Digital Commons Network^™

Collisional Dynamics Of The Rubidium 52P Levels, Matthew D. Rotondaro

Theses and Dissertations

The collisional dynamics of the 5²P levels in rubidium has been examined using steady-state laser absorption and spectrally-resolved laser induced fluorescence techniques. State-to-state cross-sections for energy transfer between Zeeman split levels ranged from 16-248 ^°A² for collisions with nitrogen and rare gases. These energy transfer cross-sections exhibit a significant dependence on (J,mj) state and certain symmetry relationships are demonstrated. A sub-Doppler spectrum of the Zeeman split levels indicating the isotopic shift in the D₁ line of 106 ± 35 was obtained using laser saturation spectroscopy.

Comparison Of Branching Ratio And Sum-Rule Analyses Of Magnetic Circular Dichroism In X-Ray-Absorption Spectroscopy, James G. Tobin, George Daniel Waddill, Alan F. Jankowski, Philip A. Sterne, David P. Pappas

Physics Faculty Research & Creative Works

Two localized picture methods of analyzing the magnetic circular dichroism in x-ray absorption will be applied to experimental results: the branching ratio (BR) and sum rule (SR) approaches. A derivation of the BR formulas and detailed comparison to the SR expressions will be made, including error estimations. The BR approach will be seen to be a limiting case form of the SR spin-moment expression and provide a simple picture of the underlying physics in magnetic x-ray circular dichroism absorption in 3d magnetic materials.

A Novel Design For A Small Retractable Cylindrical Mirror Analyzer, D.N. Mcilroy, Peter A. Dowben, A. Knop, E. Ruhl

Peter Dowben Publications

In this paper we will review the performance of a “miniature” single pass cylindrical mirror analyzer (CMA) which we have used successfully in a variety of experiments. The underlying premise behind this CMA design was to minimize spatial requirements while maintaining an acceptable level of instrumental resolution. While we are presenting the results of a single pass cylindrical mirror analyzer, improvements on the present design, such as going to a double pass design, will undoubtedly improve the instrumental resolution.

Controlled Biomineralization Of Magnetite (Fe3O4) And Greigite (Fe3S4) In A Magnetotactic Bacterium, Dennis A. Bazylinski, Richard B. Frankel, Brigid R. Heywood, Stephen Mann, John W. King, Percy L. Donaghay, Alfred K. Hanson

Physics

A slowly moving, rod-shaped magnetotactic bacterium was found in relatively large numbers at and below the oxic-anoxic transition zone of a semianaerobic estuarine basin. Unlike all magnetotactic bacteria described to date, cells of this organism produce single-magnetic-domain particles of an iron oxide, magnetite (Fe₃O₄), and an iron sulfide, greigite (Fe₃O₄), within their magnetosomes. The crystals had different morphologies, being arrowhead or tooth shaped for the magnetite particles and roughly rectangular for the greigite particles, and were coorganized within the same chain(s) in the same cell with their long axes along the chain …

Non-Imaging Infrared Spectral Target Detection, Matthew R. Whiteley

Theses and Dissertations

Automatic detection of time-critical mobile targets using spectral-only infrared radiance data is explored. A quantification of the probability of detection, false alarm rate, and total error rate associated with this detection process is provided. A set of classification features is developed for the spectral data, and these features are utilized in a Bayesian classifier singly and in combination to provide target detection. The results of this processing are presented and sensitivity of the class separability to target set, target configuration, diurnal variations, mean contrast, and ambient temperature estimation errors is explored. This work introduces the concept of atmospheric normalization of …

Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak

Theses and Dissertations

The material parameters and crystalline quality of undoped, MBE-grown InAs_1-xSb_x nearly lattice-matched to (100) GaSb (-0.617% ≤ Δ a-a ≤ +0.708%) similar to material used for mid-infrared semiconductor lasers were determined by optical characterization. Absorption measurements at temperatures between 6-295 K determined the energy gap and wavelength-dependent absorption coefficient for each sample. The compositional dependence of the energy gap was anomalous when compared to previously reported data, suggesting phase separation existed in the material. The samples were also studied by temperature- and excitation-dependent photoluminescence (PL), which, for the majority of cases, showed only a single band-edge peak, …

Trajectory Mapping And Applications To Data From The Upper Atmosphere Research Satellite, Gary A. Morris, Mark R. Schoeberl, Lynn C. Sparling, Paul A. Newman, Leslie R. Lait, Lee Elson, Joe Waters, Robert A. Suttie, Aidan Roche, Jack Kumer, James M. Russell Iii

