Such a complete absence of damping had not been observed in nature, and this anomaly weakened Boltzmann’s then-controversial claim to have established a microscopic, atomistic basis for thermodynamics. Only recently has non-damping of a monopole mode in lower-dimensional systems been reported in cold-atom experiments performed in highly elongated trap geometries. The difficulty in generating a sufficiently spherical harmonic confinement for cold atoms has so far prevented the observation of Boltzmann’s fully 3D, isotropic case. Here, thanks to a new magnetic trap capable of producing near-spherical harmonic confinement for cold atoms, we report a long-delayed vindication for Boltzmann: the observation of a 3D monopole mode for which the collisional contribution to damping vanishes.
    No preview · Article · Oct 2015 · Nature Physics
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    Daniel N. Gresh · Kevin C. Cossel · Yan Zhou · Jun Ye · Eric A. Cornell
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    ABSTRACT: A number of extensions to the Standard Model of particle physics predict a permanent electric dipole moment of the electron (eEDM) in the range of the current experimental limits. Trapped ThF$^+$ will be used in a forthcoming generation of the JILA eEDM experiment. Here, we present extensive survey spectroscopy of ThF$^+$ in the 700 - 1000 nm spectral region, with the 700 - 900 nm range fully covered using frequency comb velocity modulation spectroscopy. We have determined that the ThF$^+$ electronic ground state is $X$ $^3\Delta_1$, which is the eEDM-sensitive state. In addition, we report high-precision rotational and vibrational constants for 14 ThF$^+$ electronic states, including excited states that can be used to transfer and readout population in the eEDM experiment.
    Full-text · Article · Sep 2015 · Journal of Molecular Spectroscopy
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    ABSTRACT: Well before the atomistic nature of matter was experimentally established, Ludwig Boltzmann's audacious effort to explain the macroscopic world of human experience in terms of the workings of an unseen microscopic world met with vigorous opposition. A contentious point was the problem of irreversibility: the microscopic equations of motion are reversible, yet friction and viscosity cause things always to slow down and warm up, never to speed up and cool down. What was worse, Boltzmann himself discovered that his transport equation predicts special cases in which gases never come to thermal equilibrium, a particular example being that the monopole "breathe" mode of gas will never damp if it is confined in 3D to a perfectly isotropic harmonic potential. Such absences of damping were not observed in nature. Nondamping of a monopole mode in lower dimensional systems has only very recently been observed, using cold atoms. Kinoshita et al. and Chevy et al. have experimentally observed suppressed relaxation in highly elongated geometries. The difficulty in generating sufficiently spherical harmonic confinement for ultracold atoms, however, has meant that Boltzmann's fully 3D, isotropic case has never been observed. With the development of a new magnetic trap capable of producing near-spherical harmonic confinement for ultracold atoms, we have been able to make the first observation of this historically significant oddity. We observe a monopole mode for which the collisional contribution to damping vanishes, a long-delayed vindication for Boltzmann's microscopic theory.
    No preview · Article · Sep 2015
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    Kang-Kuen Ni · Huanqian Loh · Matt Grau · Kevin C. Cossel · Jun Ye · Eric A. Cornell
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    ABSTRACT: We use (1+1$'$) resonance-enhanced multiphoton photodissociation (REMPD) to detect the population in individual rovibronic states of trapped HfF$^+$ with a single-shot absolute efficiency of 18%, which is over 200 times better than that obtained with fluorescence detection. The first photon excites a specific rotational level to an intermediate vibronic band at 35,000-36,500 cm$^{-1}$, and the second photon, at 37,594 cm$^{-1}$ (266 nm), dissociates HfF$^+$ into Hf$^+$ and F. Mass-resolved time-of-flight ion detection then yields the number of state-selectively dissociated ions. Using this method, we observe rotational-state heating of trapped HfF$^+$ ions from collisions with neutral Ar atoms. Furthermore, we measure the lifetime of the $^3\Delta_1$ $v=0,\, J=1$ state to be 2.1(2) s. This state will be used for a search for a permanent electric dipole moment of the electron.
