Physical Sciences and Mathematics Commons^™

Surface Plasmons And The Reflectivity Of N-Type Insb, William E. Anderson, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

The Reflectivity of N-Type InSb Has Been Measured in the Far Infrared. the Doping of the Samples Was Such that the Free-Carrier Plasma Frequency Was Near the LO Mode Frequency. the Results Suggest that Samples with a Sufficiently Thick Damage Layer Show Effects Due to Surface Plasmons. Use of a Simple Model Indicates that the Surface-Plasma Excitations Are Coupled to the Phonons. © 1971 the American Physical Society.

Scattering Of Waves In Many Dimensions, I. Adawi

Physics Faculty Research & Creative Works

Scattering by a spherical potential is discussed in all dimensions by one formulation using the partial-wave expansion method. The optical theorem relating the total scattering cross section σ to the forward scattering amplitude f(0) is derived.

Experimental And Theoretical Study Of The Sign Preference In The Nucleation Of Water Vapor, Daniel R. White, James L. Kassner

Physics Faculty Research & Creative Works

The nucleation of water vapor on ions in atmospheres of helium and argon was studied using an expansion type cloud chamber. Separation of the positive and negative ions was achieved so that the nucleation could be studied as a function of both the sign of the ionic charge and the supersaturation. A semiphenominological theory was developed as an extension of the classical liquid drop theory to include the effects of the ionic charge on the nucleation process. The theoretical model of the prenucleation embryo was assumed to possess an oriented dipole surface layer with the direction of orientation dependent on …

Heisenberg Ferromagnet With Biquadratic Exchange, Harry A. Brown

Physics Faculty Research & Creative Works

The usual Heisenberg Hamiltonian with bilinear exchange -2JS→1•S→2 has been extended to include a biquadratic term -2αJ(S→1•S→2)2, with an adjustable parameter α. A method equivalent to constant coupling was employed to calculate the effect of the biquadratic exchange term on the Curie temperature, magnetization, susceptibility, specific heat, and entropy for lattices with spin-1 atoms. As α goes from 0 to 1, the Curie temperature falls by a factor 2 to 3, while the asymptotic Curie temperature is reduced by the factor 2. The magnetization rises much more rapidly below TC, and the specific heat has a peak and discontinuity several …

Interplanar Force Constants Of Symmetry Planes In Close-Packed Structures, Paul G Khoury

Archived Theses and Dissertations

No abstract provided.

Mössbauer Studies Of Bifeo₃-Pbtio₃ Perovskite-Type Solid Solutions, C. M. Yagnik, Robert Gerson, William Joseph James

Physics Faculty Research & Creative Works

The Mössbauer spectra of the ferroelectric solid solutions (BiFeO₃)_x(PbTiO)1-x have been studied as a function of temperature, mainly between room temperature and 600°C, using ⁵⁷Fe in the solutions as an absorber. The quadrupole splitting increased and the isomer shift decreased between x = 0.05 and x = 0.70, a range in which the solutions are tetragonal and paramagnetic, and in which the unit cell volume increases with increasing x. The isomer shift, in particular, was primarily determined by the unit cell volume. Data are presented on the internal magnetic field of the antiferromagnetic …

Surface Plasmon-Longitudinal Optical Phonon Contribution To The Reflectivity Of N-Type Insb, William Eugene Anderson

Doctoral Dissertations

"The reflectivity of n-type InSb has been measured in the far infrared. The doping of the samples was such that the free-carrier plasma frequency was near the longitudinal optical phonon frequency. The results suggest that samples with a sufficiently thick damage layer show effects due to surface plasmons. The results also indicate that the surface plasma excitations are coupled to the phonons. A simple model of this coupling is presented which agrees qualitatively with the observed reflectivity. A somewhat more rigorous theory of the coupling is also presented"--Abstract, page ii.

An Investigation Of The Temperature Dependence Of The Electrical Resistivity Of Concentrated Strong-Scattering Alloys, An-Ban. Chen

Dissertations, Theses, and Masters Projects

No abstract provided.

