Separating Non-Linear Optical Signals Of A Sample From High Harmonic Radiation In A Soft X-Ray Free Electron Laser,
2022
The University of Tokyo
Separating Non-Linear Optical Signals Of A Sample From High Harmonic Radiation In A Soft X-Ray Free Electron Laser, Toshihide Sumi, Masafumi Horio, Tomoaki Senoo, Tetsuya Wada, Yuki Tsujikawa, Xiaoni Zhang, Paul Manset, Mihoko Araki, Yasuyuki Hirata, Walter S. Drisdell, John W. Freeland, Angelique Amadno, Michael Zuerch, Yuya Kubota, Shigeki Owada, Kensuke Tono, Makina Yabashi, Craig P. Schwartz, Iwao Matsuda
Nevada Extreme Conditions Laboratory Faculty Research
Second harmonic generation (SHG) is a unique non-linear optical effect that can be used to investigate chemical states of molecules at surfaces/interfaces. By the use of soft X-rays, SHG gains element selectivity through the inner-core excitation resonance. However, it is challenging to observe SHG signals separately from the second-order light generated from the undulator. Here, we report a new ellipsometry method for soft X-ray SHG to suppress the contribution of second-harmonic radiation from the light source. Through measurements of a GaAs(100) crystal, we demonstrate that pure SHG signals can be obtained for the horizontally polarized component. The present method is …
Cu2+ And Cu3+ Acceptors In Β-Ga2O3 Crystals: A Magnetic Resonance And Optical Absorption Study,
2022
Air Force Institute of Technology
Cu2+ And Cu3+ Acceptors In Β-Ga2O3 Crystals: A Magnetic Resonance And Optical Absorption Study, Timothy D. Gustafson, Nancy C. Giles, Brian C. Holloway, Christopher A. Lenyk, J. Jesenovec, J. S. Mccloy, M. D. Mccluskey, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) and optical absorption are used to characterize Cu2+ (3d9) and Cu3+ (3d8) ions in Cu-doped β-Ga2O3. These Cu ions are singly ionized acceptors and neutral acceptors, respectively (in semiconductor notation, they are Cu− and Cu0 acceptors). Two distinct Cu2+ EPR spectra are observed in the as-grown crystals. We refer to them as Cu2+(A) and Cu2+(B). Spin-Hamiltonian parameters (a g matrix and a 63,65Cu hyperfine matrix) are obtained from the angular dependence of each spectrum. Additional electron-nuclear double resonance …
Atomistic Simulation Of Na+ And Cl- Ions Binding Mechanisms To Tobermorite 14Å As A Model For Alkali Activated Cements,
2022
The American University in Cairo AUC
Atomistic Simulation Of Na+ And Cl- Ions Binding Mechanisms To Tobermorite 14Å As A Model For Alkali Activated Cements, Ahmed Abdelkawy
Theses and Dissertations
The production of ordinary Portland cement (OPC) is responsible for ~8% of all man-made CO2 emissions. Unfortunately, due to the continuous increase in the number of construction projects, and since virtually all projects depend on hardened cement from the hydration of OPC as the main binding material, the production of OPC is not expected to decrease. Alkali-activated cement produced from the alkaline activation of byproducts of industries, such as iron and coal industries, or processed clays represents a potential substitute for OPC. However, the interaction of the reaction products of AAC with corrosive ions from the environment, such as Cl-, …
Morphological Phenotypes, Cell Division, And Gene Expression Of Escherichia Coli Under High Concentration Of Sodium Sulfate,
2022
University of Arkansas, Fayetteville
Morphological Phenotypes, Cell Division, And Gene Expression Of Escherichia Coli Under High Concentration Of Sodium Sulfate, Khanh Nguyen, Pradeep Kumar
Physics Faculty Publications and Presentations
Sodium and sulfate ions are among the suggested abundant ions on Europa, a moon of Jupiter. In order to investigate the potential habitability of Europa, we study the effects of sodium sulfate (Na2SO4) on a non-halophilic bacterium by subjecting Escherichia coli (E. coli) to a wide range of Na2SO4 concentrations (0–1.0 m). We discover that, as the concentration of sodium sulfate increases, the biomass doubling time increases and the cell growth is completely inhibited at 1.0" role="presentation" style="box-sizing: border-box; max-height: none; display: inline; line-height: normal; font-size: 13.2px; text-align: left; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: …
Development Of Advanced Machine Learning Models For Analysis Of Plutonium Surrogate Optical Emission Spectra,
2022
Air Force Institute of Technology
Development Of Advanced Machine Learning Models For Analysis Of Plutonium Surrogate Optical Emission Spectra, Ashwin P. Rao, Phillip R. Jenkins, John D. Auxier Ii, Michael B. Shattan, Anil K. Patnaik
