Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T31: Scattering Science and MethodsRecordings Available
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Sponsoring Units: GIMS Chair: Alex Frano, UC San Diego Room: McCormick Place W-192A |
Thursday, March 17, 2022 11:30AM - 11:42AM |
T31.00001: Calculation of Polarized Neutron Scattering Cross Sections from Prototypical Spin-Manipulated Hyperpolarized Molecules in Solution Michael Kotlarchyk, George M Thurston We present preliminary results for calculated angular cross sections of polarized thermal neutrons scattered from prototypical molecules that are hyperpolarized and spin-manipulated (via NMR techniques) in solution. Such molecules include, for example, pyridine or methyl nicotinate, for which it has already been proven that high degrees of nuclear spin hyperpolarization are achievable at room temperature through polarization transfer from para-hydrogen (1). We investigate these cross sections, and on an absolute scale, for both neutron spin-flip and no-spin-flip cases since we have already predicted (2) that experiments combining these two scenarios can yield partial structure factors that would be useful for determining distances between user-selected nuclei. We demonstrate some calculated cross sections and resulting partial structure factors for representative molecules with varying degrees of initial hyperpolarization. Preliminary calculations that incorporate the effects of T1 spin relaxation on the scattering signal will also be discussed. |
Thursday, March 17, 2022 11:42AM - 11:54AM |
T31.00002: A High Power ESR Spectrometer for Microwave Stimulated Neutron Scattering Timothy Reeder, Jonas Kindervater, Veronica Stewart, Qiang Ye, Yiming Qiu, Jose A Rodriguez, Yamali Hernandez, Nicholas Maliszewskyj, Tyrel M McQueen, Collin L Broholm The physical properties of magnetic condensed matter systems are typically measured while the sample is in thermal equilibrium with its surroundings. We describe the commissioning of a high power, high frequency microwave spectrometer designed to drive magnetic phases out of equilibrium while measuring the inelastic neutron scattering spectrum. A 105 (210) GHz signal is generated at 1 (0.3) W, and directed through a compact, 3D quasi-optical bridge to the sample. By tuning to a resonance condition with a magnetic field, we are able to select our excitation of interest. Reflected microwaves are detected by a heterodyne mixer, and a Martin Puplett Interferometer on the bridge isolates the reflected signal into co-polarized and cross-polarized channels. This unique design allows for compatibility with many top loading magnet systems, the power to induce a statistically significant population inversion required for neutron scattering, and the ability to do Pulsed Electron Spin Resonance experiments as a standalone unit. Performance of the system is shown by Saturation Recovery on a single crystal of Ruby with 0.05% Cr/Al by weight. |
Thursday, March 17, 2022 11:54AM - 12:06PM |
T31.00003: Use of Molecular Dynamics Simulations to Study Signal-to-Noise Aspects for obtaining Polarized Neutron Scattering Cross Sections from Spin-Manipulated Hyperpolarized Molecules in Solution* George M Thurston, Pratik P Dholabhai, Michael Kotlarchyk We use molecular dynamics (MD) simulations of methyl nicotinate in methanol to calculate angular cross sections of polarized thermal neutrons scattered from hyperpolarized and spin-manipulated molecules (via NMR techniques) in solution. Methyl nicotinate is a prime candidate because very high nuclear spin hyperpolarization has been attained through polarization transfer from para-hydrogen (1). Using MD simulations, we study these cross sections on an absolute scale and in the presence of simulated detector noise. This permits study of combinations of methyl nicotinate concentration, state of polarization, sample size, geometry, neutron flux, experiment duration, detector configuration, and detector efficiency that provide for signals that permit measuring site-site correlation functions between NMR-selected, hyperpolarized methyl nicotinate nuclei. To do so we use cross sections established for neutron spin-flip and no-spin-flip cases (2). We study prospects for obtaining useful signals from current neutron scattering sources, suitably configured. |
Thursday, March 17, 2022 12:06PM - 12:18PM |
