Physics Commons^™

Harvesting Single Ferroelectric Domain Stressed Nanoparticles For Optical And Ferroic Applications, Gary Cook, J. L. Barnes, S. A. Basun, Dean R. Evans, Ron F. Ziolo, Arturo Ponce, Victor Yu. Reshetnyak, Anatoliy Glushchenko, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

We describe techniques to selectively harvest single ferroelectric domain nanoparticles of BaTiO3 as small as 9 nm from a plethora of nanoparticles produced by mechanical grinding. High resolution transmission electron microscopy imaging shows the unidomain atomic structure of the nanoparticles and reveals compressive and tensile surface strains which are attributed to the preservation of ferroelectric behavior in these particles.

We demonstrate the positive benefits of using harvested nanoparticles in disparate liquid crystal systems.

Study Of The Photoinduced Surface Relief Modulation In Photopolymers Caused By Illumination With A Gaussian Beam Of Light, Tzvetanka Babeva, Dana Mackey, Suzanne Martin, Izabela Naydenova, Vincent Toal

Articles

The formation of surface relief profile in photopolymerisable systems when illuminated with a focused beam of light is simulated numerically using a two-way diffusion model that takes account both for monomer and short polymer chains diffusion. The concentration and spatial distribution dynamics of monomer and short and long polymer chains are calculated. The surface profile is obtained from calculated components concentrations considering different densities of monomer and polymer. The influence of the illumination time, intensity and spot diameter on the surface profiles dynamics is discussed. A good agreement between the calculated and the experimentally measured profiles is observed thus demonstrating …

Mapping The Distribution Of Electron Temperature And Fe Charge States In The Corona With Total Solar Eclipse Observations, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, Adrian Daw, Judd Johnson, A. Ding, Martina Arndt, R. Esser, V. Rusin, I. Scholl

Physics Faculty Publications

The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 …

Total Solar Eclipse Observations Of Hot Prominence Shrouds, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, I. Scholl, V. Rusin, Adrian Daw, Judd Johnson, Martina B. Arndt

Physics Faculty Publications

Using observations of the corona taken during the total solar eclipses of 2006 March 29 and 2008 August 1 in broadband white light and in narrow bandpass filters centered at Fe x 637.4 nm, Fe xi 789.2 nm, Fe xiii 1074.7 nm, and Fe xiv 530.3 nm, we show that prominences observed off the solar limb are enshrouded in hot plasmas within twisted magnetic structures. These shrouds, which are commonly referred to as cavities in the literature, are clearly distinct from the overlying arch-like structures that form the base of streamers. The existence of these hot shrouds had been predicted …

Reflectivity Of A Cholesteric Liquid Crystal, Justin Lawson

Physics

In this paper we investigate the light properties of a chiral liquid crystal or a crystal for which the director angle relative to some fixed axis changes as a function of the crystal depth. Sometimes a dopant can introduce a chirality or "twist" in a nematic liquid crystal. For such cases of non-linear depth dependence (where chirality is determined by a diffusion equation) we may use this research to work backwards from a crystal's light properties to intensity and duration of dopant exposure.

Field-Induced Quantum Phase Transitions In The Spin-1/2 Triangular-Lattice Antiferromagnet Cs2cubr4, Nathanael Alexander Fortune, Scott T. Hannahs, Y. Takano, Y. Yoshida, T. Sherline, A. A. Wilson-Muenchow, T. Ono, H. Tanaka

Physics: Faculty Publications

In classical magnetic spin systems, geometric frustration leads to a large number of states of identical energy. We report here evidence from magnetocaloric and related measurements that in Cs2CuBr4 — a geometrically frustrated Heisenberg S= 1/2 triangular antiferromagnet — quantum fluctuations stabilize a series of gapped collinear spin states bounded by first-order transitions at simple increasing fractions of the saturation magnetization for fields directed along the c axis. Only the first of these quantum phase transitions has been theoretically predicted, suggesting that quantum effects continue to dominate at fields much higher than previously considered.

