Physics Commons^™

Singular-Value Decomposition And The Grassberger-Procaccia Algorithm, Alfonso M. Albano, J. Muench, C. Schwartz, A. I. Mees, P. E. Rapp

Physics Faculty Research and Scholarship

A singular-value decomposition leads to a set of statistically independent variables which are used in the Grassberger-Procaccia algorithm to calculate the correlation dimension of an attractor from a scalar time series. This combination alleviates some of the difficulties associated with each technique when used alone, and can significantly reduce the computational cost of estimating correlation dimensions from a time series.

Division-Of-Wave-Front Thin-Film Beam Splitter For Generating Binary Patterns Of Orthogonal Elliptical Polarization States, R. M.A. Azzam

Electrical Engineering Faculty Publications

A division-of-wave-front thin-film beam splitter is described that reflects monochromatic light at oblique incidence with orthogonal elliptical polarization states. It consists of a metallic substrate partially covered with a transparent thin film that inverts the ratio ρ of the complex p and s reflection coefficients at the principal angle of the metal. Any pattern of coated and uncoated areas of the substrate is imprinted upon the reflected wave front as a corresponding two-dimensional spatial binary polarization pattern. A specific design is given that uses a Au substrate at a wavelength of 632.8 nm. The effects of small errors in the …

Thin-Film Devices For Polarized Light- Introduction, R. M.A. Azzam, William H. Southwell

Electrical Engineering Faculty Publications

No abstract provided.

Explorers Of The Nuclear Cyclotron Experiment 190, Robert Fuller

Robert G. Fuller Publications

Physics is the world view espoused by the community of people called physicists. Some of them use a common facility with many other physicists to increase the cost-effectiveness of the facility. The life style of such physicists shares many features with a wide variety of professions that use very expensive equipment. For example, personal time schedule of the equipment as much for television producers as for cyclotron physicists.

Two-Photon Detachment Of The Negative Chlorine Ion, Tsin-Fu Jiang, Anthony F. Starace

Anthony F. Starace Publications

Theoretical calculations of the two-photon detachment cross section of the negative chlorine ion are presented in the energy region from threshold to the single-photon ionization threshold using a transition-matrix method. Detailed analyses are presented of the effects of various kinds of electron correlations, whose net effect is a reduction of the uncorrelated Hartree-Fock model cross sections by up to 30%. Our cross sections have a much flatter variation with energy and a much lower magnitude (by up to a factor of 2 or 3) than the frozen-core free-electron results of M. Crance [J. Phys. B 20, 6553 (1987)] or the …

Growth Of Epitaxial Ybba2Cu3O7 Superconductor By Liquid-Gas-Solidification Processing, H.S. Chen, Sy_Hwang Liou, A.R. Kortan, L.C. Kimerling

Sy-Hwang Liou Publications

Superconductive films of YbBa₂Cu₃O₇ have been epitaxially grown on SrTiO₃ substrate by a novel liquid-gas-solidification process. A layer of metallic YbBa₂Cu₃ melt was coated on the substrate and in situ oxidized. The oxide films grown on the SrTiO₃ (100) substrate are epitaxially oriented in structure with the c axis normal to the plane film. Values of T _c (R =0) of 82 K with a transition width of 1 K have been achieved. The critical current density J _c is typically 10⁵ A/cm² at 50 K and …

Metastable Conduction States In Mo2S3: Pulse Conductivity And Thermoelectric Power, Roger D. Kirby, R.L. Fagerquist

Roger Kirby Publications

Mo₂S₃ is a linear-chain-structure compound which has two inequivalent zig-zag Mo chains parallel to the b axis. It undergoes at least two phase transitions below room temperature (at 182 and 145 K upon cooling). X-ray-diffraction measurements show that both incommensurate and commensurate structural distortions are associated with the phase transitions. We repot here the results of electrical-conductivity and thermoelectric-power measurements on Mo₂S₃ . By using pulsed electric currents to rapidly heat and cool the sample while electrical-resistivity or thermoelectric-power measurement are being made, we are able to show that below the lower-temperature phase transition, …

