Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session D1: Poster Session I (4:00 - 6:00PM) |
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Room: 400A |
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D1.00001: SPECIAL TOPICS |
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D1.00002: Oblique-Length Contraction Factor in Special Relativity Florentin Smarandache The Special Theory of Relativity asserts that all lengths in the direction of motion are contracted, while the lengths at right angles to the motion are unaffected. But it didn't say anything about lengths at oblique angle to the motion (i.e. neither perpendicular to, nor along the motion direction), how would they behave? Following the STR we find that the lengths traveling with speed v, at oblique angle $\theta $ to the motion, are contracted with the \textbf{Oblique-Length Contraction Factor:} \[ OC(v,\theta )=\sqrt {C(v)^{2}\cos^{2}\theta +\sin^{2}\theta } , \] \begin{center} where 0 $\le $ OC(v,$\theta ) \quad \le $ 1, \end{center} which is a \underline {generalization of Lorentz Contractor} $C(v)=\sqrt {1-\frac{v^{2}}{c^{2}}} $because: when $\theta \quad =$ 0, or the length is moving along the motion direction, then \textit{OC(v, 0) }$= C(v); s$imilarly OC(v, $\pi )$ $=$ OC(v, 2$\pi ) \quad =$ C(v). Also, if $\theta \quad = \quad \pi $/2, or the length is perpendicular on the motion direction, then \textit{OC(v, }$\pi $\textit{/2) }$=$\textit{ 1, }i.e. no contraction occurs; and similarly for OC(v, 3$\pi $/2) $=$ 1. [Preview Abstract] |
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D1.00003: Cs Trilobite Molecules and Rydberg Atom Interactions Donald Booth, Jonathan Tallant, Patrick Zabawa, Gregory Parker, James Shaffer We present results on our Cs ultracold Rydberg atom experiments involving trilobite molecules and Rydberg atom interactions. A novel binding mechanism arises from the attractive, low-energy scattering of a Rydberg electron from a neighboring ground state atom. The states formed by this binding mechanism are referred to as trilobite states. Trilobite molecules are predicted to have giant, body-fixed permanent dipole moments ($\sim 1 $kD). To verify these dipole moments, it is necessary to observe the response to the molecules to an electric field. We present measurements of the Stark shifts of the trilobite states in Cs due to the application of a constant external electric field. We also will present progress on studies of anisotropic Rydberg atom interactions including collision calculations. We will compare and contrast Cs trilobite molecules and Rydberg atom macrodimers. [Preview Abstract] |
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D1.00004: Stabilizing Bohr wavepackets by electron-electron interaction M. Scheucher, D. Wirtitsch, M. Hiller, S. Yoshida, J. Burgdorfer, S. Ye, X. Zhang, F.B. Dunning Recently, so-called Bohr wavepackets have been realized experimentally in which a radially- and angularly-localized electron wavepacket travels along a circular orbit around the nucleus. Due to the non-equidistant energies of the constituent energy eigenstates, these Bohr wavepackets disperse but can be stabilized by external electric fields. Here we investigate the possibility of stabilizing such wavepackets in helium-like doubly excited Rydberg atoms through the electron-electron interaction without the need to resort to external driving fields. Our stability analysis indicates that a non-dispersive wavepacket can be created following the previously suggested ``shape preserving'' orbit for which the exchange of angular momentum between the two electrons is suppressed. The important role of electron-electron correlations in this stabilization mechanism is discussed. [Preview Abstract] |
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D1.00005: Towards a low entropy gas of fermionic polar molecules Bryce Gadway, Steven Moses, Bo Yan, Jacob Covey, Deborah Jin, Jun Ye In recent years, ultracold gases of polar molecules have garnered much attention, owing in part to their prospects for emulating condensed matter systems with long-range interactions. To enable the observation of long-range dipolar interactions, which has so far been precluded by insufficient molecular densities, we aim to create a high-filling-fraction sample of ground state polar KRb molecules in a three-dimensional optical lattice. This can be accomplished by disposing an initial Bose--Fermi lattice mixture towards the formation of preformed pairs - one boson and one fermion per lattice site - via control over the interspecies interactions, followed by efficient conversion to deeply bound ground state molecules. To characterize the entropy in our system, we shall study two-body losses due to reactive collisions occurring in molecular rotational-state mixtures. [Preview Abstract] |
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D1.00006: Non-destructive imaging of spinor Bose-Einstein condensates E. Carlo Samson, Anshuman Vinit, Chandra Raman We present a non-destructive differential imaging technique that enables the observation of the spatial distribution of the magnetization in a spinor Bose-Einstein condensate (BEC) through a Faraday rotation protocol. In our procedure, we utilize a linearly polarized, far-detuned laser beam as our imaging probe, and upon interaction with the condensate, the beam's polarization direction undergoes Faraday rotation. A differential measurement of the orthogonal polarization components of the rotated beam provides a spatial map of the net magnetization density within the BEC. The non-destructive aspect of this method allows for continuous imaging of the condensate. This imaging technique will prove useful in experimental BEC studies, such as spatially resolved magnetometry using ultracold atoms, and non-destructive imaging of non-equilibrium behavior of antiferromagnetic spinor condensates. [Preview Abstract] |
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D1.00007: A high temperature lithium vapor glass cell for laser frequency stabilization Jiaming Li, Wen Xu, Jordan Baughman, Le Luo, Zinxin Wang, Tianshu Lai We present a high temperature lithium-6 vapor glass cell for the application of laser frequency locking and sensitive Faraday rotation measurement. Traditionally glass cells are not compatible with lithium due to the low vapor pressure at the room temperature and irreversible lithium coating on the optical windows when the temperature is high. By constructing long cooling arms with buffer gas and implementing gradient heating, we can control the density distribution of lithium vapors inside the cell to avoid window coating. This cell can work continuously at 400$^{\circ}$C regime to implement saturated absorption spectroscopy for frequency stabilization of diode laser system. To achieve both power and temperature insensitive locking, a homemade high common mode rejection ratio auto-balanced photo detector and lock-in technique are used to improve the SNR of locking signal. In addition we develop a sensitive method to measure small Faraday rotation of lithium vapors. [Preview Abstract] |
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D1.00008: Instrumentation for diode laser spectroscopy using 32-bit microcontrollers and a Nexus 7 Android tablet Edward Eyler Last year, I described a low-cost ramp and timing generator using a 32-bit microcontroller, connected via USB to an Android tablet that provides a bidirectional touch-screen interface. I have since developed several additional designs to support experiments involving diode laser spectroscopy and cold atom manipulation.\footnote{http://www.phys.uconn.edu/$\sim$eyler/microcontrollers/. See also E.E. Eyler, RSI \textbf{82}, 013105 (2011).} One circuit card can be used either as a high-resolution temperature controller or as a dual high-voltage driver for PZT positioners. A second provides a flexible user interface to commercial laser current driver modules, with support for floating ground connections. A third supports a pair of inexpensive rf frequency synthesizer chips (ADF4351) that are usable from 35-4000 MHz. A fast rf switch provides numerous options, including phase-coherent frequency shifting at MHz rates for high-bandwidth laser stabilization and studies of polychromatic optical forces. Additional circuits for laser frequency locking are under development. All of these devices are controllable from a Google Nexus 7 tablet, which is inexpensive yet has graphics processing speeds that allow seamless real-time updates of charts and oscilloscope-like displays. [Preview Abstract] |
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D1.00009: Trapping and probing atoms in one-dimensional photonic crystals Chen-Lung Hung, Sean Meenehan, Darrick E. Chang, Oskar Painter, H. Jeff Kimble Realization of strong radiative interactions between single atoms and the fields of nanoscopic optical waveguides and resonators presents new opportunities in atomic, molecular, and optical physics and quantum information science. A major challenge to this scientific frontier is trapping atoms in vacuum near dielectric surfaces ($\sim$100nm) while at the same time achieving strong interactions between one atom and photon. Here, we describe one-dimensional photonic crystals that support a guided mode suitable for atom trapping within a unit cell, as well as a second mode with strong atom-photon interactions [1]. We have identified new trapping opportunities combining optical forces from guided modes and vacuum forces from surface interactions to form stable traps for neutral atoms in dielectric nanostructures. With photonic band structure engineering, atomic decay rate to the guided mode can reach more than ten times higher than the vacuum spontaneous decay rate. We report on progress toward device fabrication, characterization, and experimental realization of trapping and probing ultracold cesium atoms in such nanophotonic waveguides. \\[4pt] [1] C.-L. Hung, S. M. Meenehan, D. E. Chang, O. J. Painter, and H. J. Kimble, arXiv:1301.5252 (2013). [Preview Abstract] |
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D1.00010: Photoemission from femtosecond multiphoton ionization of bulk GaAs. Evan Brunkow, Nathan Clayburn, Micah LeDoux, Timothy Gay GaAs photocathodes produce spin polarized electron beams when illuminated with circularly polarized light with photon energy approximately equal to the bandgap energy ($\lambda \approx $ 800 nm) [1]. Such photocathodes are prepared with a negative electron affinity (NEA) in order to allow electrons excited to the conduction band to be emitted into the vacuum. We propose a novel source of spin polarized electrons based on multiphoton absorption in bulk GaAs using a 20 femtosecond pulse laser. Preliminary results are presented where linearly polarized light, incident on non-NEA bulk GaAs, produced a photocurrent that was measured using a channel electron multiplier. We determined that the number of photoemitted electrons per laser pulse, N, varies as N$=$k*P$^{3.72\, }$where k$=$ 3*10$^{-5}$ and P is the average power of the laser in mW. This result is expected because the spectral width of the laser is such that much of the spectrum has energies that require four photons to be absorbed to emit an electron but some of the energies require only three photons to emit an electron. Future experiments will use a Mott polarimeter and circularly polarized light to investigate the polarization of the emitted electron beam. \\[4pt] [1] D.T. Pierce, F. Meier, P. Zurcher, Appl. Phys. Lett. 26 670 (1975). [Preview Abstract] |
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D1.00011: Sub-millisecond Transient Absorption Frequency Comb Spectroscopy in the Mid-Infrared Spectral Region Bryce Bjork, Adam J. Fleisher, Thinh Bui, Kevin Cossel, Mitchio Okumura, Jun Ye The study of highly-reactive transient reaction intermediates is fundamental to understanding chemical dynamics and is particularly relevant to applications such as atmospheric chemistry. Their study often poses a significant challenge for traditional spectrometers, which typically provide broad bandwidth or fast temporal resolution, but not both without long acquisition times. We introduce a cavity-enhanced frequency-comb solution that allows for high-resolution, sensitive spectra to be captured at millisecond intervals in the mid-infrared spectral region using a VIPA dispersive etalon. Once individual comb teeth are resolved, the spectral resolution of the system is limited by the comb linewidth ($<$40 kHz) while the temporal resolution is limited by the minimum integration time of the InSb detector array (10 $\mu$s). In this presentation, I will present the application of this real-time spectroscopic system to small molecule photodissociation. [Preview Abstract] |
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D1.00012: Compact Laser System for Field Deployable Ultracold Atom Sensors Juan Pino, Ben Luey, Mike Anderson As ultracold atom sensors begin to see their way to the field, there is a growing need for small, accurate, and robust laser systems to cool and manipulate atoms for sensing applications such as magnetometers, gravimeters, atomic clocks and inertial sensing. In this poster we present a laser system for Rb, roughly the size of a paperback novel, capable of generating and controlling light sufficient for the most complicated of cold atom sensors. The system includes \textgreater 100dB of non-mechanical, optical shuttering, the ability to create short, microsecond pulses, a Demux stage to port light onto different optical paths, and an atomically referenced, frequency agile laser source. We will present data to support the system, its Size Weight and Power (SWaP) requirements, as well as laser stability and performance. [Preview Abstract] |
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D1.00013: Analysis of Picosecond Pulses by Optical Heterodyning Steven Hoke, Jeffrey Johnson In earlier work [Hoke, Johnson. http://meetings.aps.org/link/BAPS.2012.DAMOP.Q1.148] we extended optical heterodyning (OH) methods into the picosecond realm. A reference beam in OH must have a much narrower linewidth than the pulse to be analyzed; a requirement readily achieved, with respect to picosecond pulses, by nanosecond pulses from a seeded single-longitudinal-mode nanosecond laser. Fourier analysis methods have been refined and yield consistent measurements of the frequency variation within each picosecond pulse. The method is used to examine the output of a second harmonic generator (with and without third harmonic generation) in our picosecond laser system, as well as an optical parametric oscillator (OPO.) Our source pulses display a positive linear chirp near their centers. The third harmonic generator accentuates the chirp already present in these pulses, while the OPO reshapes the chirp more significantly, often reversing the direction of chirp. The resolution limit of this technique on our streak camera is explored. (Approved for Release.) [Preview Abstract] |
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D1.00014: Optimization in optical systems revisited: Beyond genetic algorithms Denis Gagnon, Joey Dumont, Louis J. Dub\'e Designing integrated photonic devices such as waveguides, beam-splitters and beam-shapers often requires optimization of a cost function over a large solution space [1]. Metaheuristics -- algorithms based on empirical rules for exploring the solution space -- are specifically tailored to those problems. One of the most widely used metaheuristics is the standard genetic algorithm (SGA), based on the evolution of a population of candidate solutions. However, the stochastic nature of the SGA sometimes prevents access to the optimal solution. Our goal is to show that a parallel tabu search (PTS) algorithm is more suited to optimization problems in general, and to photonics in particular. PTS is based on several search processes using a pool of diversified initial solutions. To assess the performance of both algorithms (SGA and PTS), we consider an integrated photonics design problem, the generation of \emph{arbitrary} beam profiles using a two-dimensional waveguide-based dielectric structure [2].\\[4pt] [1] A. Vukovic, P. Sewell, and T. M. Benson, J. Opt. Soc. Am. A \textbf{27} (2010), no.~10, 2156--2168. \newline [2] D. Gagnon, J. Dumont, and L. J. Dub\'{e}, J. Opt. Soc. Am. A \textbf{29} (2012), no.~12, 2673--2678. [Preview Abstract] |
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D1.00015: Enhancement of X-ray dose absorption for medical applications Sara Lim, S. Nahar, A. Pradhan, R. Barth A promising technique for cancer treatment is radiation therapy with high-Z (HZ) nanomoities acting as radio-sensitizers attached to tumor cells and irradiated with X-rays. But the efficacy of radiosenstization is highly energy dependent. We study the physical effects in using platinum (Pt) as the radio-sensitizing agent, coupled with commonly employed broadband x-ray sources with mean energies around 100 keV, as opposed to MeV energies produced by clinical linear accelerators (LINAC) used in radiation therapy. Numerical calculations, in vitro, and in vivo studies of F98 rat glioma (brain cancer) demonstrate that irradiation from a medium energy X-ray (MEX) 160 kV source is far more effective than from a high energy x-ray (HEX) 6 MV LINAC. We define a parameter to quantify photoionization by an x-ray source, which thereby provides a measure of subsequent Auger decays. The platinum (Z = 78) results are also relevant to ongoing studies on x-ray interaction with gold (Z = 79) nanoparticles, widely studied as an HZ contrast agent. The present study should be of additional interest for a combined radiation plus chemotherapy treatment since Pt compounds such cis-Pt and carbo-Pt are commonly used in chemotherapy. [Preview Abstract] |
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D1.00016: A high accuracy FTS for laser frequency combs, lamps and other sources Alexander Glenday, Chih-Hao Li, Nicholas Langellier, Gabor Furesz, GUOQING Chang, Hung-Wen Chen, JINKANG Lim, Franz Kaertner, David Phillips, Andrew Szentgyorgyi, Ronald Walsworth We present results from a custom Fourier Transform Spectrograph (FTS) optimized for characterizing broadband, high repetition-rate laser frequency combs (``astro-combs'') as well as other sources such as calibration lamps and solar spectra. The FTS is a 2.4 m maximum optical path difference (OPD) Michelson interferometer with a resolving power at 500 nm of $R\sim8$ million for a single transverse mode and long coherence length source (e.g., a laser frequency comb) and $R\sim1$ million for a source with multiple transverse modes and short coherence length (e.g., Th:Ar lamp). In our FTS, the reference laser co-propogates with the light being characterized, canceling finite aperture frequency shifts and is locked to an atomic clock via a laser frequency comb providing intrinsic accuracy of the FTS at the part per trillion level. Due to residual systematic effects, we realize an accuracy of $<2$ MHz on multiple transverse mode sources. We will present results from our ongoing use of the FTS to characterize various sources. [Preview Abstract] |
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D1.00017: Green Astro-comb for exoplanet searches Nicholas Langellier, Alexander Glenday, Chih-Hao Li, Gabor Furesz, Guoqing Chang, Hung-Wen Chen, Jinkang Lim, Franz Kaertner, David Phillips, Andrew Szentgyorgyi, Ronald Walsworth Searches for extrasolar planets using the precision stellar radial velocity (RV) measurement are approaching Earth-like planet sensitivity. Astro-combs, which consist of a laser frequency comb, coherent wavelength shifting mechanism (such as a doubling crystal and photonic crystal fiber), and a mode-filtering Fabry-Perot cavity (FPC), provide a promising route to increased accuracy and long-term stability on the astrophysical spectrograph calibration. Here, we present the design of a green astro-comb from an octave spanning Ti:Sapphire laser, spectrally broadened by custom tapered PCF to the visible band via fiber-optic Cherenkov radiation for frequency shifting, and filtered by a broadband FPC, constructed by a pair of complementary chirped mirrors. Performance of this astro-comb in both the laboratory and at the HARPS-N spectrograph will be presented. [Preview Abstract] |
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D1.00018: Negative-Ion Catalysis of Methane to Methanol without CO$_2$ Emission A. Tesfamichael, K. Suggs, Z. Felfli, A.Z. Msezane We have carried out a theoretical investigation of the catalytic activities of the atomic Y$^{-}$, Ru$^{-}$, At$^{-}$, In$^{-}$, Pd$^{-}$, Ag$^{-}$, Os$^{-}$ and Pt$^{-}$ ions for the selective partial oxidation of methane to methanol without CO$_{2}$ emission. The objective was to identify effective atomic negative ion catalysts using the data for the atomic Au$^{-}$ ion as the benchmark. The role of the atomic negative ions in catalysis is essentially to disrupt the C-H bonding in CH$_{4}$ oxidation thereby eliminate the competition from the carbon dioxide formation [1]. Dispersion-corrected density-functional theory has been used for the investigation. From the energy barrier calculations and the thermodynamics of the reactions, we conclude that the catalytic effect of the atomic Ag$^{-}$, At$^{-}$, Ru$^{-}$, and Os$^{-}$ ions is higher than that of the atomic Au$^{-}$ ion catalysis of CH$_{4}$ conversion to methanol. By controlling the temperature around 290, 300, 310, 320 and 325 K methane can be completely oxidized to methanol without the emission of the CO$_{2}$ through the atomic Os$^{-}$, Ag$^{-}$, At$^{-}$, Ru$^{-}$ and Au$^{-}$ ion catalysts, respectively. We conclude by recommending the investigation of the catalytic activities of combinations of the above negative ions for significant enhancement of the selective partial oxidation of methane to methanol. \\[4pt] [1] A. Z. Msezane \textit{et al,} \textit{Gold Bull.} \textbf{45}, 17 (2012) [Preview Abstract] |
