Digital Commons Network^™

Optical And Magneto-Optical Properties Of Mnpt3 Films (Abstract), Segate Corporation, Pittsburgh, Pa, J. N. Hilfiker, Renat F. Sabirianov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam

Physics Faculty Publications

Optically thick films of MnPt₃ were prepared by magnetron sputtering onto quartz substrates. Postdeposition annealing at 850 °C resulted in highly textured (111) films with the L1₂ (Cu₃Au) structure. MnPt₃ films are ferromagnetic with a Curie temperature of 380 °C, and they show large magneto-optical effects in the visible.^1,2 These films also show a high degree of long-range order. The diagonal components of the dielectric tensor were determined using variable angle spectroscopic ellipsometry measurements over the spectral range 1.2–2.4 eV. Magneto-optic Kerr rotation and ellipticity measurements were made at near normal incidence over the …

Study Of Impurity Modes In Photonic Crystals And Study Of Power Gaas Mesfets, Michael G. Khazhinsky

Dissertations

The dissertation consists of two projects. In the first project, impurity modes in Photonic Crystals are studied in one- and two-dimensional Photonic Crystals. Onedimensional systems are formed from an infinite layered array of dielectric slabs and are studied for linearly polarized electromagnetic waves propagating perpendicular to the plane of slabs. Two-dimensional systems consist either of parallel cylindrical dielectric rods in vacuum or cylindrical holes containing vacuum in dielectric medium. These rods/holes are arranged in a square lattice array. The electromagnetic waves in these system propagate perpendicular to the axes of the rods and are of E or H polarization. Green’s …

Conformation Of Interacting Polymer Chains: Effects Of Temperature, Bias, Polymer Concentration, And Porosity, Grace M. Foo, Ras B. Pandey

Faculty Publications

The conformations of interacting polymer chains driven by a biased field in heterogeneous media are studied using Monte Carlo simulations in three dimensions. In addition to excluded volume, a nearest-neighbor interaction is considered with polymer-polymer repulsion and polymer-solvent attraction. Two types of heterogeneous media are considered: (i) a homogeneous-annealed system consisting of mobile polymer chains and solvents and (ii) quenched porous media, generated by adding a random distribution of quenched barriers. Effects of polymer concentration (p), bias (B), temperature (T), and porosity (p_s) on the magnitude of the radius of gyration (R_g) of the …

Search For Neutrinoless Τ Decays: Τ→Eγ And Τ→Μγ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

A search for the lepton-family-number-violating decays τ→eγ and τ→μγ has been performed using CLEO II data. No evidence of a signal has been found and the corresponding upper limits are B(τ→eγ) < 2.7X10^-6 and B (τ→μγ),3.0 X 10^-6 at 90% C.L.

High Resolution Wavelength Modulation Spectroscopy For Precise Gaseous Characterization, Audra Michiele Bullock

Electrical & Computer Engineering Theses & Dissertations

Wavelength modulation spectroscopy is a highly sensitive, non-intrusive technique for probing gaseous species. Parameters such as velocity, density, and temperature can be measured and monitored with a high degree of precision. In addition, with the use of this technique multiple molecular species may be identified with a single laser probe. This measurement technique utilizes the well-known principles of modulation absorption spectroscopy in a novel way.

The research focuses on harmonic detection and the advantages gained by performing detection at higher harmonics, those greater than the commonly used second harmonic. We show that there is an increase in the sensitivity to …

Nonanalytic Behavior Of The Spin Susceptibility In Clean Fermi Systems, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

The wave vector and temperature-dependent static spin susceptibility, X_s(Q, T), of clean interacting Fermi systems is considered in dimensions 1 ≤ d ≤ 3. We show that at zero temperature X_s is a nonanalytic function of |Q|, with the leading nonanalyticity being |Q|^d-1 for 1 < d < 3, and Q²ln|Q| for d = 3. For the homogeneous spin susceptibility we find a nonanalytic temperature dependence T^d-1 for 1 < d < 3. We give qualitative mode-mode coupling arguments to that effect, and corroborate these arguments by a perturbative calculation to second order in the electron-electron interaction amplitude. The implications of this, in particular for itinerant ferromagnetism, are discussed. We also point out the relation between our findings and established perturbative results for one-dimensional systems, as well as for the temperature dependence of X_s(Q = 0) in d = 3.

