Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session C3: Focus Session: AMO Applications |
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Chair: Elizabeth McCormack, Bryn Mawr College Room: Grand Ballroom E |
Tuesday, June 5, 2012 2:00PM - 2:30PM |
C3.00001: Low-energy electron interactions with biomolecules Invited Speaker: Carl Winstead Low-energy electron interactions with biomolecules have been the focus of sustained attention over the past decade. The demonstration by Sanche and coworkers that even subexcitation and subionization electrons can induce strand breaks in DNA opened a new frontier in understanding radiation damage to living systems. Many studies of DNA subunits and their analogues, both experimental and theoretical, have elucidated likely mechanisms by which slow electrons attach to and disrupt DNA, although the full picture is far from clear and some elements of it remain controversial. Increasing attention is also being given to low-energy electron collisions with amino acids in order to explore possible mechanisms of electron-mediated radiation damage to proteins. In a completely different context, electron-biomolecule collisions are fundamental to spark ignition and cumbustion of biofuels such as methanol and ethanol. Not to be overlooked, either, is the simplest but most ubiquitous biomolecule of all, water, whose low-energy electron cross sections remain surprisingly ill-characterized. This talk will survery recent \textit{ab initio} computational studies using the Schwinger multichannel method of DNA- and protein-related molecules, alcohols, and water. Much of the work to be presented was carried out in collaboration with experimentalists who undertook complementary measurements, allowing for useful comparisons to be made. Although the primary focus will be on electronically elastic collisions relevant to dissociative attachment and electron transport, electron-impact excitation cross sections for water will be presented and discussed. [Preview Abstract] |
Tuesday, June 5, 2012 2:30PM - 2:42PM |
C3.00002: Atom counting system to measure ultra-low Kr-85 contamination in liquid xenon dark matter detectors Tae Hyun Yoon, Luke Goetzke, Andre Loose, Elena Aprile, Tanya Zelevinsky The XENON experiment aims at the direct detection of dark matter in the form of Weakly Interacting Massive Particles (WIMPs) via their elastic scattering off Xe nuclei. To achieve the required sensitivity, it is necessary to suppress Kr contamination of Xe which causes background events in Xe targets through Kr-85 beta decay. Magneto-optical techniques are used to cool and trap metastable Kr atoms from a RF plasma discharge. Fluorescence from single trapped Kr atoms can be detected with a sensitive photodetector. The cold-atom apparatus has been initially tested with Ar to avoid contamination by Kr. Several recent improvements increase the capture efficiency, including source cooling and additional transverse cooling of the metastable atomic beam. Results from tests with Ar and single atom detection with Kr will be presented. [Preview Abstract] |
Tuesday, June 5, 2012 2:42PM - 2:54PM |
C3.00003: DNA detection using Laser Transmission Spectroscopy Carol Tanner, Steven Ruggiero, Frank Li, Andrew Mahon, Matthew Barnes, Scott Egan, Jeffrey Feder, David Lodge, Ching-Ting Hwang, Robert Schafer Laser transmission spectroscopy (LTS) is a new quantitative and rapid technique for measuring the size, shape, and number of nanoparticles in suspension. We report on the application of LTS as a novel detection method for species-specific DNA detection where the presence of one invasive species was differentiated from a closely related invasive sister species. The method employs carboxylated polystyrene nanoparticles functionalized with short DNA fragments that are complimentary to a specific target DNA sequence. In solution, the DNA strands containing targets bind to the tags resulting in a sizable increase in the nanoparticle diameter, which is rapidly and quantitatively measured using LTS. DNA strands that do not contain the target sequence do not bind and produce no size change of the carboxylated beads. The results show that LTS has the potential to become a quantitative and rapid DNA detection method and have additional applications for point-of-care medical diagnostics. [Preview Abstract] |
Tuesday, June 5, 2012 2:54PM - 3:24PM |