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D1.00019: Using Atom Trap Trace Analysis (ATTA) To Measure Trace Krypton Contamination in Xenon Andre Loose, Tae-Hyun Yoon, Luke Goetzke, Elena Aprile, Tanya Zelevinsky For Xe and other noble liquids used in rare process searches like the XENON dark matter experiments, Kr contamination contributes background events through the beta decay of long-lived radioactive $^{85}$Kr. To achieve the sensitivity required of the next generation of detectors, the Kr contamination must be reduced to below the part per trillion (ppt) level. While cryogenic distillation is an established technology for the purification of Xe from Kr at the ppt level, there is no conventional method capable of reliably measuring such extremely low contamination. We developed an ATTA system based on laser cooling, trapping and counting of single Kr atoms in Xe, which will enable a rapid and reliable measurement of Kr concentration at the required ppt level. A RF plasma discharge is used to excite $^{84}$Kr atoms to the metastable state. The $^{84}$Kr* are cooled and trapped in a MOT using traditional magneto-optical techniques. The low contamination level of Kr in Xe leads to an average population of the MOT of less than one atom. Since Ar and Kr have similar wavelengths, the apparatus has been initially setup up using Ar, to avoid contamination with Kr. We will discuss switching from Ar to Kr in Xe, and initial measurements using Xe with defined levels of Kr contamination. [Preview Abstract] |
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D1.00020: Spectroscopy of Strongly-Coupled Spins Using Spin-Lock Induced Crossing Stephen DeVience, Ronald Walsworth, Matthew Rosen We present a novel pulse sequence called Spin-Lock Induced Crossing (SLIC) for the manipulation of strongly-coupled spins, based on the splitting and shifting of dressed-state energy levels in response to spin-locking. We demonstrate how SLIC can be used to acquire spectra from groups of spins with unresolvable resonance lines. Performing NMR with SLIC at 6.5 mT, we measured a J-coupling spectrum for both hydrated and dehydrated ethanol, without the addition of a heteronucleus, thereby making chemical identification possible despite the lack of resolvable chemical shifts. We also demonstrated how SLIC can perform spin operations between dressed states. Performing NMR at 4.7 T, we used SLIC to create long-lived nuclear spin singlet states in two nearly-equivalent proton pairs. We discuss how SLIC might be applied to novel spin measurements and quantum memories in the solid state. [Preview Abstract] |
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D1.00021: Optical magnetic imaging of living cells using NV centers in diamond David Le Sage, Keigo Arai, David Glenn, Stephen DeVience, Linh Pham, Ronald Walsworth Nitrogen-vacancy (NV) color centers in diamond can function as sensitive atomic-scale magnetometers with optical initialization and read-out. By imaging the fluorescence from a dense surface layer of NV centers ($\sim$10 nm deep) onto a sCMOS camera, we demonstrated rapid 2D vector magnetic field imaging over a wide field of view and with diffraction-limited spatial resolution. Here we apply this technology to image the magnetic field patterns produced by living magnetotactic bacteria placed on the diamond surface. We reconstruct images of the vector magnetic field projections along all three coordinates with sub-micron resolution, and spatially correlate these magnetic field patterns with optical images of the bacteria concurrently recorded. The measured magnetic field patterns agree well with models of the expected fields from the bacteria. We expect that this NV optical magnetic imaging will enable the first time-resolved measurements of dynamic magnetic field patterns produced throughout the life cycle of a single magnetotactic bacterium, and may open up a wide variety of other biologically-relevant measurement capabilities as well. [Preview Abstract] |
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D1.00022: Towards single electron spin detection at room temperature using nitrogen-vacancy centers Nicholas Chisholm, Igor Lovchinsky, Alex Sushkov, Minako Kubo, Peggy Lo, Eric Bersin, David Hunger, Alexey Akimov, Steven Bennett, Norman Yao, Hongkun Park, Mikhail Lukin We present recent progress on single electron spin detection at room temperature using nitrogen-vacancy (NV) centers in diamond. Sensing a small number of electron spins outside of the measurement substrate at room temperature remains an outstanding goal and would enable many applications, including detection of magnetic resonance signals from biological molecules, determination of free radical concentrations in living cells and real-time monitoring of action potentials in neurons.~~By monitoring the population relaxation rate of an NV center we demonstrate detection of gadolinium spins located outside the diamond lattice. [Preview Abstract] |
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D1.00023: FUNDAMENTAL SYSTEMS AND PRECISION MEASUREMENTS |
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D1.00024: Proposal for parity nonconservation measurements in a single trapped Ba ion Anupriya Jayakumar, Matthew R. Hoffman, Spencer Williams, E.N. Fortson, Boris B. Blinov The interaction of the weak neutral currents between the atomic nucleus and electrons through the exchange of $Z_{o}$ Bosons results in parity violations in atomic systems. The precision of a single Ba$^+$ parity nonconservation (PNC) experiment is predicted to be 0.13{\%} (three fold improvement over the recent atomic PNC measurements in Cs [1]). This combined with the atomic theory of Ba$^+$ will act as a means to test the electroweak physics. We propose to measure the parity violation in Ba$^+$ by coherently exciting the transition $6S_{1/2} \leftrightarrow 5D_{3/2} $ with a 2051 nm laser. Interference between $E1_{PNC} $ (non-vanishing electric dipole transition amplitude between transition $6S_{1/2} \leftrightarrow 5D_{3/2} )$ and $E2$ (electric quadrupole transition amplitude) or $M1$ (magnetic dipole transition amplitude) gives a measure of the parity violating light shifts. Controlling the polarization of the 2051 nm laser and measuring the associated Rabi frequency in each case enables the extraction of $E1_{PNC} $ and $E2/M1$ amplitude from these measurements.\\[4pt] [1] Phys. Rev. Lett. \textbf{82}, 2484 [Preview Abstract] |
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D1.00025: Progress toward measuring the electron EDM in a cryogenic beam of polar molecules Elizabeth Petrik, Jacob Baron, Wesley Campbell, David DeMille, John Doyle, Gerald Gabrielse, Yulia Gurevich, Paul Hess, Nicholas Hutzler, Emil Kirilov, Brendon O'Leary, Benjamin Spaun, Amar Vutha We report on the progress of the ACME Collaboration experiment to measure the electric dipole moment (EDM) of the electron using thorium monoxide. We have demonstrated a statistical sensitivity of $1 \times 10^{-28}$ $\mathrm{e \cdot cm}$ in one day of averaging time. We discuss our studies of several potential sources of systematic error, various apparatus diagnostics, and improvements in the measurement and data analysis scheme. [Preview Abstract] |
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D1.00026: Progress toward a continuous polar molecular beam source for the ACME eEDM experiment Jacob Baron, Wesley Campbell, David DeMille, John Doyle, Gerald Gabrielse, Yulia Gurevich, Paul Hess, Nicholas Hutzler, Emil Kirilov, Brendon O'Leary, Elizabeth Petrik, Benjamin Spaun, Amar Vutha A slow, high-flux beam of thorium monoxide (ThO) is an essential component of the ACME collaboration experiment to measure the electric dipole moment of the electron. The experiment currently employs a buffer gas cooled, pulsed beam source of $\sim 10^{13}$ molecules sr$^{-1}$ s$^{-1}$ at 170 m/s in a single rovibrational level. We present progress toward the realization of a continuous source of ThO via a high-temperature reaction between Th and ThO$_2$. This source offers many potential advantages over the current pulsed ablation source, including higher fractional, peak, and time-averaged yields. [Preview Abstract] |
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D1.00027: Progress towards a measurement of the electron electric dipole moment with trapped molecular ions Kevin Cossel, Huanqian Loh, Kang-Kuen Ni, Matt Grau, Dan Gresh, Jun Ye, Eric Cornell Trapped molecular ions are well suited to searches for the electric dipole moment of the electron (eEDM) due to the long coherence times possible. The current experiment at JILA focuses on the metastable $^3\Delta_1$ level of HfF$^+$ in a Paul trap. We have now demonstrated the ability to state-selectively transfer population to the desired $^3\Delta_1$ $J = 1$ states in the ion trap and to efficiently read-out the population using photodissociation. Using these techniques, we performed detailed characterizations of the hyperfine and Zeeman states with the application of rotating electric fields and magnetic fields. This has enabled initial attempts at Ramsey spectroscopy of the eEDM sensitive states. [Preview Abstract] |
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D1.00028: Characterization and Suppression of Systematic Errors in the ACME Electron Electric Dipole Moment Search Brendon O'Leary, Jacob Baron, David DeMille, John Doyle, Gerald Gabrielse, Paul Hess, Nick Hutzler, Elizabeth Petrik, Ben Spaun In the search for the electron's electric dipole moment (eEDM) in the H $^{3}\Delta_{1}$ state of ThO, the ACME collaboration has characterized and suppressed a number of systematic errors on the order of the experiment's statistical sensitivity $\delta d_{e}\approx 10^{-28} e\cdot cm/\sqrt{T/days}$, where T is experiment duration. Through intentional experimental parameter variation we have explored the impact of imperfect field reversals, laser polarization gradients, changes in field magnitudes, and other potential sources of systematic error on the measured value of the eEDM. In particular, we report on the details of an eEDM mimicking effect caused by the coupling of an imperfect electric field reversal to a laser detuning dependent molecule phase obtained during optical pumping. We discuss ways in which this effect was suppressed to a level below the experiment's statistical error by technical means. [Preview Abstract] |
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D1.00029: Application of Electric Fields to Alkali Vapor Cells with Alkene-based Antirelaxation Coatings Brandon Gruidl, Li Wang, Cheng-Kai Chen, Maryna Longnickel, Derek Jackson Kimball Recently, a new alkene-based antirelaxation coating has been discovered [Balabas et al., Phys. Rev. Lett. 105, 070801 (2010)] which enables spin-polarized alkali atoms to bounce off vapor cell walls more than a million times before the spin polarization relaxes, yielding electron spin relaxation times on the order of a minute. This new technology may open the possibility of conducting a search for the parity- and time-reversal violating permanent electric dipole moment (EDM) of the electron using a cesium vapor contained in an alkene-coated cell. Previous antirelaxation coatings have demonstrated dramatic vapor density variations upon application and reversal of the large electric fields required for an EDM experiment [Jackson Kimball et al., Phys. Rev. A 79, 032901 (2009)]. We have found that in the new alkene-coated cells these electric-field-induced vapor density variations can be mitigated for particular choices of cell and alkali metal reservoir temperatures. Future work will involve demonstrating the long spin-relaxation times during application and reversal of electric fields and direct measurement of the electric field using the Stark shift of excited states in Cs. [Preview Abstract] |
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D1.00030: A $^{3}$He-$^{129}$Xe co-magnetometer probed by a Rb magnetometer with Ramsey-pulse technique Dong Sheng, Aaron Kabcenell, Michael Romalis We report the recent progress in development of a new kind of co-magnetometer, benifiting from both the long spin coherence time of a noble gas and a highly sensitive alkali metal magnetometer. Due to the Fermi-contact interaction between alkali metal electron spin and noble gas nuclear spin the effective magnetization of the noble gas is enhanced by a factor of 6 to 600, allowing near quantum-limited detection of nuclear spins. Collisions between polarized alkali atoms and noble gas also introduce a large shift to the nuclear spin precession frequency. We reduce this effect by using Ramsey pulse techniques to measure the noble gas spin precession frequency ``in the dark'' by turning off the pumping laser between Ramsey pulses. A furthur reduction of the back-hyperpolarization from the noble gas can be achieved by controlling the cell temperature on short time scale. We showed that a $^{3}$He-$^{129}$Xe Ramsey co-magnetometer is effective in cancelling fluctuations of external magnetic fields and gradients and developed cells with sufficient $^{129}$Xe $T_2$ time without surface coatings. The new co-magnetometer has potential applications for many precision measurements, such as searches for spin-gravity couplings, electric dipole moments, and nuclear spin gyroscopes. [Preview Abstract] |
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D1.00031: QUANTUM INFORMATION |
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D1.00032: Calculations of Entanglement Entropy in Two-Electron Atomic Systems Using Highly-Correlated Hylleraas Functions Yew Kam Ho, Chien-Hao Lin, Yen-Chang Lin We have calculated the linear entropy $L=1-Tr(\rho_{A}^{2} )$ of two-electron atomic systems as a practical quantitative measure for the amount of quantum entanglement in the helium atom, the hydrogen negative ion and the positronium negative ion, with $\rho_{A} =Tr_{B} (\left| \right\rangle_{AB} { }_{AB}\left\langle \phi \right|)$ being the one-electron reduced density matrix, obtained after tracing the two-electron density matrix over the degrees of freedom of the other electron. We have used highly correlated Hylleraas-type wave functions (up to $N=$203 terms) with which the inter-electronic coordinates are explicitly included. Due to the use of $r_{12}$ (the distance between the two electrons) factors in the wave functions, calculations of $L$ would require the need to solve four-electron integrals. We will present our detailed calculations at the meeting, including investigations of systematic convergence of the linear entropy for increasing number of terms in the wave functions. Comparisons are made with other available results [1-3] for the helium atom.\\[4pt] [1] J. P. Coe and I. D'Amico, \textit{J. Phys.: Conf. Ser.} \textbf{254}, 012010 (2010).\\[0pt] [2] J. S. Dehesa\textit{ et al}, \textit{J. Phys. B }\textbf{45}, 015504 (2012).\\[0pt] [3] Y. C. Lin, C. Y. Lin, and Y. K. Ho, to be published. [Preview Abstract] |
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D1.00033: NV electronic spin coherence time approaching one second Linh Pham, Nir Bar-Gill, Andrey Jarmola, Dmitry Budker, Ronald Walsworth We demonstrate an improvement of more than two orders of magnitude in the spin coherence time (T2) of NV centers compared to previous measurements: T2 $\sim$ 0.5 s at 77K. By employing dynamical decoupling pulse sequences to suppress NV spin decoherence due to magnetic noise, we found that T2 is limited to approximately half of the longitudinal spin relaxation time (T1) over a wide range of temperatures, which we attribute to phonon-induced decoherence. Our results apply to ensembles of NV spins and do not depend on the optimal choice of a specific NV, which could advance quantum sensing, enable squeezing and many-body entanglement in solid-state spin ensembles, and open a path to simulating a wide range of driven, interaction-dominated quantum many-body Hamiltonians. [Preview Abstract] |
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D1.00034: Entanglement of remote solid-state qubits in diamond Alp Sipahigil, Michael L. Goldman, Alexey V. Akimov, Emre Togan, Matthew Markham, Daniel J. Twitchen, Liang Jiang, Alexander Kubanek, Mikhail D. Lukin Entanglement generation between remote quantum emitters is of great interest for many applications such as long distance quantum communications [1]. In particular, entanglement of two quantum emitters embedded in a solid state matrix is an attractive candidate due to the system's potential scalability. We will present our results for entangling the electronic spins of two Nitrogen-Vacancy (NV) centers in diamond that are spatially separated by 2 meters. \\[4pt] [1] H.J. Kimble ``The quantum internet'' \textit{Nature} \textbf{453}, 1023-1030 (19 June 2008) [Preview Abstract] |
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D1.00035: Electron Tunneling in Quantum Rings in an Electric Field Oluwafemi Adelegan, Branislav Vlahovic, Igor Filikin, Sergei Matinyan, James Nimmo Double concentric quantum rings (DCQRs) composed of InGaAs in a GaAs substrate utilizing a kp-perturbation single sub-band approach with the effective potential approach were theoretically studied. Two dimensional (2D) objects were considered. Statistical analysis of these DCQRs in the absents of an applied electric field were compared with these DCQRs when a static electric field was applied to them. The statistical analysis consist of taking the difference of the probability of finding an electron in the inner ring and outer ring, dividing by the sum of these probabilities. [Preview Abstract] |
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D1.00036: A compact system for single site atom loading of a neutral atom qubit array Brad Dinardo, Steven Hughes, Sterling McBride, Joey Michalchuk, Dana Z. Anderson We present progress towards single atom loading from a magneto optical trap reservoir to a bottle beam (BoB) array trap site for use in quantum computation. Our procedure involves vertically transporting cesium atoms via a moving molasses MOT from a 3D MOT chamber into a six sided, AR-coated, high optical access UHV science chamber. The cesium atoms are to be horizontally displaced 100 $\mu $m to a 7 x 7 array of blue-detuned BoB traps. Displacement of the atoms will be accomplished by means of a moving standing wave dipole trap. The single-site loading experiment will take place in the Atomic Qubit Array Cell (AQuA Cell) which is a compact, high performance UHV system that utilizes new miniature silicon and glass ion pump technology. The entire AQuA Cell is 0.6 liters. The cell, cooling, and transport optomechanics is incorporated in a package occupying about 0.028 cubic meters. [Preview Abstract] |
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D1.00037: Single and pair-wise manipulation of atoms in a 3D optical lattice Theodore A. Corcovilos, Yang Wang, David S. Weiss We describe the hardware used in a quantum computing experiment using individual Cs atoms in a $5\,\mu\mathrm{m}$-spaced 3D optical lattice as qubits. Far-off-resonance addressing beams can be steered to any site in the array using MEMS mirrors within $10\,\mu\mathrm{s}$, allowing the translation of individual atoms between lattice sites, for example to remove vacancies in the atom array, and the manipulation of single atoms for single qubit gates in $<100\,\mu\mathrm{s}$. Two-qubit gates on adjacent atoms can be performed via the Rydberg blockade mechanism using a second MEMS system and high-NA imaging objective. The lasers for the Rydberg excitation are built using a new extended cavity diode laser design utilizing an interference filter as the frequency selecting element following Baillard, et al. (\emph{Opt. Comm.} 266: 609 (2009)), but using commercially available components. [Preview Abstract] |
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D1.00038: Atom-mediated optical cooling of a mechanical resonator Collin Reynolds, Srivatsan Chakram, Belinda Pang, Keith Schwab, Mukund Vengalattore We present our experimental progress toward the realization of a hybrid quantum system consisting of a high-Q mechanical oscillator coupled to ultracold ${}^{87}$Rb atoms. We observe quality factors and $\omega$-Q products as high as $3 \times 10^{7}$ and $6 \times 10^{13}$ respectively for stoichiometric silicon nitride membranes [1,2] at room temperature, putting us in a regime to achieve quantum ground-state cooling[3]. A novel sympathetic cooling scheme is presented which relies on coupling internal states of ${}^{87}$Rb atoms to the mechanical motion of the resonator via a non-degenerate two-photon Raman process. Proof-of-principle experiments give projected cooling rates of $10^{12}$ phonons/s, leading to the possibility of atom-mediated cooling from room temperature down to the quantum ground state. Our scheme does not rely on the optomechanical system being in the ``good cavity'' regime, thereby enabling the optical cooling of mechanical resonators with low quality factors and poor optical properties such as graphene nanoresonators.\\[4pt] [1] B. M. Zwickl {\em et al}, Appl. Phys. Lett. \textbf{92}, 103125 (2008); \\[0pt] [2] D. J. Wilson {\em et al}, Phys. Rev. Lett. \textbf{103}, 207204 (2009); \\[0pt] [3] F. Marquardt {\em et al}, Phys. Rev. Lett. \textbf{99}, 09390 [Preview Abstract] |
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D1.00039: ABSTRACT WITHDRAWN |
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D1.00040: Analytical calculation of the susceptibility for three-level atomic systems Heung-Ryoul Noh, Eun Hyun Cha, Han Seb Moon We present calculation of the analytical solutions of the susceptibility in Doppler-broadened three-level atomic systems using a diagrammatic method. The optical coherences are obtained from the optical Bloch equations for Ladder (upper or lower transition driven), V, and Lambda-type three-level atoms up to the first order in the probe field Rabi frequency and arbitrary order in the coupling field Rabi frequency, and are averaged over a Maxwell-Boltzmann velocity distribution. We obtain general analytical solutions of the susceptibility for four different three-level atomic systems where either the wavelengths of the probe and coupling fields are equal to or different from each other. [Preview Abstract] |
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D1.00041: Nanoscale thermometer based on color defects in diamond Georg Kucsko, Peter Maurer, Minako Kubo, Norman Yao, Hongkun Park, Mikhail Lukin Measuring local temperature changes with confocal spatial resolution is of great interest to an array of scientific disciplines. Here we demonstrate a novel nanoscale temperature sensor with remarkable sensitivity by taking advantage of the quantum mechanical spin properties of nitrogen-vacancy color centers in diamond. This approach enables us to sense temperature variations with a sensitivity down to a few milli-kelvin and a spatial resolution of $\sim 200$~nm. This remarkable sensitivity is achieved by using dynamical decoupling techniques in combination with the long spin coherence properties of our systems. We also demonstrate local temperature control on a sub-cellular level by laser heating of individual gold nanoparticles and measuring the local temperature using individual nanodiamonds induced into the cytoplasm of single biological cells. These results pave the way for a variety of potential applications ranging from physical to life sciences. [Preview Abstract] |