Sea Brightness Temperature And Effects Of Spray And Whitecaps, Richard P. Barber Jr., Jin Wu

Physics

Following the approach of Tang [1974], the microwave brightness of the sea surface is recalculated with recent parameterizations in terms of wind velocity for the slope distribution and whitecap coverage of the sea surface and the contribution of sea spray. The difference between this revised calculation with no free parameters and the earlier one becomes more significant as the wind velocity increases; it reaches 10 K or more at a wind velocity of 20 m s-1. Present predictions compare favorably with experimental results, suggesting that this model does include the essential physical mechanisms.

Grains In Ionized Nebulae. Ii. Heavy-Element Depletion, J. B. Kingdon, Gary J. Ferland

Physics and Astronomy Faculty Publications

The presence of grains in gaseous nebulae can have significant effects on the thermal balance and radiative line transfer in these objects. The depletion of condensable elements onto grains provides evidence that dust exists in the ionized regions of nebulae. In this paper, we consider the elements Sc, Ti, V, and Cr, all of which are strongly depleted in the general interstellar medium. We construct simple three-level atoms for several ions of these elements, and incorporate them into our photoionization code CLOUDY. For both a model planetary nebula and a model H II region, we find that several lines of …

Physical And Managed Risk Of Nuclear Waste, Lennart Sjöberg, Britt-Marie Drottz-Sjöberg

RISK: Health, Safety & Environment (1990-2002)

The authors describe their work on the perceived risk of nuclear waste in Sweden. Three levels of waste were studied, and comparisons between the perceptions of the public, politicians and nuclear experts are made.

Book Review Of Alla Yaroshinskaya, Chernobyl: The Forbidden Truth, John M. Gleason

RISK: Health, Safety & Environment (1990-2002)

Review of the book: Alla Yaroshinskaya, Chernobyl: The Forbidden Truth (Michele Kahn & Julia Sallabank, trans. University of Nebraska Press 1995). Introduction, foreword, list of illustrations, photographs. ISBN 0-8032-4912-8. [136 pp. Cloth $25.00; Paper $10.00. 312 N. 14th Street, Lincoln NE 68588-0484.]

Bifurcation Of The Equilibrium States Of A Weightless Liquid Bridge, Lev A. Slobozhanin, J. Iwan D. Alexander, Andrew Resnick

Physics Faculty Publications

The bifurcation of the solutions of the nonlinear equilibrium problem of a weightless liquid bridge with a free surface pinned to the edges of two coaxial equidimensional circular disks is examined. The bifurcation is studied in the neighborhood of the stability boundary for axisymmetric equilibrium states with emphasis on the boundary segment corresponding to nonaxisymmetric critical perturbations. The first approximations for the shapes of the bifurcated equilibrium surfaces are obtained. The stability of the bifurcated states is then determined from the bifurcation structure. Along the maximum volume stability limit, depending on values of the system parameters, loss of stability with …

Three-Body Dispersion Coefficients For Alkali-Metal Atoms, Mircea Marinescu, Anthony F. Starace

Anthony F. Starace Publications

We study the nonadditive part of the long-range interaction among three alkali-metal atoms in their ground states. Using nondegenerate perturbation theory, up to the third order, we have computed the dispersion coefficients C for three alkali-metal atoms interacting via their electric dipole moments. Both heteronuclear and homonuclear cases are considered. The numerical values for the C coefficients suggest that such three-body dipole interaction effects may not be neglected in the description of the long-range surface potential interaction for alkali-metal atoms. Furthermore, we show that approximate formulas for C of Midzuno and Kihara [J. Phys. Soc. Jpn. 11, 1045 (1956)] give …