T31.00004: Relating the aerosol particle structure to the particle transport properties using ultra small angle X-ray scattering Kabir Rishi, Greg Beaucage, Bon-Ki Ku, Pramod Kulkarni The structure and morphology of airborne particles has a significant effect on its transport properties and deposition characteristics in human respiratory systems. A number of studies have investigated fractal characteristics of aerosol particles and their mobility equivalent diameters, particularly the proportionality between the mobility size and fractal dimension,1-6 however, the impact of the fractal topology7,8 that includes the branch content, branch length, aggregate mass, and size have not yet been explored. The objective of this study was to probe the fractal structure of aerosol agglomerates using USAXS and application of the Kirkwood-Riseman theory9 using a recently developed monomer-cluster growth simulation10. For this purpose, size classified nanoaggregates of silver generated in a laboratory and commercial fumed silica with mobility sizes smaller than 200 nm were examined using X-ray scattering. Correlations between the fractal structure from USAXS, the theoretically estimated mobility size and experimentally measured mobility size will be reported. |
Thursday, March 17, 2022 12:18PM - 12:30PM |
T31.00005: Multislice model to simulate Grazing Incidence Small Angle X-ray Scattering (GISAXS) of micro-scale patterns Peco Myint, Ashish Tripathi, Jiang Zhang, Miaoqi Chu, Jin Wang, Suresh Narayanan Multislice simulations are widely used in transmission geometry electron microscopy and X-ray transmission experiments such as conventional lensless X-ray coherent diffraction imaging (CDI). To study nanostructures on thick substrates, a reflection-geometry scattering technique such as Grazing Incident Small Angle X-ray Scattering (GISAXS) is required. Here, we prove that multislice simulations are also applicable to the GISAXS geometry and can reproduce dynamical scattering from multiple layers on substrate. We took GISAXS images of many micro-scale multi-layered 3D patterns and simulated the scattering patterns using the multislice formalism. |
Thursday, March 17, 2022 12:30PM - 12:42PM |
T31.00006: Automated Laue pattern analysis for multi-grain strain imaging of nanocrystals at 34-ID-C Yueheng Zhang, Matthew Wilkin, Anastasios Pateras, Ross J Harder, Wonsuk Cha, Anthony D Rollett, Richard L Sandberg, Robert M Suter, Reeju Pokharel, Saryu Fensin The 34-ID-C beamline of the Advanced Photon Source recently acquired the capability to conduct Laue diffraction for indexing arbitrarily oriented nanocrystals [1], thus, facilitating the collection of Bragg coherent diffraction imaging (BCDI) data from multiple Bragg reflections and reconstructing the volumetric six-component Eulerian strain tensor [2]. A polychromatic (pink) x-ray beam illuminates a single nanocrystal, or cluster of crystals, causing multiple reflections to simultaneously fulfill the Bragg condition casting a unique Laue pattern on a pixel array. When many grains are simultaneously illuminated, multiple Laue patterns appear on the detector and must be separately indexed. We developed a workflow for beamline users that automates the analysis of overlapping Laue patterns. We demonstrate our algorithms with synthetic data and verify them by comparing the result of indexing Laue patterns recorded from a patch of arbitrarily oriented gold nanocrystals with the results from electron back-scattering diffraction. Such tools will provide reliable indexing of grains of polycrystalline materials and allow us to probe embedded grains with BCDI experiments, at a scale that is challenging for other techniques. |
Thursday, March 17, 2022 12:42PM - 12:54PM |
T31.00007: Real-space recovery and super-resolution of ultrafast scattering and diffraction using natural scattering kernels Adi Natan Directly resolving in real-space multiple atomic motions using ultrafast x-ray scattering or ultrafast electron diffraction is generally limited by the finite detector range. As a result, signal interpretation mostly relies on modeling and simulations of specific excitation pathways. Here, we demonstrate a model-free approach to resolve ultrafast diffuse scattering signals in real space and recover multiple atomic motions that take place simultaneously. We introduce a scattering basis representation that is composed of the measurement parameters and constraints and the subsequent inversion analysis. We then leverage signal priors, such as smoothness and sparsity to deconvolve and super-resolve the spatially transformed signals using convex optimization. We validate the approach on simulated data with detection limits similar to X-ray free-electron laser experiments and discuss the resolution limits and noise dependence on the accuracy of the recovery. This approach may bridge the widely used pair-distribution function analysis that requires much higher momentum transfer ranges with ultrafast X-ray scattering and electron diffraction experiments that are done in advanced light sources such as the LCLS. |
Thursday, March 17, 2022 12:54PM - 1:06PM |
