Bulletin of the American Physical Society
2013 Annual Fall Meeting of the APS Prairie Section
Volume 58, Number 15
Thursday–Saturday, November 7–9, 2013; Columbia, Missouri
Session H1: Atomic, Molecular and Optical Physics; Industrial Physics |
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Chair: Ping Yu, University of Missouri Room: Physics Building 120 |
Saturday, November 9, 2013 8:30AM - 8:42AM |
H1.00001: Classical Trajectory Studies of the Hydrogen Peroxyl Radical HO$_{2}$ Jamin Perry, Albert Wagner, Donald Thompson The intramolecular dynamics, intramolecular vibrational redistribution of energy (IVR), isomerization and unimolecular dissociation of the hydrogen peroxyl radical, HO$_{2}$* $\to $ H $+$ O$_{2}$~have been studied using classical trajectories. Mode specific effects are found to affect the IVR, isomerization and the rate of dissociation. Exchange of the hydrogen atom between the oxygen atoms increases the rate of energy transfer between the vibrational modes of the radical. The relaxation mechanism of the vibrationally excited radical embedded in a dense gas environment is also presented. [Preview Abstract] |
Saturday, November 9, 2013 8:42AM - 8:54AM |
H1.00002: Experimental Evidence for a non-Globally Trace-Preserving POVM Raymond Jensen A well-known experiment from 1986 involving entangled photon pairs is examined. The data, which until now have not been modeled quantitatively, are shown to be in agreement with quantum theory upon application of a positive operator valued measure (POVM). The POVM has a peculiarity: it is not complete (trace-preserving) on the entire Hilbert space but on a proper subset although they are positive semidefinite observables on the entire space. In spite of this, the state vector of the aforementioned experiment is in the subset where completeness holds. [Preview Abstract] |
Saturday, November 9, 2013 8:54AM - 9:06AM |
H1.00003: Channelling radiation from a 4 MeV electron beam interaction with a diamond crystal Wade Rush, Jack Shi Fermilab is conducting experiments with a round 4 MeV electron beam bunch interacting with a diamond crystal. If the crystal is oriented such that one of its (hkl) planes are parallel to the beams ideal trajectory, some of the beam would essentially channel through the diamond and emit coherent soft X-ray radiation instead of the weaker bremsstrahlung radiation. We are attempting to simulate the expected spectral brilliance and replicate some of the primary linewidth contributors which could emerge from this channelling radiation experiment. [Preview Abstract] |
Saturday, November 9, 2013 9:06AM - 9:18AM |
H1.00004: Graphene Synthesization by Direct Sonication Exfoliation Daniel R. Soden, Jincheng Bai, Lifeng Dong The emergence of graphene in the scientific community over the last several years has been the cause of much excitement among material scientists and physicists due to its many unusual physical and photovoltaic properties. However, the much sought after monolayer graphene has proven to be difficult to produce in sufficient quantities, with most processes outputting high layer or even defect ridden graphene instead. This experiment aims to correct some of these problems, concerning itself with the synthesis of high quality graphene through continuous sonication with surfactant added throughout, as well as the issue of graphene quality as a function of sonication time. This was accomplished through the creation and addition of a Triton X-100 surfactant solution to a graphite suspension during sonication lasting for 50, 80, 110, 140, 170, and 200 minutes. The resulting suspension was then filtrated to separate out the graphene, before being tested for quality through Raman spectroscopy and SEM microscopy. This completely physical method of graphene synthesis provides a much simpler and more environmentally safe way to achieve the highly desired few layer graphene, and will hopefully allow for greater use of the substance in industry. [Preview Abstract] |
Saturday, November 9, 2013 9:18AM - 9:30AM |
H1.00005: Investigation of nitrogen-doped graphene as catalyst and catalyst support for oxygen reduction in both acidic and alkaline solutions Jincheng Bai, Lifeng Dong Fuel cells are promising energy devices with low pollutant emission and high energy conversion efficiency. However, the performance of fuel cells depends on oxygen reduction reaction. In order to solve the slow kinetics of oxygen reduction reaction, carbon materials have been utilized as catalyst supports for fuel cells. In this study, graphene and nitrogen-doped graphene were synthesized through a solvothermal method and investigated as catalysts for oxygen reduction reactions. Electrochemical measurements demonstrated that N-doped graphene possessed higher electrocatalytic activity than graphene in both acidic and alkaline solutions. N-doped graphene can directly act as a catalyst to facilitate four-electron oxygen reductions in alkaline solution but two-electron reductions in acidic solution. On the other hand, when employed as catalyst supports for platinum and Pt-ruthenium nanoparticles, N-doped graphene can contribute to four-electron oxygen reductions in acidic solution, yet in alkaline solution the kinetics of reduction reaction is slow. So N-doped graphene can work as an efficient catalyst for oxygen reductions to substitute the precious Pt catalysts in alkaline solution and and Pt-Ru catalysts in acidic solution. [Preview Abstract] |
