Eric R. Hudson

University of California, Los Angeles, Los Angeles, California, United States

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Publications (65)176.03 Total impact

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    ABSTRACT: The photodissociation cross-section of SrCl$^+$ is measured in the spectral range of 36000 -- 46000 cm$^{-1}$ using a modular time-of-flight mass spectrometer (TOF-MS). By irradiating a sample of trapped SrCl$^+$ molecular ions with a pulsed dye laser, X$^1\Sigma^+$ state molecular ions are electronically excited to the repulsive wall of the A$^1\Pi$ state, resulting in dissociation. Using the TOF-MS, the fragments are detected and the photodissociation cross-section is determined for a broad range of photon energies. Detailed $\textit{ab initio}$ calculations of the molecular potentials and spectroscopic constants are also performed and are found to be in good agreement with experiment. The spectroscopic constants for SrCl$^+$ are also compared to those of another alkaline earth chalcogen, BaCl$^+$, in order to highlight structural differences between the two molecular ions. This work represents the first spectroscopy and $\textit{ab initio}$ calculations of SrCl$^+$.
    The Journal of chemical physics. 04/2014; 141(1).
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    Kuang Chen, Scott T Sullivan, Eric R Hudson
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    ABSTRACT: A single ion immersed in a neutral buffer gas is studied. An analytical model is developed that gives a complete description of the dynamics and steady-state properties of the ions. An extension of this model, using techniques employed in the mathematics of economics and finance, is used to explain the recent observation of non-Maxwellian statistics for these systems. Taken together, these results offer an explanation of the long-standing issues associated with sympathetic cooling of an ion by a neutral buffer gas.
    Physical Review Letters 04/2014; 112(14):143009. · 7.73 Impact Factor
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    ABSTRACT: Mass spectrometry is used in a wide range of scientific disciplines including proteomics, pharmaceutics, forensics, and fundamental physics and chemistry. Given this ubiquity, there is a worldwide effort to improve the efficiency and resolution of mass spectrometers. However, the performance of all techniques is ultimately limited by the initial phase-space distribution of the molecules being analyzed. Here, we dramatically reduce the width of this initial phase-space distribution by sympathetically cooling the input molecules with laser-cooled, co-trapped atomic ions, improving both the mass resolution and detection efficiency of a time-of-flight mass spectrometer by over an order of magnitude. Detailed molecular dynamics simulations verify the technique and aid with evaluating its effectiveness. Our technique appears to be applicable to other types of mass spectrometers.
    04/2014;
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    B. Zygelman, Zelimir Lucic, Eric R. Hudson
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    ABSTRACT: Using both quantum and semi-classical methods, we calculate the rates for radiative association and charge transfer in cold collisions of Yb+ with Ca.
    Journal of Physics B Atomic Molecular and Optical Physics 08/2013; 47(1). · 2.03 Impact Factor
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    ABSTRACT: Samples of ultracold ^{174}Yb^{+} ions, confined in a linear radio-frequency Paul trap, are heated via micromotion interruption, while their temperature, density, and therefore structural phase are monitored and simulated. The observed time evolution of the ion temperature is compared to a theoretical model for ion-ion heating allowing a direct measurement of the Coulomb logarithm in a linear Paul trap. This result permits a simple, yet accurate, analytical description of ion cloud thermodynamic properties, e.g., density, temperature, and structural phase, as well as suggests limits to and improvements for ongoing trapped-ion quantum information efforts.
    Physical Review Letters 04/2013; 110(17):173003. · 7.73 Impact Factor
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    ABSTRACT: Compared with atoms, molecules have a rich internal structure that offers many opportunities for technological and scientific advancement. The study of this structure could yield critical insights into quantum chemistry, new methods for manipulating quantum information, and improved tests of discrete symmetry violation and fundamental constant variation. Harnessing this potential typically requires the preparation of cold molecules in their quantum rovibrational ground state. However, the molecular internal structure severely complicates efforts to produce such samples. Removal of energy stored in long-lived vibrational levels is particularly problematic because optical transitions