Physics and Astronomy Faculty Publications

The problem of creating synoptic maps from asynoptically gathered trace gas data has prompted the development of a number of schemes. Most notable among these schemes are the Kalman filter, the Salby-Fourier technique, and constituent reconstruction. This paper explores a new technique called "trajectory mapping." Trajectory mapping creates synoptic maps from asynoptically gathered data by advecting measurements backward or forward in time using analyzed wind fields. A significant portion of this work is devoted to an analysis of errors in synoptic trajectory maps associated with the calculation of individual parcel trajectories. In particular, we have considered (1) calculational errors; (2) …

Mercury Surface-Plasmon Dispersion: Experiment And Theory, Bong-Ok Kim, Geunseop Lee, E. Ward Plummer, Peter A. Dowben, A. Liebsch

Peter Dowben Publications

Momentum-resolved inelastic electron spectroscopy has been utilized to measure the surface-plasmon dispersion and damping for thick Hg films grown onto a Cu(100) substrate. Hg has been investigated since it offers an opportunity to examine the effects of the crystal potential on the surface-plasmon dispersion, and to correlate the measurements on a surface with those for collective excitations in clusters. The effects of the electronic band structure of Hg can be seen in the energy and width of the surface plasmon as a function of momentum transfer q∥. Dynamical response calculations were performed for a semi-infinite electron gas where several important …

Polarized Light Emission In Kev He ²⁺+Na(3s) Collisions, S. Schippers, P. Boduch, J. Van Buchem, F. W. Bliek, R. Hoekstra, R. Morgenstern, Ronald E. Olson

Physics Faculty Research & Creative Works

We investigated l- and m-distributions of He Pi (n=4) states formed during 2-13.3 keV amu -1 He 2++Na(3s) collisions by measuring profiles and the linear polarization of the He Pi (4 to 3) emission. We found that at these energies capture into He +(4f) dominates over capture into other He +(4l) states. Over the indicated energy range the polarization of the 4He Pi (4 to 3) photon emission increases from 0.2 to 0.3 indicating a strong alignment of the captured projectile charge cloud along the internuclear axis. Due to the non-zero nuclear spin the polarization is up to 10% lower …

Polarized Light Emission In Kev He²⁺ + Na(3s) Collisions, S. Schippers, P. Boduch, J. Van Buchem, F. W. Bliek, R. Hoekstra, R. Morgenstem, Ronald E. Olson

Physics Faculty Research & Creative Works

We investigated l- and m-distributions of He u (n = 4) states formed during 213.3 keV amu'1 He2+ + Na(3s) collisions by measuring profiles and the linear polarization of the He u (4→ 3) emission. We found that at these energies capture into He+(4f) dominates over capture into other He+(4i) states. Over the indicated energy range the polarization of the4He u (4 → 3) photon emission increases from 0.2 to 0.3 indicating a strong alignment of the captured projectile charge cloud along the intemuclear axis. Due to the non-zero nuclear spin the polarization is up to 10% lower when using3He2+ …

Electron Emission From Foils Induced By Heavy-Ion Collisions, R. A. Sparrow, Ronald E. Olson, D. Schneider

Physics Faculty Research & Creative Works

Absolute double differential yield per ion has been calculated for forward and backward electron emission produced by collisions of highly charged uranium ions with carbon foils of varying thicknesses. A Monte Carlo method has been developed which employs multiple ionization of the carbon and subsequent energy and angular straggling of freed electrons through the foil. A comparison with experimental double differential electron emission yields shows general agreement. Calculated total electron emission is in agreement with experiment at 44 fig cm-2 as well as the results of Rothard et el. In addition, the radial distribution of energy deposited by the electrons …

Phononic Band Structure In A Mass Chain, Samantha Parmley, Tom Zobrist, Terry Clough, Anthony Perez-Miller, Mark Makela, Roger Yu

All Faculty Scholarship for the College of the Sciences

The vibrational properties of a finite one‐dimensional string‐mass chain are studied experimentally and theoretically. In the experiment both normal mode analysis and pulse analysis are used to obtain the eigenfrequencies of the string‐mass chain. The theoretical predictions are made based upon the numerical solution to the wave equation. The phononic band structure for a periodically massed string as well as Anderson localized gap modes for a disordered system are found. The theoretical and experimental results match satisfactorily well.

