Bulletin of the American Physical Society
2005 7th Annual Meeting of the Northwest Section
Friday–Saturday, May 13–14, 2005; Victoria, BC, Canada
Session G3: AMO, Chemical |
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Chair: Maciej Gutowski, Pacific Northwest National Laboratory Room: MacLaurin D103 |
Saturday, May 14, 2005 2:00PM - 2:36PM |
G3.00001: Density functional theory applied to iron electron transfer systems Invited Speaker: Electron transfer can be thought of as the simplest chemical reaction; a single electron moves, via tunneling or hopping, from one molecular species to another. However, the cascade of events which follows that electron transfer is not so simple, and the physical properties of the electron donor, acceptor and surrounding molecules can change quite dramatically across both quantum and classical mechanical dimensions of space and time. This complexity makes electron transfer reactions good candidates for theoretical investigation. The process of electron transfer is essential to living things as manifested in cellular respiration and photosynthesis. Inter- and intra-molecular electron transfer reactions in biological systems are good prototypes for density functional methods (DFT), which have highly desirable features such as good parallel scalability, which makes such large quantum mechanical calculations possible, and electron correlation, which is crucial to accurately model energetic properties of metallic systems. DFT's positive and negative aspects will be discussed in the context of theoretical studies which model such properties as reduction potentials and electron hopping probabilities in iron metalloenzymes and smaller model systems. [Preview Abstract] |
Saturday, May 14, 2005 2:36PM - 3:12PM |
G3.00002: Coherence and correlations in quantum degenerate atomic gases Invited Speaker: This talk will provide an overview of some recent experiments exploring the complementary properties of coherence and correlations in quantum degenerate gases. Experiments with both bosonic and fermionic ensembles will be discussed. The primary emphasis will be on new developments in the realization and study of the phases of strongly correlated quantum systems. [Preview Abstract] |
Saturday, May 14, 2005 3:12PM - 3:37PM |
G3.00003: COFFEE BREAK
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Saturday, May 14, 2005 3:37PM - 3:49PM |
G3.00004: Infrared Absorbance of SF-6 E.B. Nieschmidt, S.H. Vegors The infrared absorbance spectrum of sulfur hexafluoride has been studied using a Fourier Transform Infrared Spectrometer ( FTIR ). Eighty two different absorbance lines were observed and definitely assigned to be SF-6 absorbances. Twenty seven other absorbance lines were observed and are tentatively assigned to be SF-6 absorbances. These absorbance energies will be reported. Three energy levels in each of the vibrational spectra nu1, nu3, nu4, nu5 and nu6 as well as two energy levels in nu2 have been assigned and also will be reported. [Preview Abstract] |
Saturday, May 14, 2005 3:49PM - 4:01PM |
G3.00005: Impossibility of negative group velocity in a passive periodic layer structure with or without loss Louis Poirier, Robert I. Thompson, Alain Hach\'{e} Imagine receiving a signal through a transmission line before it was sent. The theory for group velocity allows superluminal tunneling times and some believe negative tunneling times as well. We shall discuss experimental results from our own work [1] and other published materials [2] that claim to observe both superluminal and negative group velocities in a simple coaxial cable periodic system driven in the MHz regime. Detailed computational analysis of the system reveals that negative velocities are not possible in a linear passive periodic system. A simple error analysis will show that it is possible to obtain uncertainties as large as the measurements themselves, which can lead to some misleading interpretations of results. [1] ${\rm A}$. Hach\'{e} and L. Poirier, Phys. Rev. E \textbf{65}, 036608 (2002) [2] J. N. Munday and W. M. Robertson, App. Phys. Lett. \textbf{81}, 2127 (2002) [Preview Abstract] |
Saturday, May 14, 2005 4:01PM - 4:13PM |
G3.00006: Novel microresonator with broken angular momentum symmetry Alexander A. Govyadinov, Evgenii E. Narimanov, Viktor A. Podolskiy Dielectric microcavity resonators are the essential components of modern high-performance microsensors and microlasers. We present a novel, ``ratchet''-shaped, class of microresonators with broken angular momentum symmetry. We develop the description of scattering in such resonators and demonstrate their fundamental difference from circular systems. The ratchet structures do not support any stable ray trajectories, and therefore no ``conventional'' whispering-gallery mode can exist in these systems. However, the long-lived (high-Q) modes do exist in the ratchet resonator and are exponentially localized in the angular momentum space, explicating Anderson dynamical localization. We demonstrate that in contrast to conventional microdisks, the proposed system has a low leakage loss accompanied with strong coupling to the incident radiation. This, in turn, leads to orders-of-magnitude performance advantage of the devices based on ratchet resonators over the conventional systems. [Preview Abstract] |