T31.00008: Automated polarization control for application in time-resolved second harmonic generation experiments Karna Morey, Bryan T Fichera, Baiqing Lyu, Nuh Gedik Rotational anisotropy second harmonic generation (RA-SHG) is a non-linear optical technique used to probe condensed matter systems. In order to fully fit the independent components of the SHG susceptibility tensor, both S and P polarized input and output combinations need to be measured, meaning that the incoming and outgoing polarizers need to be physically rotated to realize all the physically meaningful polarization combinations. However, doing this rotation manually takes time and adds significant labor costs to taking data, especially when taking time-resolved data. We implement automated polarization rotators for use in time-resolved RA-SHG, in order to improve the technique’s robustness to low-frequency noise. Instead of sweeping the polarizations sequentially, automated polarization rotation allows for repeatedly toggling between polarization combinations, allowing averaging of a particular polarization combination over long timescales. These polarization rotators utilize small stepper motors within the rotating RA-SHG setup and demonstrate high fidelity in time-resolved RA-SHG experiments. We show this system's functionality in time-resolved RA-SHG in the test-sample GaAs. |
Thursday, March 17, 2022 1:06PM - 1:18PM |
T31.00009: Charge-orbital ordering in A-site ordered NdBaMn2O6 perovskite Md Shafiqul Islam, Daisuke Morikawa, Shigeki Yamada, Kenji Tsuda, Masami Terauchi A-site ordered perovskite-type manganites RBaMn2O6 (R= La, Pr, Nd, Sm, Tb) have attracted considerable attention in recent years because mutual interaction among charge, orbital, and spin degrees of freedom cause wide range of structural and physical properties. Unlike others, NdBaMn2O6 perovskite is unique for its multicritical feature and multiple phase transitions. So far, X-ray diffraction study determine the space-group as P4/mmm, Cmmm, and P21am at 450 K, 300 K, and 100 K, respectively [1]. The structure determined at low temperature (LT≈100 K) phase has a single Mn site, suggesting no charge ordering but exhibits dx2-y2 orbital ordering in the ab-plane. However, recently J. Blasco et al., report that there is no charge-orbital ordering at the LT phase [2]. In this study, we investigate the structures and electron densities to understand the charge and orbital ordering pattern at the mentioned three different temperature phases by combination of convergent-beam electron diffraction and density functional theory. We find that the LT phase has four nonequivalent Mn sites, suggesting charge ordering and the compression of octahedra indicates dx2-y2 orbital ordering. |
Thursday, March 17, 2022 1:18PM - 1:30PM |
T31.00010: A machine learning inversion scheme for determining effective interaction of charged colloidal suspensions using scattering Chi-Huan Tung, Ming-Ching Chang, Shou-Yi Chang, Jan-Michael Y Carrillo, Yangyang Wang, Bobby G Sumpter, GUAN-RONG HUANG, Changwoo Do, Wei-Ren Chen We outline a machine learning strategy for determining the effective interaction of charged colloidal suspensions using scattering. We showed that the effective potential can be probabilistically inferred from the scattering spectra without any restriction imposed by model assumptions. Comparisons to existing parametric approaches demonstrate the superior performance of this method in accuracy, efficiency, and applicability. This method can effectively enable quantification of interaction in highly correlated systems using scattering and diffraction experiments. |
Thursday, March 17, 2022 1:30PM - 1:42PM |
T31.00011: Dual Measurements of Temporal and Spatial Coherence of Light using a Single Experimental Setup Shouvik Datta, Mohit K Singh Temporal coherence is commonly measured with Michelson and Mach-Zehnder interferometers, whereas for spatial coherence measurement, Young’s double slit interferometer is typically used. However, it is not easy to place double slits with variable slit widths and slit separations within a cryostat in close proximity of the sample for spatial coherence measurements at cryogenic temperatures. Here we report an experimental technique to simultaneously measure both temporal and spatial coherences of a light source by altering a Michelson interferometer. Instead of using simple plane mirrors, two retroreflectors and their longitudinal and lateral movements are utilized to incorporate spatial coherence measurement using this modified Michelson interferometer. This modified interferometer can be kept at room temperature outside a cryostat to measure spatio-temporal coherence of a light source placed at cryogenic temperatures. This avoids the added complexities of modulation of interference fringe patterns due to single slit diffraction as well. The process of mixing of spatial-temporal parts of coherences is addressed using a method of ‘temporal filtering’. Similarly, ‘curve overlap’ method is designed to extend the range of the experimental setup without compromising the precision. |
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