Physical Sciences and Mathematics Commons^™

Electrical Conductivity In Nh4Cl And Nd4Cl Single Crystals, Robert Fuller, F.W. Patten

Robert G. Fuller Publications

Electrical conductivity measurements are reported for normal and deuterated ammonium chloride single crystals in the temperature regions which characterize the pure and the impurity-dominated materials. We conclude from the data that conductivity in ammonium chloride is due to the formation of either cation or anion vacancies and a subsequent process controlled by a proton transfer. Our results are found to be consistent with a model proposed by Herrington and Staveley.

Note On "Approximate Free Energies For Heisenberg Ferromagnets", J. H. Hemmann, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

Optical Phenomena In Diatoms, Richard B. Hoover, Miriam J. Hoover

Journal of the Arkansas Academy of Science

Diatoms are unicellular algae which fabricate siliceous shells that are frequently marked with intricate ornamentations and patterns. The nature and characteristics of the siliceous shells provide a basis for diatom taxonomy and give rise to a number of interesting and colorful optical phenomena. This paper presents the results of investigations of diffraction phenomena, complementary color behavior, Rayleigh scattering and optical activity in diatoms.

Rbe, Let, And Z/ΒΑ, Robert Katz

Robert Katz Publications

A call has been issued by Turner and Hollister in this journal for nomination of a suitable combination of charge and velocity to replace LET. It is the purpose of this communication to point out that no single combination of these variables can fully characterize track effects, as these are affected by the ratio of the range r_m of the delta ray of maximum energy to the radius a₀ of the sensitive volume.

Radiative Lifetime Of The A¹Π State And The Transition Moment Variation Of The Fourth Positive Band System Of Carbon Monoxide, Joseph George Chervenak

Doctoral Dissertations

"The lifetime of the A¹π state of carbon monoxide has been measured using a pulsed invertron excitation source and delayed coincidence measurement technique on the fourth positive system. Eighteen bands, originating from the upper states v' = 0 to 5, were examined at pressures between 500 and 50 microns, with no pressure dependence noted. The data were corrected for photon "pile up" and least-squares fitted to the sum of two exponentials. The transition moment was found to vary and was expanded about the r-centroid of the v' = 0 to v" = 0 transition. Oscillator strengths are calculated and compared …

Auger Electrons From Argon With Energies 150-210 Ev Produced By H+ And H2 Impacts, D. J. Volz, M. Eugene Rudd

M. Eugene Rudd Publications

Secondary electrons in the energy range 150-210 eV produced by 125-300-keV H⁺ and H₂⁺ impacts on argon gas are measured as a function of their energy and angle of emission. Discrete line spectra are due to Auger transitions from L₂ and L₃ vacancy states as well as satellite transitions from multivacancy states. The widths, energies, and branching ratios of the L₂ and L₃ vacancy states are presented. Widths of these states are appreciably greater than those obtained with electron impact excitation. This can be attributed to the recoil velocities of the target atom …

Experimental Evidence For The Mechanism Of Charge Transfer Into Continuum States, G. B. Crooks, M. Eugene Rudd

M. Eugene Rudd Publications

We have observed a prominent peak in the energy spectrum of electrons ejected in the forward direction from helium bombarded by protons ranging in energy from 100 to 300 keV. The peak occurs at an ejected-electron velocity equal to the velocity of the incident proton. The experimental results verify the existence of the mechanism of charge transfer into continuum states of the incident ion.

Shell Source Burning Stars With Highly Condensed Cores, S. Refsdal, A. Weigert

Department of Physics and Astronomy: Faculty Publications

Simple analytical relations are derived - similar to the homology relations for homogeneous stam - which describe the behaviour of shell source burning models with highly condensed cores. Many features which are known from evolutionary calculations (and partly &om observations) of such stars can be understood as coming essentially from the increase of the mass M₆ of the core.

Cross Section For Excitation Of The Fourth Positive Band System In Carbon Monoxide By 20-120 Kev Protons, John T. Park, D. R. Schoonover, George W. York

Physics Faculty Research & Creative Works

Excitation cross sections for the fourth positive band system in carbon monoxide have been determined from studies of the energy-loss spectra of 20-120-keV protons incident on gaseous CO targets. The energy-loss spectra had an energy resolution of about 2 eV. Prominent peaks in the spectra were observed at 8.5 and 13.8 eV. The first peak is believed to be due to excitation of the fourth positive band system of CO (X+1A 1, while the 13.8-eV peak covers a number of possible states, including the B+2 and the C+1 states. Changes in the slope of the ionization continuum were noted at …

Theory Of Droplet Growth In Clouds. I. The Transient Stage Of The Boundary-Coupled Simultaneous Heat And Mass Transport In Cloud Formation, John C. Carstens, Joseph T. Zung