Study Of The Crystallization Of Zeolite Naa By Quasi-Elastic Light-Scattering Spectroscopy And Electron Microscopy, Leszek Gora, Kiril A. Streletzky, Robert W. Thompson, George D.J. Phillies

Physics Faculty Publications

A study of the crystallization of the molecular sieve zeolite NaA from clear aluminosilicate solutions is reported. It was determined by powder X-ray diffraction that zeolite NaA was the only phase in the solid precipitate. The syntheses were monitored in situ by quasi-elastic light scattering spectroscopy. Characteristics of the products were examined by scanning and transmission electron microscopy. Our data show that nuclei formed from the clear aluminosilicate solution, that crystal growth occurred from the solution, that crystal growth was accelerated at elevated temperatures, and that aging the solution at room temperature before raising the synthesis temperature increased both the …

Thermal Fluctuations In Systems With Continuous Symmetry, Ulrich Zürcher

Physics Faculty Publications

We investigate relaxation and thermal fluctuations in systems with continuous symmetry in arbitrary spatial dimensions. For the scalar order parameter ζ(r, t) with r∈ℛd, the deterministic relaxation is caused by hydrodynamic modes η∂ζ(r, t)/∂t= K∇2ζ(r, t). For a finite volume V, we expand the scalar field in a discrete Fourier series and then we study the behavior in the limit V→∞. We find that the second moment is well defined for dimensions d≥3, while it diverges for d=1, 2. Furthermore, we show that for d<4, the decay of the scalar field does not define an "effective" relaxation time. For dimensions d<4, these two properties suggest scale-invariant properties of the scalar field in the limit V→∞. We show that thermal fluctuations are described by fractional Brownian motion for d ≤ 3 and by ordinary Brownian motion for d ≥ 4. The spectral density of the stochastic force follows 1/f for d=1 and d=2, for d=3, and "white noise," f0 for d≥4. We find explicit representation of the equilibrium distribution of the conserved scalar field. For d≥4 it is a Gaussian distribution, while for d=1 and d=2, it is the Cauchy distribution.

Naturalness Lowers The Upper Bound On The Lightest Higgs Boson Mass In Supersymmetry, Greg W. Anderson, Diego Castano, Antonio Riotto

Chemistry and Physics Faculty Articles

We quantify the extent to which naturalness is lost as experimental lower bounds on the Higgs boson mass increase, and we compute the natural upper bound on the lightest supersymmetric Higgs boson mass. We find that it would be unnatural for the mass of the lightest supersymmetric Higgs boson to saturate its maximal upper bound. In the absence of significant fine-tuning, the lightest Higgs boson mass should lie below 120 GeV, and in the most natural cases it should be lighter than 108 GeV. For modest tanβ, these bounds are significantly lower. Our results imply that a failure to observe …

Scattering Of A Diagonally Incident Focused Gaussian Beam By An Infinitely Long Homogeneous Circular Cylinder, James A. Lock

Physics Faculty Publications

I expand the radiation potential of an arbitrary monochromatic electromagnetic wave in the cylindrical coordinate eigenfunctions of the scalar Helmholtz equation. Since the resulting beam shape coefficients are found to be an inverse Fourier transform of the z component of the beam fields, the incident Gaussian beam is parameterized by a Fourier angular spectrum of plane waves. The beam's partial-wave coefficients are then obtained, as well as the scattered fields produced by the interaction of the beam with an infinitely long homogeneous circular cylinder. The fields are evaluated analytically in the far zone by the method of stationary phase, and …

Morphology-Dependent Resonances Of An Infinitely Long Circular Cylinder Illuminated By A Diagonally Incident Plane Wave Or A Focused Gaussian Beam, James A. Lock

Physics Faculty Publications

The S matrix for scattering a diagonally incident focused Gaussian beam by an infinitely long circular cylinder is calculated, and the diagonal and off-diagonal elements of the matrix are physically interpreted. In addition, the TE and TM morphology-dependent resonances of the cylinder for plane-wave incidence are examined, and it is found that the cylinder size parameter at resonance increases as the angle of incidence of the plane wave increases. The size parameter increase is explained in terms of the heuristic model of morphology-dependent resonances. The presence of both TE and TM resonances in each of the epsilon-polarized and mu-polarized partial-wave …