Theory Of Nucleation Of Water Properties Of Some Clathrate Like Cluster Structures, Mehdi Daee

Doctoral Dissertations

"The tranquility of classical homogeneous nucleation theory has been disturbed by the introduction of statistical mechanical correction factors to a basically thermodynamic theory. These factors, which appear to be essential, destroy much of the agreement with experiment in the case of water vapor. A molecular model for the pre-nucleation water clusters is proposed with a view toward resolving some of these difficulties. As a first step, the Properties of a few specific cluster configurations have been examined. Clathrate-like structures containing 16 to 57 water molecules are discussed. The hydrogen bonds were treated as simple harmonic oscillators for the purpose of …

Homogeneous Nucleation Of Water Vapor In Inert Gas Atmospheres, Arthur Henry Biermann

Doctoral Dissertations

"The homogeneous nucleation of water vapor in atmospheres of helium, neon, argon, krypton, and xenon was studied using an expansion type cloud chamber. A strong dependence of the nucleation rate on the particular inert carrier gas was observed. At present the only dependence upon the nature of the carrier gas included in classical nucleation theories is a small factor arising from kinetic considerations which is in the wrong direction to explain the observations. To explain the dependence of the rate on the nature of the carrier gas, a molecular cluster model is assumed allowing inert gas atoms to occupy the …

Absolute Cross Sections For Excitation Of Neon By Impact Of 20-180 Kev H , H₂ And He Ions, George William York

Doctoral Dissertations

"The technique of heavy-ion energy-loss spectrometry has been used to measure excitation cross sections for the (2p⁵)3s and (2p⁵)3p electronic configurations of Neon. The incident particles used were H⁺ , H⁺₂ and He⁺ at impact energies from 20-180 keV. The results are compared with previous optical measurements of the emission cross sections of lines from these levels as excited by H⁺ and He⁺ impact. Agreement is not good, either in shape or in absolute magnitude for excitation of the (2p⁵)3s configuration. However, agreement is surprisingly good for excitation of the (2p⁵)3p configuration. A curve fitting technique has been applied to …

MöSsbauer Studies Of Stable Interstitial And Substitutional Sites Of Cobalt In Gold, Charles Freeland Steen

Dissertations and Theses

Precision measurements of the Debye-Waller factor of Fe⁵⁷ in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error arises from Au L_y x-rays which are unresolved by the radiation detection system from the 14.4 KeV gamma ray. The K absorption edge of Br has been used to correct for the presence of x-rays.

These measurements have revealed the existence of two nonequivalent lattice sites which the Co⁵⁷ impurity (parent of Fe⁵⁷) may occupy. One of the sites has been …

Nuclear Magnetic Resonance Investigation Of The Metal-To-Semiconductor Transition In Crystalline Cdo, R. P. Benedict, David C. Look

Physics Faculty Publications

Measurements of the Cd¹¹³ nuclear-spin-lattice relaxation time (T₁) and resonance frequency shift (K) were carried out in several samples of polycrystalline n-type CdO over the temperature (T) range 1.4-300°K, frequency (ν) range 2-10 MHz, and carrier concentration (N_e) range 3.3-44×10¹⁸ cm^-3. For N_e>10¹⁹ cm^-3, we find that T₁∝N_e^-2/3T^-1 and K∝N_e^1/3, showing that the nuclei are interacting with degenerate conduction electrons. Furthermore, the Korringa relationship holds and the calculated electron density at a nucleus is almost the same as …

Nuclear Orientation Of 253Es In Neodymium Ethylsulfate, A. J. Soinski, Richard B. Frankel, Q. O. Navarro, D. A. Shirley

Physics

Einsteinium-253 nuclei were oriented at low temperatures in a neodymium ethylsulfate lattice. From the temperature-dependent α-particle angular distribution a nuclear magnetic moment |μ|=(2.7±1.3)μ_N was deduced. From the values for the angular distribution function at the lowest temperatures it was possible to test the predictions of the Mang shell-model theory for the relative phases and amplitudes of the α-partial waves. As predicted, the waves of angular momentum L=0 and 2 are in phase, and the L=0 and 4 waves are out of phase. The predicted wave amplitudes are in error, especially that of the L …

Perturbation Theory Of The Hooke's Law Model For The Two‐Electron Atom, Ronald White, W. Byers Brown

Center for Advanced Mineral and Metallurgical Processing (CAMP)

The Hooke model for the two‐electron atom replaces the electron–nuclear interaction by a harmonic oscillator potential, but retains the Coulomb repulsion of the electrons. The first‐order perturbation equation for the electron repulsion is solved analytically, and the exact first‐, second‐, and third‐order perturbation energies are obtained. A similar Z^-1 perturbation treatment is carried out for the Hartree–Fock equation and other variational approximations. The Z^-1 of the correlation energy is compared with that for helium-like atoms and found to be similar.

