Bulletin of the American Physical Society
2019 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 64, Number 18
Friday–Saturday, October 25–26, 2019; Lubbock, Texas
Session E01: Atomic, Molecular, and Optical Physics |
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Chair: Yannis Chatzakis, Texas Tech University Room: Student Union Building Canyon Room |
Friday, October 25, 2019 1:30PM - 1:42PM |
E01.00001: Spectral X-ray Scatter Correction with an Energy Resolved Photon-Counting Detector Cale Lewis, Mini Das Photon-counting detectors (PCDs) with energy-resolving capabilities are being investigated for x-ray imaging in medical applications. The spectral information obtained with PCDs allow for quantitative material identification of structures within the imaged object. Radiation that scatter from the object obscures the transmitted primary intensity and impedes accurate material identification. Although scatter correction methods have been widely developed for conventional energy-integrating detectors (EIDs), the spectral impact of the object scatter is only recently being investigated. We have explored the effectiveness of a scatter correction method previously designed for conventional EID imaging when applied to spectral imaging with PCDs. This technique relies on a scatter map database generated from homogeneous slabs of varying thickness with equivalent material and geometry as the object. Subtracting the object projection by the appropriate scatter map improves the image quantification. This practical technique provides an effective scatter correction without relying on additional exposure to the patient. [Preview Abstract] |
Friday, October 25, 2019 1:42PM - 1:54PM |
E01.00002: Understanding Quantum Defect Theory for Cold Atoms and Molecules Alyson Laskowski Interactions between ultracold diatomic molecules are characterized by a deep potential energy well at short range, with a shallow long-range tail that prevails to large molecular separation. Quantum defect theory (QDT) exploits this separation of length and energy scales so that in the simplest single-channel approximation, one parameter which is weakly dependent on energy, the \textit{quantum defect}, can be used to describe the short-range properties of the collision. The quantum defect can either be calculated numerically from an \textit{ab initio }method or found from the solution of an effective short-range potential designed such that it reproduces the essential short-range physics. The long-range solutions are efficiently found using the Milne phase amplitude method. We present simple single-channel QDT models that make use of this separation of length and energy scales to treat real properties of ultracold atomic and molecular collisions. [Preview Abstract] |
Friday, October 25, 2019 1:54PM - 2:06PM |
E01.00003: Study of the optical absorption of metallic surfaces coated with a VO2 thin layer Ahmad Khayyat Jafari Optical coatings are key components in modern optoelectronic devices such as smart windows. One of the materials which have recently found some applications as a uniform or patterned layer in optical devices is vanadium dioxide (VO$_{\mathrm{2}})$. The optical properties of VO$_{\mathrm{2}}$ change when it undergoes phase transformation from an insulating to a metallic phase near 68 $^{\mathrm{0}}$C. This phase transformation is accompanied by a crystalline structural change from monoclinic to tetragonal provides a unique opportunity for designing photonic devices with tunable optical properties which can be employed as a passive radiative cooling coating. In all these applications, the effect of the VO$_{\mathrm{2}}$ coating layer thickness on the absorption spectrum is of great significance which has been not explored in any detail. In this work, we numerically investigated the absorption of a single thin VO$_{\mathrm{2}}$ layer on different metallic films over a wide range of wavelengths at normal and oblique incident angles. We found that in the insulating phase, the air/VO$_{\mathrm{2}}$/metal structure can be considered as an asymmetric Fabry-Perot resonant cavity which resonant absorption wavelength depends on both the VO$_{\mathrm{2}}$ layer thickness and the type of metallic layer. In the metallic phase, there is always a narrow wavelength region with zero reflection which is independent of the of the metallic layer. [Preview Abstract] |
Friday, October 25, 2019 2:06PM - 2:18PM |
E01.00004: Raman scattering from magnetic excitations in CrI3 atomic layers Zhipeng Ye, Pouyan Rezaie, Fabian Diaz, Saad Siddiq, Eric Eric, Rui He, Hyun Ho Kim, Bowen Yang, Adam Tsen, Wencan Jin, Siwen Li, Liuyan Zhao Two-dimensional (2D) magnetism has been long sought-after and only very recently realized in atomic crystals of magnetic van der Waals materials. So far, a comprehensive understanding of the magnetic excitations in such 2D magnets remains missing. Here we report polarized micro-Raman spectroscopy studies on a 2D honeycomb ferromagnetic CrI3. Two sets of magnetic excitations at frequencies of 76 and 125 cm-1 are observed in CrI3 atomic layers down to the monolayer limit. By tracking the thickness dependence of both modes from magnetic excitations, we reveal that both are surface modes. Our results demonstrate intriguing spin dynamics and intricate interplay with fluctuations in the 2D limit, thus opening up opportunities for spintronics applications incorporating 2D magnets. [Preview Abstract] |
Friday, October 25, 2019 2:18PM - 2:30PM |
E01.00005: An unorthodox study of bidirectional light waves Ankit Pandey, Bill Poirier, Luis Peralta, Muhammad Siddique, Yu-Che Ho, Hira Farooq We consider linear superpositions of electromagnetic waves of similar frequencies, moving in opposite directions. Surprisingly, these superpositions have a lot more complexity than what has been reported in the literature. On the one hand, it is fairly intuitive that one should expect to see slowly translating standing waves. This feature may have its own applications in precise control of nanoparticles. An experiment to observe these is underway. On the other hand, a hardly studied superluminal wave is observed, which has startling parallels with quantum mechanics. An effective ``rest mass'', which is relativistically invariant, can be assigned to these bidirectional waves. This in itself is surprising, because the unidirectional electromagnetic wave components are themselves massless. Further, the superluminal wavelength is found to be exactly the same as the relativistic de Broglie wavelength. The subluminal (standing) waves on the other hand, have exactly the same wavelength as the corresponding Compton wavelength, thus having parallels with the Zitterbewegung oscillations of the Dirac equation. Finally we show that, by considering small non-linear modifications of the electromagnetic wave equation, it is possible to end up with Schrodinger-like solutions. [Preview Abstract] |
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