Physical Sciences and Mathematics Commons^™

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant

Physics Theses & Dissertations

The demand to improve the corrosion resistance of steel sheet, particularly for use within the automotive industry, has led to a dramatic increase in the use of coated steels in place of cold-rolled sheet steel. Galvanneal steel results from the post annealing of the zinc-coated steel sheet, in which iron and zinc are interdiffused to form an iron-zinc alloy coating. Within this alloy coating, four main iron-zinc phases, Zeta, Delta, Gamma-1, and Gamma may be present. Manufacture of the most suitable coating requires identifying which phases form during the galvannealing process, an understanding of the properties of each phase and …

Measurement Of Hyperfine Coupling Constants Of The 5d²D₃/₂ And 5d²D₅/₂ Levels In Atomic Cesium Using Polarization Quantum Beat Spectroscopy, Wo Yei

Physics Theses & Dissertations

Accurate measurements of hyperfine constants have revealed effects that can not be explained by a simple hydrogenic picture of the alkali atoms such as cesium [1-3]. More precise experimental results and theoretical treatments are in demand for the alkali elements, especially for atomic cesium because of its wide range of applications. Therefore, it is essential to understand its atomic and nuclear structure. Precision measurement of its excited-states properties such as hyperfine structure provides global information on nuclear charge and current distributions and also serves as a check to the theory and a calibration of calculated excited state wave functions. Accurate …

Statistical Properties Of Schriidinger Real And Imaginary Cat States, Victor V. Dodonov, Serguei Y. Kalmykov, Vladimir I. Man'ko

Serge Youri Kalmykov

We study the photon statistics in the superpositions of coherent states |\alpha> and |\alpha*> named “Schroedinger real and imaginary cat states”. The oscillatory character of the photon distribution function (PDF) emerging due to the quantum interference between the two components is shown, and quadrature squeezing is observed for moderate values |\alpha| ~ 1. In spite of the quantity <\delta n^2> / tending to unity (like in the Poissonian PDF) at |\alpha| >> 1, the photon statistics is essentially non-Poissonian for all values of |\alpha|. The factorial moments and cumulants of the PDF are calculated, and oscillations of their ratio are demonstrated.

Measure Of Fine Tuning, Greg W. Anderson, Diego Castano

Chemistry and Physics Faculty Articles

Fine-tuning criteria are frequently used to place upper limits on the masses of superpartners in supersymmetric extensions of the standard model. However, commonly used prescriptions for quantifying naturalness have some important shortcomings. Motivated by this, we propose new criteria for quantifying fine tuning that can be used to place upper limits on superpartner masses with greater fidelity. In addition, our analysis attempts to make explicit the assumptions implicit in quantifications of naturalness. We apply our criteria to the minimal supersymmetric extension of the standard model, and we find that the scale of supersymmetry breaking can be larger than previous methods …

Heavy Quark Solitons: Towards Realistic Masses, Joseph Schechter, A. Subbaraman, S. Vaidya, H. Weigel

Physics - All Scholarship

A generalization of the effective meson Lagrangian possessing the heavy quark symmetry to finite meson masses is employed to study the meson mass dependence of the spectrum of S-- and P wave baryons containing one heavy quark or anti-quark. These baryons are described as respectively heavy mesons or anti-mesons bound in the background of a soliton, which is constructed from light mesons. No further approximation is made to solve the bound state equation. For special cases it is shown that the boundary conditions, which have to be satisfied by the bound state wave--functions and stem from the interaction with the …

Resolving Ordering Ambiguities In The Collective Quantization By Particle Conjugation Constraints, Joseph Schechter, H. Weigel

Physics - All Scholarship

We formulate the particle conjugation operation and its convenient realization as G--parity in the framework of several chiral soliton models. The Skyrme model, the Skyrme model with vector mesons and the chiral quark model are specifically treated. The vector and axial vector currents are classified according to their behavior under G--parity. In the soliton sector particle conjugation constrains {\it a priori} ambiguous orderings of operators in the space of the collective coordinates. In the Skyrme model with vector mesons and in a local chiral model with an explicit valence quark this classification scheme provides consistency conditions for the ordering of …