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D1.00042: QUANTUM OPTICS, MATTER OPTICS, AND COHERENT CONTROL |
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D1.00043: Bloch Oscillations of Cold Atoms in a Cavity: Effects of Quantum Noise B. Prasanna Venkatesh, D.H.J. O'Dell We extend our theory of Bloch oscillations of cold atoms inside an optical cavity [Venkatesh \textit{et al.}, Phys. Rev. A \textbf{80},063834 (2009)] to include the effects of quantum noise. The noise acts as a form of quantum measurement backaction by perturbing the coupleddynamics of the atoms and the light. We take it into account by solving the Heiseberg-Langevin equations for linearized fluctuations about the atomic and optical meanfields and examine how this influences the signal-to-noise ratio of a measurement of external forces using this system. In particular, we investigate the effects of changing the number of atoms, the intracavity lattice depth, and the atom-light coupling strength, and show how resonances between the Bloch oscillation dynamics and the quasiparticle spectrum have a strong influence on the signal-to-noise ratio. One of the hurdles we overcome along the way is the proper treatment of fluctuations about \emph{time-dependent} meanfields in the cold atom cavity-QED context. [Preview Abstract] |
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D1.00044: Dissipation-driven two-mode mechanical squeezed states in optomechanical systems Huatang Tan, Gaoxiang Li, Pierre Meystre We propose two quantum optomechanical arrangements that permit the dissipation-enabled generation of steady two-mode mechanical squeezed states. In the first setup, the mechanical oscillators are placed in a two-mode optical resonator while in the second setup the mechanical oscillators are located in two coupled single-mode cavities. We show analytically that for an appropriate choice of the pump parameters the two mechanical oscillators can be driven by cavity dissipation into a stationary two-mode squeezed vacuum, provided that mechanical damping is negligible. The effect of thermal fluctuations is also investigated in detail and shows that ground state pre-cooling of the oscillators in not necessary for two-mode squeezing. These proposals can be realized in a number of optomechanical systems with current state-of-the-art experimental techniques. [Preview Abstract] |
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D1.00045: Coherent control in hybrid materials Chao Tian, Maxim Sukharev, Svetlana Malinovskaya A quickly growing field of hybrid materials is emerging on the base of latest advancements in nanoplasmonic science. Here one merges plasmonics with atomic and molecular physics considering systems comprised of quantum emitters and metal nano-structures. Such systems exhibit a wide variety of new phenomena. It has long been realized that quantum control could be successfully applied to optically active nano-systems. In this paper we explore the ideas of stimulated Raman adiabatic passage (STIRAP) applied to ensembles of atoms optically coupled to plasmonic systems. We demonstrate the implementation of STIRAP as a tool to control scattering, reflection, and transmission properties of hybrid systems. As an example we consider a core-shell silver nanowire with resonantly coupled layer of three-level atoms. A self-consistent model of Maxwell-Liouville-von Neumann equations is implemented that allows taking into account the collective effects between atoms. We show that both linear and nonlinear optical properties of atomic ensembles may be controlled by coupling to plasmonic nano-structures. [Preview Abstract] |
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D1.00046: Femtosecond electron switching with plasmonic antennae and nano-fabricated gratings. Maria Becker, Wayne Cheng-Wei Huang, Roger Bach, Herman Batelaan We have shown that the optical response of a plasmonic antenna is faster than 20 fs [1]. We report on this measurement and our proposal to use such a device for femtosecond electron switching. Plasmonic antennae and nano-scale gratings may exhibit near-field enhancement. This phenomenon can increase the intensity of an input electric field by up to a factor of one thousand in the near field of the structure. Cross-correlation measurements of femtosecond laser pulses reflected from an antenna indicate that the duration of the enhanced near-fields is of the same order as the incident excitation pulses. Thus, we propose that enhanced near-fields of a plasmonic antenna may be used to influence the motion of free electrons at the femtosecond time scale. Our estimates indicate that the antenna can cause deflection angles of approximately 0.1 radian upon applying a 10 nJ, 10 fs laser pulse. In a separate experiment we have observed electron beam deflection induced by a laser beam when the electrons pass closely over the surface of a nano-grating. This effect is currently under investigation.\\[4pt] [1] Maria Becker, Wayne Cheng-Wei Huang, Herman Batelaan, Elisabeth J. Smythe, and Federico Capasso, \textit{Ann. Phys.} published online (2012). [Preview Abstract] |
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D1.00047: Raman transitions in ultracold 85Rb by chirped nanosecond-time-scale pulses Gengyuan Liu, Svetlana Malinovskaya Ultracold alkali atoms have been conventionally used for quantum operations. Previously it has been shown theoretically that a single nanosecond, linearly chirped pulse may be implemented to perform population inversion in hyperfine levels of 5S shell in Rb [1]. Here, within a rigorous semiclassical model that involves all optically allowed transitions between hyperfine states of D1 and D2 lines in the $^{85}$Rb atom, we demonstrate a possibility of controlled population transfer using pulses having the duration from one to a few nanoseconds and chirped to induce Raman transitions in the hyperfine state manifold. Experimentally the chirping of nanosecond pulses may be performed in the time domain using fiber-based electro-optical modulators [2]. We will discuss the role of the chirp rate, the pulse duration and the field intensity as control parameters.\\[4pt] [1] T. A. Collins, S. A. Malinovskaya, {\em Opt. Lett.} {\bf 37,} 2298-2300 (2012).\\[0pt] [2] Rogers III, C.E., Wright, M.J., Carini, J.L., Pechkis, J.A., Gould, P.L., {\em J. Opt. Soc. Am. B} {\bf 24,} 1249-1253 (2007). [Preview Abstract] |
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D1.00048: Deterministic macroscopic quantum superpositions of motion by quadratic optomechanical coupling Huatang Tan, Francesco Bariani, Gaoxiang Li, Pierre Meystre We propose a scheme to prepare macroscopic quantum superpositions of motion of nanomechanical oscillators coupled quadratically to a driven cavity field. These superpositions result from the fact that the nonlinear optomechanical coupling can lead to an effective degenerate three-wave mixing of the mechanical and cavity modes. We show analytically and confirm numerically that different kinds of quantum superpositions can be realized deterministically, depending on the initial mechanical state. The effect of mechanical damping is also quantified by the negativity of the Wigner function. Besides various optomechanical systems, the present scheme could also be applied to other physical systems in which degenerate three-wave mixing can be engineered. [Preview Abstract] |
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D1.00049: Adiabatic passage for quantum gates in mesoscopic atomic ensembles I.I. Beterov, M. Saffman, E.A. Yakshina, V.P. Zhukov, D.B. Tretyakov, V.M. Entin, I.I. Ryabtsev, C.W. Mansell, C. MacCormick, S. Bergamini, M.P. Fedoruk We present schemes for geometric phase compensation in adiabatic passage which can be used for implementation of quantum logic gates with atomic ensembles consisting of an arbitrary number of strongly interacting atoms. Protocols using double sequences of stimulated Raman adiabatic passage (STIRAP) or adiabatic rapid passage (ARP) pulses are analyzed. Switching the sign of the detuning between two STIRAP sequences, or inverting the phase between two ARP pulses, provides state transfer with well defined amplitude and phase independent of atom number in the Rydberg blockade regime. Using these pulse sequences we present protocols for universal single-qubit and two-qubit operations in atomic ensembles containing an unknown number of atoms. [Preview Abstract] |
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D1.00050: Super-resolution optical imaging and magnetometry using NV centers in diamond Jean-Christophe Jaskula, Alexei Trifonov, David Glenn, Nir Bar-Gill, Ronald Walsworth We report progress done on the development and application of depletion-based techniques for super-resolution (nanoscale) optical imaging and magnetometry using NV centers in diamond. In particulare we are integrating stimulated emission depletion (STED) and ground state depletion (GSD) imaging techniques with advanced pulsed sequences for AC magnetometry. NV centers in diamond do not bleach under optical excitation, have long-lived electronic spin coherence and spin-state-dependent fluorescence, and are not biotoxic. Thus NV-diamond has great potential in quantum science and as a nanoscale magnetic biosensor. [Preview Abstract] |
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D1.00051: A Superradiant Raman Laser as a Hybrid Active/Passive Atomic Sensor Justin G. Bohnet, Joshua M. Weiner, Kevin C. Cox, Zilong Chen, James K. Thompson We have realized an atomic sensor that combines active, wideband sensing with passive measurement periods using dynamic control of a cold-atom, superradiant Raman laser. In a superradiant laser, collective emission of the atomic ensemble maps the quantum phase stored in the atoms onto the detected cavity field. We discuss the fundamental precision of the superradiant mapping and show theoretically that the precision of the non-demolition measurement is only a factor of two worse than the standard quantum limit on phase estimation for a coherent spin state. Using the superradiant readout, we experimentally demonstrate a repeated, non-demolition conditional Ramsey sequence that has the potential to combine the benefit of a high-bandwidth active frequency reference with a high-accuracy passive device. We also present an experimental realization of a superradiant Raman laser operated as a hybrid active/passive atomic magnetometer. [Preview Abstract] |
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D1.00052: Hybrid optomechanical systems in the strong coupling regime Yogesh Patil, John Lombard, Kristina Colladay, Mukund Vengalattore We present our progress toward the realization of a hybrid optomechanical system consisting of an ultracold atomic gas parameterically coupled to the optomechanical whispering gallery modes of a microtoroidal resonator. These resonators admit both high-Q mechanical modes as well as optical modes that exhibit very low loss. The strong coupling between the optical and mechanical degrees of freedom has been exploited for the optical cooling and quantum-limited detection of the mechanical micromotion [1]. In addition, the small optical mode volume of the evanescent wave optical fields allows for strong optical coupling to proximally confined atoms [2]. We are constructing a hybrid quantum system wherein a gas of ultracold atoms is confined near the microtoroid in a two-color evanescent wave optical dipole trap. The atomic coupling to the microtoroid allows for atom-mediated optomechanical interactions and the control of the mechanical motion of the microtoroid using the atomic medium.\\[4pt] [1] G. Anetsberger {\em et al}, Nature Phys. \textbf{5}, 909 (2009).\\[0pt] [2] T. Aoki {\em et al}, Nature \textbf{443}, 671 (2006). [Preview Abstract] |
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D1.00053: Quantum interface between DC-SQUID and trapped ion Dvir Kafri, Prabin Adhikari, Jacob Taylor We show how to couple the motional state of a trapped ion to a quantized electrical circuit. The circuit, a DC-SQUID with an inductive nonlinearity, has resonant frequency much larger than that of the ion motion, so a coupling using direct Coulomb interaction is not feasible. Instead, this is achieved through careful modulation of the SQUID inductance with an external magnetic field. By coupling the ion motion to its internal state, this allows for an effective interface between an ion qubit and the circuit, with rates comparable to those of current ion-ion motional gates. [Preview Abstract] |
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D1.00054: Spontaneously generated coherence effects in an inverted Y-type system Jianbing Qi We investigate the spontaneous emission from the upper excited state of an inverted Y-type atomic system coupled by three coherent fields. We use the Schr\"{o}dinger equation to calculate the probability amplitudes of the wave function of the system and derive an analytical expression of the spontaneous emission spectrum to trace the origin of the spectral features. Spectral features of the spontaneous emission depend on the amplitude of the coupling fields and the preparation of the initial quantum state of the atom. The number of spectral components, the spectral linewidth, and the relative height of each spectral component depend on the physical parameters of the system and the external fields. A variety of quantum interference effects, such as spectral line narrowing, spectrum splitting, and dark resonance, can be observed. [Preview Abstract] |
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D1.00055: Probing magnetic noise near a conductor with a single spin qubit Shimon Kolkowitz, Quirin Unterreithmeier, Vladimir Manucharyan, Arthur Safira, Steven Bennett, Alexander Zibrov, Mikhail Lukin Noise emanating from conductors and their surfaces can limit the coherence times and relaxation rates of many promising quantum information systems, ranging from superconducting qubits and gate-defined quantum dots to atoms and ions on chips. In many systems, the physical mechanism behind this noise is not fully understood, particularly at low frequencies. Here we present experimental progress towards the use of single electronic spin qubits in diamond to probe the spectral, spatial, and temperature dependent properties of magnetic noise near conductors and superconductors. Using nitrogen vacancy centers implanted at shallow depths we investigate the spectral properties of the magnetic noise at distances down to 10 nm from the metal surface, a length scale not currently achievable in other systems, over a wide range of temperatures, from 6 to 300 K. [Preview Abstract] |
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D1.00056: Towards ultracold Li Cs mixtures on an atom chip Asaf Paris-Mandoki, Sonali Warriar, Matt Jones, Jonathan Nute, Peter Kr\"uger, Lucia Hackerm\"uller Ultracold mixtures hold the promise of understanding new phases of matter and collisions at very low energies. By combining the capabilities of the atom chip with optical dipole trapping, it will be possible to trap these mixtures in low dimensions and tune their scattering lengths via Feshbach resonances. In this way it will also be possible to realise experiments with additional magnetic potentials, position dependent interactions or impurity dynamics. Here we present the current status of our Lithium and Cesium experiment. We detail the cooling schemes for both atom species and include the recent development of implementing an optical dipole trap. We discuss ideas for future measurements with separately addressable Bose-Fermi mixtures in optical dipole traps, such as transport and impurity studies in low dimensions, close to a chip surface. [Preview Abstract] |
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D1.00057: Deterministic Coupling of a Single Atom to a Nanoscale Optical Cavity Lee Liu, Jeff Thompson, Tobias Tiecke, Nathalie de Leon, Johannes Feist, Michael Gullans, Alexey Akimov, Alexander Zibrov, Vladan Vuletic, Mikhail Lukin Deterministic control over interactions between isolated ultra-cold atoms and nanoscale solid-state systems is an outstanding problem in quantum science. It is of interest for understanding the fundamental limits of quantum control over complex systems, as well as for realizing hybrid quantum systems, combining the excellent coherence properties atoms with strong interactions and scalability. We propose and demonstrate a technique for deterministically interfacing a single rubidium atom with a nanoscale photonic crystal cavity by trapping the atom in the near-field of the cavity. By controlling the atom's position, we probe the cavity field non-invasively with a resolution below the diffraction limit. A single-photon single-atom coupling rate of $2g \simeq 2\pi \times 0.5$ GHz is measured by a reduction in the cavity transmission. We discuss prospects for integrated, strongly-coupled quantum nano-optical circuits, and their potential applications. [Preview Abstract] |
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D1.00058: Measurement of the Rydberg ionization current in thermal vapor cells Robert Loew, Daniel Barredo, Renate Daschner, Harald Kuebler, Ralf Ritter, Tilman Pfau Rydberg atoms confined in atomic vapor cells are promising candidates for the realization of single photon sources and quantum optical devices. To date, most information about the behavior of the Rydberg ensembles in thermal vapors has been extracted by absorptive measurements, e.g. EIT. However, to access directly quantities, like the population of the excited states, new methods are needed. In this task, the detection of the Rydberg ionization current provides a complementary and direct insight in the atomic processes. We show measurements of the Rydberg-ion current in thermal vapor cells equipped with field plates inside the vacuum. arXiv:1209.655 [Preview Abstract] |
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D1.00059: A Road Map to Ultracold Polyatomic Molecules Sotir Chervenkov, Xing Wu, Josef Bayerl, Andreas Rohlfes, Barbara Englert, Rosa Gl\"ockner, Alexander Prehn, Martin Ibr\"ugger, Martin Zeppenfeld, Gerhard Rempe Producing ensembles of polyatomic molecules at ultracold temperatures is a challenge. In pursuit of this goal, we propose a very general scheme combining sequentially three promising techniques. First, high-flux continuous supersonic beams of internally cold polar molecules are produced from a buffer-gas cell [1,2] operated in hydrodynamic regime. Then those beams are guided in an electrostatic guide [3] and decelerated by the centrifugal potential in a rotating frame. The decelerated beams are delivered to an electrostatic trap, where the molecules are further cooled down via a Sisyphus process [4] employing laser, microwave, and radiofrequency radiation. Here we demonstrate experimental results from the three techniques and give evidence for the viability of their joint operation en route to achieving sub-milliKelvin ensembles of polyatomic polar molecules.\\[4pt] [1] L.D. van Buuren et al., Phys. Rev. Lett. {\bf 102}, 033001 (2009)\\[0pt] [2] C. Sommer et al., Faraday Discuss. {\bf 142}, 203 (2009)\\[0pt] [3] S.A. Rangwala et al., Phys. Rev. A {\bf 67}, 043406 (2003)\\[0pt] [4] M. Zeppenfeld et al., Nature {\bf 491}, 570 (2012) [Preview Abstract] |
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D1.00060: COLD ATOMS, MOLECULES, AND PLASMAS I |
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D1.00061: Thermodynamics of systems of aligned dipoles K.M. Daily, D. Blume The high-temperature thermodynamics of two-component Fermi gases with interspecies $s$-wave scattering length is well described by the virial equation of state. This work determines the virial equation of state of weakly-interacting dipolar Bose and Fermi gases under external spherically symmetric confinement. The second-order virial coefficients for two identical dipolar bosons, two identical dipolar fermions and two distinguishable dipoles are calculated from the trap energy spectra. Away from resonance, we employ the Born approximation and find that the virial coefficient for two identical fermions depends quadratically on the dipole length. This suggests that dipolar effects are suppressed in the high temperature limit. Fine tuning the scattering properties of two identical fermions, we identify conditions in which the second-order virial coefficient depends linearly on the dipole length. Analytical expressions are derived and corroborated by numerical calculations. [Preview Abstract] |
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D1.00062: Electric-field and two-photon excitation calculations for BEC-ion interaction experiments Stephanie Miller, David Anderson, Georg Raithel We present progress toward implementing experiments investigating the interactions between Bose-Einstein Condensates (BEC) and ultra-cold ions. In such experiments, the interaction region needs to be free of stray electric fields in order to avoid premature extraction of the ion from the BEC, which requires field control of less than 100 $\mu $V/cm. Here, we report on the modeling of the electric-field and the ion-imaging characteristics for several setups. To further improve the electric-field shielding of the ion-BEC interaction region, we consider a two-photon excitation and adiabatic wave function control scheme in which a high-n circular-state Rydberg atom is prepared on a BEC. The circular Rydberg atom has a small quadratic Stark shift, which serves to efficiently shield electric fields from the center of the atom, where the atom's ionic core interacts with BEC atoms. Towards this novel approach, we calculate two-photon Rydberg-atom excitation rates for different combinations of laser polarizations and ground states in weak crossed electric and magnetic fields, which are required in the utilized circular-state preparation scheme. [Preview Abstract] |
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D1.00063: Collective Excitations in quasi-2D Condensates Dan Lobser, Lin Xia, Andrew Barentine, Eric Cornell Quantum gases confined to lower dimensions exhibit remarkable physical properties such as the Berezkinskii-Kosterlitz-Thouless transition or the Tonks-Girardeau gas. Confinement effects in a quasi-2D condensate are predicted to shift the frequency of certain collective excitations, in particular the monopole mode [1,2]. In our experiment, quasi-2D condensates are created by loading a 3D condensate into a 1D optical lattice, collective modes are then parametrically driven by modulating the strength of the trap. We present current results on our measurements of these collective excitations and how they compare with radial trapping frequency.\\[4pt] [1] Olshanii et al., Phys. Rev. Lett. 105, 095302 (2010).\\[0pt] [2] Hu et al., Phys. Rev. Lett. 107, 110401 (2011). [Preview Abstract] |
