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Phase Changes In Plasma‐Sprayed Zinc‐Nickel Ferrite, T. A. Dooling, Desmond C. Cook

Physics Faculty Publications

The magnetic and crystalline properties of a plasma‐sprayed coating of the microwave absorbing zinc‐nickel ferrite, (Zn_0.41Ni_0.59 )Fe₂O₄ have been studied at 300 K using the Mössbauer effect and x‐ray diffraction (XRD). Both techniques indicate that the plasma‐sprayed material separated into two phases. The first is a nickel‐rich phase with magnetic fields of 47.5 and 44.5 T at the tetrahedral and octahedral sites, respectively. The second is a zinc‐rich phase, zinc meta‐ferrite, having a small magnetic field of 4.2 T. The quadrupole splitting of this second phase is ΔE=0.34 mm s⁻¹, …

Intraconfiguration Interactions In Barium 6p1/2Nf Autoionizing States, Xiao Wang, J. Greg Story, William E. Cooke

Physics Faculty Research & Creative Works

Measurements are reported of the energies and linewidths of the J=2, 3, and 4 components of the 6p_1/214f and 6p_1/219f states of barium. These states are anomalously broad, having autoionization lifetimes of approximately 1/2 of a classical Rydberg orbit period, and previously measurements have discerned no differences among the various J components. This work shows that the differences can be observed, and are consistent with calculations. The variations between states would be large if the states were LS coupled, but the large 6p ionic fine-structure forces recoupling into jj configurations. The spherical symmetry of the 6p …

Extrapolation Of The Experimental Data Of Electron Scattering, Hansen Chen

Opportunities for Undergraduate Research Experience Program (OURE)

Our problem of interest is electron-atom scattering. One type of experiment is to measure the number of electrons exciting an atom from a initial s-state to a final p-state. These measurements are proportional to the differential cross section (DCS)….

The plane wave Bom approximation is known not to be accurate enough. However Lassetre claims that even if PWBA (plane wave Bom approximation) is not reliable, a more accurate theory should still extrapolate to the optical oscillator strength.

The theory we are using is significantly better than the PWBA. According to Lassetre’s theorem, our theory should extrapolate to the optical oscillator …

Aerosol Particle Bounding In Cascade Impactors, Bisma Husen

Opportunities for Undergraduate Research Experience Program (OURE)

Particle deposition characteristics were observed from the aerosol sampling results of a UNICO cascade impactor. A simple model of particle motion combined with Hiemenz flow of stagnation flow on a flat plate were developed and discussed.

Both results and analysis were compared to recent models on particle bouncing errors or secondary deposition which included vortices formation around the edge of the slot, back spin (Magnus effect), and hydrodynamic conditions of the particles. The analysis was limited to a laminar inviscid and incompressible case. The main obstacle in the observation was the fact that impactor nozzles were unsymmetrical to a considerable …

Process For Scanning Photographic Slides Of Laser Light Scattering With A Transmission Densitometer, Don Newburry

Opportunities for Undergraduate Research Experience Program (OURE)

Non-symmetric variations in photographic slides of polarized laser light scattering experimental results are difficult to see. This paper explains a process developed for measuring the light density at points throughout the slide area using a transmission densitometer, so an accurate description of the laser light scattering may be obtained. A slide was tested using the described process and the results are presented. The results turned out well, but there were some errors introduced by the instability of the densitometer and by human error in reading the chart recorder output.

A Measurement Of The Relative Efficiency Of A Channeltron, Steve Scott

Opportunities for Undergraduate Research Experience Program (OURE)

The original goal of this project was to determine the characteristics of a channeltron, a device used to detect electrons. While most channeltrons have entrance cones which are quite small, the channeltron we were to study had a significantly larger one. Due to its large size, the possibility existed that the channeltron would be more efficient at detecting electrons which hit near the center of the channeltron entrance than at detecting the electrons which hit near the edge. The main purpose of the experiment was to determine the relative detection efficiency of the channeltron as a function of the position …

Rotationally Resolved Laser Spectroscopy Of The 3s2Σ+ ← 2p2ii Transition In 6li20ne And 7li20ne Van Der Waals Molecules, Chang Jae Lee

Physics Theses & Dissertations

The rotationally resolved absorption spectrum of the ⁶Li²⁰Ne and ⁷Li²⁰Ne 3s²Σ⁺ ← 2p² II transition has been observed. For each isotope, thirteen vibrational transitions from four vibrational levels (v"=0, 1, 2, and 3) of the lower 2p² II to six (v’=0, 1, 2, 3, 4, and 5) of the upper 3s*Σ⁺ electronic state have been rotationally analyzed. Adiabatic potentials and dissociation energies for both states have been obtained through an inverse perturbation analysis. For the 2p²II state, a well depth of 212(5) cm^-1 and an …