    Full-text · Article · Jan 2014 · Journal of Molecular Spectroscopy
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    ABSTRACT: Polar molecules are desirable systems for quantum simulations and cold chemistry. Molecular ions are easily trapped, but a bias electric field applied to polarize them tends to accelerate them out of the trap. We present a general solution to this issue by rotating the bias field slowly enough for the molecular polarization axis to follow but rapidly enough for the ions to stay trapped. We demonstrate Ramsey spectroscopy between Stark-Zeeman sublevels in 180Hf19F+ with a coherence time of 100 ms. Frequency shifts arising from well-controlled topological (Berry) phases are used to determine magnetic g-factors. The rotating-bias-field technique may enable using trapped polar molecules for precision measurement and quantum information science, including the search for an electron electric dipole moment.
    Full-text · Article · Dec 2013 · Science
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    ABSTRACT: Understanding the rich behavior that emerges from systems of interacting quantum particles, such as electrons in materials, nucleons in nuclei or neutron stars, the quark-gluon plasma, and superfluid liquid helium, requires investigation of systems that are clean, accessible, and have tunable parameters. Ultracold quantum gases offer tremendous promise for this application largely due to an unprecedented control over interactions. Specifically, $a$, the two-body scattering length that characterizes the interaction strength, can be tuned to any value. This offers prospects for experimental access to regimes where the behavior is not well understood because interactions are strong, atom-atom correlations are important, mean-field theory is inadequate, and equilibrium may not be reached or perhaps does not even exist. Of particular interest is the unitary gas, where $a$ is infinite, and where many aspects of the system are universal in that they depend only on the particle density and quantum statistics. While the unitary Fermi gas has been the subject of intense experimental and theoretical investigation, the degenerate unitary Bose gas has generally been deemed experimentally inaccessible because of three-body loss rates that increase dramatically with increasing $a$. Here, we investigate dynamics of a unitary Bose gas for timescales that are short compared to the loss. We find that the momentum distribution of the unitary Bose gas evolves on timescales fast compared to losses, and that both the timescale for this evolution and the limiting shape of the momentum distribution are consistent with universal scaling with density. This work demonstrates that a unitary Bose gas can be created and probed dynamically, and thus opens the door for further exploration of this novel strongly interacting quantum liquid.
    Preview · Article · Aug 2013 · Nature Physics
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    ABSTRACT: Precision spectroscopy of trapped HfF^+ will be used in a search for the permanent electric dipole moment of the electron (eEDM). While this dipole moment has yet to be observed, various extensions to the standard model of particle physics (such as supersymmetry) predict values that are close to the current limit. We present extensive survey spectroscopy of 19 bands covering nearly 5000 cm^(-1) using both frequency-comb and single-frequency laser velocity-modulation spectroscopy. We obtain high-precision rovibrational constants for eight electronic states including those that will be necessary for state preparation and readout in an actual eEDM experiment.
    Full-text · Article · Sep 2012 · Chemical Physics Letters
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    ABSTRACT: The spectrum of electronic states at 30000--33000 cm$^{-1}$ in hafnium fluoride has been studied using (1+1) resonance-enhanced multi-photon ionization (REMPI) and (1+1$'$) REMPI. Six $\Omega' = 3/2$ and ten $\Pi_{1/2}$ vibronic bands have been characterized. We report the molecular constants for these bands and estimate the electronic energies of the excited states using a correction derived from the observed isotope shifts. When either of two closely spaced $\Pi_{1/2}$ electronic states is used as an intermediate state to access autoionizing Rydberg levels, qualitatively distinct autoionization spectra are observed. The intermediate state-specificity of the autoionization spectra bodes well for the possibility of using a selected $\Pi_{1/2}$ state as an intermediate state to create ionic HfF$^+$ in various selected quantum states, an important requirement for our electron electric dipole moment (eEDM) search in HfF$^+$.
    Full-text · Article · Jun 2012 · Journal of Molecular Spectroscopy
  • Matt Grau · Huanqian Loh · Eric A. Cornell
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    ABSTRACT: Trapped molecular ions are an ideal platform for precision measurement of the electron electric dipole moment (eEDM). The low lying ^3δ1 electronic state of HfF^+ is predicted to contribute a large sensitivity enhancement to an eEDM measurement. We create HfF^+ by optically exciting a supersonic beam of HfF with two photons to an autoionizing state. We then load the HfF^+ into a novel Paul trap optimized for fluorescence collection and field uniformity. We report on recent experiments in the trap, and on our general progress towards the eEDM measurement. This work is funded by the National Science Foundation and the Marsico Endowed Chair.