Physics Faculty Research & Creative Works

Two solutions to the system of equations describing the simultaneous heat and mass transport involved in the condensational growth of a droplet in a supersaturated atmosphere are presented. The first, valid for very short times, describes the transient stage of such growth; the second, valid for longer times, presupposes the establishment of a steady-state condition. The two are shown to be complementary for the cases examined. The equations examined satisfy the usual boundary conditions imposed on a drop in a concentric sphere as required by the cellular model for cloud formation. Hence our results can be immediately extended to the …

Energy-Loss Spectra And Collision Cross Sections For Impact Of 20-120-Kev Positive Ions On Molecular Nitrogen, F. D. Schowengerdt, John T. Park

Physics Faculty Research & Creative Works

Inelastic energy-loss spectra induced by impact of H+, H2+, and Ar+ on N2 have been measured at incident ion energies of 20-120 keV, with an energy resolution of about 2 eV. Prominent peaks are observed at energy losses of 9.5 and 13.8 eV. The first of these is well resolved and is attributed to excitation of the Lyman-Birge-Hopfield (LBH) system of N2. The peak at 13.8 eV is believed due primarily to excitation of the bu1 band of the Worley-Jenkins series. The locations of these features on the energy-loss scale do not agree with results of the electron impact work …

Measurements Of Excited-State Population Ratios Of Atomic Hydrogen Produced By Charge-Exchange Neutralization Of Energetic Proton Beams, Robert H. Mcfarland, Archer H. Futch

Physics Faculty Research & Creative Works

Excited-state population ratios for atomic hydrogen have been measured for energetic hydrogen ions neutralized by charge exchange with a number of different metallic vapors and permanent gases. Electric field ionization techniques were used to determine excitation ratios. Detection of the energetic ions and neutrals was accomplished using partially depleted surface-barrier detectors. Counting, using phase-detection techniques in which an add-subtract scaler was phased to the signal, provided an improved signal-to-noise ratio. Two methods were used to provide desired targets. Metallic vapor and permanent-gas thin targets of the order of 10-5 mTorr cm were produced as chopped neutral beams, using conventional crossed-beam …

Antimatter, Claudia Morgan Griffin

Honors Theses

Very little is known about the mysterious world of antimatter. The idea that such particles could exist was not even proposed until forty years ago. Perhaps the story of the discovery of antimatter began when scientists were trying to unify the Theory of Relativity and the Theory of Quanta. The trouble was that the quantities in the classical wave equation are in the second derivatives. In Schrodinger's wave equation of the Quantum Theory, x, y, and z are second derivatives, but i is a first derivative.

Following Einstein's basic ideas, H. Minkowski proposed the concept of a four-dimensional time-space continuum …

Theory Of Shallow Donor Impurity Surface States, Vidal Emmanuel Godwin

Doctoral Dissertations

"A variational approach has been used to solve the effective-mass equation, when the impurity ion is located at a depth d from the surface of a semiconductor, where 0 < d < d_b and d_b represents the case when the impurity ion is in the bulk of the semiconductor. The ground state and the excited state having the largest electric dipole coupling to the ground state have been determined. We have plotted the energy dependence on the depth of the impurity ion from the surface of the semiconductor. The energy has also been calculated as a function of the orientation of the …

A Study Of Far Infrared Grid Filters, Harold Victor Romero

Doctoral Dissertations

"The diffraction theory for the transmission of electromagnetic fields through a grid in a dielectric is derived and experimentally checked in the visible wavelength region. In the far infrared, an approximate mathematical representation is found to describe the grids in dielectrics. The empirical equations in the far infrared are combined with the electrical circuit-transmission line analog for inductive grids. Detailed structure of the transmittance versus wave number curves are presented. Then the theory of multielement grid filters is derived and compared with experiment. The properties of the filters can be predicted from a knowledge of the characteristics of the individual …

A Quasi-Lattice Model Of Simple Liquids, Jesse Herbert Collins

Doctoral Dissertations

"A cellular model of simple liquids is proposed which eliminates the objectionable feature of long range order found in other cell models. The volume is divided into N identical spherically symmetric cells, each occupied by one molecule. The cell-center density distribution relative to an average given cell center forms a series of Gaussian peaks whose width is proportional to the square root of the distance from the given cell center. The number of cell centers and average radial distance represented by each of the peaks correspond to a face-centered cubic lattice. The molecular pair distribution function is determined for several …

Ground-State Wave Function Of Shallow Donors In Uniaxially Stressed Silicon: Piezohyperfine Constants Determined By Electron-Nuclear Double Resonance, Edward B. (Boyd) Hale, Theodore G. Castner