The Ubiquitous Coffee Filter, Norman F. Derby, Robert Fuller, Phil W. Gronseth

Robert G. Fuller Publications

What analyst would have predicted that Mr. Coffee^TM would diversify into the scientific supplies market? Nevertheless, that coffeemaker's filters, with their flat bottoms and fluted sides, have been popular in physics classroom experiments for some time now. Besides being cheap and readily available, coffee filters allow students to work experimentally with non-constant forces and, because the filters can be easily stacked without changing their aerodynamic profile, the variation in drag force with velocity can be studied. Since stacks of a few filters fall at speeds of about a meter per second and even a stack of ten reaches terminal …

Monte Carlo Simulations Of The Dynamical Behavior Of The Coulomb Glass, Torsten Wappler, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We study the dynamical behavior of disordered many-particle systems with long-range Coulomb interactions by means of damage-spreading simulations. In this type of Monte Carlo simulation one investigates the time evolution of the damage, i.e., the difference of the occupation numbers of two systems, subjected to the same thermal noise. We analyze the dependence of the damage on temperature and disorder strength. For zero disorder the spreading transition coincides with the equilibrium phase transition, whereas for finite disorder we find evidence for a dynamical phase transition well below the transition temperature of the pure system.

Minimal Dynamical Triangulations Of Random Surfaces, Simon Catterall, Mark Bowick, Gudmar Thorleifsson

Physics - All Scholarship

No abstract provided.

Minimal Dynamical Triangulations Of Random Surfaces, Mark Bowick, Simon Catterall, Gudmar Thorleifsson

Physics - All Scholarship

We introduce and investigate numerically a minimal class of dynamical triangulations of two-dimensional gravity on the sphere in which only vertices of order five, six or seven are permitted. We show firstly that this restriction of the local coordination number, or equivalently intrinsic scalar curvature, leaves intact the fractal structure characteristic of generic dynamically triangulated random surfaces. Furthermore the Ising model coupled to minimal two-dimensional gravity still possesses a continuous phase transition. The critical exponents of this transition correspond to the usual KPZ exponents associated with coupling a central charge c=1/2 model to two-dimensional gravity.

Physical Coupling Schemes And Qcd Exclusive Processes, David G. Robertson

Physics Faculty Scholarship

I discuss application of the BLM method to obtain commensurate scale relations connecting QCD exclusive amplitudes to other observables, in particular the heavy quark potential.

The Poisson Ratio Of Crystalline Surfaces, Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson

Physics - All Scholarship

A remarkable theoretical prediction for a crystalline (polymerized) surface is that its Poisson ratio (\sigma) is negative. Using a large scale Monte Carlo simulation of a simple model of such surfaces we show that this is indeed true. The precise numerical value we find is (\sigma \simeq -0.32) on a (128^2) lattice at bending rigidity (kappa = 1.1). This is in excellent agreement with the prediction (\sigma = -1/3) following from the self-consistent screening approximation of Le Doussal and Radzihovsky.

A Telescopic Approach To Modeling Leachate Dynamics And Migration At The St. Johns Landfill, Portland, Oregon, Thomas Stephen Lowry

Dissertations and Theses

The St. Johns Landfill is a 225-acre site that lies near the confluence of the Columbia and Willamette Rivers, in the North Portland Industrial District of Portland, Oregon. A slough system surrounds the landfill on three sides with the fourth side adjacent to a shallow lake. The landfill first opened in 1930 when it was operated as an open dump. It operated as an open dump until 1969 when it was converted to a sanitary landfill, employing daily cover and compaction. The landfill was closed in 1991.