Excitation Of The (2P2)3P State Of Helium Near Threshold, Paul Burrow

Paul Burrow Publications

The trapped-electron method is applied to the excitation by electron impact of the (2p²)³P state, the lowest doubly excited state of helium which is stable against auto-ionization. The energy of this state, 59.64±0.08 eV, is in good agreement with theory. An estimate of the slope of the total cross section for excitation of the (2p²)³P state at threshold gives a value of 4 × 10^-20 cm²/eV.

Doppler Shift In Frequency In The Transport Of Electromagnetic Waves Through An Underdense Plasma, Jerry Peacher, Kenneth M. Watson

Physics Faculty Research & Creative Works

In an earlier publication, the validity of the radiation transport theory was studied for the calculation of multiple scattering of electromagnetic waves by a turbulent plasma. In the present paper, we extend the transport theory to include a description of the Doppler shift in frequency caused by electron motion.

Are There Magnetic Moments At The Transition Metal Sites In Feal, Coal, And Nial?, Richard B. Frankel, D. J. Sellmeyer, N. A. Blum

Physics

Measurements of the hyperfine interactions in ⁵⁷Fe in the CsCl structure intermetallic compounds FeAl, CoAl and NiAl are reported.

De Haas-Van Alphen Effect In Dilute Beryllium-Copper Alloys , I.S. Goldstein, David J. Sellmyer, B.L. Averbach

David Sellmyer Publications

The de Haas-van Alphen effect was investigated in pure beryllium and in Be-Cu alloys containing up to 0.34 at.% Cu. The extremal cross-sectional areas of the cigar-shaped third-band electron pieces of Fermi surface decreased with alloying. The areas of the coronet-shaped second-band hole piece increased with alloying. The magnitude of the area changes were compared with rigid-band-theory predictions. Corrections for lattice-parameter changes were included when possible. In the low-concentration limit, the theory is able to account for the observed area changes. For the highest-concentration alloy, there are deviations, for all areas measured, to greater changes than are predicted by the …

Transient Optical Absorption By Self-Trapped Excitons In Alkali Halide Crystals, Robert Fuller, R.T. Williams, M.N. Kabler

Robert G. Fuller Publications

Transient absorption spectra produced by pulsed electron excitation at low temperature have been identified as due to transitions originating in the lowest triplet states of the self-trapped exciton. The current model, comprising an electron plus a self-trapped hole, is shown to provide electronic configurations for the higher excited states which give a good account of the principal features of the spectra.

12th Annual Rocky Mountain Spectroscopy Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 12th annual meeting of the Rocky Mountain Spectroscopy Conference, sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 3-4, 1970.

The 1963-64 Lake Mead Survey, J. M. Lara, J. I. Sanders, Bureau Of Reclamation

Publications (WR)

The 1963-64 Lake Mead survey was run to compute the reservoir capacity. Results of the geodetic and hydrographic surveys and sediment sampling equipment are described. The geodetic survey showed Hoover Dam subsided an average of 118 mm since 1935. Sonic sounding, photogrammetry, and crosssectional profiling methods were used to run the hydrographic survey. Reservoir area and capacity tables were generated using an electronic computer. The present lake capacity is 29,755,000 acre-ft and the reservoir surface area is 162,700 acres at elevation 1229 ft. 2,720,000 acre-ft of sediments accumulated in the lake since 1935. A unit weight of 60 Ib/cu ft …

X-Ray Induced Luminescence Of Sapphire And Ruby, Ivan Collier Jr.

Masters Theses & Specialist Projects

Over the past decade the luminescence properties of sapphire (∝-AL₂O₃) and ruby (Al₂O₃:Cr₂O₃) have been the subject of many investigations because of their importance in materials technology. Sapphire and ruby are at present used as lasing materials, radiation dosimeters, and as optical windows. In order that these operations may be made more efficient, and that other useful luminescent properties may be systematically explored and developed, much attention has been given to understanding the luminescent mechanisms from the standpoint of the physics of the solid state. However, mechanisms have …

Small Angle Elastic Scattering Of 1.33 Mev Photons From Lead, Chwan-Kang Chiang

Masters Theses

No abstract provided.