Anaerobic Magnetite Production By A Marine, Magnetotactic Bacterium, Dennis A. Bazylinski, Richard B. Frankel, Holger W. Jannasch

Physics

Bacterial production of magnetite represents a significant contribution to the natural remanent magnetism of deep-sea and other sediments1–5. Because cells of the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum require molecular oxygen for growth and magnetite synthesis6, production of magnetite by magnetotactic bacteria has been considered to occur only in surficial aerobic sediments7. Moreover, it has been suggested that deposits of single-domain magnetite crystals are palaeooxygen indicators presumably having been formed under predominantly microaerobic conditions5–8. In contrast, some nonmagnetotactic, dissimilatory iron-reducing bacteria, such as the recently described strain GS-15 by Lovley et al. 7, synthesize extracellular magnetite from hydrous ferric oxide under …

Extrema Of The Magnitude And The Phase Of A Complex Function Of A Real Variable: Application To Attenuated Internal Reflection, R. M.A. Azzam

Electrical Engineering Faculty Publications

Given a complex function F(ω) = |F(ω)|exp[jΔ(ω)] of a real argument ω, the extrema of its magnitude |F(ω)| and its phase Δ(ω), as functions of ω, are determined simultaneously by finding the roots of one common equation, Im[G(ω)] = 0, where G= (F′/F)² and F′ = ∂F/∂ω. The extrema of |F| and Δ are associated with Re G < 0 and Re G > 0, respectively. This easy-to-prove theorem has a wide range of applications in physical optics. We consider attenuated internal reflection (AIR) as …

Simulation Of The Polarizable-Ion Dynamics Of Rb2Zncl4, P. J. Edwardson, John R. Hardy

John R. Hardy Papers

The promotion yet prevention of structural stability in the paraelectric phase of Rb₂ZnCl₄ by ionic polarizability is explored with both constant-lattice and variable-lattice simulations. As many as 168 ions ( 3 x 1 x 2 cells) under periodic boundary constraints are allowed to polarize in nonlinear response to forces which are obtained from the electron-gas model of Gordon and Kim. No assumption about the rigidity of the ZnCl₄^2- ion is made. The cause of polarization catastrophe in linear models is examined, and a cure is implemented via nonlinearity of the dipole moment versus field strength. …

Effect Of Closed Classical Orbits On Quantum Spectra: Ionization Of Atoms In A Magnetic Field. I. Physical Picture And Calculations, M. L. Du, John B. Delos

Arts & Sciences Articles

This is the first of two papers that develop the theory of oscillatory spectra. When an atom is placed in a magnetic field, and the absorption spectrum into states close to the ionization threshold is measured at finite resolution, so that individual energy levels are not resolved, it is found that the absorption as a function of energy is a superposition of sinusoidal oscillations. These papers present a quantitative theory of this phenomenon. In this first paper, we describe the physical ideas underlying the theory in the simplest possible way, and we present our first calculations based upon the theory. …

Effect Of Closed Classical Orbits On Quantum Spectra: Ionization Of Atoms In A Magnetic Field. Ii. Derivation Of Formulas, M. L. Du, John B. Delos

Arts & Sciences Articles

A formula is derived for oscillations in the near-threshold absorption spectrum of an atom in a magnetic field. Three approximations are used. (1) Near the atomic nucleus, the diamagnetic field is negligible. (2) Far from the nucleus, the waves propagate semiclassically. (3) Returning waves are similar to (cylindrically modified) Coulomb-scattering waves. With use of these approximations, together with the physical picture described in the accompanying paper, an algorithm is specified for calculation of the spectrum.

