Physical Sciences and Mathematics Commons^™

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 …

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 …

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 …

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

Masters Theses

No abstract provided.

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 …

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 …

Analytic Approach To Electron Correlation In Atoms, Ronald White, Frank Stillinger

Center for Advanced Mineral and Metallurgical Processing (CAMP)

A novel perturbative treatment of electron correlation in N‐electron atoms is devised. The unperturbed starting point is a central‐force “hydrogenic” problem in the full dN‐dimensional configuration space (d = dimensionality). The central potential in this solvable “hydrogenic” problem is obtained by averaging the actual electron–electron and electron–nucleus potentials over all dN − 1dN − 1 hyperspherical polar angles in the configuration space. The relevant projected Green's functions are computed for the ground states of the model one‐dimensional two‐electron atom (with delta function interactions), as well as for the real three‐dimensional helium isoelectronic sequence. The corresponding first‐order wavefunctions exhibit weakly singular …

-Ray Induced Luminescence Of Ruby, Wayne Cooke

Masters Theses & Specialist Projects

Since the advent of the laser there has appeared a multitude of scientific papers describing the various parameters that would affect the lasing action of the ruby laser. Many investigations have been carried out to determine the efficiency of the R-line fluorescence in ruby: however very little work has been done concerning the X-ray-induced luminescence of ruby.

Certainly the applications to laser technology would be of sufficient importance to merit a study of ruby under continuous irradiation, although this was not the main stimulus that motivated this investigation. The original program of study was undertaken to determine if there existed …

Propagation Of Ultrasound In Plastic Crystals, Carl E. Scheie

Physics & Astronomy ETDs

The study of the organic solid state, and in particular of plastic crystals, is a relatively new branch of physics (1,2). Timmermans first surmised the existence of these solids from the anomalous values of the entropies of fusion. The solids possess many of the characteristics of liquids. They are easily deformed by pressure and they show dielectric properties that can be described on the basis of rotation of the molecules in their lattice positions. Still they have a definite crystal structure. Thus, even though the molecules are not symmetric, they appear to be to some degree because of the rotation. …

An Investigation Of A Gas Measurement Technique Employing Ultraviolet Excitation, Alphonso Vincent Diaz

Physics Theses & Dissertations

A study was undertaken to determine the general applicability of a temperature measurement technique which uses the fluorescence stimulated by a vacuum ultraviolet continuum as the indicator. This study was directed toward determining the temperature of nonradiating carbon monoxide. A number of ultraviolet radiation sources which produced high intensity in the region of l,150 A were investigated. This study led to the conclusion that the technique was not applicable to measurements in carbon monoxide within the present limits of' detectability.

Hot Electron Injection Into Liquid Argon From A Tunnel Cathode, Pavel Smejtek, David G. Onn, M. Silver, P. Kumbhare

Physics Faculty Publications and Presentations

Hot electrons from a tunnel cathode have been injected into liquid argon (99.998% pure) at 87°K. The current vs voltage characteristics indicate that the injected hot electrons thermalize very slowly, losing their energy only by elastic scattering processes and finally by capture by the dilute impurities. The deduced thermalization time and distance are very long compared with that in helium, where bubble formation is responsible for energy loss.

Asymptotic Behavior Of Fluid Jets, Ronald Walter Godfrey

All Master's Theses

In this paper we shall consider the steady-state, two dimensional, irrotational flow of an inviscid, incompressible fluid under gravity.

Elastic Scattering Of 1.33 Mev Gamma Rays From Uranium, Joan Sue De Vries

Masters Theses

No abstract provided.

A Study Of Defects In Platinum Using Positron Annihilation, Clarence D. Esseltine

Masters Theses

No abstract provided.

A Direct Measurement Of The Ratio Of The Reaction Cross Sections For Two-Photon And Three-Photon Annihilation Of A Positron And An Electron In Aluminum, Jeffrey Ira Siegel

Masters Theses

No abstract provided.

Calculations Of The Intensity Of X-Ray Diffuse Scattering Produced By Point Defects In Cubic Metals, John W. Flocken, John Hardy

John R. Hardy Papers

We have calculated isointensity profiles for the diffuse x-ray scattering associated with certain types of defects in Cu, Al, Na, K, Li, and a theoretical model lattice. These profiles were computed for high-symmetry planes very close to reciprocal-lattice points of the (S, 0,0), (S,S,0), and (S,S,S) type. Both cubic and double-force defects were treated. The calculations were done using a technique presented by Kanzaki for the theoretical model lattice. Kanzaki's general conclusion that cubic defects produce leminiscate profiles and that double-force defects produce ellipsoidal profiles is confirmed for all the material studied. Our profiles for the model lattice agree with …

Asymptotic Lattice Displacements About Point Defects In Cubic Metals, John W. Flocken, John R. Hardy

John R. Hardy Papers

We have calculated the asymptotic displacements (a) about a single vacancy in Al, Na, K, and Li, (b) about a single interstitial Cu atom in a Cu host lattice, and (c) about a unit single double force along a (100) direction in A1 and Cu. These calculations were made using the asymptotic equations of the method of lattice statics which, in its full form, is based on the Fourier transformation of the direct-space force equations between the detect and the host atoms in a large "supercell" of the lattice. Results were also obtained for each of the defect types in …

Stress-Induced Angular Momentum Quenching In Mgo: Fe2+ As Observed By Mössbauer Spectroscopy, J. Chappert, A. Misetich, Richard B. Frankel, N. A. Blum

Physics

Under the influence of a suitable uniaxial stress, the quenching of the electronic angular momentum of the low-lying threefold degenerate Γ_5g level of Fe²⁺ in cubic MgO has been observed by Mössbauer spectroscopy. The result is consistent with Ham's model for the appearance of a quadrupole doublet at low temperatures. A value for the strain coefficient of Fe²⁺ in MgO has been obtained: G₁₁=585 cm^-1.