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Analysis Of Space Radiation Effects In Gallium Arsenide And Cadmium Selenide Semiconductor Samples Using Luminescence Spectroscopic Techniques, Brad Lee Shaffer Dec 1990

Analysis Of Space Radiation Effects In Gallium Arsenide And Cadmium Selenide Semiconductor Samples Using Luminescence Spectroscopic Techniques, Brad Lee Shaffer

Theses and Dissertations

Analysis of space radiation effects in gallium arsenide and cadmium selenide semiconductor samples using luminescence spectroscopic techniques. The M0006 semiconductor samples were placed into a 28.5 degree inclination, 480 km altitude, near-circular orbit aboard the Long Duration Exposure Facility satellite and exposed to direct space environment for a period of 11 months, and were shielded by 0.313 inches of aluminum for another 58 months. The samples were examined for changes using cathodoluminescence and photoluminescence in various wavelength regions from 0.5 to 1.8 microns. Samples were cooled to approximately 10 degrees Kelvin in a vacuum of 10-8.

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An Evolution Operator Solution For A Nonlinear Beam Equation, Carl E. Crockett Dec 1990

An Evolution Operator Solution For A Nonlinear Beam Equation, Carl E. Crockett

Theses and Dissertations

A nonlinear partial differential equation, motivated by the transverse vibration of a beam, is shown to have a unique solution. The existence theory, which is in the setting of semigroups and evolution operators, is a composite and synthesis of theorems of Kato. The formulation of the problem and the verification that the formulation leads to a solution are new. The introductory chapter provides background on the topic generally. Chapter 2 provides detailed formulations for the constant coefficient case. Chapter 3 describes nonautonomous cases. The general theorem is presented here. In Chapter 4, a more general case is considered. Namely, Kelvin …

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United States Patent: Metaginsulator Composites Having Improved Properties And Method For Their Preparation, Chia-Ling Chien, Gang Xiao, Sy-Hwang Liou Nov 1990

United States Patent: Metaginsulator Composites Having Improved Properties And Method For Their Preparation, Chia-Ling Chien, Gang Xiao, Sy-Hwang Liou

Sy-Hwang Liou Publications

Improved cermets having superior properties comprising a ferromagnetic metal and an insulator. By controlling process conditions, cermets having high magnetization and high coercivity as well as chemical stability, wear resistance and corrosion resistance are prepared. The cermets of this invention find particular utility as high density recording media.

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Anomalous Dimensions Of Anisotropic Gauge Theory Operators, David G. Robertson, Frank Wilczek Nov 1990

Anomalous Dimensions Of Anisotropic Gauge Theory Operators, David G. Robertson, Frank Wilczek

Physics Faculty Scholarship

The anomalous dimensions of the anisotropic dimension four operators in SU(N) gauge theory coupled to fermions are calculated to lowest order. The possibility of comparison with numerical simulations is pointed out.

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Effects Of Magnetic Field And Temperature On The Critical Current Hysteresis In Tl-Ca-Ba-Cu-O Thin Films, Hung-Lun Chang, Jenh-Yih Juang, Sy_Hwang Liou, Tzeng-Ming Uen, Yih-Shun Gou Nov 1990

Effects Of Magnetic Field And Temperature On The Critical Current Hysteresis In Tl-Ca-Ba-Cu-O Thin Films, Hung-Lun Chang, Jenh-Yih Juang, Sy_Hwang Liou, Tzeng-Ming Uen, Yih-Shun Gou

Sy-Hwang Liou Publications

The behavior of the critical current density of Tl-Ca-Ba-Cu-O superconducting thin films in a cycling magnetic field was investigated. The hysteresis of the transport Jc manifested similar features to those found in polycrystalline Y-Ba-Cu-O and granular Nb, Al thin films in zero-field cooling. However, a novel result of the transport Jc in field-cooled samples has been observed. The results were attributed to the presence of a saturated trapped magnetic flux in the weaklink network. The effects of temperature on both the trapped flux and the transport Jc suggest the existence of various states of the trapped flux …