Variational Calculation Of Multiphoton Ionization Processes For The H Atom, Bo Gao, Anthony F. Starace

Anthony F. Starace Publications

Well-known variational principles for second-order perturbation matrix elements are extended to higher-order multiphoton processes for atomic hydrogen. Numerical applications to two- and three-photon ionization of the hydrogen ground state provide results comparable to those of analytic calculations, even near intermedaite-state resonances, yet without the complications involved in summation over intermediate states. Extensions to multiphoton processes for many-electron atoms are discussed briefly.

Magnetic Properties Of Magnetotactic Bacteria, B. M. Moskowitz, Richard B. Frankel, P. J. Flanders, R. P. Blakemore, Brian B. Schwartz

Physics

This paper reports on the magnetic properties of magnetosomes in the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum. The magnetosomes are well crystallized particles of magnetite with dimensions of 40 to 50 nm, which are arranged within the cells in a single linear chain and are within the single-magnetic-domain (SD) size range for magnetite. A variety of magnetic properties have been measured for two samples of dispersions of freeze-dried cells consisting of (1) whole cells (M-1) and (2) magnetosomes chains separated from cells (M-2). An important result is that the acquisition and demagnetization of various type of remanent magnetizations are markedly …

Magnetic Properties Of Tunicate Blood Cells. I. Ascidia Nigra, Seunghee Lee, Kenneth Kustin, William E. Robinson, Richard B. Frankel, K. Spartalian

Physics

The magnetic properties of intact and freeze-dried blood cells of the tunicate Ascidia nigra and of model vanadium(III) and (IV) compounds as polycrystalline solids and in aqueous solution have been measured up to 50 kOe with a SQUID susceptometer. Corrections for the samples' diamagnetism were extracted from the temperature dependence of the data without any further assumptions. For vanadium(IV), measured values of the magnetic moment at different values of the applied magnetic field over the temperature range 2–100 K obey a Brillouin function with spin 1/2. For vanadium(III), the magnetic moment data did not obey a Brillouin function and were …

Dynamics Of Antimatter-Atom Collisions, R. E. Olson, Timothy J. Gay

Timothy J. Gay Publications

Classical-trajectory Monte Carlo calculations have been used to study ionizing collisions between charged particles (p, p̅ , ℯ⁺, ℯ^-) and He atoms at an incident velocity of 2.83 a.u. While differences in the total single-ionization cross sections for these projectiles are small, our calculations reveal large effects at all angles in the ionized electron spectra, and provide qualitative evidence for a Barkas effect in p and p̅ collisions. Experimental data agree well with our fully classical calculations, including cross sections involving ejected electrons of long wavelength.

Erratum: Micellar-Shape Anisometry Near Isotropic–Liquid-Crystal Phase Transitions, Foek T. Hioe

Physics Faculty/Staff Publications

In lieu of an abstract, below is the first paragraph:

In our paper the binary sodium dodecyl (lauryl) sulfate (SLS)–water system was investigated by small-angle x-ray scattering in the isotropic (I) phase up to the I-hexagonal (H_a) transition and the ternary system (with decanol added to a binary system containing 26 wt% of SLS in water) up to what was considered to be an I-nematic cylindrical (N_c) phase transition. Our paper did not focus on the phase diagram of the studied system but rather on the detailed modeling of the …

High-Pressure Neutron-Scattering Studies Of Graphite And Stage-Two Graphite-Sbcl₅, B. Alzyam, Clive H. Perry, C. Zahopoulos, Oran Allan Pringle, Robert M. Nicklow

Physics Faculty Research & Creative Works

The longitudinal-acoustic (LA) phonons propagating along the c axis in highly oriented pyrolytic graphite (HOPG) were investigated as a function of pressure up to 20 kbar using inelastic-neutron-scattering techniques. The phonon frequencies varied as (P,q)=A(P)sin[c(P)q/2], where A(P) and c(P) indicate the pressure dependences of the zone-center LO frequency of B_1g1 symmetry and of the c-axis lattice spacing, respectively. From the measurements, the mode Grüneisen parameter for the LA branch was estimated to be 1.5 x 10^-2 kbar^-1 (independent of q); the elastic constant C₃₃ for HOPG was found to be 3.40 x 10¹¹ dyn/cm …