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D1.00064: Study of ground state optical transfer for ultracold alkali dimers Nadia Bouloufa-Maafa, Beatriz Londono, Dimitri Borsalino, Romain Vexiau, Jorge E. Mahecha, Olivier Dulieu, Eliane Luc-Koenig Control of molecular states by laser pulses offer promising potential applications. The manipulation of molecules by external fields requires precise knowledge of the molecular structure. Our motivation is to perform a detailed analysis of the spectroscopic properties of alkali dimers, with the aim to determine efficient optical paths to form molecules in the absolute ground state and to determine the optimal parameters of the optical lattices where those molecules are manipulated to avoid losses by collisions. To this end, we use state of the art molecular potentials, R-dependent spin-orbit coupling and transition dipole moment to perform our calculations. R-dependent SO coupling are of crucial importance because the transitions occur at internuclear distances where they are affected by this R-dependence. Efficient schemes to transfer RbCs [1], KRb and KCs to the absolute ground state as well as the optimal parameters of the optical lattices will be presented. \\[4pt] [1] M. Debatin, et al., Phys. Chem. Chem. Phys., 13, 18926 (2011) [Preview Abstract] |
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D1.00065: Rapid Production of Bose-Einstein Condensates at a 1 Hz Rate Daniel Farkas, Jaime Ramirez-Serrano, Evan Salim The speed at which Bose-Einstein condensates (BECs) can be produced is a key metric for the performance of ultracold-atom inertial sensors, gravimeters, and magnetometers, where production cycle time of ultracold atoms determines sensor bandwidth. Here, we demonstrate production of $^{87}$Rb BECs at rates exceeding 1 Hz. Not only can we create a BEC from a hot vapor in less than one second, but we can continuously repeat the process for several cycles. Such speeds are possible because of the short evaporation times that result when atoms are confined in tight traps. In our case, we magnetically trap atoms with an atom chip that seals the top of one of ColdQuanta's RuBECi\textregistered vacuum cells. With RF evaporative cooling sequences as short as 450~ms, we attain nearly pure condensates of 2x10$^{4}$ atoms. In the future, the apparatus described here will be integrated into a portable system that houses all of the components needed to produce BECs (e.g. lasers, vacuum, electronics, imaging, etc.) in a volume less than 0.3 m$^{3}$. [Preview Abstract] |
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D1.00066: Rapid formation of atomic Bose-Einstein condensates in a three-beam crossed dipole trap Chih-Yuan Huang, C.-C. Chen, H.-Y. Liu, Y.-H. Cheng, K.-S. Wu, Ming-Shien Chang We report on the rapid formation of Rubidium condensates in a three-beam crossed dipole trap. Our experiment comprises a simple vapor cell MOT and three single-focused and crossed Nd:YAG laser beams. Two stronger laser beams are focused and crossed at a small angle, which are responsible for collecting atoms from the MOT. Crossing two single-focused beams at a small angle allows us to greatly increase the longitudinal trap frequency and thus the atom density and collision rate in the trap. The third and weaker beam is then crossed perpendicularly to create a potential dimple for subsequent efficient evaporation. Laser-cooled atoms are directly loaded into this three-beam dipole trap, and the initial density in the dimple region is measured as high as $10^{14} cm^{-3}$, which is limited by the 3-body collision loss. Evaporation is then forced for $3$ sec till the formation of BEC. We will report the details of our studies and future direction of this experiment. [Preview Abstract] |
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D1.00067: Spin textures in Bose-Einstein condensates Azure Hansen, Justin T. Schultz, Nicholas P. Bigelow Using a coherent, two-photon Raman spin imprinting technique, we create and characterize a variety of complex, non-equilibrium spin textures, in a ${}^{87}$Rb Bose-Einstein condensate. This Raman technique allows us to engineer the internal and external momenta, superfluid velocities, and spatial spin distribution of the condensate as well as controlling the complex relative phases of the spin components. Spin textures with spatially-varying population distributions in multiple spin states can provide cold-atom analogs of systems in condensed matter, particle, and solid state physics as well as singular optics. A variety of topological excitations can be created, including coreless vortices, fractional vortices, skyrmions, monopoles, and knots. [Preview Abstract] |
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D1.00068: Towards Chemically Stable Fermionic Ground State Molecules with Strong Dipolar Interactions Sebastian Will, Jee Woo Park, Cheng-Hsun Wu, Jennifer Schloss, Martin Zwierlein Quantum gases with dipolar interactions will open new avenues for the creation of novel quantum many-body systems with intriguing properties, ranging from crystalline over magnetic to topological phases. A promising route for the experimental realization of dipolar quantum gases is the formation of fermionic ground-state molecules with a large electric dipole moment, giving rise to long-range anisotropic interactions. With our experiment we work towards the realization of fermionic ground state molecules of $^{23}$Na$^{40}$K. The NaK ground state molecule is chemically stable and possesses a large induced electric dipole moment of 2.72 Debye. In pioneering studies, we have created nearly degenerate samples of weakly bound $^{23}$Na$^{40}$K Feshbach molecules. With a long lifetime and a significant admixture of the electronic spin singlet state, the Feshbach molecules are an ideal starting point to reach the singlet rovibrational ground state with a two-photon STIRAP transfer. Aiming for an efficient transfer path, we have performed spectroscopic studies on excited and ground state molecular potentials of $^{23}$Na$^{40}$K and will report on our current progress. [Preview Abstract] |
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D1.00069: The 1D-3D Crossover of A Spin-Imbalanced Fermi Gas Melissa Revelle, Ben A. Olsen, Yean-An Liao, Randall G. Hulet We have previously mapped the phase diagram of a 1D spin-imbalanced Fermi gas by confining lithium atoms in an array of tubes using a 2D optical lattice.\footnote{Y.A. Liao et al., Nature 467, 567 (2010).}. Within each tube we observed separation of the atoms into a partially polarized superfluid core and fully paired or fully polarized wings (depending on the spin polarization) In 3D, the phase separation is inverted, such that the cloud center is fully paired.\footnote{G. B. Partridge et al., Science 311, 503 (2006); Y. Shin et al., Phys. Rev. Lett. 97, 030401 (2006).} We investigate the transition from a 1D to 3D gas by reducing the lattice depth in order to change the tunneling between the tubes. The dynamics of spin transport may be investigated by a sudden change in lattice depth. [Preview Abstract] |
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D1.00070: Progress towards the creation of an ultracold RbYb mixture Varun Vaidya, Creston Herold, Xiao Li, Jiraphat Tiamsuphat, Steven Rolston, Trey Porto Alkali metals such as rubidium-87 have become the workhorse in degenerate gas experiments, and large condensates of up to $10^7$ atoms have been created. On the other hand, alkaline earth metals like ytterbium offer a range of isotopes, both Fermionic and Bosonic, and have closed ground shells and narrow intercombination transitions that offer different possibilities than alkali gases. We describe progress made towards creating a degenerate mixture of rubidium-87 and ytterbium and discuss the scope of experiments planned with this apparatus. In particular we discuss the production of a rubidium-blind optical lattice and the possibility of using a rubidium-87 BEC to cool lattice-trapped ytterbium atoms. We will also discuss exploiting the narrow intercombination transition in ytterbium to explore long-lived optical Feshbach resonances between rubidium and ytterbium. In addition, we will present the results of a recent experiment to accurately determine the dipole matrix elements of the 5s$\rightarrow$6p transition in rubidium-87. [Preview Abstract] |
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D1.00071: Towards site-resolved imaging of fermionic lithium in a two-dimensional optical lattice Sebastian Blatt, Florian Huber, Maxwell F. Parsons, Anton Mazurenko, Markus Greiner Recent successes in site-resolved imaging and control of bosonic $^{87}$Rb atoms trapped in optical lattices enable new possibilities for studying strongly-correlated quantum systems with ultracold atoms. We aim to extend this technique to fermionic atoms, where quantum magnetism arises naturally due to fermionic statistics. We plan to load ultracold $^6$Li atoms into a two-dimensional square lattice 10 $\mu$m below a high-resolution microscope objective. The light mass of $^6$Li leads to system dynamics on fast timescales, and its broad Feshbach resonances give us control over the atomic interaction strength. A major challenge with $^6$Li is cooling the atoms during imaging. The hyperfine structure of $^6$Li's excited 2P electronic state is not resolved, and cooling techniques are limited. In addition, $^6$Li has a large recoil energy of 75 kHz. We expect that these difficulties may be solved by combining Raman sideband cooling with a deep optical lattice, and we report our progress on this front. [Preview Abstract] |
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D1.00072: High-Precision Measurement of the Rydberg Constant Kaitlin Moore, Georg Raithel A new spectroscopic method is proposed to couple circular Rydberg states of rubidium using lattice modulation. This excitation strategy could allow for a competitive measurement of the Rydberg constant while relying very little on the accuracy of QED calculations and being insensitive to nuclear charge distribution. The spectroscopic method requires preparing circular-state Rydberg atoms via an RF adiabatic passage method and confining prepared atoms in an optical lattice. Excitation of a two-photon electric quadrupole transition between circular Rydberg states can be accomplished through electro-optic modulation of the lattice at the microwave transition frequency between these states. Detection of the target-state population as a function of the modulation frequency can be accomplished through state-selective electric-field ionization. We discuss frequency shift corrections that will contribute to determining the Rydberg constant from this frequency, along with theoretical and experimental progress. [Preview Abstract] |
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D1.00073: Negative absolute temperature for mobile particles and expansion dynamics of interacting bosons in optical lattices Simon Braun, Philipp Ronzheimer, Michael Schreiber, Sean Hodgman, Immanuel Bloch, Ulrich Schneider We present recent experiments with ultracold bosonic 39K atoms in an optical lattice, implementing the Bose-Hubbard Hamiltonian. Absolute temperature is usually bound to be strictly positive. However, in systems with an upper energy bound, negative absolute temperature states are possible, where the occupation probability of states increases with their energy. We realized a negative absolute temperature state for motional degrees of freedom which strikingly revealed itself by strong occupation peaks at maximum kinetic energy. We found that the negative absolute temperature state is close to degeneracy and intrinsically stable. Additionally, we investigated the out-of-equilibrium expansion dynamics of interacting bosons in one- and two-dimensional Hubbard systems. We found that the fastest, ballistic expansions occur in the integrable limits. In 1D, these are both the non-interacting and the strongly interacting limit. In 2D, the system expands ballistically only in the noninteracting case, and even small interactions lead to strongly diffusive behavior. In addition we characterized the dimensional crossover between 1D and 2D for these dynamics. We also show recent results on the timescale of the emergence of coherence when crossing the Mott insulator to superfluid transition. [Preview Abstract] |
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D1.00074: Investigations of quantum pendulum dynamics in a spin-1 BEC Thai Hoang, Corey Gerving, Ben Land, Martin Anquez, Chris Hamley, Michael Chapman We investigate the quantum spin dynamics of a spin-1 BEC initialized to an unstable critical point of the dynamical phase space. The subsequent evolution of the collective states of the system is analogous to an inverted simple pendulum in the quantum limit and yields non-classical states with quantum correlations. For short evolution times in the low depletion limit, we observe squeezed states\footnote{C.D. Hamley, C.S. Gerving, T.M. Hoang, E.M. Bookjans, and M.S. Chapman, ``Spin-Nematic Squeezed Vacuum in a Quantum Gas,'' Nature Physics 8, 305-308 (2012).} and for longer times beyond the low depletion limit we observe highly non-Gaussian distributions.\footnote{C.S. Gerving, T.M. Hoang, B.J. Land, M. Anquez, C.D. Hamley, and M.S. Chapman, ``Non-equilibrium dynamics of an unstable quantum pendulum explored in a spin-1 Bose-Einstein condensate,'' Nature Communications 3, 1169 (2012).} [Preview Abstract] |
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D1.00075: Improving prospects for experimental realization of exotic quantum magnetism in alkaline earth atoms Kaden Hazzard, Salvatore Manmana, Lars Bonnes, Gang Chen, Stefan Wessel, Victor Gurarie, Michael Hermele, Ana Maria Rey We show how one can use recently developed experimental tools for cold atoms in optical lattices -- alkaline earths, reduced dimensionality, and artificial gauge fields -- to improve the feasibility of reaching exotic phases of matter. A first unambiguous experimental identification of these exotic phases, such as topological phases and spin liquids, would transform many-body physics. Alkaline earth atoms are predicted to harbor such a ``chiral spin liquid'' state at zero temperature. However, cold systems have struggled to reach sufficiently low temperatures, even for conventional phases such as antiferromagnets. Here we show that the large nuclear spin, $I\le9/2$, and special SU($N=2I+1$) symmetry of alkaline earths allow magnetism to persist to substantially higher entropies as $N$ is increased [1]. This enhancement is even more dramatic in one dimension [2,3]. Finally, artificial gauge fields may enlarge the parameter regime occupied by the chiral spin liquid and facilitate its adiabatic preparation. \\[4pt] [1] KRA Hazzard, V Gurarie, M Hermele, and AM Rey, PRA \textbf{85}, 041604 (R) (2012)\\[0pt] [2] SR Manmana, KRA Hazzard, G Chen, AE Feiguin, and AM Rey, PRA \textbf{84}, 043601 (2011)\\[0pt] [3] L Bonnes, KRA Hazzard, SR Manmana, AM Rey, and S Wessel, PRL \textbf{109}, 205305 (2012) [Preview Abstract] |
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D1.00076: A Matterwave Transistor Oscillator Seth C. Caliga, Cameron J.E. Straatsma, Dana Z. Anderson We perform experiments with an Rb87 Bose-condensed gas in a magnetic trap separated into three regions by a pair of blue-detuned optical barriers, forming a transistor-like structure having large ``source'' and ``drain'' regions separated by a narrow ``gate'' region. A condensate is produced in the source by forced RF evaporative cooling. While atom number and chemical potential of the source atoms are determined by traditional time of flight methods, we observe the flux and energy of the drain atoms emerging from the gate-drain barrier with a high resolution (NA$=$0.6) in-trap absorption imaging system. Asymmetric cooling of the trap causes a thermo-mechanically induced superfluid current to flow from the source to the gate over the source-gate barrier. Feedback through superfluid coupling between the source and the gate maintains near equality of the source and gate chemical potentials while superfluid flow continues to cause atoms to emerge from the gate into the drain. A resonant ``terminator'' beam illuminating the drain region effectively couples emerging gate atoms to the vacuum. By turning off the terminator beam shortly before snapping an absorption image we determine both the atom flux and the atom energy. With an appropriate choice of cooling schedule, barrier heights, and separations, the gate emits a monoenergetic beam of atoms. We establish that this system is a superfluid analog of an antenna-coupled transistor- oscillator circuit in which the dual of the electromagnetic wave is a matterwave. [Preview Abstract] |
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D1.00077: Creating, imaging, and analyzing magnetic structures in a spinor BEC Sean Lourette, G. Edward Marti, Ryan Olf, Andrew MacRae The rich and varied order parameter spaces of spinor Bose-Einstein Condensates admit a wide range of collective excitations, non-trivial topological structures, and out-of-equilibrium dynamics. However, creating, imaging, and interpreting such states can be difficult. Here, we present techniques developed in our labs to create spinor structures and to image them \textit{in situ} with high signal to noise, as well as results from applying these techniques to a spin-1 $^{87}$Rb BEC. Our imaging technique accesses a large part of the order parameter space in a single run, simplifying the task of interpreting and analyzing complex spin structures. [Preview Abstract] |
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D1.00078: Dynamical extraction of lattice-localized atoms from a superfluid Jeremy Reeves, Ludwig Krinner, Dominik Schneble Bosonic quantum-gas mixtures in optical lattices allow for a wide range of studies including disordered systems, dissipative phenomena and out-of-equilibrium effects. Using a rubidium condensate, we study the coherent transfer of atoms between a superfluid and the orbitals of a deep state-dependent optical lattice, achieved by driving the atoms between two hyperfine ground states. We observe a nontrivial dependence of the transfer efficiency on the coupling strength, linked to the mean-field dynamics of the superfluid. [Preview Abstract] |
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D1.00079: Decoherence of spin oscillations in an ultracold F=1 sodium gas Arne Schwettmann, Hyewon Pechkis, Jonathan Wrubel, Ryan Barnett, Eite Tiesinga, Paul Lett An ultracold F=1 sodium gas prepared in a superposition of the m=+1, 0, -1 magnetic sublevels displays nonlinear spin dynamics. The dynamics are driven by coherent spin mixing collisions, where a pair of m=0 atoms is converted into a pair with m=+1 and m=-1. In the noncondensed thermal gas, we find that the resulting population oscillations decay over several hundred milliseconds. We present measurements of the decay time as a function of applied magnetic field and initial state, and discuss possible causes of the decay. [Preview Abstract] |
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D1.00080: Three-dipole recombination in parallel 1D-tubes Edmund Meyer, Shai Ronen, B.D. Esry We present a study of three interacting dipoles in parallel 1D tubes. It has been predicted that two dipoles in separate tubes can have a cross-tube bound state [1]. We use an adiabatic hyperspherical formalism to construct the hyperradial three-dipole potentials along with the non-adiabatic couplings. We will use these quantities to help qualitatively understand the dynamics as well as quantitatively calculate the recombination rate. The dependence of the recombination rate on the incident energy and the ratio of the dipole length to tube separation will be shown. In addition, we will examine the question of universality for the observables and any impact of short range two-body physics within the tube on the recombination rate.\\[4pt] [1] N. T. Zinner et. al., Phys Rev A 84, 063606 (2011) [Preview Abstract] |
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D1.00081: Photoassociation spectroscopy of ultracold highly excited NaCs molecules Maitreyi Jayaseelan, Marek Haruza, Nicholas Bigelow We report on our spectroscopic investigations of translationally ultracold NaCs molecules. Photoassociation from laser cooled mixtures of ground state sodium and excited cesium atoms creates molecules in excited states detuned from the Na(3s) + Cs(6d) dissociation asymptote. This is an as yet unexplored asymptote for molecule formation. We infer properties of the scattering wave from the PA spectra, and investigate the populated ground states using photoionization and depletion spectroscopy. [Preview Abstract] |
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D1.00082: Old and new physics with ultracold $^{88}$Sr$_2$ molecules in optical lattices Gael Reinaudi, Mickey McDonald, Bart H. McGuyer, Christopher B. Osborn, Tanya Zelevinsky Ultracold molecules provide an exciting testing ground for studies of fundamental interactions, new states of matter, and metrology. Diatomic molecules based on two-electron atoms are especially suitable for precise tests of interatomic interactions, molecular QED, electron-proton mass ratio variations, and deviations from Newtonian gravity at the nanoscale. We describe the efficient production of $^{88}$Sr$_2$ in an optical lattice, detection via ultracold optical fragmentation, and studies of molecular loss processes. We also present high-Q spectra of the molecules in magnetic fields that point to possible QED sensitivity as well as to strong-coupling effects that are not yet well understood. Current and future work made possible by this new type of long-lived molecule is discussed. [Preview Abstract] |