Saturday, May 14, 2005 4:13PM - 4:25PM |
G3.00007: Three Photon Absorption and the Nonlinear Index of Refraction in GaAs Walter Hurlbut, Bryan Norton, Naaman Amer, Jeremy Danielson, Yun-Shik Lee, Konstantin Vodopyunov, Martin Fejer, Vladimir Koslov We demonstrate and quantitatively measure the previously unknown nonlinear absorption and refraction in GaAs in the spectral range from 1200 to 2630 nm using the Z-Scan Technique. We measured the transmission of the femtosecond pulses tightly focused on a 350-$\mu$m-thick GaAs wafer as a function of incident pump intensity by scanning the sample position with respect to the focal plane. The intensity dependent two-photon and three photon absorption coefficients are obtained by analyzing the data. The nonlinear index of refraction, n$^{2}$, is acquired by the closed-aperture z-scan in which a small aperture in the far field is inserted and the self-lensing was measured by the change in on-axis transmittance. Scaling rules based on a quasi-dimensional analysis confirms the experimental results. [Preview Abstract] |
Saturday, May 14, 2005 4:25PM - 4:37PM |
G3.00008: Simulating Compsosite Materials with Giant Anisotropy Justin Elser, Evgenii Narimanov, Viktor Podolskiy We study the optical properties of a novel class of composite materials based on plasmonic nanostructures embedded into a dielectric host. Due to the phenomena of plasmon resonance, the plasmonic inclusions have a dramatic effect on the effective dielectric constant of the system even when the concentration of inclusion is small. We develop a numerical technique to simulate these structures, and compare the numerical results to the generalized Maxwell-Garnett predictions. We demonstrate that in contrast to most bulk media where the difference between the values of dielectric constant in different directions is of the order of a few percent, the effective anisotropy of the proposed structures can exceed 100{\%}. Proposed applications include polarizers, reflectors, high-energy-density nano-waveguides, and the recently discovered non-magnetic low-loss left-handed media. [Preview Abstract] |
Saturday, May 14, 2005 4:37PM - 4:49PM |
G3.00009: Non-Magnetic Negative Refraction Index Materials Robyn Wangberg, Evgenii Narimanov, Viktor Podolskiy Novel phenomena in recently discovered materials with a negative refraction index include inversed Doppler Effect, reversal of Snell law, subwavelength imaging, and reversed Cherenkov radiation. The conventional designs to build these exciting media typically require simultaneously negative values of dielectric permittivity and magnetic permeability, and often rely on resonance to achieve the non-trivial magnetic response. This resonance leads to large losses in the system and makes the present negative-n materials almost impractical. In this work we develop a new approach to build a material with negative index of refraction. In contrast to conventional designs, our material is intrinsically non-magnetic and uses an anisotropic dielectric constant to provide a negative-n (left-handed) behavior in waveguide geometry. We describe optical properties of the proposed structure and its realizations for frequency ranges from GHz to THz to infrared to optics. We also illustrate the effect of finite conductance waveguide walls on the electromagnetic properties of the system. [Preview Abstract] |
Saturday, May 14, 2005 4:49PM - 5:01PM |
G3.00010: Minimum Beam Size of a Lens Exhibiting 3rd Order Spherical Aberrations Thomas Jones, Jens Elstner, Robert Word, Gertrude F. Rempfer, Rolf Koenenkamp In the field of electron microscopy, an important property is the minimum beam waist that electron beams can be focused to. The two main effects that determine this parameter are spherical aberration and diffraction. The goal of electron lens designers is to minimize these two effects. To accomplish this task the two effects are assumed to be independent of one an another and thus their deviations can be added in quadrature to determine the minimum beam size and the aperture angle for which this occurs. We have used an alternative method that makes no assumptions about the independence of the effects of spherical aberrations and diffraction. The method is based on a wavemechanical determination of the image intensity distribution. We calculate the optimum aperture angle and the minimum beam waist by numerically integrating the relevant Fresnel integrals incorporating third order aberration effects. Our values differ from those obtained in the conventional method that assumes the independence of spherical aberration and diffraction. [Preview Abstract] |
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