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Articles 1 - 30 of 45
Full-Text Articles in Physics
Reactive Quantum Scattering In Two Dimensions, Roy S. Calfas
Reactive Quantum Scattering In Two Dimensions, Roy S. Calfas
Theses and Dissertations
In an effort to develop a more efficient time dependent approach for calculating scattering matrix elements, absorbing boundary conditions are combined together with the channel packet method. As an introduction to scattering, scattering matrix elements are presented for a one-dimensional square well and a one-dimensional potential consisting of a Gaussian well with symmetric Gaussian barriers. Next, the combination of the channel packet method together with absorbing boundary conditions yields an order of magnitude savings in the time necessary to compute the correlation function for the collinear H+H
A Large Scintillation Detector For Nuclear Physics Experiments At Indiana University Cyclotron Facility, Apurva Pathak
A Large Scintillation Detector For Nuclear Physics Experiments At Indiana University Cyclotron Facility, Apurva Pathak
Masters Theses
A new, large, scintillation detector, called the "K" detector has been designed and built for use in a series of nuclear physics experiments being performed at the Indiana University Cyclotron Facility (IUCF). This project describes the design, construction and testing of this scintillation detector. The K detector was designed to augment an existing detector stack at IUCF, and will serve to increase the energy range of previous studies of neutral pion production in proton-proton collisions near threshold. The test data for the current project came from a proton-proton scattering experiment, during which several runs were carried out between the bombarding …
Displacement Of The Earth's Bow Shock And Magnetopause Due To An Impinging Interplanetary Shock Wave, William A. Olson
Displacement Of The Earth's Bow Shock And Magnetopause Due To An Impinging Interplanetary Shock Wave, William A. Olson
Theses and Dissertations
Interplanetary shock waves (ISWs) propagating through the solar wind can collide with the earth's bow shock, resulting in a series of new shocks, contact discontinuities, and rarefaction waves which interact to effectively move the bow shock and magnetopause toward the earth. A one dimensional MacCormack predictor corrector algorithm with Flux Corrected Transport (FCT) was developed to model the ISW bow shock and magnetopause interactions, and to numerically predict their propagation speeds after collision. Analytic relationships for the Mach numbers and propagation speeds of the generated shock waves and contact discontinuities were used to validate the model and to compare numerical …
Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler
Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler
Theses and Dissertations
An understanding of spontaneous emission processes within microcavities is crucial in addressing the need to make tomorrow's microlasers more efficient. One approach to improving the device efficiency is to reduce the threshold input energy at which lasing begins to occur. It has been suggested that the threshold in a microcavity laser can be decreased by increasing the fraction of spontaneous emission into the lasing mode, this can be accomplished by preferentially coupling the gain medium of the laser to the electromagnetic cavity mode of interest. It therefore becomes necessary to understand the mechanism by which this coupling takes place. This …
Photoluminescence Study Of Gan Implanted With Erbium And Erbium-Oxygen, Lori R. Everitt
Photoluminescence Study Of Gan Implanted With Erbium And Erbium-Oxygen, Lori R. Everitt
Theses and Dissertations
Erbium emits at 1540 nm, which propagates well through fiber optic cables. This work studies the photoluminescence (PL) from GaN, GaN implanted with Er alone, and GaN implanted with both Er and O as functions of excitation laser energy and sample temperature. When the exciton bound to a neutral donor recombined, a photon was emitted at 3.47 eV. A photon emitted at 3.457 eV may have been evidence of the recombination of an exciton bound to a neutral acceptor. Second, the Er-ion transitions were observed in two groups around 0.805 and 1.25 eV. The PL intensity was measured at four …
Time Resolved Photoluminescence Spectra Of A Mid-Infrared Multiple Quantum Well Semiconductor Laser, Anthony L. Franz
Time Resolved Photoluminescence Spectra Of A Mid-Infrared Multiple Quantum Well Semiconductor Laser, Anthony L. Franz
Theses and Dissertations