An Erasable Optical Memory Based On Stimulated Electronic Transition Concept, James D. Satira

Electrical & Computer Engineering Theses & Dissertations

Erasable optical memory systems with a high storage density and a large data transfer rate are required for many real time data acquisition systems such as those placed aboard NASA's space born platforms. A new concept for erasable optical memory involving stimulated electronic transitions (SET) will meet these requirements. The SET concept useful in erasable optical storage systems was demonstrated in MgS and SrS doped with Eu and Sm. The optical properties of these materials were studied. The reading and writing wavelengths for these samples were determined to be 950 and 514 nm respectively. The peaks of the emission spectra …

Biological Effectiveness Of High-Energy Protons: Target Fragmentation, Francis A. Cucinotta, Robert Katz, John W. Wilson, Lawrence W. Townsend, Judy Shinn, Ferenc Hajnal

Robert Katz Publications

High-energy protons traversing tissue produce local sources of high-linear-energy-transfer (LET) ions through nuclear fragmentation. We examine the contribution of these target fragments to the biological effectiveness of high-energy protons using the cellular track model. The effects of secondary ions are treated in terms of the production collision density using energy-dependent parameters from a high-energy fragmentation model. Calculations for mammalian cell cultures show that at high dose, at which intertrack effects become important, protons deliver damage similar to that produced by γ rays, and with fragmentation the relative biological effectiveness (RBE) of protons increases moderately from unity. At low dose, where …

Anderson Localization Effects In The Light Transmitted Through A Rough Thin Metal Film, Naimah Mohd. Shafie

Masters Theses

The theory of Anderson localization is used to study transmission enhancements in the diffusely transmitted light through a rough thin metal film. These transmission enhancements arise due to phase coherent effects associated with Anderson localization of surface polaritons and are manifested as a well-defined peak in the angular distribution of the intensity of the diffuse component of the transmitted light for light moving opposite to the specularly reflected beam.

The dependence of the widths and heights of the localization related transmission peak is investigated with computer programming and calculations by McGurn and Maradudin (1989). The peak is found to depend …

Long-Range Dipole Field Effects On H– Detachment Processes Above The H(N=2) Threshold, Anthony F. Starace

Anthony F. Starace Publications

The long-range dipole field interaction between a low energy electron and the hydrogen atom in the n = 2 state is shown to be the key for understanding significant features of a number of H^– detachment processes. Collisional, single photon, and two-photon detachment processes are examined, each of which is shown to be sensitive to different aspects of low-energy H(n=2)–e^– interactions. Specifically, these detachment processes are best suited respectively for exhibiting the finite threshold cross sections for certain ¹S^e, ¹P⁰, and ¹D^e final-state channels, the shape resonance in one of …

Third‐Order, Nonlinear Optical Interactions Of Some Benzporphyrins, D.V.G.L.N. Rao, Francisco J. Aranda, Joseph F. Roach, David E. Remy

Physics Faculty Publications

We measured third‐order, nonlinear optical susceptibility χ⁽³⁾ for a series of tetrabenzporphyrins in solution in tetrahydrofuran at 532 nm using degenerate four‐wave mixing with picosecond pulses and obtained values of molecular second hyperpolarizability 〈γ〉. The corresponding macroscopic χ⁽³⁾ values calculated for nine compounds with different substituent groups are four to five orders larger than CS₂. For five of the compounds the χ⁽³⁾ values are in the range 1.2–2.8×10⁻⁸ esu. Our experiments indicate that the nonlinearity is predominately electronic in origin with a response time faster than the 15 ps resolution of our system.

Fluctuations In Astronomical Masers, Moshe Elitzur

Physics and Astronomy Faculty Publications

The radiation of astronomical masers fluctuates on the time scale 1/Gamma, where Gamma is the levels' loss rate. These intensity fluctuations reflect fluctuations of the level poulations around their mean, steady state values over the length scale λ_c = c/Γ. In saturated masers, the intensity fluctuations are dominated by passage through the unsaturated core. The effects of the saturated zones and of the seed radiation that the masers amplify can be neglected.

These fluctuations may have been detected in recent observations by Clegg and Cordes (1991) of Galactic H II/OH masers, providing a possible direct determination of the …

Polarization Of Astronomical Maser Radiation, Moshe Elitzur

Physics and Astronomy Faculty Publications

The polarization of maser radiation when the source is permeated by an aligned magnetic field is derived for arbitrary angular momenta of the transition states. This generalization is made possible by an analysis of the structure of the propagating waves in a frame aligned with the magnetic axis. The key elements in determining the polarization properties are the assumption of independent and incoherent pump and loss processes for all magnetic sublevels, and the beaming of maser radiation. The radiation propagating in the direction of maximal intensity growth is polarized according to the solutions derived by Goldreich, Keeley, and Kwan for …

Relativistic Wave Equation For Anyons, R. Jackiw, V. Parameswaran Nair

Publications and Research

Construction of one-particle states as unitary representations of the Poincare algebra in 2 + 1 dimensions shows that an anyon has one polarization state. However, for nonzero spin manifestly linear and covariant realizations of Lorentz transformations require more than one field component, and an infinite number is needed when the value of spin is not an integer or half-integer. We discuss the relation between these two aspects of Poincare symmetry. In particular, we construct a relativistic equation for anyons where the number of physical polarizations is reduced to one by virtue of a gauge symmetry or equivalent constraint.