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Coincident Charge State Production In F⁶⁺+Ne Collisions, D. R. Schultz, Ronald E. Olson, C. O. Reinhold Nov 1990

Coincident Charge State Production In F⁶⁺+Ne Collisions, D. R. Schultz, Ronald E. Olson, C. O. Reinhold

Physics Faculty Research & Creative Works

Total cross sections are presented for the production of various stages of multiple ionization of the target in coincidence with the final projectile charge state for collisions of F6+ with Ne at 10 and 15 MeV. In particular, the current measurements are compared with the results of a classical trajectory Monte Carlo method in which electrons are included explicitly on both target and projectile (nCTMC) and with those based on the conventional independent electron model (IEM). It is shown by the good agreement with experiment that the nCTMC model simultaneously represents well the ionization, charge transfer and excitation channels …

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Average Reaction Cross Sections For 74- To 112-Mev Α Particles On 127I And 133Cs, R. E. Warner, H. W. Wilschut, W. F. Rulla, Gary Felder Nov 1990

Average Reaction Cross Sections For 74- To 112-Mev Α Particles On 127I And 133Cs, R. E. Warner, H. W. Wilschut, W. F. Rulla, Gary Felder

Physics: Faculty Publications

The average reaction cross section for 74- to 112-MeV α particles on 127I and 133Cs was measured by a new method using a magnetic spectrograph and a CsI scintillation detector. The result, σR=2220±50 mb, is in good agreement with optical model calculations and finite-range microscopic calculations. Zero-range microscopic calculations underpredict σR by about 10%, while strong absorption theories overpredict σR by large amounts.

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Radiative Transfer In Astronomical Masers. I. The Linear Maser, Moshe Elitzur Nov 1990

Radiative Transfer In Astronomical Masers. I. The Linear Maser, Moshe Elitzur

Physics and Astronomy Faculty Publications

This is the first in a series of three papers presenting a comprehensive, unified approach for radiative transfer in astronomical maser sources. This paper provides the general formalism and presents the detailed analytic solution of the linear maser, including the case of a source illuminated by background radiation.

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Using Refraction Caustics To Monitor Evaporation Of Liquid Drop Lenses, James A. Lock, Jearl D. Walker, James H. Andrews Nov 1990

Using Refraction Caustics To Monitor Evaporation Of Liquid Drop Lenses, James A. Lock, Jearl D. Walker, James H. Andrews

Physics Faculty Publications

Irregularities in the perimeter of a water droplet adhering to a vertical pane of glass cause perturbations in the curvature of the droplet surface. When laser light passes through such a droplet, the perturbations produce a far field refraction caustic, which is a section of the caustic known as the parabolic umbilic in the catastrophe theory classification. As the water evaporates and the droplet surface curvature changes, the section of the parabolic umbilic caustic on the viewing screen also changes. We determine the evolution of curvature of the droplet surface by observing the evolution of the far field caustic and …

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Dynamic Origin Of Non-Abelian Berry's Phase Effects In A Simple Atomic System, Martin K. Ligare Nov 1990

Dynamic Origin Of Non-Abelian Berry's Phase Effects In A Simple Atomic System, Martin K. Ligare

Faculty Journal Articles

The full effect of adiabatically varying Hamiltonians on systems prepared in eigenstates of the stationary Hamiltonian often includes geometric Berry's phases. For degenerate systems these effects may result in transitions between distinct degenerate eigenstates that can be described in terms of a non-Abelian gauge potential. I demonstrate the explicit dynamic origin of such transitions between degenerate angular-momentum sublevels in an atom that is subject to collinear electric and magnetic fields that rotate adiabatically. The origin of the effects becomes clear when eigenstates of the total Hamiltonian, which includes the rotating fields, are calculated. The total Hamiltonian removes the degeneracy, and …

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Microscopic Calculations Of Low-Energy Reaction Cross Sections, R. E. Warner, Gary Felder Nov 1990

Microscopic Calculations Of Low-Energy Reaction Cross Sections, R. E. Warner, Gary Felder

Physics: Faculty Publications

Microscopic calculations of nuclear reaction cross sections and total reaction probabilities are compared with measurements for the d+Si, 3,4He+Si, and d+Ge systems at energies ranging from 2 to 53 MeV/nucleon. Good agreement is obtained, except for 3He+Si at the very lowest energies, when zero-range nucleon-nucleon forces are assumed and realistic nuclear density distributions are used in the tail regions, where the models are most sensitive. The agreement is less good for finite-range forces. A strong absorption model gives much poorer agreement with the recent 4He+Si measurements than do the microscopic models.