Recombination mechanisms in mid-IR semiconductor lasers are strongly dependent on the carrier density of the active region. The objective of this research is to improve previous carrier density estimates through the incorporation of spectral information. One hundred photoluminescence (PL) spectra were calculated for a variety of carrier densities. Calculations were made for an InAsSb/InAlAsSb multiple quantum well laser sample assuming parabolic bands. The widths of the calculated spectral profiles were tabulated as a function of carrier density. Actual spectra were measured using the Ultrafast Mid-Infrared Photoluminescence System, which uses upconversion to measure the PL intensity in time steps smaller than …
Microelectromechanical Optical Beam Steering Systems, David M. Burns
Microelectromechanical Optical Beam Steering Systems, David M. Burns
Theses and Dissertations
The development of microelectromechanical systems (MEMS) has matured to the point where the fabrication of micron sized devices is feasible. State of the art MEMS construction processes now support the fabrication of novel optical devices that could not previously be built. This dissertation reports on the development of innovative micro optical devices such as Variable Blaze Gratings (VBGs) using state of the art MEMS construction processes. The principle application of the micro optical devices described in this dissertation is steering optical beams; however other applications such as spectral analysis are identified. Specific optical beam steering systems developed and characterized in …
Reduced Computational Cost, Totally Symmetric Angular Quadrature Sets For Discrete Ordinates Radiation Transport, Joseph M. Oder
Reduced Computational Cost, Totally Symmetric Angular Quadrature Sets For Discrete Ordinates Radiation Transport, Joseph M. Oder
Theses and Dissertations
Several new quadrature sets for use in the discrete ordinates method of solving the Boltzmann neutral particle transport equation are derived. These symmetric quadratures extend the traditional symmetric quadratures by allowing ordinates perpendicular to one or two of the coordinate axes. Comparable accuracy with fewer required ordinates is obtained. Quadratures up to seventh order are presented. The validity and efficiency of the quadratures is then tested and compared with the Sn level symmetric quadratures relative to a Monte Carlo benchmark solution. The criteria for comparison include current through the surface, scalar flux at the surface, volume average scalar flux, and …
Collisional Broadening Of Spectral Lines In The X → B System Of O2 And The First Vibrational Band Of No By The Noble Gases, John J. Cornicelli
Collisional Broadening Of Spectral Lines In The X → B System Of O2 And The First Vibrational Band Of No By The Noble Gases, John J. Cornicelli
Theses and Dissertations
Collisional broadening of the rotational spectral lines of the X to b system of O2 and the first vibrational band of NO by the noble gases is examined by Fourier transform spectroscopy. Peaks of the individual rotational lines are modeled with a Voigt function, from which Lorentzian half widths are extracted. Lorentzian widths are plotted vs. pressure of foreign gas, from which the pressure broadening coefficients and pressure broadening cross sections are calculated. The pressure broadening coefficients are compared to theoretical values determined by past research for O2. NO coefficients are compared to similar research using N …
An Analytical Method To Calculate Activity From Measurements Affected By Coincidence Summing, Anthony P. Popovich
An Analytical Method To Calculate Activity From Measurements Affected By Coincidence Summing, Anthony P. Popovich
Theses and Dissertations
An analytical method is developed and applied to find the activities of two radioisotopes based on measurements influenced by true coincidence summing. The method incorporates the solid angle subtended by the detector, the macroscopic cross sections of the materials present, the absolute peak and total efficiencies of the detector, and the modes and probabilities of decay of the radioisotope. With this information, the method corrects for both summing-in and summing-out events. Summing events affect peak counts and cause the calculated activity to differ from the true activity. Thin disk sources of Mo-99 and Cs-136 on the face of a closed-end, …
Collision Spectroscopy Of Low Energy Capture By Multiply Charged Ions From Atomic Targets, Kadir Akgungor
Collision Spectroscopy Of Low Energy Capture By Multiply Charged Ions From Atomic Targets, Kadir Akgungor
Dissertations
State-selective differential cross sections for single-electron capture processes in very slow collisions of Ar^q+ (q = 4 - 6) ions with Ne, and Ar^6+ ions with He have been studied experimentally at laboratory collision energies between 15 and 100 qeV, and at scattering angles between 0° and 8° by means of translational energy-gain spectroscopy technique. The translational energy spectra show that only a few final states are populated depending on the charge state of the projectile, the projectile laboratory scattering angle, and the collision energy. These measurements also show that the dominant reaction channels are due to capture into excited …
Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes
Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes
Dissertations and Theses
It has been proposed in the literature that a novel class of biosensors can be based on a bimolecular layer of lipids supported on one side by a metallic surface. In order to estimate the potential of this system for the design of membrane sensors, we have studied properties of a two-electrode system consisting of a tefion insulated metallic wire and a Ag/ AgCl electrode, both immersed in KCl solution. The lipid bimolecular layer was formed on the metal surface of the cut tefion insulated wire. The electrical conductivity properties of such a device were studied in the frequency range …
A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby
A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby
Theses and Dissertations
The most current version of the Parameterized Real-time Ionospheric Specification Model (PRISM), version 1.7b, was validated using Digital Ionospheric Sounding System (DISS) measurements of F2 layer critical frequency (foF2) and F2 peak electron density height (hmF2) as the "ground truth." PRISM was executed, first, with no real-time input parameter and, second, with Global Positioning System (GPS) Total Electron Content (TEC) measurements as the sole real-time parameter. Hourly values of hmF2 and foF2 over 123 days in 1994-1996 (solar minimum conditions) and covering three seasons (equinox, summer solstice, and winter solstice) were compared for Wallops Island, Virginia, and Point Arguello, California, …
Analysis Of Uranium Oxide Weathering By Molecular Spectroscopy, Matthew S. Zickafoose
Analysis Of Uranium Oxide Weathering By Molecular Spectroscopy, Matthew S. Zickafoose
Theses and Dissertations
A preliminary study of the weathering of uranium oxide particles diluted in diamond dust at ambient environmental conditions is presented. The primary weathering reaction is oxidation of the uranium from the 4 to 6 oxidation state, although formation of compounds such as carbonates and hydroxides is possible. Identification of the state of uranium oxide has been attempted using luminescence spectroscopy and diffuse reflectance Fourier transform infrared spectroscopy DRIFTS. Luminescence spectra of nominal samples of three common oxides, UO3, U3O8, and UO2, have been measured showing significant spectral differences in peaks at 494 nm, 507 nm, 529 nm, and 553 nm. …
Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker
Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker
Theses and Dissertations
Fabrication of silicon carbide SiC semiconductor devices are of interest for aerospace applications because of their high-temperature tolerance. Growth of an insulating SiO2 layer on SiC is a poorly understood process, and sometimes produces interface defects that degrade device performance. Accurate theoretical models of surface chemistry, using quantum mechanics QM, do not exist because of the huge computational cost of solving Schroedingers equation for a molecular cluster large enough to represent a surface. Molecular mechanics MM, which describes a molecule as a collection of atoms interacting through classical potentials, is a fast computational method, good at predicting molecular structure, …
Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun
Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun
Theses and Dissertations
An analysis and assessment of three mechanisms describing plasma/shock wave interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of ion-acoustic wave damping, post-shock energy addition and thermal inhomogeneities were examined by numerically solving the Euler equations with appropriate source terms adapted for each mechanism. Ion-acoustic wave damping was examined by modeling the partially ionized plasma as two fluids in one spatial dimension using the Riemann problem as a basis. Post-shock energy addition in the form of nonequilibrium vibrational energy relaxation was also examined in one spatial dimension using the Riemann problem as a …
Symmetry, Symmetry Breaking, And The Current View Of The Dirac Monopole, Erik Kristian Leder
Symmetry, Symmetry Breaking, And The Current View Of The Dirac Monopole, Erik Kristian Leder
Dissertations and Theses
The ideas of symmetry and symmetry breaking are considered in the context of classical gauge theory. Local U(l) symmetry is developed for a complex scalar field and electromagnetism is identified as the associated gauge field. Local S0(3) theory for a triplet of real scalar fields is derived and the incorporation of additional gauge fields is demonstrated. Symmetry breaking for the S0(3) gauge theory is performed and the gauge fields are shown to acquire mass by the Higgs mechanism. The equations of the t'Hooft-Polyakov monopole are derived and compared to those of the magnetic monopole of Dirac.