Faculty Publications
This work investigates and applies machine learning paradigms seldom seen in analytical spectroscopy for quantification of gallium in cerium matrices via processing of laser-plasma spectra. Ensemble regressions, support vector machine regressions, Gaussian kernel regressions, and artificial neural network techniques are trained and tested on cerium-gallium pellet spectra. A thorough hyperparameter optimization experiment is conducted initially to determine the best design features for each model. The optimized models are evaluated for sensitivity and precision using the limit of detection (LoD) and root mean-squared error of prediction (RMSEP) metrics, respectively. Gaussian kernel regression yields the superlative predictive model with an RMSEP of …
Preparing A Gamma Ray Instrument For Space Flight,
2022
University of Alabama in Huntsville
Preparing A Gamma Ray Instrument For Space Flight, Peter A. Jenke, Michael Briggs
Summer Community of Scholars (RCEU and HCR) Project Proposals
No abstract provided.
Polarimetric Characterization Of Unique Optical Elements,
2022
University of Alabama in Huntsville
Polarimetric Characterization Of Unique Optical Elements, Don A. Gregory
Summer Community of Scholars (RCEU and HCR) Project Proposals
No abstract provided.
Design Of A High-Power Terahertz Emitter Array Using A High-Temperature Superconductor,
2022
University of Central Florida
Design Of A High-Power Terahertz Emitter Array Using A High-Temperature Superconductor, Ruqayyah Shouk
Electronic Theses and Dissertations, 2020-2023
By applying a dc voltage V across the stack of intrinsic Josephson junctions naturally present in the high-temperature superconductor consisting of two parts bismuth, two parts strontium, one part calcium, two parts copper, and a bit more than eight parts oxygen, several groups have been able to obtain coherent THz emission at output powers in the µW range. In order to enhance the output power well into the mW range suitable for many applications, we have studied a compact design of a stand-alone mesa array with gold layers on the top and bottom of the superconductor. In this design, an …
Imaging Based Beam Steering For Optical Communication And Lidar Applications,
2022
University of Central Florida
Imaging Based Beam Steering For Optical Communication And Lidar Applications, Sajad Saghaye Polkoo
Electronic Theses and Dissertations, 2020-2023
Optical beam steering is a key component in any application that requires dynamic (i.e. realtime control) of beam propagation through free-space. Example applications include remote sensing, spectroscopy, laser machining, targeting, Lidar, optical wireless communications (OWC) and more. The pointing control requirements for many of these applications can be met by traditional mechanical steering techniques; however, these solutions tend to be bulky, slow, expensive, power hungry and prone to mechanical failures leading to short component lifetimes. Two emerging applications, Lidar imaging and OWC, truly need improved beam-steering capabilities to flourish and support the advancement of self-driving cars or relieve the congestion …
Characterization Of Nanoparticles Using Inductively-Coupled Plasma Mass Spectrometry,
2022
Missouri State University
Characterization Of Nanoparticles Using Inductively-Coupled Plasma Mass Spectrometry, Jabez D. Campbell
Graduate Theses/Dissertations
Nanomaterials are a relatively new class of materials that have many applications which span a wide host of fields from medical products to consumer products. The possible compositions and forms of nanomaterials are just as varied as the applications. Therefore, a versatile characterization method is needed for researchers and regulators alike to ensure nanomaterials are properly used. Single Particle Inductively Coupled Plasma Mass Spectrometry (SP-ICP-MS) is a functional method that could fill the characterization need in the nanomaterial research field. Using data from both SP-ICP-MS tests and data from literature established characterization methods, the viability of making SP-ICP-MS the standard …
A Modulated Structure Derived From The Xa-Type
Mn2Rusn Heusler Compound,
2022
University of Nebraska-Lincoln
A Modulated Structure Derived From The Xa-Type Mn2Rusn Heusler Compound, Xingzhong Li, Wen-Yong Zhang, Ralph Skomski, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
