Bulletin of the American Physical Society
2018 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 63, Number 18
Friday–Saturday, October 19–20, 2018; University of Houston, Houston, Texas
Session E03: Atomic, Molecular, and Optical Physics |
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Chair: John Wilson, Sam Houston State University Room: Science and Engineering Classroom (SEC) 203 |
Friday, October 19, 2018 4:15PM - 4:27PM |
E03.00001: Spectroscopic and theoretical investigations of π-type intramolecular hydrogen bonding of 3-cyclopenten-1-ol and 3-cyclopenten-1-amine Esther Juliana Ocola, Jaan Laane The infrared and Raman spectra of 3-cyclopenten-1-ol (3CPOL) and 3-cyclopenten-1-amine (3CPAM) have been recorded and analyzed. Theoretical CCSD/cc-pVTZ computations have also been carried out. Both molecules can exist in six different conformers, two pairs of which are mirror images of each other. 3CPOL has a conformer that possesses an OH group which forms a π-type hydrogen bond with the C=C double bond across the five-membered ring. 3CPAM has two NH2 mirror image conformers with a π-type hydrogen bond with the C=C double bond across the ring. The theoretical computations indicate that for 3CPOL and 3CPAM these π bonding conformations lie about 300 cm-1 (for 3CPOL) and 200 cm-1 (for 3CPAM) lower in energy than the minima for the other conformers. The vapor-phase infrared and Raman spectra of both molecules show the presence of all of the predicted conformers and their frequency differences correspond well to those predicted by the theoretical computations. |
Friday, October 19, 2018 4:27PM - 4:39PM |
E03.00002: Quantitative phase retrieval of multi-material heterogeneous objects from spectral X-ray measurements Ivan Vazquez, Mini Das We recently proposed a simple yet robust method to retrieve the complete refractive properties of a sample from a single phase-enhanced spectroscopic X-ray measurement, which can be obtained using photon counting detectors. The idea was demonstrated via simulations and bench-top lab experiments for two prominent phase contrast imaging techniques, i.e. free-space propagation and coded aperture. Unlike some popular alternatives, our method is not restricted to overly simplified geometries and homogeneous materials in order to yield quantitative results. The only requirement is a set of well-constrained values that accurately describe the effective energies corresponding to each measurement. A persisting challenge with this approach relates to the photon count starvation caused by energy binning, which typically deteriorates the signal-to-noise ratio of the data. Another challenge involves the accuracy of retrieved quantities when dealing with heterogeneous objects, particularly when different constituents demonstrate significantly different properties. This work will illustrate how our technique and its implementation address these two problems. |
Friday, October 19, 2018 4:39PM - 4:51PM |
E03.00003: Mid-infrared methane sensor system using self-adaptive interband cascade laser absorption spectroscopy. Fang Song, Chuantao Zheng, Frank K Tittel In order to suppress sensor noises with unknown statistical property, a novel self-adaptive direct laser absorption spectroscopy (SA-DLAS) technique was proposed in a 3.291 µm continuous-wave (CW) interband cascade laser (ICL) based mid-infrared methane (CH4) sensor system. Background noises can be well evaluated and suppressed by introducing an additional electrical-domain noise-channel and a modern expectation-known-based recursive least square (RLS) self-adaptive denoising (SAD) algorithm. Both numerical simulations and experiments were carried out to study the SA-DLAS sensor’s denoising and gas detection performances by imposing low-frequency/high-frequency/White-Gaussian/composite noises on the laser scan signal. Both indoor and outdoor atmospheric CH4 measurements were conducted to evaluate the field sensor performance. Under an unknown noise environment, the reported SA-DLAS technique shows enhanced sensitivity and reliability compared to a DLAS sensor using classic sensing architecture and filtering method, which can also be extended to other infrared gas sensing applications. |
Friday, October 19, 2018 4:51PM - 5:03PM |
E03.00004: Anomaly on quantum gases in one and two dimensions Carlos R. Ordóñez, Chris L Lin, Wilder S Daza Romero, Joaquin Drut Nonrelativistic quantum scale anomalies have recently received some attention in the AMO community, especially in the context of cold atoms. Based on previous formal work by H. Camblong (USF) and C. Ordonez, in 2015 it was proposed a systematic study of anomalous effects in such systems using path integrals, with the initial emphasis on the thermodynamics of 2D systems. After several formal studies, a recently developed framework for the understanding of the virial expansion in homogeneous 2D gases (Fermions in particular). This framework helped us develop a description of anomalies in 1D, 3-body Fermionic systems. The purpose of this talk is to give a review of the conceptual background and philosophy of our approach and of recent results, as well as of current and future collaborations and projects. |
Friday, October 19, 2018 5:03PM - 5:15PM |