Optically Thin Broad-Line Clouds In Active Galactic Nuclei, Joseph C. Shields, Gary J. Ferland, Bradley M. Peterson

Physics and Astronomy Faculty Publications

The broad-line region (BLR) in Seyfert galaxy nuclei exhibits correlated variations in continuum and emission-line luminosity that are qualitatively consistent with photoionization of ionization-bounded (optically thick) clouds. However, evidence is growing that a nonnegligible fraction of the BLR cloud population is optically thin to the Lyman continuum and fully ionized in hydrogen. We consider the implications of this nebular component for observed line emission and find that inclusion of thin clouds in photoionization calculations can resolve several outstanding puzzles of Seyfert variability, notably the behavior of the C IV λ1549/Lyα ratio as a function of continuum luminosity.

A …

Energy And Angular Distributions Of Electrons From Ion Impact On Atomic And Molecular Hydrogen. I. 20- 114-Kev H+ + H2, M. W. Gealy, G. W. Kerby, Iii, Y.-Y. Hsu, M. Eugene Rudd

M. Eugene Rudd Publications

Apparatus and procedures are described for the measurement of absolute cross sections, differential in ejected electron energy and angle, for ionization of atomic and molecular hydrogen by ion impact. A hemispherical electrostatic energy analyzer, rotatable from 15° to 165° with respect to the direction of the incident ion beam, was used to measure energy spectra of secondary electrons from 1.5 to 300 eV. Cross sections at ten angles (nine at some energies) and five incident-ion energies from 20 to 114 keV for H⁺ +H₂ collisions are given. The doubly differential cross sections were integrated over angle and electron …

Electron-Impact Ionization Of Na, A.R. Johnston, Paul Burrow

Paul Burrow Publications

Recent convergent close-coupling calculations of the ionization cross section of Na by Bray [Phys. Rev. Lett. 73, 1088 (1994)] are in poor agreement with the experimental determinations, most of which were carried out in the 1960s. We report here a measurement of the ratio of the peak ionization cross section to the cross section for excitation of the 3²P state near threshold. By normalizing the latter to the theoretical cross section computed by Moores and Norcross [J. Phys. B 5, 1482 (1972)] and more recently by Trail et al. [Phys. Rev. A 49, 3620 (1994)], we find …

Ion‐Implanted Charge Collection Contacts For High Purity Silicon Detectors Operated At 20 Mk, Betty A. Young, K. M. Yu

Physics

We have developed a technique for fabricating high resolution, ohmic contacts for cryogenic silicon detectors operated at temperatures well below 1 K. In this paper, we give a detailed description of the techniques used to fabricate these boron‐implanted contacts, and present characterization data obtained on 24 test samples studied during the design phase of our program. We then describe the fabrication and operation of a 23 g prototype silicon hybrid detector which simultaneously senses both the phonons and ionization produced by a single event, and which incorporates these new contacts into its design. Finally, we present data obtained using a …

Challenging Weak-Scale Supersymmetry At Colliders, Greg W. Anderson, Diego Castano

Chemistry and Physics Faculty Articles

Experimental searches for supersymmetry are entering a new era. As future experiments explore the mass range above the current lower bounds on superpartner masses, a failure to observe signals of superpartner production will begin to erode the central motivation for supersymmetry at the weak scale. In this article we present a detailed examination of which regions of supersymmetric parameter space are most natural and the extent to which weak-scale supersymmetry becomes unnatural if no superpartners are observed at CERN LEP II, the Fermilab Tevatron, possible upgrades of these machines, and the CERN LHC.