    No preview · Article · Jun 2012
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    ABSTRACT: A low lying ^3δ1 state in HfF^+ and ThF^+ is an ideal candidate for a precise measurement of the electron electric dipole moment (eEDM). However, the electronic level structure of these species is not very well studied, and theoretical uncertainties are on the order of 1000 cm-1 for many levels. We have used a recently developed novel technique, frequency comb velocity modulation spectroscopy (VMS), as well as cw-laser VMS for high-sensitivity, high-resolution, ion sensitive detection from 675-1000 nm (10000-14700 cm-1). We report the measurement and assignment of 15 ro-vibrational bands in HfF^+ including accurate fits for the ^3δ1 metastable state and the ^1σ^+ ground state. In addition, we have characterized six excited states and discuss the implications for state preparation and readout in the eEDM experiment. This system will allow rapid characterization of ThF^+, which should further improve the sensitivity of the eEDM experiment. In addition to supporting the eEDM experiment, these studies provide data for testing and refining relativistic molecular structure calculations.
    No preview · Article · Jun 2012
  • Lin Xia · Daniel Lobser · Eric Cornell
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    ABSTRACT: In lower-dimensional gases, remarkable physical phenomena arise due to confinement effects, for example the Berezinskii-Kosterlitz-Thouless transition or the Tonks-Girardeau gas. In a quasi-2D condensate, the frequency of collective excitations are shifted because of 2D effects [1,2]. We report our latest results on the measurements of collective excitation frequencies in quasi-2D condensates. These frequencies are normalized by precise measurements of the trapping frequency. [4pt] [1] Y. Hu et al., Phys. Rev. Lett. 107, 110401 (2011).[0pt] [2] M. Olshanii et al., Phys. Rev. Lett. 105, 095302 (2010).
    No preview · Article · Jun 2012
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    R J Wild · P Makotyn · J M Pino · E A Cornell · D S Jin
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    ABSTRACT: A powerful set of universal relations, centered on a quantity called the contact, connects the strength of short-range two-body correlations to the thermodynamics of a many-body system with zero-range interactions. We report on measurements of the contact, using rf spectroscopy, for an (85)Rb atomic Bose-Einstein condensate (BEC). For bosons, the fact that contact spectroscopy can be used to probe the gas on short time scales is useful given the decreasing stability of BECs with increasing interactions. A complication is the added possibility, for bosons, of three-body interactions. In investigating this issue, we have located an Efimov resonance for (85)Rb atoms with loss measurements and thus determined the three-body interaction parameter. In our contact spectroscopy, in a region of observable beyond-mean-field effects, we find no measurable contribution from three-body physics.
    Full-text · Article · Apr 2012 · Physical Review Letters
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    ABSTRACT: The molecular ion HfF+ is the chosen species for a JILA experiment to measure the electron electric dipole moment (eEDM). Detailed knowledge of the spectrum of HfF is crucial to prepare HfF+ in a state suitable for performing an eEDM measurement [1]. We investigated the near-infrared electronic spectrum of HfF using laser-induced fluorescence (LIF) of a supersonic molecular beam. We discovered eight unreported bands, and assign each of them unambiguously, four to vibrational bands belonging to the transition [13.8]0.5 ← X1.5, and four to vibrational bands belonging to the transition [14.2]1.5 ← X1.5. Additionally, we report an improved measurement of vibrational spacing of the ground state, as well as anharmonicity ωexe.
    Preview · Article · Feb 2012 · Journal of Molecular Spectroscopy
  • E. A.cornell · C. E.wieman
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    ABSTRACT: Bose-Einstein condensation, or BEC, has a long and rich history dating from the early 1920s. In this article we will trace briefly over this history and some of the developments in physics that made possible our successful pursuit of BEC in a gas. We will then discuss what was involved in this quest. In this discussion we will go beyond the usual technical description to try and address certain questions that we now hear frequently, but are not covered in our past research papers. These are questions along the lines of "How did you get the idea and decide to pursue it? Did you know it was going to work? How long did it take you and why?" We will review some of our favorites from among the experiments we have carried out with BEC. There will then be a brief encore on why we are optimistic that BEC can be created with nearly any species of magnetically trappable atom. Throughout this article we will try to explain what makes BEC in a dilute gas so interesting, unique, and experimentally challenging.