E03.00005: Chemical Surface-Enhanced Coherent Raman Scattering by Semiconductor Nanoparticles Anton D. Shutov, Zhenhuan Yi, Jizhou Wang, Alexander M. Sinyukov, Zhe He, Chenwei Tang, Jiahao Chen, Esther J. Ocola, Jaan Laane, Alexei V. Sokolov, Dmitri V. Voronine, Marlan O. Scully Raman spectroscopy is a powerful tool for molecular chemical analysis and bio-imaging, which shows an astonishing sensitivity when combined with huge enhancement by the coherence and surface effects. Typically, the surface enhancement is provided by two mechanisms: electromagnetic (EM), i.e. an enhancement of local electric fields, and chemical (CM) enhancement due to the interaction between an analyte and colloidal nanoparticles (NPs). Noble metal NPs have been commonly used for the surface-enhanced coherent anti-Stokes Raman scattering (SECARS) spectroscopy, as they provide large enhancement factors predominantly via the EM mechanism. In turns, the cheaper semiconductor NPs can be a great substitute for noble metals in SECARS applications. In this work, we demonstrate the time resolved SECARS on the pyridine-ethanol solution, containing molybdenum disulfide (MoS2) nanocrystals and investigate the enhancement provided by these semiconductor NPs. We show that the pure CM enhancement factor can be as high as 109. The decreased vibrational dephasing times indicate the charge transfer in pyridine-ethanol-MoS2 system. |
Friday, October 19, 2018 5:15PM - 5:27PM |
E03.00006: Comparing Material Decomposition Methods using Dual Energy Subtraction and Spectral Computed Tomography Ian E Harmon, Nathaniel R Fredette, Mini Das Material decomposition using spectral computed tomography (CT) and dual energy subtraction methods can both be utilized in medical imaging to better discern a sample containing multiple different materials. These two methods are able to give an estimate of material attenuation of an object over specified energy ranges, while conventional CT and x-ray imaging only give an estimate of x-ray attenuation of an object over all x-ray energies. The additional information can be utilized in post-processing operations like material decomposition, which can reveal more information about the object than conventional methods. Spectral CT and dual energy subtraction are both methods used which provide enhanced interpretation of an attenuation image of an object, but both have differing data collection methods and resultant images. Both methods will acquire data on a sample containing three different materials using a Medipix3RX Silicon photon counting detector which was developed at CERN. With these two results we can compare how well each method is able to discern multiple different materials within the same object. |
Friday, October 19, 2018 5:27PM - 5:39PM |
E03.00007: Spectral X-Ray Scatter Characterization with an Energy Resolved Photon Counting Detector Cale Lewis, Mini Das Photon counting detectors with energy-resolving capabilities are being investigated for x-ray imaging in medical applications. Biological materials have only minor differences in their spectral attenuation properties, and therefore accurate estimations rely on the precise measurement of the transmitted x-ray beam. Scattered x-rays reaching the detector reduce image quality and distort the measured energy spectrum, contributing additional photon counts to lower energies. Previous work characterizing x-ray scatter has been limited to conventional energy-integrating detectors, which do not provide spectral information. Our work provides a detailed investigation of the spectral contributions of x-ray scattering from biological-equivalent material using energy-resolving photon counting detectors. We show that spectral distortions due to the object scatter produce large quantitative inaccuracies, particularly at low energies where image contrast is optimal. These spectral distortions are reduced by increasing the distance between the scattering sample, though remain unsatisfactory for sample thicknesses relevant to mammography. |
Friday, October 19, 2018 5:39PM - 5:51PM |
E03.00008: Single-Exposure Contrast Enhanced Spectral Mammography Raul Torrico, Mini Das Contrast enhanced mammography exploits the K-edge, a sharp increase in the x-ray attenuation coefficient, of contrast agents for improved tumor detection. Conventionally, the process involves the subtraction of two separate exposures from a high and low energy spectra. We propose and demonstrate the use of electronic energy thresholds in a photon counting spectral detector in lieu of multiple exposures, thereby potentially allowing for single-exposure contrast enhanced mammography. A weighted logarithmic subtraction technique is applied to remove the soft tissue background and obtain the contrast enhanced image. We also studied the effects of aluminum filtration on the contrast enhanced image. We use the integral mode data and effective attenuations to estimate suitable weights in this contrast enhanced imaging. This idea is demonstrated using the Medipix3RX detector with CdTe sensor and an iodinated contrast phantom of up to 10 mg/ml with PMMA as the background material. Further studies will involve the use of an anthropomorphic breast phantom as well as the testing of lower iodine concentrations and dose benefit investigations. |
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