Formation Of Ground And Excited States Of Antihydrogen, Sultana N. Nahar, J M. Wadehra

Physics and Astronomy Faculty Research Publications

Differential and integrated cross sections for the formation of antihydrogen by the impact of intermediate-energy (20–500 keV) antiprotons on positronium are calculated using the first Born approximation. The calculations are carried out for the formation of antihydrogen in ground and various excited electronic states (n=1–3) when positronium, the target atom, is in the ground state, and for the formation of antihydrogen in the ground state when the positronium is in various excited electronic states (n=1–2). The 1/n^3 behavior for the capture cross sections is used to calculate the total (that is, all states added together) integrated cross sections. The cross …

Three-State Systems Driven By Resonant Optical Pulses Of Different Shapes, C. E. Carroll, Foek T. Hioe

Physics Faculty/Staff Publications

New analytic solutions to the problem of a three-state system driven simultaneously by resonant optical pulses of different shapes are presented. The solutions are useful for prescribing the conditions for complete population transfer from one state to another or for complete population return.

Electronic Excitations Of The Yba2Cu3O7-X Superconductor: A Study By Transmission Electron-Energy-Loss Spectroscopy With An Electron Microprobe, C.H. Chen, L.F. Schneemeyer, Sy_Hwang Liou, M. Hong, J. Kwo, H.S. Chen, J.V. Waszczak

Sy-Hwang Liou Publications

Interband and core-level transitions and plasmon resonance in the high-temperature oxide superconductor YBa₂Cu₃O_7-x were studied by transmission electron-energy-loss spectroscopy using an electron microprobe ∼5-10 Å in size. Both single-crystal and polycrystalline ceramic samples have been examined. No significant change in electronic structure was observed at the grain boundaries. A 13.5-eV interband-transition peak was found to be sensitive to damages created by ion-beam bombardment.

Incommensurate Superlattice And 90° Twist Boundaries In The Superconducting Phase Of Bi-Sr-Ca-Cu-O, C.H. Chen, D.J. Werder, Sy_Hwang Liou, H.S. Chen, M. Hong

Sy-Hwang Liou Publications

We have observed an incommensurate superlattice structure in the Bi-Sr-Ca-Cu-O system using electron diffraction. The wave vector of the superlattice, q=(0,1/4.7,1), has an incommensurate component along the b axis and a commensurate component along the c axis. Twist boundaries perpendicular to the c axis, across which the crystallographic a and b axes are rotated 90°, are commonly observed in this system.

Atomic Electrons In Strong Magnetic Fields: Transition From Elliptical To Helical Behavior., John B. Delos, Stephen Knudson, Shena Sikora, Robert Leonard Waterland, S. Whitworth

Arts & Sciences Articles

The behavior of an atomic electron in a static magnetic field strong enough to correspond to the transition regime is examined. The field strength is characterized by the parameter L^, the effective component of angular momentum. A Floquet-Mathieu analysis shows that the bifurcation of classical trajectories into elliptical and helical families is related to the 2:1 resonance which occurs at L^=L^T. Quantum mechanics gives an avoided crossing at L^T; we examine the nature of the wave functions as L^ passes through the resonance. Semiclassical calculations accurately reproduce the quantum eigenvalues and produce trajectories which underlie the quantum wave functions. …

Possible Origins Of High-TC, Superconductivity, John R. Hardy, J. W. Flocken

John R. Hardy Papers

A new mechanism is proposed to explain high-T_c superconductivity in copper-oxide-based, open perovskitelike systems. It is shown that, should the oxygen ions be moving in a double-well potential, an order-of-magnitude enhancement of the electron-lattice coupling follows automatically from a consistent treatment of this motion. Both theoretical and experimental evidence for the presence of such double wells is cited.

