Bulletin of the American Physical Society
2007 APS Four Corners Section/SPS Zone 16 Joint Fall Meeting
Volume 52, Number 14
Friday–Saturday, October 19–20, 2007; Flagstaff, Arizona
Session K4: Atomic, Molecular, and Optical Physics |
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Chair: Bruce Doak, Arizona State University Room: Physical Sciences (Bldg. 19) Room 321 |
Saturday, October 20, 2007 2:00PM - 2:12PM |
K4.00001: Controlling atom motion through the dipole-dipole force Michael Wall, Francis Robicheaux, Robert Jones We describe simulations that illustrate the possibility for manipulating the position correlation of atoms in a magneto-optical trap (MOT) using the dipole--dipole interaction. The control scheme utilizes a narrow band laser that is detuned to the high-frequency side of a single-photon Rydberg transition in an isolated atom. As two atoms move near each other, they can be laser excited to repelling diatomic Rydberg-Rydberg potential energy curves which halt their approach. By chirping the laser from large to small detunings, atoms in a MOT can be pushed apart by dipole-dipole forces, thereby controlling nearest- neighbor interactions. Alternatively, by holding the frequency of the Rydberg excitation laser fixed as the MOT is loaded, it should be possible to limit the minimum distance between atoms to a prescribed value. [Preview Abstract] |
Saturday, October 20, 2007 2:12PM - 2:24PM |
K4.00002: Investigation of DUV generation for a Si quantum computer David Fairbank, Robert Merrill, Siu Au Lee Laser cooling and trapping of atoms in a magneto-optic trap (MOT) may be used as a source for depositing single silicon atoms with nanometer precision, which is required for making a scalable silicon quantum computer. A Si MOT requires a tunable, continuous wave laser at the cooling transition wavelength of 221.7 nm. Tens of mW are needed. Our scheme is to frequency double a Ti:Sapphire laser at 886.8 nm to 443.4 nm, then again to 221.7 nm. Resonant cavities are used to enhance the laser power. Mode matching into the cavity, phase matching in the crystal, and minimization of losses also improve efficiency. Theoretical predictions of optimal cavity parameters have been calculated. Values for crystal absorbance, walk-off, and waist size were used to predict second harmonic output power. Experimental results for the second harmonic generation will be presented. [Preview Abstract] |
Saturday, October 20, 2007 2:24PM - 2:36PM |
K4.00003: Spontaneous vortex formation during the creation of Bose-Einstein condensates Chad Weiler, Tyler Neely, David Scherer, Brian Anderson We have experimentally observed spontaneous generation and trapping of quantized vortices in single-component Bose- Einstein condensates. The BECs were created by a standard evaporative cooling procedure in a magnetic trap, without any additional methods of intentionally imparting angular momentum to the trapped atoms. After each BEC was formed, it was expanded such that the presence or absence of a vortex was determined. By observing numerous condensates, the statistical dependence of vortex formation on trapping and cooling parameters was examined. We will describe our experimental results and our interpretation of the vortex formation mechanism. [Preview Abstract] |
Saturday, October 20, 2007 2:36PM - 2:48PM |
K4.00004: Water-encapsulated protein source for x-ray serial crystallography D.P. DePonte, U. Weierstall, R.B. Doak, J.H.C. Spence, G. Hembree, J. Warner, D. Starodub, M. Hunter A reliable source of micron size water droplets has been constructed for the purpose of delivering water-encapsulated protein for x-ray serial crystallography. A linear stream of droplets of negligible divergence is produced by accelerating a liquid water jet through a high pressure gradient [1] inside a converging gas nozzle. Using a co-flowing gas rather than the nozzle walls to squeeze the liquid jet to smaller diameter eliminates the problem of clogging that has thus far limited the minimum size of Rayleigh nozzle jets [2]. Converging jets tend to align non-spherical particles suspended in the liquid and we are presently investigating the possibility of fiber diffraction from drops of aligned macromolecules produced by this method. [1] Ganan-Calvo, A.M. and A. Barrero, \textit{A novel pneumatic technique to generate steady capillary microjets.} Journal of Aerosol Science, 1999. \textbf{30}(1): p. 117-125 [2] http://arxiv.org/abs/physics/0701129 [Preview Abstract] |
Saturday, October 20, 2007 2:48PM - 3:00PM |
K4.00005: Gas NMR Characterization of Oil Shale Eric Sorte, Gernot Laicher, Brian Saam Accurate descriptions and simulations of oil reservoirs such as carbonate-rich sedimentary rock are important for the efficient development and conversion of recoverable energy reserves. These descriptions depend on reliable measures of the properties of the formation rock such as absolute and effective porosity, mineralogical composition, permeability, and tortuosity. NMR signal relaxation time (T1 and T2) and measurements of restricted diffusion of gases in porous media can be used to probe multi-pore media, yielding valuable petrophysical information and allowing the characterization of internal topology and pore size distribution. We employ NMR techniques on imbibed fluorinated and hyperpolarized noble gases - gases with the unique properties of being chemically inert and minimally invasive while exhibiting favorable NMR properties - at various pressure and temperatures to characterize the shale heterogeneity. We show current results of our characterizations and explore ideas for future work. [Preview Abstract] |
Saturday, October 20, 2007 3:00PM - 3:12PM |
K4.00006: Model and Simulation of a Polymer-Coated Fiber Bragg Grating Sensor Shao Jun Liu Embedding a fiber Bragg grating with a polymer could improve the pressure sensitivity of a sensor. Based on the theory of elastic mechanics, we considered the polymer with optical fiber as transverse isotropy, which is encapsulated in the metal tube and with the three components of stress not equal. The relation between the shift of Bragg wavelength and the pressure is built. It is found that different physics models will induce different pressure sensitivity, and both increasing the diameter of the cylinder polymer and reducing its Young's modulus can raise the pressure sensitivity. This analysis is helpful in designing a sensor according with engineering demands. [Preview Abstract] |
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