C3.00004: Low Energy Electron Scattering from Fuels Invited Speaker: M. Cristina A. Lopes We report an investigation of processes that occur during the ignition of the plasma and its consequences in post-discharge time for an internal combustion engine, in order to find the appropriate parameters to be used in cars that operate with lean mixtures air-fuel. The relevance of this theme has attracted much attention, and has been one of the subjects of collaboration between experimental and theoretical groups in the USA and Brazil. We have produced some basic information necessary to modeling spark ignition in alcohol- fuelled engines. Total cross sections of electron scattering by methanol and ethanol molecules were obtained, using the linear transmission method based on the Beer-Lambert law to first approximation. Measurements and calculations of differential cross sections for low-energy (rotationally unresolved) electron scattering were also obtained, for scattering angles of 5\r{ }--130\r{ }. The measurements were taken using the relative flow method with an aperture source, and calculations using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons. Additionally to these, computer simulation studies of electronic discharge in mixtures of ethanol were performed, using a Zero-Dimensional Plasma Kinetic solver. Previous reported models for combustion of ethanol and cross sections data for momentum transfer of electron collisions with ethanol were used. The time evolutions of the main species densities are reported and the ignition time delay discussed. [Preview Abstract] |
Tuesday, June 5, 2012 3:24PM - 3:36PM |
C3.00005: Green astro-comb for exoplanet searches Chih-Hao Li, Alexander Glenday, Nicholas Langellier, Gabor Furesz, Matthew Webber, Guoqing Chang, Li-Jin Chen, Hung-Wen Chen, Jinkang Lim, Franz Kaertner, David Phillips, Andrew Szentgyorgyi, Ronald Walsworth Astro-combs, a combination of a laser frequency comb, coherent wavelength shifting mechanism (such as a doubling crystal or photonic crystal fiber) and a mode-filtering Fabry-Perot cavity (FPC), are promising spectrograph calibrators, which will enable searches for Earth-like exoplanets and direct observation of the accelerating expansion of the universe. In this talk, I will present recent results from a green astro-comb, which will be integrated in 2012 with the HARPS-N spectrograph in the 3.6 m Telescopio Nazionale Galileo (TNG) in the Canary Islands. The green astro-comb consists of 6000 lines equally spaced by 20 GHz in the 500-600 nm optical band. The green astro-comb is generated from a 1-GHz Ti:Sapphire comb laser, a custom tapered photonic crystal fiber that spectrally shifts the comb lines to the visible, and two mode-filtering FPCs that increase the line spacing to be suitable for calibration of the R=100,000 HARPS-N spectrograph. We have also used a high-resolution Fourier Transform Spectrometer (FTS) to analyze systematic errors across the full green astro-comb spectrum. The current status of these investigations will be presented. [Preview Abstract] |
Tuesday, June 5, 2012 3:36PM - 3:48PM |
C3.00006: Wave packet dynamics for atomic projectile in solid film Gennadiy Filippov The physics of phenomena extended during the passage of a swift atomic projectile through solid has a long history. A considerable amount of works was performed and a wide class of the so-called orientation phenomena was revealed. The theory of such phenomena usually based on assumption on a strength spatial localization of massive accelerated particles (nucleons, nuclei) having a sufficiently great velocity in a solid. The other point of view was proposed by Kagan {\&} Kononetz, when it was stated a particle moving in a crystal should be described with the help of one Bloch wave and obviously should be delocalized. It was shown the channeling phenomena could be well described also with this theory. The width of a particle's wave packet is important in some physical effects, e.g., in diffraction. With the help of density matrix calculation we show a presence of a spatial localization for a projectile. We estimate the time behavior of a packet width and show the specific effects of memory and stabilization, which follow from a wave nature of a micro-world. We show also the sophistic nature of a free wave packet notion which can not be realized in reality. [Preview Abstract] |
Tuesday, June 5, 2012 3:48PM - 4:00PM |
C3.00007: Rotation of an optical angular interference pattern in a spiral phase plate etalon Yisa Rumala, Aaron Leanhardt A spiral phase plate etalon fabricated from a transparent polymer with azimuthally varying thickness and non-zero reflectivity at both surfaces is used to create an optical angular interference pattern on the output plane of the device [1]. The angular interference pattern is observed to rotate as the laser frequency is varied, and compared to a computer model of the experiment based on shot noise limited assumptions. For an ultra-low finesse device, the angular interference pattern is calculated to rotate through a 2$\pi $ radian angle when the laser frequency is varied by $\sim $100GHz with a sensitivity of a few MHz ($\sim $0.1$\pi $ milli radian rotation angle) as determined from fitting the data. This work extends the operation of the conventional Fabry-Perot etalon consisting of longitudinal interference fringes to include angular interference fringes, and is expected to have broad applications in optical frequency metrology, quantum optics and coherent control of atomic systems. \\[4pt] [1] Y.S. Rumala and A. E. Leanhardt, ``Multiple beam interference in spiral phase plates'', (APS DAMOP) Bull. Am. Phys. Soc. \textbf{56}, No. 5, p.170, 2011 (Full manuscript in preparation). [Preview Abstract] |
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