Possible Origins Of High-Tc, Superconductivity, John R. Hardy, John W. Flocken

Physics Faculty Publications

A new mechanism is proposed to explain high-T, superconductivity in copper-oxide-based, open perovskitelike systems. It is shown that, should the oxygen ions be moving in a double-well potential, an order-of-magnitude enhancement of the electron-lattice coupling follows automatically from a consistent treatment of this motion. Both theoretical and experimental evidence for the presence of such double wells is cited.

Y-Ba-Cu-O Films By Rf Magnetron Sputtering Using Single Composite Targets: Superconducting And Structural Properties, Sy_Hwang Liou, M. Hong, J. Kwo, B.A. Davidson, H.S. Chen, S. Nakahara, T. Boone, R.J. Felder

Sy-Hwang Liou Publications

High T_c superconducting Y-Ba-Cu-O films have been produced by rf magnetron sputtering using single unreacted composite targets of Y₂O₃, BaF₂, and CuO powders. Transport measurements of the films showed a sharp resistive T_c (R=0) at 89 K and a metallic behavior of resistivity versus temperature. The films show preferred orientations when deposited on single-crystal SrTiO₃ substrates (100) or (110) and followed by a post O₂ annealing at 825 °C.

Experimental Study Of Nonlinear Conductance In Small Metallic Samples, Richard A. Webb, S. Washburn, C. P. Umbach

Faculty Publications

We have directly observed current-dependent, nonlinear contributions to the conductance fluctuations of phase-coherent metallic wires and loops. The fluctuations in the current-voltage curves are reproducible, asymmetric about I=0, and in qualitative agreement with theoretical predictions. In ac measurements, the nonlinear terms also generate large harmonic signals of the conductance fluctuations whose dependence on the drive current can be understood qualitatively. The spectra of harmonics from loops and wires have different dependences on the voltage across the sample.

General Analysis And Optimization Of The Four-Detector Photopolarimeter, R. M.A. Azzam, I. M. Elminyawi, A. M. El-Saba

Electrical Engineering Faculty Publications

The four-detector photopolarimeter (FDP) is analyzed for an arbitrary spatial configuration and any reflection characteristics (r_i, ψ_i, Δ_i) of the first three detectors. The instrument matrix A, which relates the output signal vector I to the input Stokes vector S by I = AS, and its determinant are derived explicitly. The essential condition that A be nonsingular (det A ≠ 0) is satisfied in general with uncoated absorbing detector surfaces, assuming that the plane of incidence (POI) is rotated between successive reflections by other than 90°. Therefore no special coatings on …

Hylleraas Variational Perturbation Theory: Application To Correlation Problems In Molecular Systems, Robert J. Cave, Ernest R. Davidson

All HMC Faculty Publications and Research

Hylleraas variational perturbation theory is applied through second order in energy to estimate the correlation energy in several molecular systems. The specific choices for H₀ and V which are made lead to equations nearly identical to the multireference linearized coupled‐cluster method of Laidig and Bartlett. The results obtained are in virtually exact agreement where comparisons have been made. Results from test calculations are presented for BeH₂, CH₂, and C₂H₄. In addition, the utility of perturbation theory for selecting correlating configurations is examined. This procedure is found to be quite accurate while …

Projectile-Charge Dependence Of Ejected-Electron Spectra, V. D. Irby, Timothy J. Gay, J. Wm. Edwards, E. B. Hale, M. L. Mckenzie, R. E. Olson

Timothy J. Gay Publications

We have studied H⁺+He and ³He⁺⁺+He ionizing collisions at intermediate energies (60 to 120 keV/amu) and have observed a significant shift in the velocity position of the maxima in forward-ejected electron spectra when changing projectiles from protons to α particles. In ionizing collisions, a large portion of the ejected electrons are stranded near the transitory equiforce, or saddle point, position between the target ion and receding projectile. The shift in the electron spectra maxima to smaller velocities, due to changing projectiles from protons to α particles, is consistent with the shift in the saddle-point velocity …