A modulated structure derived from the inverse Heusler phase (the XA-type and the disordered variant L21B-type) has been observed in rapidly quenched Mn2RuSn ribbons. The powder X-ray diffraction pattern of the quenched ribbons can be indexed as an L21B-type structure. Electron diffraction patterns of the new structure mostly resemble those of the XA-type (and the disordered variant L21B-type) structure and additional reflections with denser spacing indicate a long periodicity. Orthogonal domains of the modulated structure were revealed by a selected-area electron diffraction pattern and the corresponding dark-field transmission electron microscopy images. The structure was …
Localization Effects And Anomalous Hall Conductivity In A Disordered 3d Ferromagnet,
2022
University of Northern Iowa
Localization Effects And Anomalous Hall Conductivity In A Disordered 3d Ferromagnet, Paul M. Shand, Y. Moua, G. Baker, Shah R. Valloppilly, Pavel V. Lukashev, Parashu Kharel
Nebraska Center for Materials and Nanoscience: Faculty Publications
We have prepared the Heusler alloy CoFeV0.5Mn0.5Si in bulk form via arc melting. CoFeV0.5Mn0.5Si is ferromagnetic with a Curie temperature of 657 K. The longitudinal resistivity exhibits a minimum at 150 K, which is attributable to competition between quantum interference corrections at low temperatures and inelastic scattering at higher temperatures. The magnetoresistance (MR) is positive and nearly linear at low temperatures and becomes negative at temperatures close to room temperature. The positive MR in the quantum correction regime is evidence of the presence of the enhanced electron interaction as a contributor to …
Physics And Applications Of Space-Time Wave Packets,
2022
University of Central Florida
Physics And Applications Of Space-Time Wave Packets, Murat Yessenov
Electronic Theses and Dissertations, 2020-2023
Space-time wave packets (STWP) constitute a broad class of pulsed optical fields that are rigidly transported in linear media without diffraction or dispersion, and are therefore propagation-invariant in absence of optical nonlinearities or waveguiding structures. Such wave packets exhibit unique characteristics, such as controllable group velocities in free space and exotic refractive phenomena. At the root of these behaviors is a fundamental feature underpinning STWP: their spectra are not separable with respect to the spatial and temporal degrees of freedom. Indeed, the spatio-temporal structure is endowed with angular dispersion, in which each spatial frequency is associated with a single prescribed …
Control Of Coherence In Attosecond Atomic Ionization,
2022
University of Central Florida
Control Of Coherence In Attosecond Atomic Ionization, Saad Mehmood
Electronic Theses and Dissertations, 2020-2023
The motion of electrons in atoms, molecules, and in condensed matter unfolds on a time scale from the attosecond (1 as = 10-18 s) to several femtoseconds (1 fs= 10-15 s). The advent of attosecond light pulses has opened the way to the time-resolved study of electronic motion and of ionization processes using pump-probe spectroscopy. In this thesis, we examine three aspects of the ionization dynamics in poly-electronic atoms: i) the coherence of the emerging charged fragments, ii) two-photon ionization pathways, and iii) the reconstruction of photoionization amplitudes from experimental observable. We focus on the role of autoionizing states and …
Apparatus Improvement And Characterisation For Experiments On Ultra-Cold Plasmas.,
2022
Colby College
Apparatus Improvement And Characterisation For Experiments On Ultra-Cold Plasmas., Jakub Bystrický
Honors Theses
Apparatus for creating ultra-cold neutral plasmas (UNPs) was improved and data on plasma expansion was collected. We increase the trapping efficiency of a quadrupole magneto-optical trap (MOT) by installing a tapered amplifier to increase the power of the cooling laser used to trap atoms. We achieve an improvement in density of trapped atoms from 1 x 1010 cm-3 to 2.5 - 4.5 x 1010 cm-3. In addition, to improve precision and decrease systematic error, the magnetic field induced by inductive current in the MOT's anti-helmholtz coils was suppressed. This was achieved by installing a KEPCO …
Applications Of A Combined Approach Of Kinetic Monte Carlo Simulations And Machine Learning To Model Atomic Layer Deposition (Ald) Of Metal Oxides,
2022
Missouri State University
Applications Of A Combined Approach Of Kinetic Monte Carlo Simulations And Machine Learning To Model Atomic Layer Deposition (Ald) Of Metal Oxides, Emily Justus
Graduate Theses/Dissertations