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Controlled Biosynthesis Of Greigite (Fe3S4) In Magnetotactic Bacteria, Brigid R. Heywood, Dennis A. Bazylinski, Anthony J. Garratt-Reed, Stephen Mann, Richard B. Frankel Nov 1990

Controlled Biosynthesis Of Greigite (Fe3S4) In Magnetotactic Bacteria, Brigid R. Heywood, Dennis A. Bazylinski, Anthony J. Garratt-Reed, Stephen Mann, Richard B. Frankel

Physics

No abstract provided.

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Some "Do's" And "Don't'S" For Using Computers In Science Instruction, Glenn A. Sowell, Robert Fuller Nov 1990

Some "Do's" And "Don't'S" For Using Computers In Science Instruction, Glenn A. Sowell, Robert Fuller

Robert G. Fuller Publications

As science researchers and professors, we have had a fairly broad collection of experiences in using computers, from batch-processing and number crunching in large computer systems using FORTRAN and symbolic languages to teaching problem-solving courses for nonscience students using personal computers. While we claim no special computer expertise, we both own computers and are frequently called upon to offer advice to our colleagues who are greater novices than we are. Hence, on the basis of reflections on our experiences and observations of what we have seen other people and institutions do, we have compiled a list of “Do’s” and “Don’ts” …

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Synchrotron Radiation Induced Chemical Vapor Deposition Of Thin Films From Metal Hexacarbonyls*, Derrick C. Mancini, Shikha Varma, John K. Simons, Richard A. Rosenberg, Peter A. Dowben Nov 1990

Synchrotron Radiation Induced Chemical Vapor Deposition Of Thin Films From Metal Hexacarbonyls*, Derrick C. Mancini, Shikha Varma, John K. Simons, Richard A. Rosenberg, Peter A. Dowben

Peter Dowben Publications

We have studied the initial stages of synchrotron radiation [SR] induced chemical vapor deposition [CVD] of metal-containing thin films from metal hexacarbonyl gases. We have measured the dependence of the initial deposition rate upon gas pressure at room temperature. Substrates were exposed to SR for single fills of the electron storage ring at constant pressure of Mo(CO)6, Cr(CO)6, or W(CO) 6 gas. Deposition was monitored in situ by Auger electron spectroscopy using the SW as the excitation source. The presence of metal, carbon, and oxygen in the deposited films was observed, and the results are consistent …

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Laser-Induced Detachment Processes In An Electric Field, Bo Gao, Anthony F. Starace Nov 1990

Laser-Induced Detachment Processes In An Electric Field, Bo Gao, Anthony F. Starace

Anthony F. Starace Publications

An analytic momentum-space wave function for an electron in both laser and static uniform electric fields is presented. It is used to obtain analytic multiphoton detachment cross sections in a static, uniform electric field which include effects of static-field-induced electron-photon interactions. These general results are not restricted to weak laser intensities or to weak static-field strengths and depend only on (a) the electric dipole approximation and (b) the approximation that final-state electron-atom interactions are ignored. Four specific predictions of our general formulas for the most interesting case of linearly polarized light polarized along the static-field direction are presented for weakly …

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Ab Initio Studies Of The Phase Transitions In K2Seo4, H. M. Lu, John R. Hardy Nov 1990