Electron Optical Study Of A Secondary Electron Multiplier, Chang Min Shen

Dissertations and Theses

Electron orbital theory was applied to the design of the geometrical structure of an electron multiplier for an image intensifier. A special structure satisfying production requirements was studied. Electron optical calculations consisted of determining the potential distribution and tracing the electron trajectories. Liebmann's procedure was used to solve Laplace's equation with constant potentials on the multiplier electrodes as boundary conditions. The trajectories were determined by solving the equation of motion in an electrostatic field using a Runge-Kutta procedure. The initial conditions for the trajectories were the initial energies, initial positions, and the initial directions of the secondary electrons. The plotted …

Far-Infrared Properties Of Lattice Resonant Modes. Iv. Paraelectric Impurities, Roger D. Kirby, A.E. Hughes, A.J. Sievers

Roger Kirby Publications

We have studied the three paraelectric defect systems KCl: Li+, RbCl: Ag⁺, and NaCl: OH^- through the temperature dependence and electric field dependence of their far-infrared absorption spectra. It is found that the motional energy states for the defects in these three systems have many properties in common. In each case the impurity ion has an associated electric dipole moment and low-lying tunneling energy levels. The defects also have higher energy levels which can be attributed, at least in part, to c. m. resonant-mode motion. The KCl: Li+ tunneling levels are found to be well described by …

Limited Resurrection Of The Born Approximation, Paul Finkler

Paul Finkler Papers

It is shown that the ordinary Born approximation for pn and pp̅ charge-exchange scattering correctly accounts for (1) the shape of the forward peak for 0 ≤ (-t) ≤ µ²/2 at P_L = 8 GeV/c, and (2) the energy dependence of the cross sections at t=0 in the energy range P_L,=2—8 GeV/c. This result is analogous to the well-known success of the electric Born approximation in Π⁺ photoproduction. It is then shown that the simplest interpretation of this surprising result within the framework of Regge-pole theory is in terms …

Photoionization Of Argon And Xenon Including Final-State Correlation, Anthony F. Starace

Anthony F. Starace Publications

Effects of final-state correlation on the photoionization cross sections for the 3p shell in argon and the 4d shell in xenon are calculated by the reaction-matrix method, starting from the Herman-Skillman model Hamiltonian, for photoelectron energies 0<~ε<~1.2 a.u. and 0<~ε<~2.52 a.u., respectively. The results for argon complement Hartree-Fock and other final-state correlation calculations; the results for xenon are the first ab initio calculations of this kind. Although length and velocity forms of the transition matrix element agree in the initial local-field approximation, they are shown to diverge necessarily when only the final state is improved.

Determination Of The Time Delay In The Arrival Of Jovian Signals At Opposite Ends Of A Long Baseline Fringe Synthesis Interferometer, Roger Scott

Masters Theses & Specialist Projects

In order to determine the size of the decametric sources, the technique of long baseline radio interferometry is being employed. The University of Florida at Gainesville is a pioneer in this field. In 1964, T. D. Carr introduced the procedure of recording the signals received at each end of an interferometer on magnetic tape and comparing the re-corded signals at a later time. This eliminated the necessity for transmission lines over the length of the baseline, allowing greater separation to attain higher resolution.

Determination Of (N, 2n) Reaction Cross-Sections For 71ga, 106cd & 138ba Using 14 Mev Neutrons, Thomas Helm

Masters Theses & Specialist Projects

The increasing trend towards the use of activation analysis as an analytic means of identifying elements and determining their relative abundance demands more accurate values of reaction cross-sections. Accurate values of cross-sections are also important in the investigation of possible shell effects in reaction mechanisms. Many activation cross-sections for reactions produced by 14 MeV neutrons have been measured because of the relative ease with which this energy of neutrons can be produced. Low voltage accelerators are capable of producing 14. MeV neutrons by the ³H( d,n)⁴He reaction. Although many people^(1-5) have measured the (n,2n) reaction cross-sections …