Combination Effects Of Irradiation And Chemical Doping On High Temperature Superconductors, Russell J. Fedewa

Honors Theses

The goal of this project is to investigate some methods that improve the critical transport current in high temperature superconductors. A superconductor is a material which can allow an electrical current to flow through it with no resistance. This makes them ideal for a wide variety of applications. Most of the present use is in science or medicine, and show promise in computer circuitry materials and electromagnetic trains. This experiment explores a means of increasing the critical current, the maximum amount of electric current that can pass, and which at present is too low to permit the use of superconductors …

Magnetic Properties Of Nanostructured Cosm/Feco Films, I.A. Al-Omari, David J. Sellmyer

David Sellmyer Publications

Co₈₀Sm₂₉/Fe₆₅Co₃₅ bilayer and multilayer films with Cr underlayers and overlayers have been fabricated and studied. All the samples prepared have in-plane anisotropy and the hysteresis loops were simple single loops for t_FeCo≤300 Å indicating that the two phases are strongly exchange coupled. The magnetization of these samples is found to increase with increasing FeCo layer thickness for a fixed CoSm layer thickness. The coercivity, anisotropy constant, and anisotropy field for films with fixed CoSm layer thickness were found to decrease with increasing FeCo layer thickness. The magnetization squareness values of the …

Broadband Dynamic, Holographically Self-Recorded, And Static Hexagonal Scattering Patterns In Photorefractive Knbo3:Fe, Nickolai Kukhtarev, Tatiana V. Kukhtareva, John Caulfield, Partha P. Banerjee, Hsueh-Ling Yu, Lambertus Hesselink

Electrical and Computer Engineering Faculty Publications

We have observed and explained three types of hexagon pattern formation in photo refractive crystal KNb03:Fe. These are:

• Dynamic (laser induced)
• Semipermanent (holographically stored)
• Permanent (induced by a static domain grid) over a wide wavelength range

Naturalness And Superpartner Masses Or When To Give Up On Weak Scale Supersymmetry, Greg W. Anderson, Diego Castano

Chemistry and Physics Faculty Articles

Superpartner masses cannot be arbitrarily heavy if supersymmetric extensions of the standard model explain the stability of the gauge hierarchy. This ancient and hallowed motivation for weak scale supersymmetry is often quoted, yet no reliable determination of this upper limit on superpartner masses exists. In this paper we compute upper bounds on superpartner masses in the minimal supersymmetric model, and we identify which values of the superpartner masses correspond to the most natural explanation of the hierarchy stability. We compare the most natural value of these masses and their upper limits to the physics reach of current and future colliders. …

College Physics Students' Conceptual Understanding Of Area And Volume, And Relationships Between These Concepts And Students' Understanding Of Physics Concepts, Jiang Yu

Dissertations

Concepts such as area and volume are foundational ideas for many concepts introduced in introductory science courses. At the college level, most instructors typically assume that incoming students have already developed an understanding of these underpinning ideas. However, doubt has surfaced in recent years about students' depth of understanding and mastery of these fundamental concepts. Because deficiencies in understanding basic concepts may relate to the learning of subsequent concepts, instructors have expressed concerns about students' understanding of fundamental ideas and if the failure to understand these ideas hinders students' subsequent progress.

This study was designed to (a) investigate the nature …

Depletion Width And Capacitance Transient Formulas For Deep Traps Of High-Concentration, David C. Look, J. R. Sizelove

Physics Faculty Publications

We derive expressions for the depletion width and capacitance transient applicable to traps which may be deep and of high concentration. The new results are compared with those obtained from the commonly used formulas, and also from an exact analysis. Experimental deep level transient spectroscopic data for EL2 in GaAs are in good agreement.

Transient Wave Mixing And Recording Kinetics In Photorefractive Barium Titanate: A Nonlinear Coupled Mode Approach, Partha P. Banerjee, John M. Jarem

Electrical and Computer Engineering Faculty Publications

By using rigorous coupled-wave diffraction theory along with a time-dependent nonlinear formulation, we analyze two- and multiplewave coupling and the grating kinetics in BaTi03 with different boundary interfaces. Efffects of electrostatic and optical anisotropy have been included in the analysis. Significant mode conversion to higher orders is observed only when the boundary interfaces are highly mismatched.