Synthesis And Superconducting Properties Of Tl-Ba-Ca-Cu-O Films, Sy_Hwang Liou, V.K. Chan, F. Foong, W.Y. Lee, Y.S. Gou, T.M. Uen

Sy-Hwang Liou Publications

Tl-Ba-Ca-Cu-O superconducting films were synthesized by sputtering either from a single target or from two oxide targets in a symmetric configuration. Films were zero resistance T_c of up to 122 K were obtained after various postannealing treatments at 870-950°C under an oxygen atmosphere. The composition of the films is not very homogeneous on the submicrometer scale. The critical current of these films at 77 K is in the 103-A/cm²-10⁴-A/cm² range, which is much smaller than that of films prepared on SrTiO₃ and LaAlO₃ substrates. The low critical current density in these films …

Redox Capacity Of Apo Mammalian Ferritin, Gerald D. Watt, Richard B. Frankel

Physics

No abstract provided.

Iron Biominerals: An Overview, Richard B. Frankel

Physics

No abstract provided.

Biomineralization Of Iron Sulfides In Magnetotactic Bacteria From Sulfidic Environments, Dennis A. Bazylinski, Richard B. Frankel, Anthony J. Garratt-Reed, Stephen Mann

Physics

No abstract provided.

Polarized X-Ray-Emission Studies Of Methyl Chloride And The Chlorofluoromethanes, Dennis W. Lindle, P. L. Cowan, T. Jach, R. E. Lavilla, R. D. Deslattes, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

A new technique sensitive to molecular orientation and geometry, and based on measuring the polarization of x-ray emission, has been applied to the Cl-containing molecules methyl chloride (CH₃Cl) and the chlorofluoromethanes (CF₃Cl, CF₂Cl₂, and CFCl₃) in the gas phase. Upon selective excitation using monochromatic synchrotron radiation in the Cl K-edge (Cl 1s) near-threshold region, polarization-selective x-ray emission studies reveal highly polarized molecular valence x-ray fluorescence for all four molecules. The degree and the orientation of the polarized emission are observed to be sensitive to the incident excitation energy near …

Intercellular Junctions, Motility, And Magnetosome Structure In A Multicellular Magnetotactic Prokaryote, Frank G. Rodgers, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel, Dennis A. Bazylinski, Denise Maratea, Christine Rodgers

Physics

A many-celled, magnetotactic, prokaryote obtained from brackish water possessed intercellular connections at points of contact between the outer membranes of constituent cells. These connections structurally resembled the "gap junctions" found in eukaryotes. Each aggregate organism consisted of 10 to 30 individual gram-negative cells containing material with the appearance of poly-𝛽-hydroxybutyrate and magnetosomes of unusual arrangement, structure and composition. The aggregate, which possessed prokaryotic-type flagella arranged at the outward surfaces of each cell, showed motility indicative of coordination between individual component cells. These results suggest that this organism is a multicellular prokaryote.

A Study Of The Liquid-Solid Interface During Rapid Resolidification Of Cooper-Titanium Using Molecular Dynamics, Craig L. Loisel

Theses and Dissertations

The behavior of the liquid-solid interface during resolidification of a condensed copper-titanium crystal is studied by atomistic simulation. A system of 1080 atoms (540 of each type) was simulated. The interface was created using monte carlo techniques and resolidification was performed by molecular dynamics. Resolidification was attempted at temperatures of 1200 K, 1100 K, 1000 K, 900 K, 818 K and 773 K. The liquid-solid interface was found to move only at 773 K, resulting in a chemically disordered crystal. The interface velocity observed in the simulation is 6.6 m/s which agrees well with the theoretical value of 5.5 m/ …

Calculated Point Defect Properties Of The Intermetallic Compounds Nickel Titanium (Niti) And Iron Titanium (Feti), Russell T. Lutton

Theses and Dissertations

Atomistic simulation with a modified version of the DYNAMO code was used to calculate the point defect properties of the intermetallic compounds nickel titanium and iron titanium. The calculated energies are believed to be experimentally accurate to within ± 0.1 eV. Vacant Ni or Fe lattice sites were preferred and had energies of 6.356 eV for NiTi and 5.899 eV for FeTi. Removing a Ti atom resulted in a neighboring antisite defect caused by migration of a Ni or Fe atom into the vacant Ti site. These configurations had energies of 7.024 eV for NiTi and 6.336 eV for FeTi. …

