Bulletin of the American Physical Society
2006 Ohio Section of the APS Spring Meeting
Friday–Saturday, March 31–April 1 2006; Detroit, Michigan
Session S3: Poster Session |
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Room: McGregor Center I |
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S3.00001: Low-Energy Electron Diffraction Study of the Adsorption Geometry for Pb(111)-($\surd $3x$\surd $3)R30$^{o}$-K Christopher M. Lemon, F.M. Pan, Mellita Caragiu, Nicola Ferralis, Renee D. Diehl Both the clean Pb(111) structure and the ($\surd $3x$\surd $3)R30$^{o}$ structure formed by potassium adsorbed on Pb(111) have been investigated by dynamical low-energy electron diffraction (LEED). The relaxation of the topmost lead layers of the clean Pb(111) surface is the main deviation from the bulk geometry, in agreement to the results of a similar study [Y.S. Li, F. Jona, P.M. Marcus, Phys. Rev. B 43 (1991) 6337]. Upon adsorption of K at room temperature, a ($\surd $3x$\surd $3)R30$^{o}$ structure is formed with K atoms occupying substitution sites. This result is rather unexpected considering that intermixing is unusual for large alkalis (larger than Li) adsorbed on close-packed substrates. The current calculation finds a K-Pb bond length of 3.62$\pm $0.3{\AA}, with no significant change to the Pb interlayer spacings [F.M. Pan, M. Caragiu, N. Ferralis, R.D. Diehl, Surf. Sci. 600 (2006) 537]. [Preview Abstract] |
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S3.00002: Terahertz detection of angular momentum states in Rydberg atoms R.J.A. Murray, C. Rangan In alkali Rydberg atoms, states with higher angular momentum $\ell \geq 3$ are degenerate in energy, and cannot be distinguished by standard methods such as field-ionization. In this poster, we propose a method of selective re-distribution of angular momentum states by terahertz frequency half-cycle pulses. The redistributed population can then be read-out easily, giving a signature of the original angular momentum. These results are expected to be an important advance in quantum information processing. \newline C. Rangan and R. J. A. Murray, Phys. Rev. A {\bf 72}, 053409 (2005). [Preview Abstract] |
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S3.00003: Lifetime and Branching Fraction Measurements for PII Stephanie Torok, Lorenzo Curtis Lifetime and branching fraction measurements using foil excitation of a fast ion beam are reported for transitions within the 3s$^2$ 3p$^2$ - 3s$^2$ 3p4s multiplet in P II. The studies were undertaken to test theoretical and semiempirical calculations which suggest that branching fractions within this multiplet can be accurately specified from intermediate coupling amplitudes deduced from measured energy level data. The results and their possible use a much-needed intensity calibration standard in the vacuum ultraviolet wavelength region will be discussed. [Preview Abstract] |
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S3.00004: Sizing melamine-formaldehyde microspheres using an electron microscope M. Garee, T.E. Sheridan Melamine-formaldehyde (MF) microspheres are widely used in complex plasma experiments because they are nearly monodisperse and are available in a wide variety of diameters. The manufacturer of these particles characterizes their mean diameter and standard deviation using a Coulter multisizer. However, measurements in complex plasma experiments, particularly of gas drag forces, indicate that the particles are smaller than their stated diameter. We have measured particle sizes using a scanning electron microscope and will compare these to the nominal diameter of $9.62\pm0.09~\mu\rm m$. [Preview Abstract] |
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S3.00005: Effect of plasma density on properties of a small Debye cluster A. Herrick, T.E. Sheridan Parameters of a two-dimensional Debye cluster with six particles in a (1, 5) configuration have been measured as a function of the density of the argon discharge in which they are suspended. Particle charge, plasma Debye length, cluster temperature and mode damping rates were determined by projecting the Brownian motion of the particles onto the center of mass and breathing modes. The Debye shielding parameter $\kappa$ is found to increase as the square root of the plasma density, and to have a value between $\approx 0.5$ and $2$, while the particle charge has a constant value $q\approx-17\,000 e$, and the cluster temperature is $ \approx 400~\rm K$, independent of plasma density. [Preview Abstract] |
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S3.00006: Characterization of two-dimensional elliptical complex plasma K.D. Wells, T.E. Sheridan An elliptical complex plasma is a system of $n$ particles with the same charge $q$ and mass $m$ confined in a two-dimensional anisotropic well. Particles interact through a screened Coulomb potential with a Debye length $\lambda$. An elliptical complex plasma has been created experimentally using a rectangular aperture (17.5~mm $\times$ 30.2~mm) placed on a flat electrode to create an anisotropic parabolic well. Measured properties of this system will be compared with computed configurations and normal modes. [Preview Abstract] |
