Eric Cornell

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

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Publications (183)574.32 Total impact

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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.
    Journal of Molecular Spectroscopy 01/2014; 300. DOI:10.1016/j.jms.2014.02.001 · 1.53 Impact Factor
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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.
    Science 12/2013; 342(6163):1220-1222. DOI:10.1126/science.1243683 · 31.48 Impact Factor
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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.
    Nature Physics 08/2013; 10(2). DOI:10.1038/nphys2850 · 20.60 Impact Factor
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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.
    Chemical Physics Letters 09/2012; 546:11--11. DOI:10.1016/j.cplett.2012.06.03 · 1.99 Impact Factor
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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$^+$.
    Journal of Molecular Spectroscopy 06/2012; s 276–277. DOI:10.1016/j.jms.2012.06.014 · 1.53 Impact Factor
  • 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.
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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.
  • 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).
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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.
    Physical Review Letters 04/2012; 108(14):145305. DOI:10.1103/PhysRevLett.108.145305 · 7.73 Impact Factor
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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.
    Journal of Molecular Spectroscopy 02/2012; 272(1):32–35. DOI:10.1016/j.jms.2011.12.006 · 1.53 Impact Factor
  • 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.
    International Journal of Modern Physics B 01/2012; 16(30). DOI:10.1142/S0217979202014681 · 0.46 Impact Factor
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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.
    Journal of Molecular Spectroscopy 11/2011; 270(1):1-25. DOI:10.1016/j.jms.2011.06.007 · 1.53 Impact Factor
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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.
    The Journal of Chemical Physics 10/2011; 135(15):154308. DOI:10.1063/1.3652333 · 3.12 Impact Factor
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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 3×10⁻⁷ 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 min.
    Physical Review Letters 08/2011; 107(9):093002. DOI:10.1103/PhysRevLett.107.093002 · 7.73 Impact Factor
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    ABSTRACT: The famous Lee-Huang-Yang (LHY) term describes the first-order correction to the mean-field energy for strongly interacting bosons [1], yet it has only been detected with bosons composed of loosely bound fermion pairs [2,3]. Tan's universal relations, originally calculated for fermions [4], connect a property called the Contact to many macroscopic parameters of a quantum gas, such as its total energy. These relations have been verified experimentally for Fermi systems [5]. We apply these relations to a Bose gas to realize a unique tool to study the LHY correction. We perform RF spectroscopy on a BEC of ^85Rb close to a Feshbach resonance, and measure the strength of the RF lineshape tail which decays as 1/w^3/2. From this we extract the Contact, which increases as a function of the interaction strength. This allows us to quantitatively study the LHY term for atomic bosons, as well as investigate time-dependent effects that arise from the rate of change of the interaction strength compared to various experimental time scales.
  • 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.
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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)
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    ABSTRACT: Trapped molecular ions provide large effective electric fields and long electron spin coherence times for the search for an electron electric dipole moment (eEDM). In particular, the ^3δ1 state of HfF^+ has been proposed as a candidate for the eEDM search. To create HfF^+, we optically excite a supersonic beam of neutral HfF with two photons to an autoionizing state, and then perform laser-induced fluorescence to detect the state of the resultant HfF^+ ions. We report on our efforts to understand the autoionization process for efficient state preparation of HfF^+ ions, and on our general progress towards an eEDM measurement. This work is funded by the US National Science Foundation.
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    ABSTRACT: We demonstrate a photon-counting technique for detecting Bragg excitation of an ultracold gas of atoms. By measuring the response of the light field to the atoms, we derive a signal independent of traditional time-of-flight atom-imaging techniques. With heterodyne detection we achieve photon shot-noise limited detection of the amplification or depletion of one of the Bragg laser beams. Photon counting for Bragg spectroscopy will be useful for strongly interacting gases where atom-imaging detection fails. In addition, this technique provides the ability to resolve the evolution of excitations as a function of pulse duration. Comment: 7 pages, 4 figures
    Physical Review A 12/2010; DOI:10.1103/PHYSREVA.83.033615 · 2.99 Impact Factor
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    S Tung, G Lamporesi, D Lobser, L Xia, E A Cornell
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    ABSTRACT: In complementary images of coordinate-space and momentum-space density in a trapped 2D Bose gas, we observe the emergence of presuperfluid behavior. As phase-space density ρ increases toward degenerate values, we observe a gradual divergence of the compressibility κ from the value predicted by a bare-atom model, κ(ba). κ/κ(ba) grows to 1.7 before ρ reaches the value for which we observe the sudden emergence of a spike at p = 0 in momentum space. Momentum-space images are acquired by means of a 2D focusing technique. Our data represent the first observation of non-mean-field physics in the presuperfluid but degenerate 2D Bose gas.
    Physical Review Letters 12/2010; 105(23):230408. DOI:10.1103/PhysRevLett.105.230408 · 7.73 Impact Factor

Publication Stats

16k Citations
574.32 Total Impact Points

Institutions

  • 1991–2014
    • University of Colorado at Boulder
      • Department of Physics
      Boulder, Colorado, United States
  • 1993–2013
    • National Institute of Standards and Technology
      • • Quantum Physics Division
      • • Time and Frequency Division
      Maryland, United States
  • 1995–2012
    • University of Colorado
      • Department of Physics
      Denver, Colorado, United States
  • 1998
    • University of Florence
      • European Laboratory for Non-Linear Spectroscopy LENS
      Florens, Tuscany, Italy