Experimental Investigation Of Nonlinear Dynamics In Single Mode Semiconductor Laser Diodes With Phase Conjugate Feedback, Gordon T. Hengst
Experimental Investigation Of Nonlinear Dynamics In Single Mode Semiconductor Laser Diodes With Phase Conjugate Feedback, Gordon T. Hengst
Theses and Dissertations
The semiconductor laser diode offers a unique system to investigate nonlinear dynamics when optical feedback is applied. Although there is extensive research of laser diodes with optical feedback from normal dielectric mirrors, very little has been done experimentally to analyze the effects of degenerate phase conjugate feedback from a BaTiO3 crystal. This research experimentally investigated the dynamics of a single-mode laser diode with weak phase conjugate feedback using both the self-pumped and double phase conjugate geometries. The experimental results validated a mathematical model which numerically evaluates the Lang-Kobayahsi coupled differential equations. The model simulated the nonlinear behavior of a …
The Use Of Operator Regularization In The Computation Of Effective Field Theories, Jeffrey M. Hersh
The Use Of Operator Regularization In The Computation Of Effective Field Theories, Jeffrey M. Hersh
Physics Theses & Dissertations
Current methods of computing low-energy effective field theories while being accurate are extremely cumbersome co implement. Operator regularization provides a way to calculate any desired effective field theory avoiding the tediousness of previous methods. This technique is shown to be an effective method in explicitly calculating the 1/mheavy corrections that match an original full theory to its low-energy effective counterpart. This is demonstrated up to two loop order for the case of a charged two field θ{4}{4} theory as well as up to one loop order for the Higgs sector of the Minimal Supersymmetric Model. Additionally, the renormalization …
Localization And Transport Effects In The Disordered Materials, Vladislav Malyshkin
Localization And Transport Effects In The Disordered Materials, Vladislav Malyshkin
Dissertations
No abstract provided.
Kinetics And Spectroscopy Of Brno, Patrick E. Godfrey
Kinetics And Spectroscopy Of Brno, Patrick E. Godfrey
Theses and Dissertations
The infrared spectra and photochemistry of nitrosyl bromide, BrNO, are important to characterizing the performance of a recently demonstrated Br(2P1/2)-NO(v=2 → v=1) transfer laser pumped by photolysis of iodine molecules. This wavelength agile, mid-infrared laser may be a desirable source for remote sensing and infrared countermeasures missions. Nitrosyl bromide also plays a role in the destruction of stratospheric ozone. The kinetics of BrNO formation and destruction were examined using time-resolved photolysis techniques. The equilibrium constant for the dark reaction Br2 + 2NO (reversible reaction) 2BrNO was determined as Keq 168 ± 23 /atm and …
Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic
Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic
Theses and Dissertations
This dissertation had three objectives. The first objective was to develop image quality metrics that characterize Adaptive Optics System (AOS) performance. The second objective was to delineate control settings that maximize AOS performance. The third objective was to identify and characterize trade-offs between fully and partially compensated adaptive. For the first objective, three candidate image quality metrics were considered: the Strehl ratio, a novel metric that modifies the Strehl ratio by integrating the modulus of the average system optical transfer function to a 'noise-effective-cutoff' frequency at which some specified image spectrum signal-to-noise-ratio level is attained, and the noise-effective-cutoff frequency. It …
Calibration Methodology And Multiple Tip Structure By Scanning Tunneling Microscopy., Michael Stephen Gossman
Calibration Methodology And Multiple Tip Structure By Scanning Tunneling Microscopy., Michael Stephen Gossman
Electronic Theses and Dissertations
The scanning tunneling microscope has been in commercial use just over a decade. Due to its Quantum Mechanical nature, experiments in this area have been widely publicized to the scientific community. The apparatus is steadily growing easier to use, though fundamental problems are still present. In the first chapter, an address is given on the modem theory of tunneling to rationalize the conclusions Physicists made long ago about this phenomenon. The expanded theory generalizes the mathematical motivation for attempting such unique experiments and serves as a lead-in for the major components of the apparatus. Many texts do not quantize what …
Molecular Fluorescence At A Rough Surface: The Orientation Effects, William Lee Blacke
Molecular Fluorescence At A Rough Surface: The Orientation Effects, William Lee Blacke
Dissertations and Theses
The interaction between an emitting molecular dipole and a conducting substrate with a periodic surface roughness is looked at with particular interest in the different orientations of the dipole with respect to the substrate surface. A previous dynamical, perturbative theory for the effects of perpendicular dipole is extended to treat a dipole oriented parallel to the surface of the substrate. The results are then applied to study the modified fluorescence characteristics of the emitting dipoles. Numerical results demonstrate that some fluorescence characteristics are extremely sensitive to the molecular orientation with the dipole oriented along the grating (x direction) exhibiting unique …
Optimization And Spectrophotometric Comparisons Of Radiochromic Dye (2,3,5-Triphenyl-2-H-Tetrazolium Chloride) In Gelatin And Agar Models: Gamma And Electron Beam Irradiations, Lakindra P. Frances
Optimization And Spectrophotometric Comparisons Of Radiochromic Dye (2,3,5-Triphenyl-2-H-Tetrazolium Chloride) In Gelatin And Agar Models: Gamma And Electron Beam Irradiations, Lakindra P. Frances
Electronic Dissertations and Theses
After irradiation, the colorless radiochromic dye, 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), changes to red triphenyl formazan pigment, and the distribution of absorbed dose in the tissue-equivalent gelatin and agar media can be studied. Using solutions 8% by weight gelatin and 8% by weight agar, both with 3 mM citric acid as buffer and 4 mM concentration of dye, the radiation-induced absorbency of a sample slowly decreased with increasing wavelength. In the gel, TTC is very light sensitive, and 7 days after irradiation, becomes less stable. The samples were irradicated by gamma and electron beam. Nine different doses were used for the 60 …
Computer Modeling Of Molecular Vibration Frequencies And Its Application To The Modeling Of Silane Compounds, Ryan T. Merrell
Computer Modeling Of Molecular Vibration Frequencies And Its Application To The Modeling Of Silane Compounds, Ryan T. Merrell
Honors Capstone Projects and Theses
No abstract provided.