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S3.00007: Emergence of continuum behavior in a finite two-dimensional complex plasma T.E. Sheridan Two-dimensional complex plasma experiments are often performed in systems having a few thousand particles, yet the results are found to agree with the predictions of continuum theory. We consider a model where the the complex plasma consists of $n$ particles interacting through a shielded Coulomb potential and confined by a parabolic potential well. The breathing frequency for this system can be found exactly in the continuum limit. The cluster radius and breathing frequency will be computed as a function of increasing particle number up to $n=3200$ for values of the Debye shielding parameter $\kappa =0$ to 5 and compared to results from continuum theory and a modified continuum theory that includes some effects of finite nearest-neighbor distance. [Preview Abstract] |
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S3.00008: Calculation of plasmon resonance shifts for dielectrically-coated proximate gold nanoparticles Darragh Rooney, C. Rangan, S. Mittler Noble metal nanoparticles exhibit surface plasmon resonances that are sensitive to particle shape. Arrays of gold hemispherical particles can be self-assembled on the surface of a waveguide, whose evanescent fields can be used to probe these resonances. The optical response is sensitive to dielectric ligands bound to the particle surface, giving the system a sensing functionality. Using the discrete dipole approximation (DDA), extinction spectra are calculated for pairs of particles separated by small distances for polarizations transverse and parallel to the waveguide surface. It is found that parallel fields yield spectra highly sensitive to particle separation, and that these spectra are shifted by the presence of dielectric coatings. Transverse fields do not show this behavior. [Preview Abstract] |
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S3.00009: Laser Assisted Study of Sessile Drop Morphology under Wind Conditions Yuri Sikorski, Ewen Chan We present a simple method to characterize sessile drop morphology including size and shape of the drop, contact angle and microscopic details of the liquid-air-solid interface shape under various wind conditions. In this method, the randomly polarized HeNe laser beam is focused on the surface of the liquid drop placed on a 5-axis micro-positioning stage. The setup is then placed inside a wind tunnel or optionally, the wind is generated by an air pump or compressed air canister. The laser beam reflected from the air-liquid interface is projected on a screen and the angle of the reflected beam measured. Also, the complex diffraction patterns created on the screen by the laser beam reflected from the liquid-air-solid interface were photographed and analyzed. The results for water, isopropyl alcohol and olive oil on glass and metal surfaces under various wind and tilt conditions are presented. [Preview Abstract] |
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S3.00010: Modeling and fabrication of Ridge Waveguides and their comparison to Photonic Bandgap Structures Kathleen Beddow, Meron Tekeste, Senthil Rajagopal, Jan Yarrison-Rice Through the implementation of a computer modeling program, the properties of ridge waveguides composed of a 200nm layer of silicon nitride (Si$_{3}$N$_{4}$) on 1.8 $\mu$m of silicon dioxide (SiO$_{2}$) were explored. The Si$_{3}$N$_{4}$ was altered from its initial 200 nm thickness in order to create a central ridge. The width and thickness of this ridge were varied in an effort to investigate the propagation of a single mode Gaussian beam of 632.8nm wavelength along both straight and curved ridge waveguides. The fabrication of these waveguides will be accomplished through the implementation of optical lithography, the exposure of the substrate, coated with either a positive or negative photoresist, with UV light. The investigation of Photonic Bandgap (PBG) structures was also done through the use of modeling software. A photonic lattice was created as a result of the etching of the substrate Si$_{3}$N$_{4}$ with a periodic array of air pores. Subsequently, a waveguide was produced through the removal of a series of these air pores. The modeling of PBG structures allowed for comparisons to be made between the photonic properties of the ridge waveguides and the PBG structures. [Preview Abstract] |
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S3.00011: Interpolation Formulas for the Packing Fraction of Binary Hard Spheres Naoki Iwamoto, Hiroki Sawamaru For several given structures, such as simple cubic, face-centered cubic, body-centered cubic and hexagonal close packing, that are formed by hard spheres of unit radius, packing of the remaining space with these structures formed by smaller hard spheres of decreasing radius is studied numerically. Random close packing of the remaining space is also considered by introducing infinitesimal gravity. The packing fraction is calculated numerically as a function of the radius of the smaller spheres and the analytic expressions for the packing fraction that accurately express the simulation results are derived. [Preview Abstract] |