Differential Double-Excitation Cross Sections In 50-150-Kev Proton-Helium Collisions, Michael Schulz, W. T. Htwe, A. D. Gaus, Jerry Peacher, Tibor Vajnai

Physics Faculty Research & Creative Works

We have measured projectile-energy-loss spectra for 50-, 100-, and 150-keV p+He collisions. From the data we obtained differential double-excitation cross sections as a function of projectile scattering angle. At 150 keV a pronounced peak structure was observed at about 0.7 mrad for double excitation to the (2p²) ¹D and (2s2p) ¹P states. Our data provide indications for the dominance of a first-order mechanism involving the electron-electron interaction in double excitation for 150 keV at small scattering angles. At lower projectile energies and larger scattering angles a second-order mechanism appears to be of the same order of …

Energy And Angular Distributions Of Electrons From Ion Impact On Atomic And Molecular Hydrogen. Ii. 20- 114-Kev H+ + H, G. W. Kerby, Iii, M. W. Gealy, Y.-Y. Hsu, M. Eugene Rudd, D. R. Schultz, C. O. Reinhold

M. Eugene Rudd Publications

Results of crossed-beam measurements of cross sections differential in ejected electron energy and angle for ionization of atomic hydrogen by 20-1 14-keV protons are reported. Secondary electrons were measured over an energy range of 1.5-300 eV and an angular range of 15°-165°. Atomic-hydrogen targets were produced in a radio-frequency discharge source with a dissociation fraction of about 74%. Ratios of cross sections for H targets to those for Hz targets were obtained from measurements on the mixed target. From these ratios, the measured dissociation fractions, and the absolute cross sections measured for H, targets, the cross sections for H targets …

Is Fundamentals Of Physics Too Violent?: Reply, Victorial Kaspi, Jearl D. Walker

Physics Faculty Publications

No abstract provided.

Mass Distribution On Clusters At The Percolation Threshold, M. F. Gyure, M. V. Ferer, Boyd F. Edwards, G. Huber

All Physics Faculty Publications

Monte Carlo simulations and a scaling hypothesis are used to study the distribution of blob masses on two-dimensional finite-mass clusters at the percolation threshold. The exponents associated with this distribution function are a combination of backbone and percolation exponents. This work offers insights into the structure and fragmentation properties of percolation clusters in particular, and provides methods applicable to other fractal distribution problems in general.

State Selective Scattering Angle Dependent Capture Cross Sections Measured By Cold Target Recoil Ion Momentum Spectroscopy, Volker Mergel, Reinhard Dorner, Joachim Hermann Ullrich, Ottmar Jagutzki, Sergio Lencinas, S. Nuttgens, Lutz Spielberger, Marc Unverzagt, C. Lewis Cocke, Ronald E. Olson, Michael Schulz, Udo Buck, E. Zanger, W. Theisinger, M. Isser, S. Geis, Horst Schmidt-Bocking

Physics Faculty Research & Creative Works

We have developed a new kind of recoil ion momentum spectroscopy technique, using a precooled supersonic gas jet target, to determine state selective, scattering angle dependent cross sections for swift ion-atom collisions ( 0. 25 , ..., , 1 MeV He²⁺ on He), by measuring the transverse and longitudinal momentum of the recoil ion. A longitudinal momentum resolution of ± 0.13 a. u. was achieved, about a factor of 30 better than ever obtained before, which enables a clear separation of K and L shell capture. In the transverse direction a resolution corresponding to a projectile scattering angle uncertainty …

Electric-Field Enhancement Of Dielectronic Recombination From A Continuum Of Finite Bandwidth, J. Greg Story, Bernard J. Lyons, Thomas F. Gallagher

Physics Faculty Research & Creative Works

A small electric field is shown to increase the dielectronic recombination, via autoionizing Rydberg states, of an electron from a continuum of finite bandwidth. The continuum of finite bandwidth is a broad autoionizing state which is part of a series converging to a higher limit, and the field enhancement of the rate occurs because the field converts the nl Rydberg states to nk Stark states, increasing the number of contributing recombination paths. The experimental results are in excellent agreement with the predictions of an isolated resonance approximation treatment and show clearly both the positive effect of Stark mixing and the …