High Altitude Neutral Particle Transport Using The Monte Carlo Simulation Code Mcnp With Variable Density Atmosphere, David L. Monti

Theses and Dissertations

The Monte Carlo transport code, MCNP was modified for purposes of two dimensional neutron-photon transport modelling in a variable density atmosphere. Calculations were performed using cylindrical (r, z) geometry and a point isotropic neutron-photon source at an elevation of 40 kilometers. Neutron and photon fluence results were computed using ring detectors for field points at constant range versus source elevation angle and for field points at constant altitude versus radius. Comparisons between the modified and unmodified versions of MCNP showed a decrease in run time by a factor of two was possible. Only a fraction of the spatial cells previously …

Realization Of A Measurement Of A Weak Value, N. W M Ritchie, J. Greg Story, Randall G. Hulet

Physics Faculty Research & Creative Works

We present the first realization of a measurement of a weak value, a concept recently introduced by Aharonov, Albert, and Vaidman (AAV). Our experiment uses a birefringent crystal to separate the two linear-polarization components of a laser beam by a distance small compared to the laser-beam waist. This weak measurement is followed by a strong measurement which translates the centroid of the beam by a distance far larger than the birefringence-induced separation. In addition, we present data corresponding to orthogonal initial and final states, for which the weak value is not defined. This interference effect may have application in the …

Theory Of An Atomic Beam Splitter Based On Velocity-Tuned Resonances, Scott Glasgow, P. Meystre, M. Wilkens, E. M. Wright

Faculty Publications

We develop the theory of an atomic beam splitter in which a monoenergetic beam of two-level atoms is incident normally to a classical standing-wave light field. The incident atomic wave function can be split into two coherent components with transverse momenta ±(2n + 1)fzk using velocity-tuned resonances, where n is the order of the resonance. We discuss the cases of zero- and first-order resonances in detail, and show that the velocity-tuned resonances are renormalized due to a high-frequency Stark shift. Numerical results that display the effects of a finite momentum spread in the incident atomic beam are presented.

Recent Advances In The Comparison Of Matter— And Antimatter—Atom Collisions, D. R. Schultz, Ronald E. Olson, C. O. Reinhold

Physics Faculty Research & Creative Works

The relatively recent advent of low energy antimatter projectiles has spurred a rapid advance in the comparison of matter- and antimatter-atom collisions. These experimental studies have in turn stimulated a great deal of theoretical effort to explain their results, and together both theory and experiment have shed new light on the dynamics of ion-atom collisions. Here we review these developments with particular emphasis on the processes of ionization and charge transfer. © 1991 IOP Publishing Ltd.

Selective Area Deposition Of Boron On Si(111) Induced By Synchrotron Radiation, R.A. Rosenberg, F.K. Perkins, D.C. Mancini, G.R. Harp, B.P. Tonner, S. Lee, Peter A. Dowben

Peter Dowben Publications

We have performed the first deposition of boron on Si(111) induced by broadband synchrotron radiation (SR). Contamination-free thin films were grown at room temperature using decaborane (B₁₀H₁₄) as the source gas. After deposition the films were examined using photoelectron microscopy, which showed that film growth was limited to the region illuminated by SR. The temperature of the substrate rose less than 10 K. These results indicate that gas-phase excitations are not important and that the films are deposited by a nonthermal, photoinduced mechanism. Masked exposures demonstrate the potential of this technique for patterned deposition.

Relativistic Approach For E± Scattering From Argon, Sultana N. Nahar, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

Differential and integrated elastic, integrated total cross sections as well as various polarization parameters–the spin polarization P and the parameters T and U describing the change in the polarization vector during scattering–for the scattering of electrons and positrons from argon in the energy range of 3–300 eV are calculated using the relativistic Dirac equation. The real part of the projectile-target interaction is represented by a sum of model potentials. The phase shifts for large angular momenta ħl are calculated using the Born approximation. The relativistic calculations for the differential and integrated elastic cross sections obtained using the pure real potential …

The Jovian Ionospheric E Region, Y. H. Kim, Jane L. Fox

Physics Faculty Publications

We have constructed a model of the Jovian ionosphere that includes direct photoionization of hydrocarbon molecules. A high resolution solar spectrum was synthesized from Hinteregger's solar maximum spectrum (F79050N) and high resolution cross sections for photoabsorption by H₂ bands in the range 842 to 1116 Å were constructed. Two strong solar lines and about 30% of the continuum flux between 912 and 1116 Å penetrate below the methane homopause despite strong absorption by CH₄ and H₂. We find that hydrocarbons (mainly C₂H₂) are ionized at a maximum rate of 55 cm^{−3 …}