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D1.00083: Multichannel study on three-body physics near Feshbach resonances Yujun Wang, Paul S. Julienne We study three-body physics for ultracold atoms in hyperspherical coordinates with multichannel two-body potentials that closely mimic the realistic atomic interactions. By using this numerical technique, we are able to study the dependence of three-body universality on realistic parameters for isolated Feshbach resonances. In particular, we show how three-body recombination rates change with the background scattering length and the resonance width, as well as their dependence on the depth of the model potential in different spin channels. For both homonuclear and heteronuclear systems, we have found universal behavior in three-body recombination even under some conditions where three-body physics was previously considered nonuniversal. As examples, we analyze the line shapes of atomic losses caused by three-body recombination in Cs/Rb and Cs/Li ultracold mixtures, and show their implication in two-body calculations for determining Feshbach resonances with higher precision. [Preview Abstract] |
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D1.00084: Imaging the evolution of an ultracold strontium Rydberg gas Xinyue Zhang, Patrick McQuillen, Trevor Strickler, F. Barry Dunning, Thomas Killian Clouds of ultracold strontium 5s48s $^{1}$S$_{0}$ or 5s47d $^{1}$D$_{2}$ Rydberg atoms are created by two-photon excitation of laser cooled 5s$^{2} \quad^{1}$S$_{0}$ atoms. The evolution of this ultracold gas of low-l states towards a plasma through l-changing collisions and collisional ionization is probed by imaging light scattered via the 5s $^{2}$S$_{1/2}$-5p $^{2}$P$_{1/2}$, core ion transition, a technique that provides both spatial and temporal resolution. For low-l states core excitation leads to rapid autoionization whereas for high-l states, and for strontium ions, strong fluorescence occurs. Evolution is seen to proceed more rapidly for S states, which display attractive interactions, than for D states which principally display repulsive interactions. Even more rapid evolution is observed in the presence of an ultracold neutral plasma allowing the number of Rydberg atoms initially produced to be measured. [Preview Abstract] |
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D1.00085: Controlling the group velocity of colliding atomic Bose-Einstein condensates with Feshbach resonances Ranchu Mathew, Eite Tiesinga We report on a proposal to change the group velocity of a small Bose Einstein Condensate (BEC) upon collision with another BEC in analogy to slowing of light passing through dispersive media. We make use of ultracold collisions near a magnetic Feshbach resonance, which gives rise to a sharp variation in scattering length with collision energy and thereby changes the group velocity. A generalized Gross-Pitaveskii equation is derived for a small BEC moving through a larger stationary BEC. We denote the two condensates by laser and medium BEC, respectively, to highlight the analogy to a laser pulse travelling through a medium. We derive an expression for the group velocity in a homogeneous medium as well as for the difference in distance, $\delta$, covered by the laser BEC in the presence and absence of a finite-sized medium BEC with a Thomas-Fermi density distribution. For a medium and laser of the same isotopic species, the shift $\delta$ has an upper bound of twice the Thomas-Fermi radius of the medium. For typical narrow Feshbach resonances and a medium with number density $10^{14}$ cm$^{-3}$ up to $85\%$ of the upper bound can be achieved, making the effect experimentally observable. We also derive constraints on the experimental realization of our proposal. [Preview Abstract] |
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D1.00086: Robust cooling of lithium for testing Einstein's equivalence principle Geena Kim, Paul Hamilton, Biswaroop Murkherjee, Daniel Tiarks, Trinity Pradhananga, Holger Mueller We demonstrate a new cooling method for lithium which combines Sisyphus cooling and adiabatic expansion. Lithium's unresolved hyperfine structure was long thought to make it impossible to reach sub-Doppler temperatures by Sisyphus cooling [1,2]. Most lithium experiments rely on evaporative cooling to achieve lower temperature. Cooling of lithium by adiabatically reducing a far-detuned lattice has been demonstrated [3], however both methods are lossy and leave a small fraction of cooled atoms. Our method cools $^{7}$Li atoms to about 3 times the recoil velocity and gives cooled fraction of about 30-50\%. The cooling easily works for frequency detuning across $^{7}$Li D1 and D2 line with moderate laser power(few tens of mW). The cooling does not require certain magnetic field and polarization orientation as Raman sideband cooling. We discuss our idea about lattice interferometer to test the Einstein equivalence principle. \\[4pt] [1] Schnemann et al., Opt. Comm {\bf 158},263 (1998)\newline [2] Duarte et al., Phys. Rev. A {\bf 84} 061406 (2011)\newline [3] Anderson et al., Phys. Rev. A {\bf 53} R3727 (1996)\newline [4] Guo et al., Phys. Rev. A. {\bf 48}, 3225 (1993)\newline [5] Chen et al., Phys. Rev. Lett. {\bf 69}, 1344 (1992) [Preview Abstract] |
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D1.00087: Towards a 3-D Magneto-Optical Trap for Molecules Alejandra Collopy, Matthew Hummon, Mark Yeo, Benjamin Stuhl, Boerge Hemmerling, Garrett Drayna, Eunmi Chae, Aakash Ravi, Hsin-I Lu, John Doyle, Jun Ye As the magneto-optical trap revolutionized atomic physics, we anticipate the molecular counterpart to open doors to unexplored molecular physics, including ultra-cold chemistry. While molecules possess more complex structure than atoms, quasi-cycling cooling transitions are still attainable in a variety of species, including the polar molecule YO. In order to remix dark states, we RF modulate the polarization of the light in our trap. In order to maintain a restoring force, we modulate the orientation of our magnetic fields in phase with the light using LC resonant in-vacuum magnetic coils. We demonstrate magneto-optical trapping in two dimensions for YO, and present progress towards a three dimensional implementation of a MOT loaded from a two-stage buffer gas cell source. [Preview Abstract] |
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D1.00088: Developing Density of Laser-Cooled Neutral Atoms and Molecules in a Linear Magnetic Trap Joe Velasquez, III, Peter Walstrom, Michael Di Rosa In this poster we show that neutral particle injection and accumulation using laser-induced spin flips may be used to form dense ensembles of ultracold magnetic particles, i.e., laser-cooled paramagnetic atoms and molecules. Particles are injected in a field-seeking state, are switched by optical pumping to a field-repelled state, and are stored in the minimum-B trap. The analogous process in high-energy charged-particle accumulator rings is charge-exchange injection using stripper foils. The trap is a linear array of sextupoles capped by solenoids. Particle-tracking calculations and design of our linear accumulator along with related experiments involving $^{\mathrm{7}}$Li will be presented. We test these concepts first with atoms in preparation for later work with selected molecules. Finally, we present our preliminary results with CaH, our candidate molecule for laser cooling. This project is funded by the LDRD program of Los Alamos National Laboratory. [Preview Abstract] |
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D1.00089: Design of a calcium oven and permanent magnet Zeeman slower for use in trapping of ultracold calcium atoms and the creation of RbCa molecules Alexandria Parsagian, Michaela Kleinert Ultracold heteronuclear molecules are of great interest for their applications in ultracold chemistry, precision spectroscopy, tests of fundamental symmetries, and quantum computation. Alkaline/Alkali-metal dimers in particular possess both a permanent electric and magnetic dipole moment, making them ideal for the study of strong long-range dipole-dipole interactions in combined electric and magnetic fields. We will discuss our progress toward the creation of ultracold RbCa with special emphasis on the permanent magnet Zeeman slower for calcium. This slower uses neodymium magnet pairs at varying distances from the calcium beam to closely match the ideal slowing field. Future work will involve using the slower to trap calcium and create the novel molecule RbCa. [Preview Abstract] |
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D1.00090: Characterization of a Crossed 1071 nm Dual Species Dipole Trap Jonathan Tallant, Carlos Menegatti, Bruno Marangoni, Luis Marcassa Several experiments involving heteronuclear molecules rely on dense atomic samples. In our experiment, overlapped magneto-optical traps (MOTs) containing $^{39}$K and $^{85}$Rb are used to load a broadband crossed dipole trap. A cooling sequence is applied to the MOTs to load the dipole trap. Several parameters are varied during the cooling sequence to optimize the loading of both species into the dipole trap with equal densities. The results of the optimization process are presented. We find that ramping the laser power during the potassium loading improves the number of potassium atoms that are captured by the dipole trap. The need for this ramp is supported by calculations of the ac Stark shift of the 4p$_{3/2}$ hyperfine manifold of states. Finally, lifetimes of both species in the dipole trap are presented. The lifetimes show a fast decay at early times which suggests a density dependent, few-body loss mechanism. Evidence is presented suggesting the mechanism is photoassociation of deeply bound KRb molecules by the 1071 nm trapping light. This work was supported by Fapesp and INCT-IQ. [Preview Abstract] |
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D1.00091: A new apparatus for studying non-equilibrium phenomena of dimensional crossover in quantum gases Wen Xu, Leonardo de Melo, Jiaming Li, Ji Liu, Le Luo We describe the design of a new apparatus targeted at the study of non-equilibrium phenomena of the crossover between 2D and 3D using resonant Fermi gases. Specifically this apparatus will allow for a fast transformation between 2D and 3D optical dipole traps as well as a fast precise magnetic field sweep for the purpose of generating non-equilibrium many-body quantum states in the dimensional crossover regime. In addition we design a high resolution imaging system comprised of phase Fresnel lens and recessed UHV windows for studying the spatial structure of the non-equilibrium system. We will also analyze possible experimental routes for creating non-equilibrium states in resonant systems including both magnetic and optical methods. [Preview Abstract] |
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D1.00092: The Bichromatic Optical Force on the Atomic Life- time Scale Christopher Corder, Brian Arnold, Harold Metcalf Our experimental and theoretical studies of the bichromatic force (BF) have shown that its strength and velocity range are very much larger than those of the usual radiative force.\footnote{Phys. Rev. Lett. {\bf 93} 213004 (2004), Phys. Rev. A {\bf 70}, 063402 (2001)} Since the BF relies on stimulated effects, the role of spontaneous emission in laser cooling has come into question.\footnote{Phys. Rev. A {\bf 77}, 061401 (2008)} We drive the $2^3S\rightarrow 3^3P$ transition of He at $\lambda = 389$ nm with laser frequencies $\omega_{\ell} = \omega_a \pm \delta$, where $\omega_a$ is the atomic transition frequency and $\delta \sim 30$ MHz. Thus the velocity range of the force is $\Delta v \sim \delta /2k = 6$ m/s. Because of the large and nearly constant strength of the BF, $F \sim \hbar k \delta / \pi$, all atoms can reach the velocity limit in a time $ \leq M\Delta v / F = \pi/4\omega_r = 380$ ns, where $\omega_r$ is the atomic recoil frequency. In our experiment a beam of He atoms crosses perpendicular through the BF laser beams in 380 ns so the relatively long lifetime of the excited state ($\tau = 106$ ns) allows one or at most two spontaneous emission events, despite $\Delta v$ of many tens of recoils. We will present our initial measurements of the BF in this new domain. [Preview Abstract] |
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D1.00093: Ground-state cooling of a single atom at the center of an optical cavity Stephan Ritter, Andreas Reiserer, Christian N\"{o}lleke, Gerhard Rempe The study of the dynamics and precise manipulation of physical systems at the quantum level requires full control over all relevant degrees of freedom. In this respect, single atoms in optical dipole traps are a well advanced system. In order to couple these atoms to single photons, optical cavities have proven very successful. However, for complete control of this coupling, the atoms have to be cooled to the ground state of the trapping potential. In our experiment, a single neutral atom is deterministically localized at the center of an optical resonator. Using a three-dimensional optical lattice with high intensities, we observe trap frequencies of several hundred kHz, such that the atom is tightly confined to the Lamb-Dicke regime. This allows us to cool the atom to the three-dimensional ground state via Raman sideband cooling. We reach the strong-coupling regime of cavity QED manifested by a clearly resolved normal-mode splitting even for a moderate cavity finesse. Thus, our system is the first to achieve simultaneous experimental control over the motional, internal and radiative properties of a single atom. [Preview Abstract] |
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D1.00094: The effect of Rydberg atoms on electron temperature in ultra-cold neutral plasmas Duncan Tate, Ethan Crockett We describe recent developments in our ongoing research in which Rydberg atoms are embedded into an ultra-cold neutral plasma (UNP). The UNP is created with initial electron temperature $T_{e,0}$ by photoionization of rubidium atoms in a MOT. At a controllable time delay (5 ns - 10 $\mu$s), atoms in a specific Rydberg state are embedded in the UNP by a narrow bandwidth pulsed laser. In such a system, it is predicted that the plasma electrons may be cooled if the Rydberg binding energy, $E_b$, is greater than $4k_BT_e$ (see, for example\footnote{T. Pohl {\it et al.}, {\it Eur. Phys. J. D}, {\bf 40}, 45 (2006)}). We have identified an experimental signature that correlates with the plasma electron temperature change, namely, whether the plasma lifetime increases or decreases when Rydbergs are added. The ``crossover'' condition, where the UNP lifetime remains the same when Rydbergs are added, can then be plotted (i.e., $E_b$ vs. $T_{e,0}$ at crossover) and compared with theoretically derived crossover conditions for UNP expansion velocity, electron temperature, etc., using a model derived from the work of Robicheaux and Hansen.\footnote{Robicheaux and Hansen, {\it Phys. Plasmas}, {\bf 10}, 2217 (2003)} [Preview Abstract] |
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D1.00095: PHOTON INTERACTIONS WITH ATOMS, IONS AND MOLECULES I |
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D1.00096: Free-free transitions in the presence of laser fields and Debye potential at very low incident electron energies Anand Bhatia We study the free-free transition in e-He$^{\mathrm{+}}$ system in the ground state and embedded in a Debye potential in the presence of an external laser field which is monochromatic, linearly polarized and homogeneous, at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function. The scattering function for the incident electron on the target is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transitions for absorption/emission of a single photon or no photon exchange. The cross sections for e-He$^{\mathrm{+\thinspace }}$system are much larger than e-H system. The results will be presented at the conference. [Preview Abstract] |
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D1.00097: Criteria for using impulse approximation to obtain Compton scattering doubly differential cross sections L.A. LaJohn, R.H. Pratt We find that the criterion often used for predicting when impulse approximation (IA) theory yields accurate doubly differential cross sections (DDCS), namely $ |
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D1.00098: Self-Organization Threshold Scaling for Thermal Atoms Kyle Arnold, Markus Baden, Murray Barrett We report a detailed experimental study of the threshold for self-organization of thermal Rb atoms coupled to a high finesse cavity. We investigate the differences between probing with a traveling wave and a retroreflected lattice over a range of atom numbers and cavity detunings. In both cases we confirm a $N^{-1}$ scaling of the threshold with atom number. Additionally, we report the trapping of $10^5$ Rb atoms in a deep two-dimensional optical lattice with a lattice spacing of the wavelength of the scattered light. In this configuration collectively enhanced scattering into the cavity is observed. This setup will enable the investigation of cavity cooling, simulation of the Dicke model, and other phenomena related to collective scattering into a cavity. [Preview Abstract] |
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D1.00099: Capabilities of the PULSAR ultrafast laser system for attosecond research K.J. Betsch, Z. Wang, Nora G. Kling, M. K\"{u}bel, B. Langdon, D. Raymondson, M. Kirchner, C.W. Fehrenbach, K.D. Carnes, V. Kumarappan, C. Trallero-Herrero, M.F. Kling, I. Ben-Itzhak We describe the new PULSAR ultrafast laser system at the J. R. Macdonald Laboratory. In its conventional mode of operation, the Red Dragon\texttrademark\ Ti:Sapphire laser amplifier from KMLabs provides 21 fs Fourier-transform-limited (FTL), 2 mJ pulses centered around 800 nm at a repetition rate of 10 kHz. Slight modifications also support sub-40 fs pulses at an increased repetition rate (0.8 mJ, 20 kHz) or 50 fs FTL pulses (2 mJ, 10 kHz). The amplifier can be carrier-envelope-phase (CEP) stabilized with RMS noise below 300 mrad over 3 hours. Spectral broadening in a gas-filled hollow core fiber and pulse compression with chirp compensation mirrors generates 4 fs pulses. We also employ a single-shot phase meter to measure and tag the CEP of every laser shot for either free-running or CEP-stabilized laser pulses. Phase tagging and CEP-stabilization can be combined to provide increased precision in measurements using CEP-stabilized pulses. [Preview Abstract] |
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D1.00100: Time-resolved Absorption Spectra of the Laser-dressed Hydrogen Atom Mitsuko Murakami, Shih-I Chu A theoretical study of the transient absorption spectra for the laser-dressed hydrogen atom based on the accurate numerical solution of the time-dependent Schr\"odinger equation is presented. The timing of absorption is controlled by the time delay between an isolated extreme ultraviolet (XUV) pulse and a dressing infrared (IR) field. We identify two different kinds of physical processes in the spectra. One is the formation of dressed states, signified by the appearance of sidebands between the XUV absorption lines separated by one IR-photon energy. We show that their population is maximized when the XUV pulse coincides with the zero-crossing of the IR field, and that their energy can be manipulated by using a chirped IR field. The other process is the dynamical AC Stark shift induced by the IR field and probed by the XUV pulse. Our calculations indicate that the accidental degeneracy of the hydrogen atom leads to the multiple splittings of each XUV absorption line whose separations change in response to a slowly-varying IR envelope. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 states using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional 3-level model that neglects the dynamical AC Stark effects. [Preview Abstract] |
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D1.00101: Off center effect on the photoabsorption spectrum of the Xe@C$_{60}$ endohedral fullerene Zhifan Chen, Alfred Z. Msezane The absolute differential oscillator strengths (DOS's) for the photoabsorption of the Xe atom encapsulated at different locations of the C$_{60}$ have been evaluated using the time-dependent-density-functional-theory. The calculations are performed in the energy region of the Xe 4$d$ giant resonance with the locations of the Xe atom at the center and 0.2 {\AA}, 0.3 {\AA}, 0.4 {\AA}, 0.5 {\AA}, 0.8 {\AA}, 1.5 {\AA}, 2.0 {\AA} away from the center. The results demonstrate that the main confinement resonances result only when the Xe atom is located in a very small region of the C$_{60}$. This region is about 0.3 {\AA} around the center of the C$_{60}$ (3.5 {\AA} is the C$_{60}$ radius). These results explain the absence of the confinement resonances in the photoionization of the encapsulated lanthanide atoms such as Ce@C$_{82}$ [1], Pr@C$_{82}$ [2] as these atoms (Ce, Pr) are usually located 1.8-2.0 {\AA} off the center of the C$_{82}$. \\[4pt] [1] K Mitsuke et al, J. Chem. Phys. {\bf 122} 064304 (2005)\\[0pt] [2] H Katayanag et al, J. Quant. Spectrosc. Radiat. Transfer, {\bf 109} 1590 (2008) [Preview Abstract] |
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D1.00102: Nuclear-Recoil Differential Cross Sections for the Two Photon Double Ionization of Helium Shahin Abdel Naby, M.F. Ciappina, T.G. Lee, M.S. Pindzola, J. Colgan In support of the reaction microscope measurements at the free-electron laser facility at Hamburg (FLASH) [1], we use the time-dependent close-coupling method (TDCC) to calculate fully differential nuclear-recoil cross sections for the two-photon double ionization of He at photon energy of 44 eV. The total cross section for the double ionization is in good agreement with previous calculations. The nuclear-recoil distribution is in good agreement with the experimental measurements. In contrast to the single-photon double ionization, maximum nuclear recoil triple differential cross section is obtained at small nuclear momenta. \\[4pt] [1] A. Rudenko \emph{et al}, Phys Rev. Letts. {\bf 101}, 073003 (2008). [Preview Abstract] |
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D1.00103: Photoabsorption spectrum of the Ce@C$_{82}$ endohedral fullerene Zhifan Chen, Alfred Z. Msezane The absolute differential oscillator strengths (DOS's) for the photoabsorption of the Ce atom encapsulated in the C$_{82}$ have been evaluated using the time-dependent-density-functional-theory (TDDFT). The geometry optimization was performed for the C$_{82}$ and Ce@C$_{82}$. The atomic coordinates were obtained by minimizing the total energy until the change in energy was less than 5x10$^{-4}$ eV. The final position of the Ce atom was found at 1.85 {\AA} off the center along the C$_2$ axis. A supercell of 23.8 {\AA} was constructed. The Kohn-Sham equation was solved to yield the eigenvalues and eigenvectors for the ground state. The dynamical polarizability of the ground state due to the external electric field perturbation was evaluated using TDDFT. The results demonstrate that the peak of the free Ce 4d giant resonance was reduced and shifted to the lower energy side. Comparison with the experimental data [1] shows great suppression of the 4f decay process for the encaged Ce atom. This calcultion confirms the experimental result which observed no confinement resonance in the Ce@C$_{82}$ endohedral fullerene photoionization.\\[4pt] [1] A M\"uller et al, Phys. Rev. Lett. {\bf 101,} 133001 (2008) [Preview Abstract] |