    No preview · Article · Jan 2012 · International Journal of Modern Physics B
  • R. J. Wild · P. Makotyn · J. M. Pino · E. A. Cornell · D. S. Jin

    No preview · Article · Dec 2011
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    ABSTRACT: Spectroscopy on a trapped diatomic molecular ion with a ground or metastable 3 Delta 1 level could prove to be a sensitive probe for a permanent electron electric dipole moment. High-resolution molecular spectroscopy is a sensitive probe of fundamental physics. A rotating electric field can be used to polarize trapped molecular ions. High-resolution spectroscopy can be performed in the presence of rapidly time-varying fields. Spectroscopy on polarized, trapped molecular ions can probe for an electron electric dipole moment.
    Full-text · Article · Nov 2011 · Journal of Molecular Spectroscopy
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    ABSTRACT: Autoionization of Rydberg states of HfF, prepared using the optical-optical double resonance technique, holds promise to create HfF(+) in a particular Zeeman level of a rovibronic state for an electron electric dipole moment search. We characterize a vibronic band of Rydberg HfF at 54 cm(-1) above the lowest ionization threshold and directly probe the state of the ions formed from this vibronic band by performing laser-induced fluorescence on the ions. The Rydberg HfF molecules show a propensity to decay into only a few ion rotational states of a given parity and are found to preserve their orientation qualitatively upon autoionization. We show empirically that we can create 30% of the total ion yield in a particular ∣J(+), M(+) state and present a simplified model describing autoionization from a given Rydberg state that assumes no angular dynamics.
    Full-text · Article · Oct 2011 · The Journal of Chemical Physics
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    Laura C Sinclair · Kevin C Cossel · Tyler Coffey · Jun Ye · Eric A Cornell
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    ABSTRACT: We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF+ and achieved a fractional absorption sensitivity of 3 x 10-7 recorded over 1500 simultaneous channels spanning 150 cm-1 around 800 nm with an absolute frequency accuracy of 30 MHz (0.001 cm-1). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 minutes.
    Full-text · Article · Aug 2011 · Physical Review Letters
  • Lin Xia · Dan Lobser · Eric Cornell
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    ABSTRACT: Quasi-2D condensate slices are created by loading a 3D Bose-Einstein condensate into a 1D optical lattice. Using a microwave pumping scheme a single layer is isolated. Bogoliubov phonons are projected onto free particles by rapidly turning off interatomic interactions. A temporal focusing technique is used to probe the momentum distribution of the resulting cloud. We measure correlations between density fluctuations at k and -k in the images and compare with Bogoliubov theory. This work funded by ONR and NSF.
    No preview · Article · Jun 2011
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    ABSTRACT: As a step towards measuring the electron electric dipole moment, we produce a sample of HfF^+ using a two-color excitation. We promote HfF from X^2 Delta3/2 to an isotope and parity-selective intermediate state, and then to one of many highly perturbed Rydberg states from which it autoionizes to the vibrational ground state of HfF^+. We measure the population of the rotational states of HfF^+ using laser-induced fluorescence and find that only a small number of states are populated, with most of the population in J < 4. Additionally, we see a strong propensity for autoionization to preserve the parity of the molecule, with one parity populating even J levels and the other populating odd J. Using polarized light to prepare the Rydberg molecules in various orientations, and then probing the ion with LIF, we see that a polarization of m_J sublevels also survives autoionization. A. Leanhardt et al, arXiv:atom-ph/1008.2997v2 (2010)
    Preview · Article · Jun 2011

Publication Stats

18k Citations
630.19 Total Impact Points

Institutions

  • 1991-2015
    • University of Colorado at Boulder
      • Department of Physics
      Boulder, Colorado, United States
  • 1995-2012
    • University of Colorado
      • Department of Physics
      Denver, Colorado, United States
  • 1993-2012
    • National Institute of Standards and Technology
      • • Quantum Physics Division
      • • Time and Frequency Division
      GAI, Maryland, United States
  • 1998
    • University of Florence
      • European Laboratory for Non-Linear Spectroscopy LENS
      Florens, Tuscany, Italy