Ab Initio Studies Of The Phase Transitions In K2Seo4, H. M. Lu, John R. Hardy

John R. Hardy Papers

An ab initio model is developed for the potentials in ionic molecular solids in which the electron covalency within the molecular ions substantially affects the interionic interactions. By treating the intermolecular and intramolecular interactions on the basis of the true electron charge densities of the molecular ions, this new model leads to an accurate parameter-free description of the potentialenergy surfaces for such crystals. We performed first-principles static structural relaxation, supercell molecular-dynamics simulation, and lattice-dynamics studies for the room-temperature paraelectric phase and the lower-temperature ferroelectric superstructure of K2SeO4 and predicted with good accuracy the transition from the former …

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Predictions Of Cell Damage Rates For Lifesat Missions, Francis A. Cucinotta, William Atwell, Alva C. Hardy, Michael J. Golightly, John W. Wilson, Lawrence W. Townsend, Judy Shinn, John E. Nealy, Robert Katz Nov 1990

Predictions Of Cell Damage Rates For Lifesat Missions, Francis A. Cucinotta, William Atwell, Alva C. Hardy, Michael J. Golightly, John W. Wilson, Lawrence W. Townsend, Judy Shinn, John E. Nealy, Robert Katz

Robert Katz Publications

Radiological experiments with cell cultures are expected to be performed on Lifesat to study possible gravitational dependence on cellular response. Predictions of cell damage rates for well-studied systems are expected to help guide in the selection of orbits and the design of experiments. In this report we estimate the fractions of cell death and neoplastic transformation of C3H10T1/2 cells (cultured mouse cells) for the proposed Lifesat orbits. The parametric cellular track model of Katz et al. (refs. 1 and 2) is employed using cellular response parameters derived from the experiments of Yang et al. (refs. 3 and 4). The contributions …

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Simple Overdense Rf Plasma Source, R. Mcwilliams, D. Edrich, R. C. Platt, D. P. Sheehan Nov 1990

Simple Overdense Rf Plasma Source, R. Mcwilliams, D. Edrich, R. C. Platt, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

A simple, gas‐fed, radio‐frequency‐driven plasma source is described. By use of lower hybrid waves, noble gas plasmas were produced with electron densities up to 10^12 cm -3 over a range of magnetic fields from 400 G to 1.5 kG and rf frequencies from 2–220 MHz.

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Continuous Wave And Pulsed Solid State Laser Model, Matthew D. Rotondaro Nov 1990

Continuous Wave And Pulsed Solid State Laser Model, Matthew D. Rotondaro

Theses and Dissertations

A solid state laser is modeled for use on a personal computer. The model can accurately represent Nd:YAG and Nd:Glass lasers during both continuous wave and repetitively pulsed operation. The large number of input variables allow the user to make changes to the cavity, optical pump source, and the cooling system. The model calculates the energy, power, and divergence angle of the beam along with other variables. Because of its user-friendly interface, it is possible for someone with limited laser experience to obtain useful information.

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Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz Oct 1990

Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz

Peer Reviewed Articles

Vibrational and rotational distributions of CO excited by collisions with 2.3 eV H atoms have been obtained by monitoring the products with vacuum ultraviolet (VUV) laser induced fluorescence. Translational-to-vibrational (T→V) transfer is dominated by the dynamics of collisions occurring in the two wells on the H+CO potential energy surface, one characterizing the HCO radical and the other characterizing COH. The measured vibrational distributions agree well with the results of trajectory calculations performed on the ab initio potential energy surface of Bowman, Bittman, and Harding (BBH). The measured rotational distributions show two significant differences from the calculated ones. First, for v …

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Heterotic Conformal Field Theory And Gepner’S Construction, Darwin Chang, Asim Gangopadhyaya, Alok Kumar, Jin Wang Oct 1990

Heterotic Conformal Field Theory And Gepner’S Construction, Darwin Chang, Asim Gangopadhyaya, Alok Kumar, Jin Wang

Physics: Faculty Publications and Other Works

We discuss some general properties of heterotic conformal field theory in which conformal anomalies c are different for the left-moving and right-moving sectors. It is precisely this type of theory that can be applied immediately to the construction of heterotic string theory. We discuss a general way of constructing such a theory using free fermions. The construction is then applied to generalize Gepner's construction of superstring solutions using the tensor products of N=2 superconformal field theories.