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S3.00012: What happened at the Davis-Besse nuclear generating facility Gordon Aubrecht The Davis-Besse pressurized water reactor was taken off line on 16 February 2002 for routine maintenance. After a hole was discovered in the reactor vessel head it was kept shut down for repairs. It did not return to producing electricity steadily until two years later, 4 April 2004! What happened, how it might have happened, how it was fixed, whether there was cause for alarm among the general public, and what effects it had on FirstEnergy will be discussed. [Preview Abstract] |
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S3.00013: America's Electricity Future Gordon Aubrecht Where will America's future electricity supply come from? According to Vice President Cheney's energy task force, the U.S. needs to build about one 1 GW generating facilty a week in perpetuity.$^{(1) }$What sort of facilities will they be? Can the economy sustain such growth? Are there other possibilities? One possibility that strikes a chord with physicists is conservation as a source of energy. In this regard, Vice President Cheney famously said that conservation is``a sign of personal virtue, but it is not a sufficient basis---all by itself---for a sound, comprehensive energy policy,''$^{(2)}$ echoing the Ayn Rand Instituite's view that ``Conservation is not a long- or short-term solution to the energy crisis. Conservation is the un-American idea of resigning oneself to doing with less.''$^{(3) }$This poster will explore the possible energy futures, their advantages and disadvantages, with and without conservation. 1. National Energy Policy Development Group (R. Cheney, C. L. Powell, P. O'Neill, G. Norton, A. M. Veneman, D. L. Evans, N. Y. Mineta, S. Abraham, J. M. Allbaugh, C. T. Whitman, J. B. Bolten, M. E. Daniels, L. B. Lindsey, and R. Barrales), \textit{National Energy Policy: Report of the National Energy Policy Development Group}, (Washington, DC: Government Printing Office, 2001). 2. M. Allen, ``Bush energy plan will emphasize production,'' \textit{The Washington Post}, 1 May 2001 3. R. Pool, ``Saving power deemed immoral,'' \textit{The Los Angeles Times}, 12 May 2001. [Preview Abstract] |
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S3.00014: Space-charge limiting of a photoinjected electron pulse Eric Preston, Clinton Thompson The classical space-charge limiting problem was solved for thermionically emitted electrons being injected at a constant rate. In various modern applications, electrons are produced from photo-emission with a non-Maxwellian energy distribution and in short duration pulses. With a dynamical 1-d plasma simulation, we show that pulsed sources often experience more severe space- charge limiting than the constant current density approximation suggests. [Preview Abstract] |
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S3.00015: Entanglement enhanced performance of atomic clocks in the presence of environmental noise Andrew Jacobs, James Clemens It has been proposed that a specific class of entangled states of $N$ atoms known as Greenberger-Horne-Zeilinger (GHZ) states could be used to enhance the performance of atomic clocks with a sensitivity that scales as $1/N$ versus $1/\sqrt{N}$ for a standard atomic clock. However, this assumes that the GHZ state has been perfectly prepared. Here we investigate the fidelity of preparation of GHZ states of $N$ qubits using a quantum circuit model with imperfect quantum gates caused by environmental noise. The symbolic calculations are carried out using the QDENSITY package for Mathematica. We find that the fidelity of the prepared state decreases with $N$. When applied to an atomic clock model this would cause the sensitivity to be decreased from it maximum value and yield an optimal value of $N$ as a function of the noise intensity. [Preview Abstract] |
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S3.00016: Revisited comparison of thermal instability theory with MARFE density limit experiment in TEXTOR. Frederick Kelly Density limit shots in TEXTOR [Tokamak EXperiment for Technology Oriented Research] that ended in MARFE [Multifaceted Asymmetric Radiation From the Edge] are analyzed by several thermal instability theories$^{1-7}$ with convective effects included. \newline \newline $^{1}$W. M. Stacey, Phys. Plasmas \textbf{3}, 2673 (1996); Phys. Plasmas \textbf{3}, 3032 (1996); Phys. Plasmas \textbf{4}, 134 (1997); Phys. Plasmas \textbf{4}, 242 (1997). \newline $^{2}$W. M. Stacey, Plasma Phys. Contr. Fusion \textbf{39}, 1245 (1997). \newline $^{3}$W. M. Stacey, Fusion Technol. \textbf{36}, 38 (1999).$^{ }$ \newline $^{4}$W. M. Stacey, Phys. Plasmas \textbf{7}, 3464 (2000). \newline $^{5}$F. A. Kelly, W. M. Stacey, J. Rapp and M. Brix, Phys. Plasmas \textbf{8}, 3382 (2001). \newline $^{6}$M. Z. Tokar and F. A. Kelly, Phys. Plasmas \textbf{10}, 4378 (2003). \newline $^{7}$M. Z. Tokar, F. A. Kelly and X. Loozen, Phys. Plasmas \textbf{12}, 052510 (2005). [Preview Abstract] |
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