between vibrational levels are not governed by strict selection rules, which makes laser cooling difficult. Additionally, traditional collisional, or sympathetic, cooling methods are inefficient at quenching molecular vibrational motion. Here we experimentally demonstrate that the vibrational motion of trapped BaCl(+) molecules is quenched by collisions with ultracold calcium atoms at a rate comparable to the classical scattering, or Langevin, rate. This is over four orders of magnitude more efficient than traditional sympathetic cooling schemes. The high cooling rate, a consequence of a strong interaction potential (due to the high polarizability of calcium), along with the low collision energies involved, leads to molecular samples with a vibrational ground-state occupancy of at least 90 per cent. Our demonstration uses a novel thermometry technique that relies on relative photodissociation yields. Although the decrease in vibrational temperature is modest, with straightforward improvements it should be possible to produce molecular samples with a vibrational ground-state occupancy greater than 99 per cent in less than 100 milliseconds. Because sympathetic cooling of molecular rotational motion is much more efficient than vibrational cooling in traditional systems, we expect that the method also allows efficient cooling of the rotational motion of the molecules. Moreover, the technique should work for many different combinations of ultracold atoms and molecules.
    Nature 03/2013; 495(7442):490-4. · 38.60 Impact Factor
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    ABSTRACT: We report the first demonstration of a UV laser using a high-Q whispering gallery mode (WGM) resonator of Ce3+: LiCaAlF6. We show that WGM resonators from LiCaAlF6 can achieve a Q of 2.6 x 107 at UV. We demonstrated a UV laser at 290 nm with a pulsed pump laser at 266 nm. The experiments showed the low pump threshold intensity of 7.5 x 109 W/m2 and slope efficiency of 25%. We have also observed lasing delay dynamics. These results are consistent with our modeling and theoretical estimates, and pave the way for a low threshold cw UV laser using WGM resonator cavity.
    Proc SPIE 02/2013;
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    ABSTRACT: Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229 Th isomer transition, Journal of Luminescence, doi:10.1016/j.jlumin.2011.09.037 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
    Journal of Luminescence 01/2013; 133:91-95. · 2.14 Impact Factor
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    ABSTRACT: The nucleus of the thorium-229 isotope possesses a first excited nuclear state (229m Th) at an exceptionally low energy of 7.8 7 0.5 eV above the nuclear ground state (229g Th), as determined by earlier indirect measurements. This is the only nuclear excited state known that is within the range of optical spectroscopy. This paper reports progress toward detecting the 229m Th state directly by luminescence spectroscopy in the vacuum ultraviolet spectral region. The estimated natural linewidth of the 229g Th2 229m Th isomer transition of 2p  0.1 to 2p  10 mHz is expected to broaden to $ 10 kHz for 229 Th 4 þ doped into a suitable crystal. The factors governing the choice of crystal system and the substantial challenges in acquiring a sufficiently large quantity of 229 Th are discussed. We show that the 229g Th2 229m Th transition energy can be identified to within 0.1 nm by luminescence excitation and luminescence spectroscopy using the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. This would open the door for subsequent laser-based measurements of the isomer transition and future applications of 229 Th in nuclear clocks. We also show that 233 U-doped materials should produce an intrinsic, continuous, and sufficiently high rate of 229m Th-229g Th luminescence and could be a useful aid in the initial direct search of the isomer transition.
    Journal of Luminescence 01/2013; 133:91-95. · 2.14 Impact Factor
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    ABSTRACT: A low-threshold solid-state UV laser using a whispering gallery mode (WGM) resonator constructed from UV transparent crystalline material is demonstrated. Using a Ce<sup>3+</sup>:LiCaAlF<sub>6</sub> resonator, we observe broad bandwidth lasing (280-330 nm) with a low threshold intensity of 7.5×10<sup>9</sup>  W/m<sup>2</sup> and an effective slope efficiency of ∼25%. The lasing time delay dynamics in the pulsed operation mode are also observed and analyzed. Additionally, a LiCaAlF<sub>6</sub> WGM resonator with Q=2×10<sup>7</sup> at 370 nm is realized. The combination of this high Q and the small WGM mode volume significantly lowers the pump power threshold compared to traditional cavity designs, opening the door for both tunable continuous-wave and mode-locked operation.
    Optics Letters 12/2012; 37(23):4961-3. · 3.39 Impact Factor