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Theoretical Description Of The Binary Peak In Clothed Ion-Atom Collisions, C. O. Reinhold, Ronald E. Olson Oct 1990

Theoretical Description Of The Binary Peak In Clothed Ion-Atom Collisions, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

The impulse or binary encounter approximation for ion-atom collisions is extended to treat the non-Coulomb interaction between a clothed projectile ion and the target electrons. This model is shown to reproduce the unexplained enhancement of the zero-degree binary peak for partially stripped ions over that for Equi velocity fully stripped ions that has recently been observed experimentally in Fq++H2, He collisions. Very good agreement is obtained between theory and experiment and, furthermore, this model is used to illuminate the underlying dynamics which leads to the observed enhancement. © 1990 IOP Publishing Ltd.

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A Loading Device For Fracture Testing Of Compact Tension Specimens In The Scanning Electron Microscope, Jügen Rödel, James F. Kelly, Mark R. Stoudt, Stephen J. Bennison Oct 1990

A Loading Device For Fracture Testing Of Compact Tension Specimens In The Scanning Electron Microscope, Jügen Rödel, James F. Kelly, Mark R. Stoudt, Stephen J. Bennison

Scanning Microscopy

A loading device for performing fracture experiments on compact tension specimens in the SEM has been designed. Its key elements are a piezoelectric translator for applying controlled displacements to the loading points on the specimen and a load cell to measure applied loads. The effective transmission of displacement from the piezoelectric driver to the specimen was found to be the major mechanical design problem. The peripheral equipment includes a function generator and a high voltage amplifier that drives the piezoelectric translator as well as a video overlay and standard video equipment to record the image continuously during the course of …

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Hyper-Resistivity To Global-Superconductivity Transition By Annealing In Quench-Condensed Pb Films, Richard P. Barber Jr., Rolfe Eldridge Glover Iii Oct 1990

Hyper-Resistivity To Global-Superconductivity Transition By Annealing In Quench-Condensed Pb Films, Richard P. Barber Jr., Rolfe Eldridge Glover Iii

Physics

The rapid rise in resistance occurring in barely conducting quench-condensed Pb films cooled through temperatures characteristic of the bulk superconducting transition is found to be strongly current dependent, the resistance increasing rapidly with decreasing current and temperature. Annealing the same film at temperatures below 40 K changes the behavior to that of a conventional superconductor with resistance that drops as the film current and temperature decrease. Experimental evidence suggests this results from a transition from quasiparticle-dominated to Josephson-dominated tunneling.

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Quantum-Mechanical Harmonic Chain Attached To Heat Baths Ii: Nonequilibrium Properties, Ulrich Zürcher, Peter Talkner Oct 1990

Quantum-Mechanical Harmonic Chain Attached To Heat Baths Ii: Nonequilibrium Properties, Ulrich Zürcher, Peter Talkner

Physics Faculty Publications

We study nonequilibrium properties of a one-dimensional harmonic chain to whose ends independent heat baths are attached which are kept at different temperatures. Using the quantum Langevin equation approach, we determine the stationary nonequilibrium state for arbitrary temperatures and coupling strength to the heat baths. This allows us to discuss several typical nonequilibrium properties. We find that the heat flux through the chain is finite as the length of the chain goes to infinity, i.e., we recover the well-known fact that the lattice thermal conductivity of the perfect harmonic chain is infinite. In the quantal case, the heat flux jqm …

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Nonalloyed Ohmic Contacts On Low-Temperature Molecular-Beam Epitaxial Gaas: Influence Of Deep Donor Band, H. Yamamoto, Z-Q. Fang, David C. Look Oct 1990

Nonalloyed Ohmic Contacts On Low-Temperature Molecular-Beam Epitaxial Gaas: Influence Of Deep Donor Band, H. Yamamoto, Z-Q. Fang, David C. Look

Physics Faculty Publications

The Ohmic nature of the nonalloyed metal contact on molecular beam epitaxial GaAs grown at 200 °C was studied. The specific contact resistances at room temperature and 120 K were 1.5×10−3 and 7.0×10−1 Ω cm2, respectively. These values are anomalously low considering that the conduction‐band electron concentration in this material is less than 1011 cm−3 at room temperature. The experimental results indicate that the carrier transport at the metal/semiconductor interface is dominated by a dense (∼3×1019 cm−3) EL2‐like deep donor band, rather than the usual conduction band.