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D1.00104: Structure generated by interchannel coupling in high-energy photoionization W. Drube, T.M. Grehk, S. Thiess, G.B. Pradhan, H.R. Varma, P.C. Deshmukh, S.T. Manson, T. Aberg The 3$d$ core level photoemission of metallic Ag and In was measured as a function of photon energy over a wide range including the 2$p$ ionization thresholds. The intensities of the 3$d_{5/2}$ and 3$d_{3/2}$ lines were observed to modulate significantly with photon energy, both absolute and relative. The modulation of the photoionization cross section is most pronounced in the vicinity of the 2$p$ thresholds, i.e., at photon energies about an order of magnitude above the 3$d$ thresholds. Theoretical calculations based on the relativistic-random-phase approximation show that this effect is due to interchannel coupling of the 3$d$ photoionization channels with the 2$p$ channels affecting the cross section over a wide range of energies. It is argued that this is a general phenomenon in high-energy photoionization throughout the periodic table as well as for molecules, clusters and condensed matter. [Preview Abstract] |
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D1.00105: Photoionization studies of Cd@C$_{60}$ Ashish Kumar, Sindhu Kalyadan, Hari R. Varma, Pranawa C. Deshmukh, Steven T. Manson Atoms trapped in fullerene (A@C$_{60})$ cages have attracted considerable attention in the recent past owing to their importance in many areas of physics [1]. The additional potential due to the fullerene cage causes significant changes to atomic ionization probabilities by inducing confinement oscillations in the photoionization parameters [2]. The existence of such oscillations has been verified in a recent experiment [3]. These developments have motivated us to extend our studies of the effect of confinement on the photoionization process. We study the photoionization of Cd which is trapped inside a fullerene molecule (Cd@C$_{60})$ to understand the combined effect of confinement, correlation and relativistic effects on photoionization in such endohedral system. The fullerene potential is simulated by using a spherical shell model potential. In the present work, the Relativistic Random Phase approximation (RRPA) method is employed to determine the photoionization parameters [4].\\[4pt] [1] M.Ya. Amusia, A. S. Baltenkov and U. Becker, Phys. Rev. A \textbf{62} 012701 (2000).\\[0pt] [2] J.P. Connerade, V. K. Dolmatov and S. T. Manson J. Phys. B \textbf{32} 2279 (2000).\\[0pt] [3] A. Muller, \textit{et al, }Phys. Rev. Lett.105, 21300 (2010).\\[0pt] [4] W. R. Johnson and C. D. Lin, Phys. Rev. A \textbf{20 }964 (1979). [Preview Abstract] |
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D1.00106: Theoretical Study of the Photoionization of small fullerenes C$_{n}$(n$=$28, 32, 40, 44, 50) using the Time-Dependent-Local-Density Approximation (TDLDA) Mohammad H. Javani, Himadri S. Chakraborty, Steven T. Manson The Time-Dependent-Local-Density Approximation (TDLDA) is used to calculate total and subshell photoionization cross section of small fullerene C$_{n}$, (n$=$28, 32, 40, 44, 50). For the various C$_{n}$, which are taken to be spherical, the core of n C$^{4+}$ ions are smeared out on the sphere with known radius to form a classical jellium shell, and the resulting potential is used to treat the dynamics of the motion of the 4n delocalized valance electrons quantum mechanically. The theoretical methodology has been described in detail elsewhere [1]. For all cases, it is found that there are two plasmon resonances in the total cross section due to phase-coherent superposition of amplitudes that causes the enhancements in the ionization from different C$_{\mathrm{n}}$ subshells in two distinct energy regions, just as in the case of C$_{60}$ [1]. In addition, each of the two plasmons, for each fullerene, is quite close in energy to each other and to the C$_{60}$ case.\\[4pt] [1] M. E. Madjet, H. S. Chakraborty, J. M. Rost and S. T. Manson, J. Phys. B \textbf{41}, 105101 (2008). [Preview Abstract] |
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D1.00107: Time Delay in the Photoionization of Xenon: Relativistic Effects Ankur Mandal, Soumyajit Saha, Pranawa C. Deshmukh, Ashish Kumar, Jobin Jose, Steven T. Manson Owing to the advent of attosecond pulses of ioning radiation, it has been possible to measure the time delay between various photoionization channels in atoms; a number of theoretical calculations have also been performed. However, none of the extant studies have included relativistic interactions. In this study, time delay in the 5s$\to \varepsilon $p$_{1/2}$,$\varepsilon $p$_{3/2}$, in 5p$_{3/2}\to \varepsilon $d$_{5/2}$, $\varepsilon $d$_{3/2}$, $\varepsilon $s$_{1/2}$ and in 5p$_{1/2}\to \varepsilon $d$_{3/2}$, $\varepsilon $s$_{1/2}$ dipole photoionization channels in Xe have been calculated within the framework of the Wigner-Eisenbud formalism [1,2] using the relativistic random phase approximation (RRPA) [3]. The RRPA includes major electron correlations which play an important role in influencing the time delay. Further, the RRPA includes relativistic effects \textit{ab initio} and is thus especially suited for determining the time delay in spin-orbit split relativistic dipole channels. New effects, due to relativity, are found in the neighborhood of Cooper minima.\\[4pt] [1] E. P. Wigner, Physical Review 98, \textbf{145} (1955).\\[0pt] [2] L. E. Eisenbud, Ph. D. thesis, Princeton Univ. (1948).\\[0pt] [3] W. R. Johnson and C. D. Lin, Physical Review A \textbf{20}, 964 (1979). [Preview Abstract] |
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D1.00108: ATOMIC AND MOLECULAR STRUCTURE AND PROPERTIES |
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D1.00109: X-ray ionization and fragmentation of IBr Dipanwita Ray, R.W. Dunford, S.H. Southworth, E.P. Kanter, G. Doumy, D.A. Walko, P.J. Ho, A. Picon We are investigating the fundamental physics of ``molecular damage'' due to x-ray absorption and vacancy cascades. Our experiment aims to understand the decay processes in IBr following K-shell ionization of the Br, or I atom. Following our prior studies of XeF$_{2}$ molecule [1], the tunable monochromatic x-ray beam at the Argonne's Advanced Photon Source was crossed with a gas beam of IBr, atomic Kr, or Xe, and the final excited ion fragments were collected for events whose initial decay was via K-alpha or K-beta fluorescence, using an improved x-ray/ion coincidence momentum imaging setup. We compare the total charge produced and the individual breakup modes for the two separate cases where the initial K-shell photoionization step creates a deep inner-shell vacancy in (i) Br and (ii) I in IBr molecule. We also compare the total charge distribution in IBr initiated by photoionization of Br to the total charge distribution following photoionization of atomic Kr and Xe, in order to identify processes unique to the molecular decay. The experimental results along with theoretical modeling enable us to get a better understanding of the dynamics of the decay processes.\\[4pt] [1] R. W. Dunford et al., Phys. Rev. A \textbf{86}, 033401 (2012). [Preview Abstract] |
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D1.00110: The role of permanent dipole transitions in strong-field molecular dissociation Brandon Rigsbee, Brett Esry The difficulty of finding signatures of permanent dipole transitions in strong-field molecular dissociation is well documented. The difficulty stems from two factors: (1) the standard strong-field laser wavelength of 800~nm is generally not well suited to driving purely nuclear transitions and (2) other mechanisms, such as non-adiabatic coupling, often compete with permanent dipole transitions, obscuring their effect on physical observables. We will present a theoretical study that helps elucidate the role each of these mechanisms plays. Numerical solutions of the time-dependent Schr\"odinger equation in the Born-Oppenheimer representation are used to calculate the kinetic energy release spectra for the dissociation of HD$^+$ exposed to short, intense laser pulses. We will analyze these solutions to isolate and quantify the effect of permanent dipole transitions and show their dependence on the laser parameters. [Preview Abstract] |
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D1.00111: Photodissociation and Photoionization of Propanaldehyde at 355nm. Theory and experiment. Carmen Cisneros, Leonardo Mu\~noz-Rugeles, Alfonso Guerrero, Ignacio Alvarez Propanaldehyde is a large component in the atmosphere, finding in concentrations around 1-2x10$^{10}$ molecules/cm$^{3}$, motivating the characterization of photodissociation and photoionization dynamics by UV multiphoton absorption. In this work we present the study of photodissociation and photoionization dynamics by multiphoton absorption with 355nm wavelength photons, using time of flight spectrometry in reflectron mode, R-TOF, and calculations of potential energy surfaces for the principal reaction coordinate using time dependent density functional theory, TD-DFT. The experimental and theoretical results suggest that the characteristics observed in the R-TOF spectra come from the generation of free radicals, by two photon absorption, that later are ionized by multiphoton absorption. [Preview Abstract] |
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D1.00112: Metastable states in microwave ionization Alexandr Arakelyan, Turker Topcu, Francis Robicheaux, Thomas Gallagher We report the excitation of metastable Li Rydberg atoms in the presence of a strong 38.3 GHz microwave field. We detect approximately 5\% of the initial population in very high Rydberg states with $n>215$ after the microwave pulse for a wide range of initial binding energies. The surviving population of atoms displays a periodic comb structure in energy with a periodicity matching the structure of the 38.3 GHz microwave field. A small static field displaces the entire comb to lower energy, and the high lying states disappear when the static field exceeds 30 mV/cm. We suggest that these atoms are trapped in metastable atom-field states during the microwave pulse, and relax to the high lying states when the field is turned off. We also perform 1-d quantum simulations at lower n using a scaled microwave frequency and field strength to elucidate the physical mechanism at play. We find that the surviving atoms are trapped in high-n states, and that the surviving population decreases as the duration of the microwave pulse becomes larger than the classical period of the electron in these states. In contrast, classical simulations predict negligible population of bound atoms after the microwave pulse, indicating that the survival of the atoms in the microwave field is a quantum effect. [Preview Abstract] |
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D1.00113: Observation of \textit{K}-shell resonances in Xe and XeF$_2$ Steve Southworth, Robert Dunford, Dipanwita Ray, Elliot Kanter, Bertold Kr\"assig, Linda Young, Don Walko We recently reported on the ion charge states and fragmentation channels of Xe and XeF$_2$ following \textit{K}-shell x-ray absorption by the Xe atom [1]. The ion spectra reveal effects of resonant excitations despite the 11.49-eV lifetime width of the vacancy states. Due to the high electronegativity of the F ligands, Xe forms stable molecules such as XeF$_2$. With 10 valence electrons, XeF$_2$ is a prime example of a hypervalent molecule and its structure has attracted interest since its discovery in the 1960s. A strong pre-edge resonance is observed in the x-ray absorption spectrum that we attribute to the antibonding 7$\sigma_u$ orbital. Excitation of the 7$\sigma_u$ resonance selects a spatially aligned ensemble of molecules as observed in our ion fragmentation spectra [1]. Analysis of the x-ray absorption spectrum also yields a measurement of the chemical shift of the Xe 1s ionization energy resulting from the F ligands. Results of new measurements on Xe and XeF$_2$ with an improved x-ray/ion coincidence instrument will also be reported.\\[4pt] [1] R. W. Dunford \textit{et al.}, Phys. Rev. A \textbf{86}, 033401 (2012). [Preview Abstract] |
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D1.00114: Molecular Frame X-Ray Photoelectron Angular Distributions and an Attempt to Detect Core Hole Localization Cynthia S. Trevisan, Joshua Williams, Thomas Rescigno, C. William McCurdy, Allen Landers We present preliminary experimental and theoretical results of the angular dependence of electrons ejected from the core orbitals of ethane (C$_{\mathrm{2}}$H$_{\mathrm{6}})$ as viewed in the frame of the molecule in search for evidence of the localization of core holes on one of two equivalent atoms following X-ray photoionization. While the probability of ionization from equivalent atoms is the same, the fragmentation pattern following ionization can be asymmetric and reveal the creation of a core hole on one atom followed by breakup dynamics that depend on its location. These experiments, together with the theoretical calculations to interpret them, may result in direct observation of the fundamental quantum phenomenon of localized hole dynamics in isolated polyatomic molecules following Auger decay. Our measurements employ the COLTRIMS method and the calculations were performed with the Complex Kohn Variational method. [Preview Abstract] |
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D1.00115: ATOMIC, MOLECULAR, AND CHARGED PARTICLE COLLISIONS I |
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D1.00116: Effects of inter-fullerene $\pi $-band mixings in the photoexcitation of hybrid plasmons in the C$_{60}$@C$_{240}$ molecule Rume De, Mohamed Madjet, Himadri Chakraborty We perform a detailed study of the ground state electronic structure of a two-layer fullerene onion molecule C$_{60}$@C$_{240}$. Calculations are carried out in a quantum mechanical framework of local density approximation (LDA) where the onion's ion-core of sixty C$^{4+}$ ions from C$_{60}$ and two hundred and forty of those from C$_{240}$ is smeared into a classical jellium distribution [1]. Significant inter-fullerene mixing between the bands of single-node radial symmetry, the $\pi $-bands, is found. We then compute the photoionization from all the levels of the system using a time-dependent version of LDA at photon energies where the ionization is dominated by the inter-layer hybridization of collective plasmon resonances [2]. It is determined, by comparing the isolated fullerene cross sections with the cross section of the onion system for both $\pi $ and $\sigma $ (having nodeless radial waves) symmetry, that the $\pi $-band mixing is predominantly responsible for the production of plasmon hybrids.\\[0pt] [1] M.E. Madjet, H.S. Chakraborty, J.-M. Rost, and S.T. Manson, \textit{J. Phys.} B \textbf{41}, 105101 (2008);\\[0pt] [2] M.A. McCune, R. De, M.E. Madjet, H.S. Chakraborty, and S.T. Manson, \textit{J. Phys.} B Fast Track Comm. \textbf{44}, 241002 (2011). [Preview Abstract] |
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D1.00117: Exterior complex scaling method in TDDFT calculations: MPI and HHG of Ar atoms Dmitry A. Telnov, Ksenia E. Sosnova, Efim B. Rozenbaum, Shih-I Chu Exterior complex scaling (ECS) method is applied in the framework of time-dependent density functional theory (TDDFT) to study multiphoton ionization (MPI) and high-order harmonic generation (HHG) of multielectron atoms in intense laser fields. ECS allows to impose correct (outgoing-wave) boundary conditions on the wave functions at large distances. In our implementation, ECS is combined with the time-dependent generalized pseudospectral method (GPS) for accurate and efficient solution of time-dependent Kohn-Sham equations. We make use of LB94 exchange-correlation potential which proved accurate in calculations of unperturbed electronic structure of Ar. Calculations of MPI and HHG are performed for the laser pulses with the wavelength 800~nm and several peak intensities. HHG spectrum exhibits an intensity-independent minimum corresponding to the photon energy of about 50~eV which is closely related to the Cooper minimum observed in photoionization cross section of Ar. We found that results obtained with the frozen-core potential (that is, not including dynamic response of the electron density to the laser field) significantly overestimate MPI probabilities as compared with those calculated by TDDFT. [Preview Abstract] |
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D1.00118: High-order harmonic generation of aligned CO molecules: a TDDFT approach Shih-I Chu, Dmitry A. Telnov, John Heslar We have performed time-dependent density functional (TDDFT) calculations of high-order harmonic generation (HHG) by aligned CO molecules subject to intense 800~nm laser pulses. We make use of LB$\alpha$ exchange-correlation potential which proved its accuracy in time-independent electronic structure calculations. The time-dependent Kohn-Sham equations are efficiently solved by the time-dependent generalized pseudospectral method (TDGPS) in prolate spheroidal coordinates. We have found that the high-energy part of the HHG spectrum exhibits a strong dependence on the alignment angle between the molecular axis and the polarization direction of the laser field with the sharp minimum at the perpendicular alignment. An analysis of the HHG spectra at the perpendicular alignment revealed also two minima, one of them corresponding to the photon energy in the range 37~eV to 45~eV, and another one in the range 63~eV to 69~eV. Positions of both minima only slightly depend on the peak intensity of the laser field. [Preview Abstract] |
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D1.00119: Transient Absorption of Attosecond Pulses by He Atoms in Presence of Near-Infrared Laser Fields: A TDDFT Analysis of Sub-Cycle Temporal Structures John Heslar, Dmitry A. Telnov, Shih-I Chu We study transient absorption of extreme ultraviolet (XUV) attosecond pulses in presence of near-infrared (NIR) laser fields by analyzing the population and photon emission of excited atomic energy levels. We consider He atoms and apply a self-interaction-free fully \textit{ab initio} time-dependent density functional theory (TDDFT). Our method is based on the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential and incorporates explicitly the self-interaction correction. We focus on the sub-cycle (with respect to NIR field) temporal behavior of the population of the excited energy levels and related dynamics of photon emission. We observe and identify sub-cycle shifts in the photon emission spectrum as a function of the time delay between the XUV and NIR pulses. In the region where the two pulses overlap, the photon emission peaks have an oscillatory structure with a period of 1.3 fs, which is half of the NIR laser optical cycle. Such a structure was also observed in recent experiments on transient absorption. [Preview Abstract] |
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D1.00120: Dynamic imaging of a nonlinear polyatomic molecule in ultrashort intense laser pulses. Catherine Lefebvre, HuiZhong Lu, Szczepan Chelkowski, Andr\'e D. Bandrauk The exact correlated electron-nuclear dynamics of a nonlinear polyatomic molecule in ultrashort intense laser pulses is studied. A numerical model, based on the quantum description of a triangular molecule, beyond the Born-Oppenheimer approximation, is developed and applied to monitor the coupled electron-nuclear dynamics, from attosecond to femtosecond time scale, of the dissociating one-electron molecular ion, H$_{3}^{2+}$. Our results using a 6 optical cycles, 800nm linearly polarized laser pulse at 3x10$^{14}$~W/cm$^{2}$, show the importance of the nuclear motion in the photoionization and harmonic generation processes. Indeed, all the vibrational modes, in the plane of the molecule, contribute to the electron recollision events. Depending on the recollision time, the harmonics are generated from different fragments of the ion, associated with different vibrational modes. Furthermore, the dynamics of fragmentation of the ion and electron recollision is influenced by the orientation of the pulse, allowing to control whether an isolated attosecond pulse or a train of attosecond pulses is generated. [Preview Abstract] |
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D1.00121: Maximum Attainable Field-free Molecular Orientation of a Thermal Ensemble with Near Single-cycle THz Pulses Sheng-Lun Liao, Tak-Son Ho, Herschel Rabitz, Shih-I Chu Recently single-cycle THz pulses has been demonstrated in the laboratory to successfully induce field-free orientation in gas-phase polar molecules at the room temperature. We examine for the first time the maximum attainable field-free molecular orientation with optimally shaped linearly polarized near single-cycle THz laser pulses of a thermal ensemble. Large-scale benchmark optimal control simulations are performed, including rotational energy levels with the rotational quantum numbers up to J=100 for OCS linear molecules. The simulations are made possible by an extension of the recently formulated fast search algorithm, the two-point boundary-value quantum control paradigm (TBQCP), to the mixed-states optimal control problems in the present work. It is shown that a very high degree of field-free orientation can be achieved by strong, optimally shaped near single- cycle THz pulses.\\[4pt] [1] S. Fleischer, Y. Zhou, R. W. Field, and K. A. Nelson, Rev. Lett. 107, 163603 (2011).\\[0pt] [2] T.-S. Ho and H. Rabitz, Phys. Rev. E 82, 026703 (2010)\\[0pt] [3] S.-L. Liao, T.-S. Ho, H. Rabitz, and S. -I Chu, Phys. Rev. A xx, xxxxxx (2013).(accepted) [Preview Abstract] |