Earth‐Moon‐Mars Radiation Environment Module Framework, Nathan A. Schwadron, L. Townsend, K. Kozarev, M. A. Dayeh, F. Cucinotta, M. Desai, M. Golightly, D. Hassler, R. Hatcher, M. Y. Kim, A. Posner, M. Pourarsalan, Harlan E. Spence, R. K. Squier

Physics & Astronomy

[1] We are preparing to return humans to the Moon and setting the stage for exploration to Mars and beyond. However, it is unclear if long missions outside of low-Earth orbit can be accomplished with acceptable risk. The central objective of a new modeling project, the Earth-Moon-Mars Radiation Exposure Module (EMMREM), is to develop and validate a numerical module for characterizing time-dependent radiation exposure in the Earth-Moon-Mars and interplanetary space environments. EMMREM is being designed for broad use by researchers to predict radiation exposure by integrating over almost any incident particle distribution from interplanetary space. We detail here the overall …

Observation Of Long-Range, Near-Side Angular Correlations In Proton-Proton Collisions At The Lhc, Vardan Khachatryan, Marc M. Baarmand, B. Dorney, Samir Guragain, Marcus Hohlmann, H. Kalakhety, Robert M. Ralich, Igor Vodopiyanov, The Cms Collaboration

Aerospace, Physics, and Space Science Faculty Publications

Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (η) and azimuthal angle (φ). Short-range correlations in Δη, which are studied in minimum bias events, are characterized using a simple "independent cluster" parametrization in order to quantify their strength (cluster size) and their extent in η (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb -1 data set at …

Plasmon Enhanced Near-Field Interactions In Surface Coupled Nanoparticle Arrays For Integrated Nanophotonic Devices, Amitabh Ghoshal

Electronic Theses and Dissertations

The current thrust towards developing silicon compatible integrated nanophotonic devices is driven by need to overcome critical challenges in electronic circuit technology related to information bandwidth and thermal management. Surface plasmon nanophotonics represents a hybrid technology at the interface of optics and electronics that could address several of the existing challenges. Surface plasmons are electronic charge density waves that can occur at a metal-dielectric interface at optical and infrared frequencies. Numerous plasmon based integrated optical devices such as waveguides, splitters, resonators and multimode interference devices have been developed, however no standard integrated device for coupling light into nanoscale optical circuits …

Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures, Nathan Bickel

Electronic Theses and Dissertations

The application of epitaxially grown, III-V semiconductor-based nanostructures to the development of electro-optical and all-optical switches is investigated through the fabrication and testing of integrated photonic devices designed using multimode interference (MMI) waveguides. The properties and limitations of the materials are explored with respect to the operation of those devices through electrical carrier injection and optical pumping. MMI waveguide geometry was employed as it offered advantages such as a very compact device footprint, low polarization sensitivity, large bandwidth and relaxed fabrication tolerances when compared with conventional single-mode waveguide formats. The first portion of this dissertation focuses on the characterization of …

Determining Metastable Densities In An Argon Discharge Through Optical Emission Spectroscopy, Jared A. Miles

Browse all Theses and Dissertations

A plasma diagnostic technique has been experimentally demonstrated where optical emission measurements of relative intensities of spectral lines in the violet range were combined with available electron-impact cross sections to yield absolute Ar metastable species concentration. An enabling factor of this analysis was that the electron excitation pattern was quite different between the Ar ground state and the metastable state. The result of this pattern was that the optical spectrum was unique depending on whether the emission was generated by direct excitation from the ground state, or by stepwise excitation from one of the metastable states. This study has shown …

Self-Energy Correction To The Hyperfine Splitting And The Electron G Factor In Hydrogenlike Ions, Vladimir A. Yerokhin, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The hyperfine structure (hfs) and the g factor of a bound electron are caused by external magnetic fields. For the hfs, the magnetic field is due to the nuclear spin. A uniform-in-space and constant-in-time magnetic field is used to probe the bound-electron g factor. The self-energy corrections to these effects are more difficult to evaluate than those to the Lamb shift. Here, we describe a numerical approach for both effects in the notoriously problematic regime of hydrogenlike bound systems with low nuclear charge numbers. The calculation is nonperturbative in the binding Coulomb field. Accurate numerical values for the remainder functions …

Tunneling Spectroscopy Study Of Calcium Ruthenate, Anthony Bautista

University of Kentucky Doctoral Dissertations

The ruthenates are perhaps one of the most diverse group of materials known up to date. These compounds exhibit a wide array of behaviors ranging from the exotic pwave superconductivity in Sr₂RuO₄, to the itinerant ferromagnetism in SrRuO₃, and the Mott-insulating behavior in Ca₂RuO₄. One of the most intriguing compounds belonging to this group is Ca₃Ru₂O₇ which is known to undergo an antiferromagnetic ordering at 56K and an insulating transition at 48K. Most intriguing, however, is the behavior displayed by this compound in the presence …

Spectroscopic And Chemometric Approaches To Radiobiological Analyses, Aidan Meade, Hugh Byrne, Fiona Lyng

Articles

No abstract provided.