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Angular Distribution Of Auger Electrons Emitted Through The Resonant Transfer And Excitation Process Following O⁵⁺+He Collisions, Malika Benhenni, Stephen M. Shafroth, J. K. Swenson, Michael Schulz, J. P. Giese, Harald Schone, Charles Randy Vane, Peter F. Dittner, Sheldon Datz Oct 1990

Angular Distribution Of Auger Electrons Emitted Through The Resonant Transfer And Excitation Process Following O⁵⁺+He Collisions, Malika Benhenni, Stephen M. Shafroth, J. K. Swenson, Michael Schulz, J. P. Giese, Harald Schone, Charles Randy Vane, Peter F. Dittner, Sheldon Datz

Physics Faculty Research & Creative Works

This Letter reports the first measurements of the angular distribution of Auger electrons emitted from the decay of the (1s2s2p2)3D O4+** doubly excited state formed predominantly through resonant transfer and excitation (RTE) in collisions of 13-MeV O5+ projectiles with He. The (1s2s2p2)3D angular distribution is strongly peaked along the beam direction, in agreement with recent calculations of the RTE angle-dependent impulse approximation. Furthermore, interference effects between the RTE and the elastic target direct-ionization channels are observed.

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Mossbauer Spectroscopy Of Fe2+ Binding To Apo And Holo Mammalian Ferritin, Richard B. Frankel, Gerald D. Watt, Georgia C. Papaefthymiou Oct 1990

Mossbauer Spectroscopy Of Fe2+ Binding To Apo And Holo Mammalian Ferritin, Richard B. Frankel, Gerald D. Watt, Georgia C. Papaefthymiou

Physics

The anaerobic binding of Fe2+ to apo and holo Mammalian ferritin has been studied in the pH range from 6.0 to 10.0. Mossbauer spectroscopy of samples in which the added Fe 2+ is enriched in Fe-57 shows that the Fe2+ ions bind to the ferritin core and exchange electrons with Fe3+ ions in the core.

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The Effect Of Externally Applied Oscillating Electric Fields On The L=1 And L=2 Diocotron Modes In Non-Neutral Plasmas, Ross L. Spencer Oct 1990

The Effect Of Externally Applied Oscillating Electric Fields On The L=1 And L=2 Diocotron Modes In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

A high-frequency oscillating electric field can change the properties of diocotron modes in non-neutral plasmas. The effect depends crucially on the azimuthal mode number, m, of the applied field. For m=0, plus or minus 1 there is no effect, and for applied standing waves there is also no effect. But if the applied field has the form of a traveling wave with the norm of m greater than or equal to 2, the frequency of stable diocotron modes can be modified and for the norm of m greater than or equal to 3, the l=2 instability of hollow density profiles …

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Deep Level Characterization Studies In Gaas, Gordhan R. Barevadia Oct 1990

Deep Level Characterization Studies In Gaas, Gordhan R. Barevadia

Electrical & Computer Engineering Theses & Dissertations

The goal of this research was to investigate deep levels in different types of GaAs, a material for high power optically controlled bulk semiconductor switches. For low resistivity semiconductors, such as silicon doped GaAs material (p =0.054 Ω cm), deep level transient spectroscopy (DLTS) was used to characterize deep levels. Three deep levels (EL6, EL3, and EL2) have been detected in this material. For high resistivity semiconductors (p > 104 Ω cm), difficulty of electrical carrier injection and of making a junction does not permit the use of DLTS technique. Therefore, an experimental set-up of the photo-induced current transient spectroscopy …

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