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D1.00122: High-order harmonic generation of Ar and Ne atoms in intense ultrashort laser fields: An all-electron time-dependent density-functional approach including macroscopic propagation effects Peng-Cheng Li, Shih-I Chu We present an accurate study of high-order harmonic generation (HHG) of rare-gas atoms (Ar and Ne) in intense ultrashort laser fields by simultaneous solution of the time-dependent Schr\"odinger equation and the Maxwell's equation. The single-atom response is calculated by means of \textit{self-interaction-free} time-dependent density-functional theoretical (TDDFT) approach, this approach allows the contributions of the valence electrons of many-electron atoms are considered explicitly and nonperturbatively. Macroscopic propagation effects are taken into account by solving Maxwell's equation using multiple electronic-shell single-atom induced dipole moment. In this study, we show the contributions of multiple electronic shells play an important role in HHG after propagation through the nonlinear medium as the intensity of laser fields is increased. [Preview Abstract] |
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D1.00123: Photoionization of H$_2^+$ in intense elliptically polarized radiation Ryan DuToit, Xiaoxu Guan, Klaus Bartschat We investigate the photoionization of the H$_2^+$ ion irradiated by intense elliptically polarized laser pulses with central photon energies between 40 and 300~eV. We solve the time-dependent Schr\"odinger equation in prolate spheroidal coordinates~[1,2] to extract the angle-integrated cross section as well as the angular distribution of the photoelectron. The polarization plane contains the molecular axis. The spatial coordinates are discretized by a finite-element discrete-variable representation. We discuss the electronic response to both short and long laser pulses. As a particular case, we analyze the ``rotational'' effect in circularly polarized laser light, which shows asymmetric angular distributions with respect to the molecular axis. The rotational effect depends on the photon energy and the internuclear separation. We also observe that the confinement effect persists in elliptically polarized radiation. Entangled confinement and rotational effects make the angular distributions more complicated than for linearly polarized light. The mechanisms behind these phenomena are discussed. \\[4pt] [1] X.~Guan, E.~Secor, R.~DuToit, and K.~Bartschat, Phys. Rev. A {\bf 86}, 053425 (2012).\\[0pt] [2] X.~Guan, E.~Secor, K.~Bartschat, and B.~Schneider, Phys. Rev. A {\bf 85} 043419 (2012). [Preview Abstract] |
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D1.00124: Manipulation of resonant Auger processes with strong optical fields Antonio Pic\'on, Christian Buth, Gilles Doumy, Bertold Kr\"assig, Linda Young, Stephen H. Southworth We recently reported on the optical control of core-excited states of a resonant Auger process in neon [1]. We have focused on the resonant excitation $1s\!\rightarrow\!1s^{-1}3p$, while a strong optical field may resonantly couple two core-excited states ($1s^{-1}3p$ and $1s^{-1}3s$) in the Rydberg manifold as well as dressing the continuum. There is a clear signature in the Auger electron spectrum of the inner-shell dynamics induced by the strong optical field: i) the Auger electron spectrum is modified by the rapid optical-induced population transfer from the $1s^{-1}3p$ state to the $1s^{-1}3s$ state during their decay. ii) The angular anisotropy parameter, defining the angular distribution of the Auger electron, is manifested in the envelope of the (angle-integrated) sidebands.\\[4pt] [1] A. Pic\'on {\em et al.}, Phys. Rev. A, in press. [Preview Abstract] |
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D1.00125: Progress on variational calculation of Li Liming Wang, Zong-Chao Yan, G.W.F. Drake In the past 15 years, significant progress has been made in precision determinations [1] of spectroscopies of Li and Be$^+$ both theoretically and experimentally. The isotope-shift measurements for some important transition lines have allowed us to extract nuclear charge radii of various isotopes, provided that the corresponding theoretical calculations, including relativistic and QED corrections, can be performed to sufficiently high accuracy. In this paper, the state-of-the-art calculations for the nonrelativistic energies of low-lying states of Li will be presented [2], together with the improved values of leading relativistic and QED corrections.\\[4pt] [1] W. N\"ortersh\"auser, et al., Phys. Rev. A {\bf 83}, 012516 (2011).\\[0pt] [2] L. M. Wang, Z.-C. Yan, H. X. Qiao, and G. W. F. Drake, Phys. Rev. A {\bf 85}, 052513 (2012). [Preview Abstract] |
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D1.00126: ABSTRACT WITHDRAWN |
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D1.00127: Relativistic atomic data for Cu-like tungsten U.I. Safronova, A.S. Safronova, P. Beiersdorfer Energy levels, radiative transition probabilities, and autoionization rates for [Ne]$3s^23p^63d^94l'nl$, [Ne]$3s^23p^53d^{10}4l'nl$ ($n$=4-6), and [Ne]$3s^23p^63d^95l'nl$,($n$=5-7) states in Cu-like tungsten (W$^{45+}$) are calculated using the relativistic many-body perturbation theory method (RMBPT code), the multiconfiguration relativistic Hebrew University Lawrence Livermore Atomic Code (HULLAC code), and the Hartree-Fock-relativistic method (COWAN code). Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the singly excited, as well as doubly excited non-autoionizing states in Cu-like W$^{45+}$ ion. Contributions from the autoionizing doubly excited states (with n up to 500), which are particulary important for calculating total DR rates, are estimated. Synthetic dielectronic satellite spectra from Cu-like W are simulated in a broad spectral range from 3 to 70~\AA. These calculations provide highly accurate values for a number of W$^{45+}$ properties useful for a variety of applications including for fusion applications. [Preview Abstract] |
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D1.00128: Two-photon adiabatic passage for excitation of Rydberg states Chao Tian, Elena Kuznetsova, Svetlana Malinovskaya Strong dipole-dipole interaction between atoms in Rydberg states is promising for many applications, from quantum computation to novel many-body effects. An atom can be transferred to the Rydberg state with a two-photon $\pi $-pulse, which requires a precise adjustment of the pulse Rabi frequency and pulse duration. A more robust approach is to excite the atom using a chirped pulse via rapid adiabatic passage. We describe a technique to realize adiabatic passage in a cascade three level system using a single and a pair of linearly chirped pulses. Modeled with the Rubidium atom, the pulse carrier frequency starts from the resonance with the frequency difference between state 1 and 2, and then is chirped to achieve zero detuning between state 2 and the Rydberg state. By applying the pump and Stokes Rabi frequencies at variable ratio, the complete population transfer to the excited Rydberg state may be achieved. We demonstrate that by slightly changing such ratio, the adiabatic passage can be dynamically switched on and off, corresponding to full population transfer or no transfer at the end of pulse. Since modulation of beam intensity is much easier and faster comparing to modification of chirp and pulse delay, this method opens a door to gain a simpler and better control over system response. [Preview Abstract] |
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D1.00129: Spectacular confinement induced peculiarities in the structure of semifilled shell atoms Valeriy Dolmatov The structure and spectra of atoms, spatially confined by various types of confinements whose sizes are commensurable with an atomic size, have seized minds of theorists starting since early days [1,2] to now [3]. This is because a confined atom concept provides insights into various aspects of interdisciplinary significance [3]. The present article reports on novel discoveries made, specifically, for semifilled shell atoms under confinement. The latter is simulated by a repulsive penetrable spherical potential of an adjustable inner radius $r_{0}$. There, spectacular confinement induced effects termed orbital breathing, fusion, fission, and re-ordering with changing $r_{0}$ have been unraveled. The discovered effects are exemplified by calculated data for confined Li($\rm 2s^{1}$), N($\rm 2p^{3}$), P($\rm 3p^{3}$), and Cr($\rm 3d^{5}$$\rm4s^{1}$). The underlying physics for the effects is explained.\\[4pt] [1] A. Michels, J. de Boer, and A. Bijl \textit{Physica} \textbf{4} 981 (1937)\\[0pt] [2] A. Sommerfeld and H. Welker {\it Ann. Phys.} {\bf 32} 56 (1938)\\[0pt] [3] In: \textit{Adv. Quant. Chem.}, Volumes \textbf{57} and \textbf{58} (2009). [Preview Abstract] |
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D1.00130: The role of configuration interaction in the LTE opacity of Fe James Colgan, David Kilcrease, Norm Magee, Gregory Armstrong, Joe Abdallah, Manolo Sherrill, Christopher Fontes, Honglin Zhang, Peter Hakel The Los Alamos National Laboratory code ATOMIC [1] has been recently used to generate a series of local-thermodynamic-equilibrium (LTE) light element opacities for the elements H through Ne [2]. Our calculations, which include fine-structure detail, represent a systematic improvement over previous Los Alamos opacity calculations using the LEDCOP legacy code [3]. Recent efforts have resulted in comprehensive new calculations of the opacity of Fe. In this presentation we explore the role of configuration interaction (CI) in the Fe opacity, and show where CI influences the monochromatic opacity [4]. We present such comparisons for conditions of astrophysical interest. \\[4pt] [1] N. H. Magee et al, {\it 14th Topical Conference on Atomic Processes in Plasmas}, Eds: J. S. Cohen, S. Mazevet, and D. P. Kilcrease, (New York: AIP), pp~168-179 (2004). [2] J. Colgan et al, ICAMDATA Proceedings, (2013). [3] N. H. Magee et al, \emph{Astronomical Society of the Pacific Conference Series} \textbf{78}, 51 (1995). [4] J. Colgan et al, High Energy Density Physics, in preparation (2013). [Preview Abstract] |
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D1.00131: Rydberg helium and the helium dimer: Relativistic and retardation effects J.F. Babb The energy level structure of a Rydberg helium atom with one electron in a highly-excited $nl$ state can be modeled with high accuracy using an effective potential based on a long-range expansion in powers of the distance $r$ between the Rydberg electron and the nucleus. In addition to the dominant Coulomb interactions, small relativistic $O( \alpha^2)$ terms and smaller quantum electrodynamical $O(\alpha^3)$ effects, as well as retardation effects, can be included. For the helium dimer He${}_2$ a similar effective potential in powers of the internuclear distance $R$ can be developed [Przybytek et al. PRL 108, 183201 (2012)]. The interpretations of the effective potentials for Rydberg He and for the He dimer are discussed. [Preview Abstract] |
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D1.00132: \emph{Ab initio} potential curves for the ground and low-lying excited states in LiBe$^+$ and NaCa$^+$ molecular ions Di Shu, Sandipan Banerjee, John Montgomery, Robin C\^ot\'e We report accurate \textit{ab initio} calculations for the ground and low-lying excited states in LiBe$^+$ and NaCa$^+$ molecular ions. Valence multireference configuration interaction (MRCI) calculations were performed using complete active space self consistent field (CASSCF) orbitals. Spectroscopic constants and bound vibrational levels are calculated, as well as Franck-Condon factors and dipole-allowed electronic transition moment between appropriate states. The static dipole and quadrupole polarizabilities, along with long range expansion coefficients are also calculated. Preliminary results for the hyperfine structure in the lowest singlet and triplet states are also reported. [Preview Abstract] |
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D1.00133: Spin-orbit coupling effect on the 2$^{3}\Pi $ state of $^{39}$K$^{85}$Rb Jin-Tae Kim, Andrey V. Stolyarov, William C. Stwalley Recently we investigated the spin-orbit components ($\Omega =$ 0$^{+}$, 0$^{-}$, 1, and 2) of the 2$^{3}\Pi $ state of $^{39}$K$^{85}$Rb by using experimental spectroscopy of ultracold molecules formed by photoassociation [1]. The separations ($\Delta (E_{\Omega = 1}-E_{\Omega = 0})$ and $\Delta (E_{\Omega = 2}-E_{\Omega = 1}))$ between $\Omega $ components were unequal due to second-order perturbations by other electronic states. In the present work we investigate the spin-orbit coupling effect on the 2 $^{3}\Pi$ state of $^{\mathrm{39}}$K$^{\mathrm{85}}$Rb in the framework of 1$^{\mathrm{st}}$ and 2$^{\mathrm{nd}}$ order non-degenerate perturbation theory based on an \textit{ab initio }method. Required potential energy curves and electronic spin-orbit coupling matrix elements are evaluated over a wide range of internuclear distance in the basis of the spin-averaged wavefunctions corresponding to the pure Hund's case (a) coupling scheme. We compare the experimental spin-orbit splittings of the 2 $^{3}\Pi$ state with its \textit{ab initio} counterparts, which agree well and elucidate the pronounced 2$^{\mathrm{nd}}$ order perturbation effects caused by nearby electronic states. \\[4pt] [1] J. T. Kim \textit{et al}., New J. of Phys. \textbf{11}, 055020 (2009). [Preview Abstract] |
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D1.00134: Properties of multiply-charged Actinide Ions from Measurements of Rydberg Ion Fine Structure Patterns Stephen Lundeen, Julie Keele, Chris Smith, Charles Fehrenbach Multiply-charged actinide ions play a central role in actinide chemistry, but as highly relativistic many-electron systems their properties are difficult to predict from first principles. Experimental checks on these calculations are very sparse. One promising approach to determine the ion properties that control their long-range interactions is to attach a single non-penetrating Rydberg electron and measure the details of its binding to the ion of interest. This can be accomplished using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique. The results of studies of the Rn-like and Fr-like ions of Th and U will be discussed. [Preview Abstract] |
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D1.00135: Current Status of Atomic Spectroscopy Databases at NIST Alexander Kramida NIST's Atomic Spectroscopy Data Center maintains several online databases on atomic spectroscopy. These databases can be accessed via the http://physics.nist.gov/PhysRefData web page. Our main database, Atomic Spectra Database (ASD) has recently been upgraded to v. 5.0, which contains critically evaluated data for about 194,000 spectral lines and 106,000 energy levels of almost all elements in the periodic table. With this version, ASD has been extended to include the ground states and ionization energies of all elements up to Ds ($Z=$110) in all ionization stages with a new Web interface for displaying them. We continue maintaining and regularly updating our bibliography databases, ensuring comprehensive coverage of current literature on atomic spectra, including energy levels, spectral lines, transition probabilities, hyperfine structure, isotope shifts, Zeeman and Stark effects. We continue maintaining other popular databases such as the Handbook of Basic Atomic Spectroscopy Data, searchable atlases of spectra of Pt-Ne and Th-Ne lamps, and non-LTE plasma-kinetics code comparisons. [Preview Abstract] |
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D1.00136: Relativistic many-body calculation of energies, lifetimes, polarizabilities, and hyperpolarizabilities in Li-like Be$^+$ Marianna S. Safronova, Ulyana Safronova Excitation energies of the $ns$, $np$, $nd$, and $nf$ ($n \leq$ 9) states in Li-like Be$^+$ are evaluated within the framework of relativistic many-body theory. All-order calculations of reduced matrix elements, oscillator strengths, transition rates, and lifetimes are given for levels up to $n$ = 9. Electric-dipole ($2s\ -np$), electric-quadrupole ($2s\ -nd$), and electric-octupole ($2s\ -nf$) matrix elements are evaluated in order to obtain the corresponding ground state multipole polarizabilities using the sum-over-states approach. Recommended values are provided for a large number of electric-dipole matrix elements. Scalar and tensor polarizabilities for the $ns$, $np_{1/2}$, $np_{3/2}$, $nd_{3/2}$, and $nd_{5/2}$ states with $n\leq 9$ are also calculated. Scalar hyperpolarizability for the ground $2s$ state is evaluated and compared with non-relativistic calculation. The uncertainties of our calculations are evaluated for most of the values listed in this work. These calculations provide recommended values critically evaluated for their accuracy for a number of Be$^+$ atomic properties useful for a variety of applications. [Preview Abstract] |
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D1.00137: Hybrid calculation of P-wave e-Li ion scattering and photoabsorption Anand Bhatia A variational wave function incorporating short range correlations via Hylleraas type functions plus long-range polarization terms of the polarized orbital type but with smooth cut-off factors has been used to calculate P-wave phase shifts for electron-Li$^{\mathrm{+2}}$ scattering. This approach gives the direct r$^{\mathrm{-4}}$ potential and a non-local optical potential which is negative definite. The resulting phase shifts have rigorous lower bonds and the convergence is much faster than those obtained without the modification of the target function. The continuum functions obtained in such calculation have been used to calculate photoabsorption cross sections of ground and metastable states in H$^{\mathrm{-}}$, He, and Li$^{\mathrm{+1}}$. These cross sections have been used to calculate recombination rate coefficients. Final results will be presented at the conference. [Preview Abstract] |
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D1.00138: Hyperfine Quantum Beat Spectroscopy of the Cs 8p level with Pulsed Pump-Probe Technique Burcin Bayram, Oleg Popov, Stephen Kelly, Patrick Boyle, Andrew Salsman Quantum beats arising from the hyperfine interaction were measured in a three-level excitation (lambda) scheme: pump for the $6s^{2}S_{1/2}\rightarrow8p^{2}P_{3/2}$ and stimulated emission pump (probe) for the $8p^{2}P_{3/2}\rightarrow5d^{2}D_{5/2}$ transitions of atomic cesium. In the technique, pump laser instantaneously excites the hot atomic vapor and creates anisotropy in the $8p^{2}P_{3/2}$ level, and probe laser comes after some time delay. Delaying the probe time allows us to map out the motion of the polarized atoms like a stroboscope. According to the observed evolution of the hyperfine structure dependent parameters, e.g. alignment and atomic polarization, by delaying the arrival time of the stimulated emission pump laser (SEP), precise values of the magnetic dipole and electric quadrupole coefficients are obtained with an improved precision over previous results. The usefulness of the PUMP-SEP excitation scheme for the polarization hyperfine quantum beat measurements without complications from the Doppler effect will also be discussed. [Preview Abstract] |
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D1.00139: Improved Modeling of D1 Optical Pumping of Optically Thick Rb and K-Rb vapors Brian Lancor, Zack DeLand, Thad Walker The production of hyperpolarized noble gas nuclei using spin exchange optical pumping (SEOP) requires the spin polarization of very optically thick Rb or K-Rb vapors through optical pumping. The efficiency of the optical pumping is the limiting factor in noble gas polarization rates with a given amount of pump laser power. Past modeling of the optical pumping process predicted efficiencies that were far higher ($\sim$10x) than those observed in experiments. By including the recent, precise measurements of the circular dichroism of Rb atoms in the presence of high pressure He and N$_{2}$ buffer gases, measurements of the absorption of Rb D1 light by K atoms, and treatments of laser heating and excited state nuclear spin relaxation, we have produced a much more accurate model. This model is a useful tool for the design of SEOP apparatuses. This work was supported by the United States Department of Energy. [Preview Abstract] |
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D1.00140: Low energy decomposition of carbon dioxide and other molecules Eugene Pamfiloff Since the observation of elevating quantities of atmospheric greenhouse gases, finding a practical method other than the capture-and-sequestration scheme for the reduction and disposal of carbon dioxide (CO$_{2})$ has been an important objective. Recently, an efficient low-energy process has been developed allowing the selective molecular decomposition of CO$_{2}$, CO, and other molecules. Thus, CO$_{2}$ can be broken down into C $+$ O $+$ O. This permits the O$_{2}$ molecules to be stored or released while the clean carbon atoms can be bagged and utilized in various industries. For the control of carbon dioxide or other gas emissions at their source, it can be scaled up for power plants or down for smaller facilities. The process also allows the production of a beam of exclusively positive ions or exclusively negative ions and contrary to other devices, excludes the probability of beam contamination by plasma or neutral particles, making it ideal for electronic thin-films manufacturing and spectroscopy systems. Because the system allows the simultaneous production of ion beams containing selectable ratios of positive to negative ions, it simplifies construction of favored or complex molecules through varied ionic bonds. Also discussed are several methods to apply the new technology as an upgrade to spectrometers and other devices. For further information contact the author: epamfiloff@mattertech.com. [Preview Abstract] |
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D1.00141: ABSTRACT WITHDRAWN |
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D1.00142: Infrared Spectroscopy and Vibronic Structure of the Nitrogen-Vacancy Center in Diamond Pauli Kehayias, Marcus Doherty, Damon English, Ran Fischer, Andrey Jarmola, Kasper Jensen, Nathan Leefer, Philip Hemmer, Neil Manson, Dmitry Budker The negatively charged nitrogen-vacancy (NV) color center in diamond has created much recent excitement. Since their ground state can be optically spin-polarized and read-out and they have a long transverse spin relaxation time at room temperature, NV centers are used in an array of applications including quantum computing, sensing, and sub-diffraction-limited imaging. Despite the progress in developing these applications, many of the basic questions about NV centers remain unresolved. We present a pump-probe spectroscopy experiment on the NV infrared transition that sheds light on the vibronic structure of NV centers. From this measurement, we were able to compare the vibronic properties of two NV electronic states and find unexpected differences between them. [Preview Abstract] |