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    ABSTRACT: A low-threshold solid-state UV laser using a whispering gallery mode (WGM) resonator constructed from UV transparent crystalline material is demonstrated. Using a Ce3+:LiCaAlF6 resonator, we observe broad bandwidth lasing (280–330 nm) with a low threshold intensity of 7.5×109 W/m2 and an effective slope efficiency of ∼25%. The lasing time delay dynamics in the pulsed operation mode are also observed and analyzed. Additionally, a LiCaAlF6 WGM resonator with Q=2×107 at 370 nm is realized. The combination of this high Q and the small WGM mode volume significantly lowers the pump power threshold compared to traditional cavity designs, opening the door for both tunable continuous-wave and mode-locked operation.
    Optics Letters 12/2012; 37(23):4961-. · 3.39 Impact Factor
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    ABSTRACT: The role of electronic excitation in inelastic collisions between ultracold Ca atoms and Ba^{+} ions, confined in a hybrid trap, is studied for the first time. Unlike previous investigations, this system is energetically precluded from undergoing inelastic collisions in its ground state, allowing a relatively simple experimental determination and interpretation of the influence of electronic excitation. It is found that while the electronic state of the ion can critically influence the inelastic collision rate, the polarizability mismatch of the neutral atom electronic states suppresses short-range collisions, and thus inelastic processes, involving electronically excited neutral atoms. As a result of these features, it is experimentally demonstrated that it is possible to mitigate inelastic collision loss mechanisms in these systems, marking an important step toward long-lived hybrid atom-ion devices.
    Physical Review Letters 11/2012; 109(22):223002. · 7.73 Impact Factor
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    ABSTRACT: We discuss our efforts to perform high-resolution spectroscopy of the BaCl^+ ion, an exciting candidate for ultracold molecular ion studies. This work details our search for a predicted predissociation channel between the first-excited B^1σ and A^1π states. It is expected that the rovibrational resolution afforded by predissociation spectroscopy will allow us to efficiently measure molecular-ion rovibrational temperatures. This is a crucial step in confirming our method to produce ultracold molecular ions via sympathetic collisions with a ^40Ca MOT. To observe the predissociation of trapped BaCl^+, we detect slight increases in fragment Ba^+ with a novel time-of-flight device using radial extraction from a linear quadrupole trap.
    06/2012;
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    ABSTRACT: The role of electronic excitation in charge exchange chemical reactions between ultracold Ca atoms and Ba$^+$ ions, confined in a hybrid trap, is studied. This prototypical system is energetically precluded from reacting in its ground state, allowing a particularly simple interpretation of the influence of electronic excitation. It is found that while electronic excitation of the ion can critically influence the chemical reaction rate, electronic excitation of the neutral atom is less important. It is also experimentally demonstrated that with the correct choice of the atom-ion pair, it is possible to mitigate the unwanted effects of these chemical reactions in ultracold atom-ion environments, marking an important step towards the next generation of hybrid devices.
    05/2012;
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    ABSTRACT: We demonstrate the integration of a linear quadrupole trap with a simple time-of-flight mass spectrometer with medium-mass resolution (m/Δm ∼ 50) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from the linear quadrupole trap into the mass analyzer, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. This provides the ability to address trapped ions with laser light and facilitates interactions with neutral background gases prior to analyzing the trapped ions. Here, we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates.
    The Review of scientific instruments 04/2012; 83(4):043103. · 1.52 Impact Factor
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    ABSTRACT: We demonstrate the implementation of a simple time-of-flight (ToF) mass spectrometer with medium-mass resolution ($m/\Delta m\sim50$) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from a linear quadrupole trap, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. Here we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates.
    02/2012;