Studies Of Mid-Latitude Mesospheric Temperature Variability And Its Relationship To Gravity Waves, Tides, And Planetary Waves, Kenneth C. Beissner
Studies Of Mid-Latitude Mesospheric Temperature Variability And Its Relationship To Gravity Waves, Tides, And Planetary Waves, Kenneth C. Beissner
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Temperature observations of the middle atmosphere have been carried out from September 1993 through July 1995 using a Rayleigh backscatter lidar located at Utah State University (42°N, 111°W). Data have been analyzed to obtain absolute temperature profiles from 40 to 90 km. Various sources of error were reviewed in order to ensure the quality of the measurements. This included conducting a detailed examination of the data reduction procedure, integration methods, and averaging techniques. eliminating errors of 1-3%. The temperature structure climatology has been compared with several other mid-latitude data sets. including those from the French lidars, the SME spacecraft, the …
Empirical Studies Of Ionospheric Electric Fields, Ludger Scherliess
Empirical Studies Of Ionospheric Electric Fields, Ludger Scherliess
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The first comprehensive study of equatorial- to mid-latitude ionospheric electric fields (plasma drifts) is presented, using extensive incoherent scatter radar measurements from Jicamarca, Arecibo, and Millstone Hill, and F-region ion drift meter data from the polar orbiting DE-2 satellite. Seasonal and solar cycle dependent empirical quiet-time electric field models from equatorial to mid latitudes are developed, which improve and extend existing climatological models. The signatures of electric field perturbations during geomagnetically disturbed periods, associated with changes in the high-latitude currents and the characteristics of storm-time dynamo electric fields driven by enhanced energy deposition into the high-latitude ionosphere, are studied. Analytical …
Angle-Resolved Study Of Ar 2p₁/₂,₃/₂⁻1Ns,D Resonant Auger Decay, Marc Andrew Humphrey
Angle-Resolved Study Of Ar 2p₁/₂,₃/₂⁻1Ns,D Resonant Auger Decay, Marc Andrew Humphrey
Honors Theses
Angle-resolved measurements of the Ar 2p1/2,3/2-14s,3d,4d and 2p3/2-14s,3d,4d resonant Auger transitions have been carried out using photons from an undulator beamline at the Advanced Light Source of Lawrence Berkeley National Laboratory. The intensity distributions and angular distribution anisotropy (β) parameters have been reported for nearly all of the possible 3p4nl final ionic states. These results further verify the predictions of the spectator model for the 2p1/2,3/2-14s resonances and the subsequent breakdown of this model for the 2p1/2,3/2-13d and 2p1/2,3/2-14d relative intensities. This work …
Evaluation And Application Of Space Telescope Aberration Sensing Using Phase Diversity, David J. Lee
Evaluation And Application Of Space Telescope Aberration Sensing Using Phase Diversity, David J. Lee
Theses and Dissertations
Due to mechanical aspects of fabrication, launch, and operational environment, space telescope optics can suffer from unforeseen aberrations, detracting from their intended diffraction-limited performance goals. This dissertation gives the results of simulation and theoretical studies designed to explore how wavefront aberration information for such "nearly diffraction-limited" telescopes can be estimated via the Gonsalves (least-squares) phase diversity technique. In traditional phase diversity, aberrations are estimated from two images—one conventional, focused image and one image that has been defocused by a known amount. These studies are original and significant in that this effort represents the first time the effects of photon noise …