Research Report 2010, College Of Arts And Sciences

Physics Research Reports

• Introduction
• From the Chairperson
• Astronomy
• Atomic and Molecular Physics
• Condensed Matter Physics
• Physics Education
• Research and Public Lectures at WMU
• Personnel January 1-December 31, 2010

Measurement Of Thermoelectric Properties Of Amorphous Silicon Based Thin Films, Rubina Sultan

Electronic Theses and Dissertations

It is important to understand thermal transport behavior in materials for technological and fundamental physics applications. Many efforts have been made in the past for explaining thermal conduction in solids. It has been observed that thermal transport properties may change with reducing size of the sample, especially as sample size approaches the nanoscale regime. The deviation in these properties, mainly in thermal conductivity, may change the choice of the material for different applications such as thermoelectricity. Thermoelectric materials are a possible source of sustainable energy and can play an important role in the fight against the present energy crisis. Recently, …

Understanding The Promotion Effect: A Density Functional Theory Study Based On High Resolution Transmission Electron Microscopy Images For Mos2-Cobalt Promoted Interfaces, Manuel A. Ramos

Open Access Theses & Dissertations

Many studies had been done in order to understand promotion effect and structure/function in unsupported catalyst. Results indicated that d-electrons play an important role promoting catalytical active sites at the edges of MoS2 catalytically structures. Sulfur removal from crude oil, occurs on the edge of molybdenum di-sulfide (MoS2) nano structures, due to promotion of MoS2 nano structures with nickel or cobalt in sulfur-terminated or molybdenum-terminated edge planes. The promotion leads to formation of so-called CoMoS phase (MoS2/Co9S8) first discovered by meaning of Mössbauer spectroscopy, much more CoMoS phase usually called unsupported catalytical particles, have been topic of great interest in …

An Ab-Initio Study Of The Elastic Properties Of Important Group Iv Diborides At High Temperatures, Manny Gonzales

Open Access Theses & Dissertations

Presented is an ab-initio Molecular Dynamics (MD) study, employing the Density Functional Theory (DFT), of the lattice parameter, thermal expansion coefficients and elastic constants of ZrB₂, TiB₂ and HfB₂ as a function of temperature. The MD trajectories provide the equilibrium lattice parameters at finite temperatures, and the gradient of the energy from these equilibrium solutions is then used to calculate the components of the stiffness tensor. The results for ZrB₂ are shown to agree well with reported experimental results for the lattice parameters and elastic constants as a function of temperature.

Spectroscopic Analysis Of Tungsten Oxide Thin Films For Sensor Applications, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

The objective of this study is targeted toward improving the quality of pure tungsten oxide (WO3) for application to the detection of poisoning gases, especially of H2S. While pure WO3 is a recognized candidate for gas sensing, its characteristics are strongly dependent on the conditions and methods used in its deposition.

Samples of WO3 thin films analyzed in this work were grown on silicon and sapphire substrates using RF magnetron sputtering at a number of different substrate temperatures and Ar:O2 pressure ratios. The properties of the samples were investigated spectroscopically with the goal of determining how variations in the above …

Structural And Electronic Properties Of Aluminum Nano Clusters By Dft, Mrudula Raparla

Open Access Theses & Dissertations

The electronic properties of Al clusters containing up to 60 atoms are investigated using an all electron density functional theory using large polarized Gaussian basis sets with 39 Gaussians per atom (NRLMOL basis). We have performed an extensive search for the lowest energy isomers for clusters up to Al 21. We build a database of candidate structures for the ground state using different strategies. First, a few structures are randomly generated and fully relaxed using plane wave pseudo potential method. We also performed simulated annealing runs using ab initio molecular dynamics for clusters up to Al20. In three sets of …