Regge Calculus As A Fourth Order Method In Numerical Relativity, Mark A. Miller

Physics - All Scholarship

The convergence properties of numerical Regge calculus as an approximation to continuum vacuum General Relativity is studied, both analytically and numerically. The Regge equations are evaluated on continuum spacetimes by assigning squared geodesic distances in the continuum manifold to the squared edge lengths in the simplicial manifold. It is found analytically that, individually, the Regge equations converge to zero as the second power of the lattice spacing, but that an average over local Regge equations converges to zero as (at the very least) the third power of the lattice spacing. Numerical studies using analytic solutions to the Einstein equations show …

Dissociative Attachment In Hot Ch3Cl: Experiment And Theory, D. M. Pearl, Paul Burrow, Ilya I. Fabrikant, Gordon A. Gallup

Paul Burrow Publications

The dissociative attachment (DA) cross section of hot CH₃Cl has been measured in a crossed electron–molecule beam apparatus at temperatures up to 750 K and electron energies from 0–0.5 eV. The results are compared to cross sections computed using a mixed ab initio-semiempirical approach, treating CH₃Cl as a quasidiatomic molecule. The theoretical treatment requires an anion potential curve in the stable region as a portion of the input data. Computations with three different basis sets show the results to be sensitive to the size of basis set from which the potential is determined. At high …

Monte Carlo Studies Of A Novel Lif Radiator For Rich Detectors, Raymond Mountain, A. Efimov, Marina Artuso, Min Gao

Physics - All Scholarship

We show that a multifaceted LiF radiator produces more Cherenkov light and has better resolution per photon than a flat radiator slab when used in a ring imaging Cherenkov counter. Such a system is being considered for the CLEO III upgrade.

Three-Body Final-State Momentum Distributions For Swift H⁺And He2+On He Collisions, R. Dömer, V. Mergel, Liu Zhaoyuan, J. Uilrich, L. Spielberger, Ronald E. Olson, H. Schmidt-Bocking

Physics Faculty Research & Creative Works

The transverse and longitudinal momentum distributions of He+ions produced by 0.25-1MeV u-1H+ and He2+impact have been measured using a precooled supersonic gas jet target (cold-target recoil ion-momentum spectroscopy—coltrims). The transverse momentum of the recoil ions is mainly determined by the impact parameter. In the longitudinal direction the recoil ions are slightly backwardly directed. The width of the longitudinal momentum distribution is close to the electron momentum distribution in the initial state. This distribution gets much broader for larger transverse momentum transfer (i.e. smaller impact parameters). The experimental results are in good agreement with nCTMC calculations. © 1995 IOP Publishing Ltd.

On The Current Status Of Maser Polarization Theory, Moshe Elitzur

Physics and Astronomy Faculty Publications

Despite recent criticism, past conflicts among theoretical studies of maser polarization are by now resolved and clarified. All analytical methods proposed thus far produce the same polarization solutions, solutions that agree with observations. Current numerical studies do not reproduce these solutions. Instead, for any pumping employed, their results are in direct conflict with both analytical theory and observations. These problems reflect the fact that the basic formulation of numerical modeling has yet to incorporate the statistical nature of the radiation field.

Phase Velocity Limit Of High-Frequency Photon Density Waves, Richard C. Haskell, Lars O. Svaasand, Steen J. Madsen, Fabio E. Rojas, Ti-Chen C. Feng, Bruce J. Tromberg

All HMC Faculty Publications and Research

In frequency-domain photonmigration (FDPM), two factors make high modulation frequencies desirable. First, with frequencies as high as a few GHz, the phase lag versus frequency plot has sufficient curvature to yield both the scattering and absorption coefficients of the tissue under examination. Second, because of increased attenuation, highfrequency photon density waves probe smaller volumes, an asset in small volume in vivo or in vitro studies. This trend toward higher modulation frequencies has led us to reexamine the derivation of the standard diffusion equation (SDE)from the Boltzman transport equation. We find that a second-order time-derivative term, ordinarily neglected in the derivation, …