Comparison Of Time-Domain Reflectometry Performance Factors For Several Dielectric Geometries: Theory And Experiments, S. V. Maheshwarla, R. Venkatasubramanian, Robert F. Boehm

Electrical & Computer Engineering Faculty Research

We propose three nontraditional dielectric geometries and present an experimental and theoretical analysis and comparison of time domain reflectometry (TDR) performances for them. The traditional geometry (the probes inserted in material of essentially infinite extent) is compared to three nontraditional geometries where the probes are affixed outside of a core sample, inside of a bore, or flat on the surface of a semi-infinite solid. Our derivation relates the velocity of electromagnetic wave propagation to the complex permittivities and permeabilities of the media and the geometry for the three nontraditional configurations. Experimental results for air, styrofoam, dry sand, wet sand of …

Guest Editorial: Special Section On Photorefractive Nonlinear Optics, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

Hand in hand with experimental work in photorefractives, there is a lot of activity in modeling photorefractive materials and experimental observations in the open literature. This special section contains a paper by Banerjee and Jarem, who use a rigorous coupled wave theory to analyze two- and multiple-wave mixing photorefractive barium titanate, modeled through the Kukhtarev equations.

Single-Layer-Coated Surfaces With Linearized Reflectance Versus Angle Of Incidence: Application To Passive And Active Silicon Rotation Sensors, R. M.A. Azzam, M. M. K. Howlader, T. Y. Georgiou

Electrical Engineering Faculty Publications

A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectanceversus- angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p-polarized, s-polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO₂ film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis …

Structure And Interaction Energies Of Kr Atoms Adsorbed On Graphitic Amorphous Carbon, Sang -Joon Lee

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The physisorption of Kr on graphitic amorphous carbon (g-C) has been investigated using a statistical approach. The interaction energy calculation process (i) established a structural model of g-C and (ii) determined the adsorbate-adsorbate and the adsorbate-substrate interaction potentials on g-C.

The structural model of g-C was divided into three regions. For the interaction potential between a Kr atom and a carbon atom the short and medium range order of g-C was described with a discrete medium model based on three ring clusters using ring statistics from Beeman's continuous random network C1120 model of g-C. For the intermediate distance region, Beeman's …

A New Photopolymer Recording Material For Holographic Applications: Photochemical And Holographic Studies Towards An Optimized System, Suzanne Martin

Doctoral

Photopolymer materials are a practical alternative to high resolution silver halide photographic emulsions for the recording of holograms and high spatial frequency holographic gratings. The new holographic recording material reported in this thesis consists of a green sensitive dye (erythrosine B), an electron donor (triethanolamine), and a monomer mixture (acrylamide and methylene bisacrylamide) in a polyvinyl alcohol binder. ON illumination with light of the appropriate wavelength the dye absorbs a photon and the excited triplet state of the dye reacts with the electron donor to produce free radicals. These free radicals may then initiate local polymerization of the monomer. The …

Coulomb Gap At Finite Temperatures, Masoud Sarvestani, Michael Schreiber, Thomas Vojta

Physics Faculty Research & Creative Works

The Coulomb glass, a model of interacting localized electrons in a random potential, exhibits a soft gap, the Coulomb gap, in the single-particle density of states (DOS) g(ε,T) close to the chemical potential µ. In this paper we investigate the Coulomb gap at finite temperatures T by means of a Monte Carlo method. We find that the Coulomb gap fills with increasing temperature. In contrast to previous results the temperature dependence is, however, much stronger than g(µ,T)~T^D-1 as predicted analytically. It can be described by power laws with the exponents 1.75 ± 0.1 for the two-dimensional model and 2.7 …

Origins And Effects Of Thermal Processes On Near-Field Optical Probes, Andres H. La Rosa, B. I. Yakobson, H. D. Hallen

Physics Faculty Publications and Presentations

An aluminum-coated tapered fiber probe, as used in near-field scanning optical microscopy (NSOM), is heated by the light coupled into it. This can destroy the probe or may modify the sample, which can be problematic or used as a tool. To study these thermal effects, we couple modulated visible light of various power through probes. Simultaneously coupled infrared light senses the thermal effects. We report their magnitude, their spatial and temporal scales, and real-time probe damage observations.Amodel describes the experimental data, the mechanisms for induced IR variation, and their relative importance.

Ionization-Excitation Of Helium By Fast Charged Particles, L. Nagy, J. Wang, Jack C. Straton, James H. Mcguire

Physics Faculty Publications and Presentations

Probabilities and cross sections for ionization plus excitation in helium produced by fast heavy-particle impact have been evaluated. In these calculations, contributions from shake-off, time ordering, and independent interactions of the frozen-target electrons with the projectile are included. A comparison is made to recent experimental observations for the ratio of excitation-ionization to single-ionization total cross sections. A comparison is also made to calculations of excitation-ionization by fast electron impact.

Instability Of The R³Xs¹ Vacuum In Low-Energy Effective String Theory, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We present and discuss a Euclidean solution of the low-energy effective string action that can be interpreted as a semiclassical decay process of the ground state of the theory.