Saturday, November 9, 2013 9:30AM - 9:42AM |
H1.00006: PLD growth of multilayered MgO/Ag(001)/MgO photocathode Daniel Velazquez, Zikri Yusof, Linda Spentzouris, Jeff Terry Films of of Ag, MgO and multilayers of these were grown via pulsed laser deposition on clean Si(111) 7x7 substrates. The films were studied using reflection high-energy electron diffraction, Kelvin probe and ellipsometry. Information about crystalline and atomic structure as well as surface condition, work function and film thickness was obtained using these techniques. Deposition at various substrate temperatures and partial oxygen pressures was performed in order to understand the parameter settings that lead to higher quality crystalline films. Epitaxial films of Ag(111) were found to grow at an optimal substrate temperature of 256 $^{\circ}$C (fig 1.). The superstructure Ag(111) $\surd $3 x $\surd $3 occurs when deposition takes place at a substrate temperature of 620 $^{\circ}$C. In addition, MgO films were found to grow with small grain size on both, Si(111) 7x7 and Ag(111)/Si(111) at room temperature with a partial oxygen pressure of 5x10$^{-5}$ Torr (fig. 2). Highly-oriented, polycrystalline growth of MgO films is evidenced by their RHEED pattern. In addition, the obliquely-shaped diffraction spots indicate the growth of secondary phase precipitates, most likely due to oxygen deficit. Measurements of the work function of these multilayers indicate that the Ag(111) work function (4.75 eV) is sharply suppressed with the first few MgO shots and has a quasi-linear increase for the first few monolayers (fig. 3). As the thickness of MgO increases (a few nanometers) the work function drops again and stabilizes at the level of MgO ($\sim$4.2 eV). [Preview Abstract] |
Saturday, November 9, 2013 9:42AM - 9:54AM |
H1.00007: Improved laser heating technique for melting dusty plasma crystals Zach Haralson, John Goree A dusty plasma is a mixture of polymer microspheres, electrons, positive ions and neutral gas atoms. The microspheres acquire an electric charge as large as many thousands of elementary charges, so that a single layer of thousands of microspheres can be electrically levitated by a vertical electric field. Due to the mutual repulsion among these microspheres, they develop such a large interparticle electric potential energy that they arrange themselves with a uniform spacing, analogous to atoms in a crystalline lattice. This so called ``dust crystal'' can then be melted by using laser heating to give the microspheres more kinetic energy. Movies of the particle motion, shown in this talk, are recorded using video microscopy. We describe experiments to optimize the sweeping of the laser beam during this heating. By tracking the random motion of the individual microspheres, we can explore the relationship between microscopic particle motions and macroscopic phenomena and calculate transport coefficients, such as the diffusion constant. [Preview Abstract] |
Saturday, November 9, 2013 9:54AM - 10:06AM |
H1.00008: Experimental test of the Fluctuation Theorem using a microsphere in a rarefied gas Chun-Shang Wong, John Goree, Bin Liu The Second Law of Thermodynamics can be violated on short time and distance scales. The extent of the violation is quantified by the Fluctuation Theorem, which was the subject of the 2004 Boltzmann Medal. A variation of the theorem, the Work Fluctuation Theorem, can be tested experimentally [G.M. Wang, PRL 2002], but these experimental tests are still few. We have devised a test using Brownian motion of a $5~\mu$m polymer sphere in a rarefied gas while pushing the sphere with a constant force applied by the radiation pressure of an incident laser beam. To avoid friction with solid surfaces, the microsphere is electrically charged and levitated by a vertical electric field, which is provided by partially ionizing the argon gas to make a plasma. A time series of the microsphere's position is measured using video microscopy with a high speed camera (400 fps), yielding a measure of the fluctuating work done. For various time intervals, $\tau$, the work done on the particle, $W_\tau$, can be calculated by integrating $\textbf{F}_{\rm{laser}} \cdot \textbf{v}$ over $d\tau$. Finally, a histogram of observed $W_\tau$ values is used to test the Fluctuation Theorem prediction ${P(W_\tau >0)}/{P(W_{\tau} < 0)} = \langle {\rm{exp}}(W_\tau) \rangle $, where $P$ is a probability. [Preview Abstract] |
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