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D1.00143: Properties of R$=$2 rotationally excited H$_{2}^{+}$ from fine structure measurements of high-L Rydberg states of H$_{2}$ using novel techniques Erica Snow Measurement of the fine structure pattern of high-angular momentum Rydberg states provides information about the basic properties of the ion core, such as the Quadrupole moment and polarizability. A novel approach to the detection techniques of Resonant Excitation Stark Ionization Spectroscopy (RESIS) allowed the first measurements of the higher rotational levels of H$_{2}$ that were previously unattainable due to their fast autoionization rates. RESIS uses a Doppler-tuned CO$_{2}$ laser to resonantly excite transitions in a fast molecular beam, which are detected by Stark ionization. Reported here are the experimental details and results along with the analysis of the fine structure measurements of the high-L Rydberg states of the rotationally excited (R$=$2) ground vibrational level of molecular hydrogen. This determines the Quadrupole moment and scalar and tensor dipole polarizabilities of (v$=$0,R$=$2) H$_{2}^{+}$. [Preview Abstract] |
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D1.00144: Critical nuclear charge to bind two-electron atoms Michael Busuttil, Hajar Al-Khazraji, Amirreza Moini, Travis Valdez, G.W.F. Drake For an atom with infinite nuclear mass, there exists a critical nuclear charge $Z_c$ that is just sufficient to bind the nucleus plus two electrons into a heliumlike structure. As recently discussed by Guevera and Turbiner [1], the value of $Z_c$ in the nonrelativistic limit is in the neighborhood of 0.91085. The objective of the present work is to present results of improved accuracy for $Z_c$ by use of our double basis set method in Hylleraas coordinates [2]. The method is particularly well adapted to the case where one electron is strongly bound and the other is at the limit of becoming unbound. The results are analysed in terms of a Puiseux expansion in fractional powers of $(Z - Z_c)$, yielding the somewhat smaller preliminary value $Z_c = 0.910730(6)$. The value of $Z_c$ is related to the analytic structure of the energy $E(Z)$ and the radius of convergence of a $1/Z$ expansion for the energy.\\[4pt] [1] N.L. Guevara and A.V. Turbiner, Phys.\ Rev.\ A {\bf 84}, 064501 (2012).\\[0pt] [2] G.W.F. Drake and Z.-C. Yan, Phys.\ Rev.\ A {\bf 46}, 2378 (1992). [Preview Abstract] |
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D1.00145: ABSTRACT WITHDRAWN |
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D1.00146: Application of the screening potential approach for Electron Impact ionization of rare-gas atoms Hari P. Saha The triple differential cross section for electron impact ionization of rare-gas atoms will be investigated using our recently extended MCHF method [1]. It is well known electron correlation effects in both the initial and the final states are very important. To incorporate these effects we will use the multi-configuration Hartree-Fock method to account for electron correlation in the initial state. The electron correlation in the final state will be taken into account using the angle-dependent screening potential approximation [2,3]. As a test case, the triple differential cross section (TDCS) will be calculated for electron impact ionization of Argon atom, which has experimental results. Our results will be compared with available experimental and the theoretical observations [4].\\[4pt] [1] H.P. Saha, (unpublished).\\[0pt] [2] M.R.H. Rudge, Rev. Mod. Phys. 40, 564 (1968).\\[0pt] [3] C.Pan and A.F Starace, Phys. Rev. Lett. 67, 185 (1991); Phys. Rev. A45, 4588 (1992).\\[0pt] [4] Ren et al., Phys. Rev. A 85, 032702 (2012). [Preview Abstract] |
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D1.00147: B-Spline R-Matrix with Pseudo-States Treatment of Electron Collisions with Argon Oleg Zatsarinny, Klaus Bartschat We have further developed the $B$-Spline $R$-matrix (BSR) code~[1] to allow for a large number of pseudo-states in the close-coupling expansion. In the present work, the BSRMPS approach~[2] was employed to perform semi-relativistic (Breit-Pauli) close-coupling calculations for elastic scattering, excitation, and ionization of argon from both the ground state and the metastable excited states. Coupling to the ionization continuum through the pseudo-states is important for low-energy elastic scattering (to represent polarizability effects), for excitation in the ``intermediate'' energy regime of about 1-3 times the ionization potential, and to allow for the calculation of ionization processes by transforming the results obtained for excitation of the positive-energy pseudo-states. The current results represent a significant extension of our earlier near-threshold work~[3].\\[4pt] [1] O.~Zatsarinny, Comp. Phys. Commun.~{\bf 174} (2006) 273.\\[0pt] [2] O.~Zatsarinny and K.~Bartschat, Phys.~Rev.~Lett.~{\bf 107} (2011) 023203.\\[0pt] [3] O.~Zatsarinny and K.~Bartschat, J.~Phys.~B~{\bf 37} (2004) 4693. [Preview Abstract] |
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D1.00148: Electron-impact ionization of neon at 100 eV: a benchmark comparison between experiment and theory for a complex target Oleg Zatsarinny, Klaus Bartschat, Thomas Pfl\"uger, Arne Senft\-leben, Xueguang Ren, Joachim Ullrich, Alexander Dorn As a fundamental test for state-of-the-art theoretical approaches, we have studied the single ionization $(2p)$ of neon at a projectile energy of 100~eV. The experimental data were acquired using an advanced reaction microscope that benefits from a high efficiency and a large solid-angle acceptance of almost $4\pi$ [1]. We put special emphasis on the ability to measure inter\-normalized triple-differential cross-sections over a large part of the phase space. The data are compared to predictions from a second-order hybrid distorted-wave plus $R$-matrix model and a fully non\-perturbative $B$-spline $R$-matrix with pseudo-states approach [2]. For a target of this complexity and the low-energy regime, unprecedented agreement between experiment and the BSR model is found. This represents a significant step forward in the investigation of (e,2e) processes involving complex targets.\\[4pt] [1] J. Ullrich, R. Moshammer, A. Dorn, R. D\"orner, L. Schmidt, and H. Schmidt-B\"ocking, Rep. Prog. Phys. {\bf 66} (2003) 1463.\\[0pt] [2] O. Zatsarinny and K. Bartschat, Phys. Rev. A {\bf 86} (2012) 022717. [Preview Abstract] |
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D1.00149: Investigation of screening effects on the shape resonances in the electron-hydrogen system using the complex-scaling method Li-Guang Jiao, Y.K. Ho In the present work we study the effects of screened Coulomb potentials on shape resonances in the electron-hydrogen system. Here we concentrate on the $^{1}S^{\mathrm{e}}$ and $^{1}P^{\mathrm{o}}$ shape resonances associated with and lying above, respectively, the H ($N=$2), (N$=$3), (N$=$4), and ($N=$5) thresholds. The complex-scaling method [1] is used to extract resonance poles, together with employing correlated Hylleraas-type wave functions up to 1078 and 1771 terms for the $S$- and $P$-wave states, respectively, to represent the two-electron system. To model the screening effect we replace the pure Coulomb interaction term for any pair of charged particles by a screened Coulomb (or Yukawa-type) interaction term. Our un-screened shape resonances agree well with those in the literature [2, 3]. We will present our latest results for the screened cases at the meeting.\\[4pt] [1] Y. K. Ho,\textit{ Phys. Rept. }\textbf{99}, 1 (1983) and references therein.\\[0pt] [2] A. B\"urgers and E. Lindroth, \textit{Eur. Phys. J. D }\textbf{10}, 327 (2000).\\[0pt] [3] S. Kar and Y. K. Ho, \textit{Phys. Rev. A }\textbf{86}, 014501 (2012). [Preview Abstract] |
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D1.00150: Eletron-helium laser-assisted free-free scattering for incident energies from 30 - 200 eV: effects of polarization direction B.A. deHarak, Benjamin Nosarzewski, Mahsa Siavashpouri, N.L.S. Martin We report on experiments that examine electron-helium scattering in the presence of an Nd:YAG laser field of 1.17 eV photons. At each incident electron energy (30, 60, and 200 eV), the laser polarization direction is varied within a plane perpendicular to the scattering plane. We compare our results with Kroll-Watson approximation (KWA)\footnote{N. M. Kroll and K. M. Watson, Phys. Rev. A 8, 804 (1973)} calculations. Of particular interest is the case where the polarization is perpendicular to the scattering plane for which the KWA predicts vanishing cross section; other workers have found that the KWA tends to be inaccurate for those cases where it predicts small cross sections.\footnote{M. O. Musa, A. MacDonald, L. Tidswell, J. Holmes, and B. Wallbank, J. Phys. B, 43 (17):175201, 2010} However, the KWA describes our results within the experimental uncertainties. [Preview Abstract] |
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D1.00151: Electron-impact excitation of Mg V and Si VII A.M. Sossah, S.S. Tayal Transition probabilities and effective collision strengths for electron-impart excitation are calculated for Mg V and Si VII ions. The calculations are performed in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multi-configuration Hartree-Fock method with term-dependant non-orthogonal orbitals is employed for an accurate description of the target wave functions. For each ion 86 fine-structure levels belonging to the 44 \textit{LS} states of 2s$^{2}$2$p^{4}$, 2s2$p^{5}$, 2$p^{6}$, 2$s$2$p^{3}$3$s$, 2$s$2$p^{3}$3$p$, and 2$s$2$p^{3}$3$d$ configurations are included in the close-coupling approximation; this leads to 3655 possible fine-structure transitions. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities. Our results are compared with previous theoretical results and available experimental data. Overall, we reached a good agreement with measured excitation energies and other calculated oscillator strengths. This work was supported by NASA grant NNX11AB62G from the Solar and Heliophysics Program. [Preview Abstract] |
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D1.00152: Transition probabilities and collision strengths for electron excitation of Fe IX A.M.S. Sossah, S.S. Tayal We present transition probabilities and effective collision strengths for electron-impact excitation of the astrophysically important Fe IX ions. The collision strengths are calculated in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multi-configuration Hartree-Fock method with term-dependant non-orthogonal orbitals is employed for an accurate description of the target wave functions. The lowest 116 fine-structure levels belonging to the 50 \textit{LS} states of 3s$^{2}$3$p^{6}$, 3$s$3$p^{6}$3$d$, 3$s^{2}$3$p^{5}$3$d$, 3$s^{2}$3$p^{5}$4$s$, and 3$s^{2}$3$p^{4}$3$d^{\mathrm{2}}$ configurations are included in the close-coupling approximation. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities. Our results are compared with previous theoretical results and available experimental data. There is very good agreement between length and velocity values of oscillator strengths. This work was supported by NASA grant NNX11AB62G from the Solar and Heliophysics Program. [Preview Abstract] |
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D1.00153: Cross sections for electron impact excitation of $O^{2+}$ Swaraj Tayal The improved radiative and collision atomic parameters calculations for $O^{2+}$ have been performed using the B-spline Breit-Pauli R-matrix method. The flexible non-orthogonal sets of spectroscopic and correlation radial functions are employed for an accurate representation of the target states and scattering functions. The close-coupling expansion includes 126 bound levels covering all possible terms of the ground $2s^22p^2$ and excited $2s2p^3$, $2p^4$, $2s^22p3s$, $2s^22p3p$, $2s^22p3d$, $2s2p^23s$, $2s^22p4s$, $2s^22p4p$, $2s2p^23p$, $2s2p^23d$, $2p^33s$, $2p^33p$, and $2p^33d$ configurations. The calculated excitation energies of the target levels are in excellent agreement with experiment and represent an improvement over the previous calculations. The present results of cross sections are compared with a variety of other close-coupling and distorted-wave calculations. The oscillator strengths and transition probabilities are in good agreement with other theories and available experimental data. The present cross sections are in good agreement with other theories for many transitions. [Preview Abstract] |
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D1.00154: Electron Capture in Low-Energy Ne$^{4+}$ - H$_{2}$O Collisions Asad Hasan, Osama Abu-Haija, Asghar Kayani, Emanuel Kamber Using translational energy-gain spectroscopy technique, we have measured the energy-gain spectra and absolute total cross sections for single-electron capture in collisions of Ne$^{4+}$ recoil ions with H$_{2}$O at laboratory impact energies between 60 and 1200 eV and scattering angles between 0$^{\circ}$ and 8$^{\circ}$. At the lowest impact energy, the zero-angle translational energy-gain spectrum shows capture into Ne$^{3+}$(2p$^{2}(^1$D)3d) to be the most important reaction channel, with contributions due to transfer excitation in the 3d excited state of the Ne$^{3+}$ accompanied by excitation of the target product into the excited state ($^{2}$A$_{1})$ of H$_{2}$O$^{+}$. There are also some contributions from capture into 4s and 4p states. However, as the scattering angle and impact energy are increased, contributions from transfer excitation and capture into 3d and 3p$^{\prime}$ become more pronounced relative to the dominant channel. The final state populations will be discussed on the basis of the reaction windows, which are calculated using the single-crossing Landau-Zener model and the extended version of the classical over-the-barrier model. [Preview Abstract] |
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D1.00155: Electron transfer, ionization, and excitation in collisions between protons and the ions He$^+$, Li$^{2+}$, Be$^{3+}$, B$^{4+}$, and C$^{5+}$ Thomas Winter Coupled-state cross sections have been determined for electron transfer, ionization, and excitation in collisions between keV-energy protons and the hydrogenic ions He$^{+}$, Li$^{2+}$, Be$^{3+}$, B$^{4+}$, and C$^{5+}$,\footnote{T. G. Winter, Phys. Rev. A (in preparation).} extending work reported 26 years ago with a limited basis for electron transfer and ionization only\footnote{T. G. Winter, Phys. Rev. A {\bf 35}, 3799 (1987).}; the C$^{5+}$ process was also considered in a later study.\footnote{T. G. Winter, Phys. Rev. A {\bf 56}, 2903 (1997).} In the present calculation, a basis of 60 Sturmians on each center has been used, and in a second calculation, a basis of 280 Sturmians on the target nucleus and a single $1s$ function on the proton, with greater overall accuracy than the previously published results. Further, cross sections for direct excitation and capture to individual excited states up to $3d$ have been determined. The extent to which high-energy scaling rules with target nuclear charge $Z$ are valid has been re-examined for transfer to the ground state, total transfer, and ionization, and is now considered also for excitation and individual-state processes at intermediate energies near where the cross sections peak. [Preview Abstract] |
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D1.00156: Measurements of the Absolute Cross Sections of Charge Transfer for the (D$_{2}^{+}$, D) System Using a Merged-Beams Technique$^{1}$ R.A. Strom, K.G. Bacani, R.M. Chi, S.L. Heczko, B.N. Singh, J.A. Tobar, A.K. Vassantachart, V.M. Andrianarijaona, D.G. Seely, C.C. Havener (H$_{2}$-H)$^{+}$ and (D$_{2}$-D)$^{+}$ are the most fundamental ion-molecule two-electron systems. These are temporary complexes which are formed during charge transfer (CT) collisions between the molecular ion and neutral atom. Using the Oak Ridge National Laboratory ion--atom merged--beams apparatus, absolute cross sections of (CT) between D$_{2}^{+}$ and D are measured from 10 eV/u to 1 keV/u collision energies. The results are consistent with the other measurements on CT between different molecular ions such as D$_{2}^{+}$, CO$^{+}$, and O$_{2}^{+}$ and H(D) which all converge to (7 $\pm$ 0.5) x 10$^{-16}$ cm$^{2}$ at 2 keV/u (Phys. Rev. A \textbf{84}, 062716, 2011). Toward the lower energies, they are also in good agreement with our previous measurements for D$_{2}^{+} +$ H, which benchmark high energy theory and vibrationally specific adiabatic theory (J. Phys. Conf. Ser. \textbf{194}, 082018,2009).\\[4pt] $^{1}$Research supported by the NASA Solar {\&} Heliospheric Physics Program NNH07ZDA001N, and the Office of Fusion Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy. VA et al. is supported by the National Science Foundation through Grant No. PHY-106887. [Preview Abstract] |
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D1.00157: Progress towards proton-lithium charge transfer collision experiments Paul Oxley We report recent progress on experiments to measure total charge transfer cross-sections for collisions between protons and lithium atoms. Initial experiments will use ground state lithium atoms and protons with energies in the range 1-10keV, while later experiments will investigate lower proton energies. Only one experimental investigation has been made at these lower energies [1] and is in disagreement with theoretical predictions. Future experiments with laser-excited lithium atoms are also envisioned. Total charge transfer cross-sections will be measured by detecting lithium ions emerging from the collision site, and by measuring the lithium beam density and the proton beam current. We describe experimental measurements of our lithium atomic beam and proton beam systems and outline the design and experimental progress made on the lithium ion detection apparatus. Our studies have interest from a fundamental physics standpoint and for their applications to fusion plasma diagnostics using injected lithium beams.\\[4pt] [1] S. L. Varghese, W. Waggoner, and C. L. Cocke, Phys. Rev. A \textbf{29}, 2453 (1984). [Preview Abstract] |
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D1.00158: On the role of projectile electrons for target recoil charge state production in intermediate-energy B$^{2+}$-Ne collisions Gerald Schenk, Marko Horbatsch, Tom Kirchner We consider $q$-fold target charge state production in 10--600~keV/u B$^{2+}$-~Ne collisions within an independent electron model. The model treats projectile and target electrons on the same footing using the same effective potential forall of them and makes use of a single-determinant wave function for the combined system [1]. Results are compared with recent experimental and theoretical data [2]. We find that the total cross sections for positive ion production as well as Ne$^{q+}$ production ($q=1,\ldots,4$) determined in coincidence with unchanged Be$^{2+}$ projectiles agree well with experiment in the 30-400~keV/u energy range. At energies below 200~keV/u the projectile electrons are shown to play a crucial role in order to reproduce the experimental data. \\[4pt] [1]~T.~Kirchner and M.~Horbatsch, Phys.~Rev.~A~\textbf{63}, 062718 (2001);\\[0pt] [2]~W.~Wolff et al, Phys.~Rev.~A~\textbf{84}, 042704 (2011). [Preview Abstract] |
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D1.00159: Single ionization of Li by 1.5 MeV/amu O$^{8+}$ projectiles M.F. Ciappina, M.S. Pindzola, J. Colgan We present fully differential cross sections (FDCS) for the single ionization of Li by O$^{8+}$ ions~[1]. We use a time-dependent close-coupling approach to model the evolution of a one-active-electron wavefunction in the field of the incoming projectile for a range of impact parameters~[2]. In addition a Fourier transform approach is used to extract FDCS for a specific projectile momentum transfer value~[3]. This scheme allows us to incorporate information about the interaction of the two heavy nuclei (the so-called NN interaction) and to assess its influence in the FDCS. We find noticeable differences in the shape of the FDCS when we include (neglect) the NN interaction. In addition our single differential cross section calculation shows excellent agreement with recent experimental data~[4]. Our scheme would be applicable to recent measurements of single ionization of Li from excited states~[5].\\[4pt] [1] M.\ F.\ Ciappina, et al., Phys. Rev. A (in preparation) (2013). \newline [2] M.\ S.\ Pindzola, et al., Phys. Rev. A {\bf 82}, 042719 (2010). \newline [3] J.\ Colgan, et al., J. Phys. B {\bf 44}, 175205 (2011). \newline [4] D.\ Fischer, et al., Phys. Rev. Lett. {\bf 109}, 113202 (2012). \newline [5] A.\ C.\ LaForge, et al. J. Phys. B {\bf 46}, 031001 (2013). [Preview Abstract] |
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D1.00160: Resonant Enhancement of Ground State H$_{2}^{+}$ Formation in Low Energy Charge Transfer between Protons and H$_2$ V.M. Andrianarijaona, J.G. King, M.F. Martin, N. de Ruette, X. Urbain We investigated the charge transfer (CT) from an H$_{2}$ or D$_{2}$ target to various fast atomic/molecular ions for a wide span of collision energies in the laboratory frame (eV to keV). Vibrationally resolved cross sections have been obtained on a relative scale, by dissociative charge transfer of the product H$_{2}^{+}$ ions with potassium atoms, and 3-D imaging of the fragments. An absolute value of the total CT cross section has been inferred from the measured ratio of the CT yield for protons and H$_{2}^{+}$, combined with the recommended H$_{2}^{+} +$H$_{2}$ cross section (ORNL). Our results on the (H$_{2}$, H$^{+}$) system benchmark state-to-state calculations at 10eV and above (Phys. Rev. A \textbf{75} 032703, 2007 and J. Phys. B \textbf{42}, 105207 2009). In particular, they confirm the vibrational excitation mechanism responsible for the resonance at 50eV, characterized by a dominant population of the ground vibrational state of H$_{2}^{+}$. The spectra for the isotopic system (D$_{2}$, H$^{+}$) will be also presented along with the results of CT performed with H$_{2}^{+}$ and D$_{2}^{+}$ projectiles. [Preview Abstract] |
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