Metal-oxides such as ZnO or Al2O3 synthesized through Atomic Layer Deposition (ALD) have been of great research interest as the candidate materials for ultra-thin tunnel barriers. In this study, I have applied a 3D on-lattice Kinetic Monte Carlo (kMC) code developed by Timo Weckman’s group to simulate the growth mechanisms of the tunnel barrier layer and to evaluate the role of various experimentally relevant factors in the ALD processes. I have systematically studied the effect of parameters such as the chamber pressure temperature, pulse, and purge times. The database generated from the kMC simulations was subsequently used …
Review Of Current Reactive Force Field Potentials For Use In Simulating The Atomic Layer Deposition Of Alumina On Aluminum,
2022
Missouri State University
Review Of Current Reactive Force Field Potentials For Use In Simulating The Atomic Layer Deposition Of Alumina On Aluminum, Devon T. Romine
Graduate Theses/Dissertations
Alumina has recently garnered quite a bit of attention for use as a tunnel barrier in Josephson tunnel junctions. The quality of the metal oxide layer in the Josephson tunnel junction is a key factor in its effectiveness. To optimize the deposition method of alumina, we need a deep understanding of the large-scale surface interactions that cannot be reached using ab initio molecular dynamics. In this study, I have compared two existing reactive force field (ReaxFF) parameters to determine their abilities to model the atomic layer deposition (ALD) of alumina on an aluminum surface. ReaxFF molecular dynamics was chosen because …
Using Powder Diffraction To Give Insight Into Structures Of Ir2(Diisocyanomenthane)4x2 [Dimen] (X = Cl; Pf6; Bph4),
2022
Claremont Colleges
Using Powder Diffraction To Give Insight Into Structures Of Ir2(Diisocyanomenthane)4x2 [Dimen] (X = Cl; Pf6; Bph4), Mairead Brownell
Scripps Senior Theses
Ir2(dimen)42+ (dimen = 1,8-diisocyanomenthane) has been studied extensively as model compound to better understand catalysis of photochemical reactions. Although Ir2(dimen)42+ has been used primarily to observe the photophysical changes of metal-metal transitions, it gives great insight into the transitions that allow other d8-d8 metal complexes to undergo photochemical processes and generate hydrogen gas. The large visible range by which Ir2(dimen)42+ (1) can be electronically excited in solution is indicative of its two solution phase ground states, which interestingly have been hypothesized to resemble two unique packing structures observed in the powder state. In this study, the powder diffraction patterns of …
Theoretical Investigation On Optical Properties Of 2d Materials And Mechanical Properties Of Polymer Composites At Molecular Level,
2022
Michigan Technological University
Theoretical Investigation On Optical Properties Of 2d Materials And Mechanical Properties Of Polymer Composites At Molecular Level, Geeta Sachdeva
Dissertations, Master's Theses and Master's Reports
The field of two-dimensional (2D) layered materials provides a new platform for studying diverse physical phenomena that are scientifically interesting and relevant for technological applications. Theoretical predictions from atomically resolved computational simulations of 2D materials play a pivotal role in designing and advancing these developments. The focus of this thesis is 2D materials especially graphene and BN studied using density functional theory (DFT) and molecular dynamics (MD) simulations. In the first half of the thesis, the electronic structure and optical properties are discussed for graphene, antimonene, and borophene. It is found that the absorbance in (atomically flat) multilayer antimonene (group …
A Local Mode Study Of Ring Puckering Effects In The Infrared Spectra Of Cyclopentane,
2022
University of Wisconsin-Madison
A Local Mode Study Of Ring Puckering Effects In The Infrared Spectra Of Cyclopentane, Edwin L. Sibert Iii, Peter F. Bernath
Chemistry & Biochemistry Faculty Publications
We report and interpret recently recorded high-resolution infrared spectra for the fundamentals of the CH2 scissors and CH stretches of gas phase cyclopentane at −26.1 and −50 ○C, respectively. We extend previous theoretical studies of this molecule, which is known to undergo barrierless pseudorotation due to ring puckering, by constructing local mode Hamiltonians of the stretching and scissor vibrations for which the frequencies, couplings, and linear dipoles are calculated as functions of the pseudorotation angle using B3LYP/6-311++(d,p) and MP2/cc-pVTZ levels of theory. Symmetrization (D5h) of the vibrational basis sets leads to simple vibration/pseudorotation Hamiltonians whose solutions …