The landfill sits directly on top of a thick layer of silty overbank …

Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher

All HMC Faculty Publications and Research

Nanometer-scale crystal silicon films surrounded by SiO₂ were prepared by oxidizing silicon-on-insulator substrates prepared from SIMOX (separation by implantation of oxygen) and crystallized hydrogenated amorphous silicon films. Average silicon layer thickness was determined from reflection spectra. When sufficiently thin (<2 >nm), all layers emitted red photoluminescence under blue and UV cw excitation, with a spectrum that did not depend on the mean layer thickness. The spectrum was roughly Gaussian with a peak energy of 1.65 eV, which is lower than for most porous silicon spectra. The time scale for the luminescence decay was ~35 μs at room temperature and …

Thermoconvective Instability Of Paramagnetic Fluids In A Uniform Magnetic Field, J. Huang, Boyd F. Edwards, D. D. Gray

All Physics Faculty Publications

The effect of a uniform oblique magnetic field on a laterally unbounded insulating paramagnetic fluid layer heated from below is studied using a linear stability analysis of the Navier–Stokes equations supplemented by Maxwell’s equations and the appropriate magnetic body force. Two-dimensional rolls in an arbitrary vertical plane are considered. Longitudinal rolls with axes parallel to the horizontal component of the field are the rolls most unstable to convection. The corresponding critical Rayleigh number and critical wavelength for the onset of such rolls are less than the well-known Rayleigh–Bénard values in the absence of magnetic fields. Vertical fields maximize these deviations, …

Improving Flavor Symmetry In The Kogut-Susskind Hadron Spectrum, James E. Hetrick, T. Blum

All Faculty Articles - School of Engineering and Computer Science

We study the effect of modifying the coupling of Kogut-Susskind quarks to the gauge field by replacing the link matrix in the quark action by a “fat link,” or sum of link plus three-link paths. Flavor symmetry breaking, determined by the mass difference between the Goldstone and non-Goldstone local pions, is reduced by approximately a factor of 2 by this modification.

An Atlas Of Computed Equivalent Widths Of Quasar Broad Emission Lines, Kirk Korista, Jack Baldwin, Gary J. Ferland, Dima Verner

Physics and Astronomy Faculty Publications

We present graphically the results of several thousand photoionization calculations of broad emission-line clouds in quasars, spanning 7 orders of magnitude in hydrogen ionizing flux and particle density. The equivalent widths of 42 quasar emission lines are presented as contours in the particle density-ionizing flux plane for a typical incident continuum shape, solar chemical abundances, and cloud column density of N(H) = 10²³ cm^-2. Results are similarly given for a small subset of emission lines for two other column densities (10²² and 10²⁴ cm^-2), five other incident continuum shapes, and a gas …

Optical And Magneto-Optical Constants Of Mnpt3, K. W. Wierman, J. N. Hilfiker, R. F. Sabiryanov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam

Department of Physics and Astronomy: Faculty Publications

Optically thick films of MnPt₃ were deposited on quartz using dc magnetron sputtering. The films were covered with an SiO_x protective overcoat and annealed in vacuum at 850 °C for 1 h to form the crystalline L1₂ (Cu₃Au) cubic structure. These films have a high degree of long-range order and are highly textured with the (111) axis along the film normal. Variable angle spectroscopic ellipsometry measurements were taken over the spectral range of 1.2–4.2 eV to determine the optical constants of both MnPt₃ and the SiO_x overcoat. Spectroscopic magneto-optic Kerr rotation and …

Centimeter-Wave Reflection In The Nitrates And Nitrites Of Sodium And Potassium: Experiment And Theory, Steven G. Cornelison, Arthur Guass, Jr., J. Krane, John R. Hardy

John R. Hardy Papers

Temperature-dependent centimeter-wave reflection is studied in powdered samples of potassium nitrate (KNO₃), potassium nitrite (KNO₂), sodium nitrate (NaNO₃), and sodium nitrite (NaNO₂). Temperature-dependent reflection measurements at centimeter-wave frequencies were performed on an HP8510B Network analyzer based reflectometer. These measurements are compared to calculations utilizing a Debye relaxation model. Reflection losses seen in KNO₂ and NaNO₂ are expected to be due to the presence of permanent dipoles that are excited to ‘‘hopping’’ modes as the temperature is raised. Although NaNO₃ shows little reflection losses, KNO₃ shows significant losses as …