Bulletin of the American Physical Society
2008 Joint Meeting of the APS Ohio-Region Section, the AAPT Southern Ohio Section, and the ACS Dayton-Section
Volume 53, Number 8
Friday–Saturday, October 10–11, 2008; Dayton, Ohio
Session C5: Atomic and Molecular Physics |
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Chair: Jerry Clark, Wright State University Room: Fawcett Hall 218 |
Saturday, October 11, 2008 8:00AM - 8:12AM |
C5.00001: Infrared spectra of the detonation fireballs Benjamin Schott, Kevin Gross, Glen Perram A rapid scanning Fourier transform infrared spectrometer was used to observe the detonation of several novel munitions. The spectral signatures from different explosive compositions are discernable and may be exploited for event classification. A simplified radiative transfer model recently developed for the spectral interpretation of rapidly evolving battlespace combustion events has been extended and applied to the data from these new field tests. In particular, the fireball radius, temperature, soot combustion, and H$_{2}$O and CO$_{2}$ concentrations are determined as a function of time. The fireball radius increased from 0 to 8 meters in about 230 ms and decreased gradually over the following 1-3 s. The fireball temperature profile revealed a rapid jump to over 1800 Kelvin immediately upon detonation followed by a short oscillation as secondary combustion kinetics dominated and a longer temperature decay. Computational methods for fitting the radiative transfer model to the observed data will be discussed, with a particular emphasis on computational efficiency. [Preview Abstract] |
Saturday, October 11, 2008 8:12AM - 8:24AM |
C5.00002: Charge Transport in DNA with Five Base Pairs Sunhee Lee, Eric Hedin, Yong Joe Recently, much interest has arisen in the process of charge transport through DNA due to its fundamental roles in biological processes and in possible novel molecular electronics. We investigate quantum mechanical electron transmission along the long axis of the DNA molecule using a one-dimensional tight-binding model. In this system, we consider a single central conduction channel in which individual sites represent a base-pair formed by either AT (TA) or GC (CG) pairs coupled via hydrogen bonds. The sites are linked by a hopping amplitude, or quantum overlap integral. The sugar-phosphate backbone and the hopping amplitude between each site of the base and the backbone are incorporated into an energy-dependent on-site potential in the main DNA site. For the sake of simplicity, a simple DNA molecule segment with five base pairs is studied, and the transmission for different values of on-site energy is calculated to determine the influence of mismatch (impurity) effects in the DNA sequence. Finally, we present results for the temperature dependence of the transmission, and the current-voltage characteristics in order to examine the extent and efficiency of charge migration. *One of the authors (E.R.H) is partially supported by a grant from the Center for Energy Research, Education, and Service (CERES) at Ball State University. [Preview Abstract] |
Saturday, October 11, 2008 8:24AM - 8:36AM |
C5.00003: Hyper-spectral imaging of aircraft exhaust plumes Spencer Bowen, Kenneth Bradley, Kevin Gross, Glen Perram, Michael Marciniak An imaging Fourier-transform spectrometer has been used to determine low spatial resolution temperature and chemical species concentration distributions of aircraft jet engine exhaust plumes. An overview of the imaging Fourier transform spectrometer and the methodology of the project is presented. Results to date are shared and future work is discussed. Exhaust plume data from a Turbine Technologies, LTD, SR-30 turbojet engine at three engine settings was collected using a Telops Field-portable Imaging Radiometric Spectrometer Technology Mid-Wave Extended (FIRST-MWE). Although the plume exhibited high temporal frequency fluctuations, temporal averaging of hyper-spectral data-cubes produced steady-state distributions, which, when co-added and Fourier transformed, produced workable spectra. These spectra were then reduced using a simplified gaseous effluent model to fit forward-modeled spectra obtained from the Line-By-Line Radiative Transfer Model (LBLRTM) and the high-resolution transmission (HITRAN) molecular absorption database to determine approximate temperature and concentration distributions. It is theorized that further development of the physical model will produce better agreement between measured and modeled data. [Preview Abstract] |
Saturday, October 11, 2008 8:36AM - 8:48AM |
C5.00004: EIT Intensity Noise Spectroscopy Michael Crescimanno, Yanhong Xiao, Maria Baryakhtar, Michael Hohensee, David Phillips, Ron Walsworth Intensity noise correlations in coherently-prepared media can reveal underlying spectroscopic detail, such as power broadening-free resonances. We analyze recent experimental results using very simple theory: The intensity noise correlation spectra can be quantitatively understood entirely in terms of static ensemble averages of the medium's steady state response. This is significantly simpler than stochastic integration of the Bloch equations, and leads to physical insights we apply to non-linear Faraday rotation and noise spectra in optically thick media. [Preview Abstract] |
Saturday, October 11, 2008 8:48AM - 9:00AM |
C5.00005: Intensity auto- and cross-correlations for a driven optical cavity coupled to a three-level atom Patrick Hemphill, James Clemens We present two-time intensity auto- and cross-correlations for the light transmitted through a driven optical cavity coupled to a single three-level atom in the $\Lambda$ configuration. The atomic transitions couple to two orthogonally polarized cavity field modes on resonance. One of the cavity modes is weakly driven by an external coherent field. We model this cavity quantum electrodynamics (QED) system using a quantum trajectory unraveling of the master equation based on direct photodetection of the transmitted light. [Preview Abstract] |
Saturday, October 11, 2008 9:00AM - 9:12AM |
C5.00006: Pressure broadening and shifting of the Cesium D1 and D2 lines by rare gases Douglas Wertepny, Greg Pitz, Glen Perram The Diode Pumped Alkali Laser (DPAL) offers a high power, electrically driven laser with excellent thermal management, lightweight packaging, and high brightness for tactical military applications. The concept of using a gas phase medium for the phasing of large diode arrays via a highly efficient, cyclical photon engine combines the best features of electrically driven lasers with the inherent thermal management advantages of a gas lasers. Matching the spectral bandwidth of the diode pump source with the atomic absorption profile is paramount and requires both the narrow banding of high power diode laser arrays and novel approaches to broadening the gas lineshape. In the present work, the rates for pressure broadening and line shifts are reported for both atomic and molecular collision partners using laser absorption and induced fluorescence techniques. The absolute absorption and stimulated emission cross-sections, including the effects of hyperfine splitting and pressure broadening at low to moderate pressures are computed and compared with experimental results. [Preview Abstract] |
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