Physical Sciences and Mathematics Commons^™

The Effects Of Low Doses (1 To 500 Kilograys) Of 100-Kev Electrons On Four Polymers, Cynthia Anne Bradbury

Physics Theses & Dissertations

Commercial films of polyetherimide (PEI), polyetheretherimide (PEEI), polyethylene terephthalate (PET), and polycarbonate (PC) were exposed in vacuum to l 00-keV electron radiation to total absorbed doses of l, l 0, l 00, 300, and 500 kilograys. The concentration of radiation-generated radicals, as measured by electron paramagnetic resonance (EPR), increased by over an order of magnitude in all four polymers. Correspondingly, the intensity of the infrared absorption peaks increased uniformly for all doses. Solubility tests resulted in decreased solubility in all polymers. IR, EPR, and solubility suggest dehydrogenation of the aliphatic C-H and phenyl C-H sites. The data indicated that cross …

30th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 30th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, July 31 - August 5, 1988.

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 …

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 …

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.

Theory Of Alpha-Nucleus Collisions At High Energies, Francis A. Cucinotta

Physics Theses & Dissertations

The interaction of high energy alpha particles with atomic nuclei is considered using multiple scattering theories. Semi-classical solutions to coupled-channel equations derived from Watson's form of the nucleus-nucleus multiple scattering series are shown to be equivalent to the Glauber multiple scattering series. Second-order solutions for the elastic amplitude are developed and used to study the effects of short-range correlations in nuclear scattering. The Jastrow method is used to model the two-particle density for ⁴He and to construct one and two particle form factors. Excellent agreement with experimental data for angular distributions, and total and reaction cross sections is found. …

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.

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. …

Single-Electron Capture And Loss Cross Sections Vs. Target Z For 1 Mev/U Oxygen Ions Incident On Gases, Scott Avery Boman

Masters Theses

Cross sections for 1 MeV/u oxygen projectile ions which have gained or lost an electron after passing through a gas target were measured as a function of target Z for several incident projectile charge states. The targets used were D_2, He, Ne, Ar and Kr, and the projectiles had charges of 5+, 6+, 7+ and 8+.

The electron capture measurements are generally in reasonable agreement with existing theoretical and empirical scaling rules. The electron loss cross sections differ appreciably from predictions of the PWBA, particularly for the heaviest targets studied. Empirical scaling relationships are derived for the present capture …

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.

The Relationship Of Pore Volume And Pore Size Distribution To The Development Of Gloss And Scattering Coefficient, John A. Cook

Masters Theses

This study describes in a quantitative manner the relationships between coating structure and optical properties. Gloss, scattering coefficient and void volume were measured after applying different blends of polystyrene spheres to mylar film. Each coating was modeled using large spherical particles of the same size ratios to measure pore size distribution. The coating structure followed well with theoretical packing characteristics of spheres. Optical properties were related to changes in coating structure. Scattering coefficient and gloss correlated better with pore size distribution than particle size. Gloss increased when total void volume was reduced, while the scattering coefficient decreased.

Thermodynamics Analysis Of Refrigeration, Joe Lam

Undergraduate Honors Capstone Projects

In this term paper, I will look indepth at refrigeration. Refrigeration is a rather long and complex topic. Therefore, I will only discuss it as detail as conditions permit. As for the parts where minute details required, I will refer you to the selected references. In discussing refrigeration, I will first look at the Carnot cycle as a fundamental issue for refrigeration.

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 …

Summary Abstract: Formation Of Cr2N Overlayers On A Fe/Cr{110} Crystal, H. Ruppender, M. Grunze, Peter A. Dowben

Peter Dowben Publications

In this communication we summarize our experiments related to the formation of chromium surface nitride layers on a Fe₇₂Cr₂₈{110} surface. These surface nitrides were produced by (i) exposure to molecular nitrogen, (ii) exposure to ammonia, and (iii) segregation of nitrogen to the crystal surface. It was found in all cases that the nitrogen concentration in the selvedge scales linearly with the chromium concentration and that chromium segregation is the rate determining step for the formation of a surface nitride.

Oxygen Defect In Yba2Cu3OX: An X-Ray Photoemission Approach, W.K. Ford, C.T. Chen, J. Anderson, J. Kwo, Sy_Hwang Liou, M. Hong, G.V. Rubenacker, J.E. Drumheller

Sy-Hwang Liou Publications

A combined x-ray photoemission and diamagnetic-susceptibility study of YBa₂Cu₃O_x with x≃6 and 7 has been performed, with emphasis on the oxygen defect and the effect of heating in vacuum. By comparing spectra taken at these two oxygen contents, the core levels observed in the O 1s and Ba 4d spectral range are identified. Peak-intensity analysis indicates (1) that the oxygen released during the in situ heating is derived from or near the Cu-O-Cu-O chains of YBa₂Cu₃O₇ and (2) that there is a random distribution of oxygen defects in …

Cayley-Tree Ising Model With Antiferromagnetic Nearest-Neighbor And Ferromagnetic Equivalent-Neighbor Interactions, Miron Kaufman, M. Kahana

Physics Faculty Publications

The phase diagram of the Ising model with antiferromagnetic nearest-neighbor interactions and ferromagnetic equivalent-neighbor interactions on the Cayley tree is determined exactly. A nonuniversal critical line separates the disordered and the ordered phases. A line of first-order transitions separating ferromagnetic order from antiferromagnetic order ends in the midst of the ordered phase at a classical ordered critical point. For a small range of values of the ratio of the two couplings, two transitions occur as the temperature is varied. In this case the uniform magnetization is not a monotonic function of the temperature.

Ab Initio Approach To The Deuteron In The Skyrme-Witten Model, Alec Schramm

Alec J Schramm

No abstract provided.

Modal Interference Techniques For Strain Detection In Few-Mode Optical Fibers, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

Interference between the modes of an optical fiber results in specific intensity patterns which can be modulated as a function of disturbances in the optical fiber system. These modulation effects are a direct result of the difference in propagation constants of the constituent modes. In this presentation it is shown how the modulated intensity patterns created by the interference of specific mode groups in few-mode optical fibers (V < 5.0) can be used to detect strain. A detailed discussion of the modal phenomena responsible for the observed strain induced pattern modulation is given and it is shown that strain detection sensitivities on the order of 10-9 can be expected. Data taken during the evaluation of an actual experimental strain detection system based on the developed theory is also presented.

Magnetic Properties Of Rare-Earth Transition-Metal Borides, S.H. Aly, E. Singleton, George C. Hadjipanayis, David J. Sellmyer, Z.R. Zhao

David Sellmyer Publications

The magnetic and structural properties of quaternary RCo_4-xFe_xB alloys with R=Nd, Sm, Er have been examined with magnetometry and x-ray diffraction. The CeCo₄B-type phase is found for all x in Er, for x≤3 in Sm, and for x=0, 1, and 2 in Nd. Maximum coercivities have been obtained in a crystallized SmFe₂Co₂B sample with H_c>17 kOe at room temperature.