Bulletin of the American Physical Society
Inaugural Fall 2009 Meeting of the Prairie Section of the APS
Volume 54, Number 17
Thursday–Saturday, November 12–14, 2009; Iowa City, Iowa
Session E2: AMO and Plasma II |
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Chair: Robin Santra, Argonne National Laboratory Room: IMU 243 (Ballroom) |
Friday, November 13, 2009 10:30AM - 10:42AM |
E2.00001: Photoionization of single-walled and double-walled fullerenes Matt McCune, Dale Hopper, Ruma De Chakraborty, Himadri Chakraborty, Mohamed Madjet We theoretically investigate the ionization of various spherical-type fullerenes illuminated by the synchrotron light. The molecular core, comprising of tetravalent carbon ions, is modeled by a classical jellium shell and the local density formalism is used to describe the ground state structure formed by the delocalized valence electrons. The ionization is then treated by a linearized time-dependent formalism [1]. At lower photon energies two plasmon resonances are obtained in the cross sections of the single-walled fullerenes. The height and the width of the giant low energy resonance show a systematic dependence on the number of the carbon atoms. But the behavior of the higher energy resonance as a function of the carbon-atom number is complicated. For the double-walled fullerenes, strong hybridization between the electrons of two carbon layers is obtained. This hybridization is found to affect the electrons collective motion, resulting in significant modifications in the plasmons.\\[4pt] [1] Madjet et al., J. Phys. B \textbf{41}, 105101 (2008). [Preview Abstract] |
Friday, November 13, 2009 10:42AM - 10:54AM |
E2.00002: Computational studies of x-ray scattering from three-dimensionally-aligned asymmetric-top molecules Stefan Pabst, Phay Ho, Robin Santra We theoretically and numerically analyze x-ray scattering from asymmetric-top molecules three-dimensionally aligned using elliptically polarized laser light. A rigid-rotor model is assumed. The principal axes of the polarizability tensor are assumed to coincide with the principal axes of the moment of inertia tensor. Several symmetries in the Hamiltonian are identified and employed to enhance the efficiency of solving the time-dependent Schr\"odinger equation for each rotational state initially populated in a thermal ensemble. Using a phase-retrieval algorithm, the feasibility of structure reconstruction from a quasi-adiabatically-aligned sample is illustrated for the organic molecule naphthalene. The spatial resolution achievable strongly depends on the laser parameters, the initial rotational temperature, and the x-ray pulse duration. We demonstrate that for a laser peak intensity of 5~TW/cm$^2$, a laser pulse duration of 100~ps, a rotational temperature of 10~mK, and an x-ray pulse duration of 1~ps, the molecular structure may be probed at a resolution of 1 \AA. [Preview Abstract] |
Friday, November 13, 2009 10:54AM - 11:06AM |
E2.00003: Design of Holographic Lightfields for Manipulation of Quantum Degenerate Gases Samantha Kreppel, Peter Engels, Chris Hamner, JiaJia Chang Experiments with ultracold quantum degenerate gases are at the forefront of modern atomic physics. Since these gases require temperatures near absolute zero, they must be well isolated. Therefore, mechanical forces that laser beams exert on atoms can be exploited for trapping and manipulating these atoms. The goal of our studies was the investigation of holographic techniques to generate nearly arbitrary lightfields for the manipulation of ultracold quantum gases.the frame of this project, a variety of techniques for the creation of interesting lightfields were investigated both theoretically and experimentally. They include diffraction fields behind material masks made by holes in a metal plate, more complex patterns produced by transmissions masks printed on overhead transparencies, as well as computer generated binary holograms. For these cases, a Mathematica program was written to calculate the light patterns and an optical setup was built for testing the generated patterns. The next major step for this predict is testing these lightfields on Fermi degenerate gases and Bose-Einstein condensates. [Preview Abstract] |
Friday, November 13, 2009 11:06AM - 11:18AM |
E2.00004: Detection of gyro-scale current layers using single spacecraft parameters Shanshan Rodriguez, Jack Scudder A single spacecraft technique using plasma, electric and magnetic field data, has been successfully performed on the detection of current layers throughout the magnetosphere. Ions have been demonstrated demagnetized at the bowshock and Chapman-Ferraro layers while electrons remain magnetized at these ion-gyroscale current layers. At the electron-gyroscale magnetic reconnection layers, this technique explicitly shows the demagnetization signatures of the electron diffusion regions (EDRs) by demonstrating a previously published reconnection event on 20010401, as well as providing a newly discovered event during a 3-year polar data search. These in-situ observations of reconnection events also illustrate that electron agyrotropy, Mach number and anisotropy passing certain thresholds as required properties of EDR implied by the 2D PIC simulation. [Preview Abstract] |
Friday, November 13, 2009 11:18AM - 11:30AM |
E2.00005: Theory for Plasma Rocket Propulsion Crockett Grabbe Electrical propulsion of rockets is developing potentially into the use of 3 different thrusters for future long-distance space missions that primarily involve plasma dynamics. These are the Magnetoplasmadynamic (MPD) Thruster, the Plasma Induction Thruster (PID), and the VASIMIR Thruster. The history of the development of electrical propulsion into these prospects and the current research of particularly the VASIMIR Thruster are reviewed. Theoretical questions that need to be addressed in that development are explored. [Preview Abstract] |
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