Method For Generating A Plasma Wave To Accelerate Electrons, Donald P. Umstadter, Eric Esarey, Joon K. Kim

Donald Umstadter Publications

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode …

Summary Of The Workshop On The Applications Of X-Ray Standing Waves In Studies Of Surfaces, Fiims, And Buik Materiais, David R. Heskett, L. Berman

Physics Faculty Publications

Highlights of the satellite workshop on the technique of x-ray standing waves which preceded the 5th International Conference on Synchrotron Radiation Instrumentation held at the State University of New York at Stony Brook, USA are presented. At the workshop, many applications of the x-ray standing-wave technique were described in both invited and contributed talks. While the predominant use of the XSW technique was to analyze the structure of adsorbates on surfaces, applications in the characterization of thin films, interfaces, clean surfaces, and bulk materials were also presented. Most of the talks concentrated on experimental results, but some theory was also …

Exploring \Pp Scattering In The \1n Picture, Joseph Schechter, Francesco Sannino

Physics - All Scholarship

In the large N_c approximation to QCD, the leading \pp scattering amplitude is expressed as the sum of an infinite number of tree diagrams. We investigate the possibility that an adequate approximation at energies up to somewhat more than one GeV can be made by keeping diagrams which involve the exchange of resonances in this energy range in addition to the simplest chiral contact terms. In this approach crossing symmetry is automatic but individual terms tend to drastically violate partial wave unitarity. We first note that the introduction of the \rho meson in a chirally invariant manner substantially delays the …

Microbes, Magnetism, And Microscopy, E. Dan Dahlberg, R. B. Proksch, Bruce M. Moskowitz, Dennis A. Bazylinski, Richard B. Frankel

Physics

An accurate quantification of magnetic force microscope images has been accomplished. The magnetosomes produced by magnetotactic bacteria, an ideal micromagnetic model system, were the specimens used for the quantification (a moment on the order of 10⁻¹³ emu).

Grains In Ionized Nebulae: Spectral Line Diagnostics, J. B. Kingdon, Gary J. Ferland, W. A. Feibelman

Physics and Astronomy Faculty Publications

The depletion of condensable elements onto grains in gaseous nebulae can provide evidence that dust is well mixed with the ionized gas. Al and CA are two of the most depleted elements in the general interstellar medium, and it is therefore important to measure their abundances within the ionized region of nebulae. We compute a large grid of photoionization models and identify sets of line ratios which are relatively insensitive to stellar and nebular parameters, and are thus excellent diagnostics for determining relative abundances. Based on the absence of the [Ca II] λλ7291, 7324 doublet and the detection of …

Heavy Ion Track-Structure Calculations For Radial Dose In Arbitrary Materials, Francis A. Cucinotta, Robert Katz, John W. Wilson, Rajendra R. Dubey

Robert Katz Publications

The δ-ray theory of track structure is compared with experimental data for the radial dose from heavy ion irradiation. The effects of electron transmission and the angular dependence of secondary electron ejection are included in the calculations. Several empirical formulas for electron range and energy are compared in a wide variety of materials in order to extend the application of the track-structure theory. The model of Rudd for the secondary electron spectrum in proton collisions, which is based on a modified classical kinematics binary encounter model at high energies and a molecular promotion model at low energies, is employed. For …

Convenient Determination Of Concentration And Energy In Deep-Level Transient Spectroscopy, David C. Look, Z-Q. Fang, J. R. Sizelove

Physics Faculty Publications

For defects or impurities with deep energy levels, such as the commonly observed EL2, EL3, and EL6 in GaAs, it is very important to take account of the so‐called λ effect in order to deduce the correct concentrations of these centers when using capacitance techniques. By measuring capacitance at several forward bias voltages for a given reverse bias voltage it is possible to determine concentration N_T and energy E_T without requiring the usual emission rate analysis. Convenient formulas for N_T and E_T are given, although only N_T can be determined with a high degree of …