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    ABSTRACT: Ultracold atoms and molecules provide ideal stages for precision tests of fundamental physics. With microkelvin neutral strontium atoms confined in an optical lattice, we have achieved a fractional resolution of 4 × 10-15 on the 1S0–3P0 doubly forbidden 87Sr clock transition at 698 nm. Measurements of the clock line shifts as a function of experimental parameters indicate systematic errors below the 10-15 level. The ultrahigh spectral resolution permits resolving the nuclear spin states of the clock transition at small magnetic fields, leading to measurements of the 3P0 magnetic moment and metastable lifetime. In addition, photoassociation spectroscopy performed on the narrow 1S0–3P1 transition of 88Sr shows promise for efficient optical tuning of the ground state scattering length and production of ultracold ground state molecules. Lattice-confined Sr2 molecules are suitable for constraining the time variation of the proton–electron mass ratio. In a separate experiment, cold, stable, ground state polar molecules are produced from Stark decelerators. These cold samples have enabled an order-of-magnitude improvement in the measurement precision of ground state, Λ doublet microwave transitions in the OH molecule. Comparing the laboratory results to those from OH megamasers in interstellar space will allow a sensitivity of 10-6 for measuring the potential time variation of the fundamental fine structure constant Δα/α over 1010 years. These results have also led to improved understandings of the molecular structure. The study of the low magnetic field behavior of OH in its 2Π3/2 ro-vibronic ground state precisely determines a differential Landé g factor between opposite parity components of the Λ doublet.
    International Journal of Modern Physics D 01/2012; 16(12b). · 1.03 Impact Factor
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    ABSTRACT: Ultracold 174Yb+ ions and 40Ca atoms are confined in a hybrid trap. The charge exchange chemical reaction rate constant between these two species is measured and found to be 4 orders of magnitude larger than recent measurements in other heteronuclear systems. The structure of the CaYb+ molecule is determined and used in a calculation that explains the fast chemical reaction as a consequence of strong radiative charge transfer. A possible explanation is offered for the apparent contradiction between typical theoretical predictions and measurements of the radiative association process in this and other recent experiments.
    Physical Review Letters 12/2011; 107(24):243201. · 7.73 Impact Factor
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    ABSTRACT: The formation of (40)Ca(2)(+) molecular ions is observed in a hybrid (40)Ca magneto-optical and ion trap system. The molecular ion formation process is determined to be photo-associative ionization of ultracold (40)Ca atoms. A lower bound for the two-body rate constant is found to be beta ≥ 2 ± 1 × 10(-15) cm(3) Hz. Ab initio molecular potential curves are calculated for the neutral Ca(2) and ionic Ca(2)(+) molecules and used in a model that identifies the photo-associative ionization pathway. As this technique does not require a separate photo-association laser, it could find use as a simple, robust method for producing ultracold molecular ions.
    Physical Chemistry Chemical Physics 07/2011; 13(42):18859-63. · 4.20 Impact Factor
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    ABSTRACT: We demonstrate a simple technique for molecular ion spectroscopy. BaCl^+ molecular ions are trapped in a linear Paul trap in the presence of a room-temperature He buffer gas and photodissociated by driving an electronic transition from the ground X^1&+circ; state to the repulsive wall of the A^1π state. The photodissociation spectrum is recorded by monitoring the induced trap loss of BaCl^+ ions as a function of excitation wavelength. Accurate molecular potentials and spectroscopic constants are determined. Comparison of the theoretical photodissociation cross-sections with the measurement shows excellent agreement. This study represents the first spectroscopic data for BaCl^+ and an important step towards the production of ultracold ground-state molecular ions. Future steps include investigating a strong predissociation channel between the first excited ^1σ and A^1π states where it is expected that the rovibrational resolution afforded by predissociation spectroscopy will allow us to efficiently measure molecular ion rovibrational temperatures.
    06/2011;

Publication Stats

691 Citations
176.03 Total Impact Points

Institutions

  • 2008–2014
    • University of California, Los Angeles
      • Department of Physics and Astronomy
      Los Angeles, California, United States
    • Yale University
      • Department of Physics
      New Haven, CT, United States
  • 2009
    • Keele University
      • School of Physical and Geographical Sciences
      Newcastle under Lyme, ENG, United Kingdom
  • 2004–2007
    • National Institute of Standards and Technology
      Maryland, United States
  • 2004–2006
    • University of Colorado at Boulder
      • Department of Physics
      Boulder, Colorado, United States
  • 2005
    • University of Colorado
      • Department of Physics
      Denver, CO, United States