Physics Faculty Research & Creative Works

Stress-induced changes in the ENDOR spectra of a shallow donor electron interacting with various Si29 nuclei neighboring the donor have been experimentally and theoretically investigated. For each of the three measured donors - As, P, and Sb - the compressional, uniaxial stress was applied along the [001] axis and its magnitude corresponded to strains up to 10-3. To describe the observed linear and quadratic shifts and splitting's of the lines in an ENDOR shell, we have defined a set of piezo hyperfine constants. One piezo hyperfine constant was measured for each axis-class shell; three independent piezo hyperfine constants were measured …

The Design And Construction Of A Constant Acceleration Drive System For Mössbauer Experiments, James Donald Russell

University of the Pacific Theses and Dissertations

An excited nucleus may undergo a transition to its ground state by the emission of a gamma ray. The nucleus, if free to do so, will recoil and take some of the transition energy as recoil energy leaving less energy for the emitted gamma ray. This gamma ray does not have enough energy to excite a similar nucleus and will, therefore, not by resonantly absorbed due to the fact that the natural linewidth of the gamma ray is so much smaller than the energy taken by the emitting atom and the similar energy needed by the absorbing atom.

In 1958 …

Structures And Relationships Of Some Perovskite-Type Compounds, Christian Michel

Doctoral Dissertations

"A model for crystallographic transitions in perovskites is proposed. The model consists of regular octahedra sharing corners and topologically able to rotate without distortion around their three-fold axes. This model, with R3̄c symmetry (18e position) can be described in terms of a continuous rotation of angle, w, of octahedra from two ideal symmetry forms: the hexagonal close-packed and the cubic face-centered configurations. A parametric relation is derived between w and the rhombohedral cell angle, α, or the corresponding hexagonal axial ratio c/a . A wide range of atomic structures based on a framework of regular or slightly distorted octahedra sharing …

An Experimental And Theoretical Study Of The Nucleation Of Water Vapor On Ions In Helium And Argon, Daniel R. White

Doctoral Dissertations

"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 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 the sign …

The Surface Effects Of Alkali Halides In The Infrared, Vincent Joseph Llamas

Doctoral Dissertations

"The surface state extension of the shallow donor theory is reviewed. The surface state theory and its applications to F-centers of alkali halides is presented. Experimental infrared data show an absorption which seems to correspond with the ground state to first excited state transition. Surface state concentrations of F-centers as a function of depth into the crystal are given. The ratio of surface to bulk cross sections in KBr and experimental calculations of effective masses in various alkali halides are in excellent agreement with theory. The theoretical cross sections are derived from transition probabilities. However, lack of excited states, the …

Realistic Impulsive P Wave Source In An Infinite Elastic Medium, Joseph Hugo Hemmann

Doctoral Dissertations

"The generally assumed instantaneous impulsive pressure sources for an elastic P wave in an infinite medium lead to basic contradictions, a step function source yielding infinite displacements as the shear modulus goes to zero, and the total energy radiated by a delta function (or any derivative of the delta function) source being infinite. By noting that the character of the solution in the elastic region must match the acoustic case near the source, a realistic impulsive pressure source is postulated which has a finite time history. The elastic field produced by this source is then obtained in closed form. A …

Application Of The Weiss Molecular Field Theory To The Lattice Of The B-Site Spinel, Wayne Edmund Holland

Masters Theses

"The Weiss molecular field theory has been applied to the lattice of the B-site spinel. The forms of the ordering temperatures and the asymptotic Curie temperature have been determined for a sixteen-sublattice model with collinear spins. The theory has been applied to the problem of determining the exchange integrals for systems of the form Aa₁₋ₓAbₓCr₂X₄ and ACr₂Xa_4(1-y)Xb_4y. The theoretical results have been compared to the experimental data for the systems Hg₁₋ₓCdₓCr₂S₄, Zn₁₋ₓCdₓCr₂Se₄, and CdCr₂S_4(1-y)Se_4y in an attempt to determine the exchange integrals"--Abstract, page ii.

Investigation Of The Alpha-Sub-Gamma Phase In Alnico 6, Cortez Samuel

Dissertations and Theses

The purpose of this research project was to study the αᵧ phase in Alnico 6. Other phases were studies for comparison. Also the effect of an applied magnetic field on the formation of the αᵧ phase was investigated.

Three single crystals of Alnico 6 were heat treated for one hour—one at 1250°C, one at 1000°C, and one at 800°C—and water-quenched. The microstructure of each sample was observed with the optical microscope, and X-ray diffraction patterns were taken to determine the crystal structure of the phases present.

Several single crystal samples of Alnico 6 were heat treated at 1000°C and furnace-cooled. …

Excitation Of Hydrogen Atoms By Fast Protons, Edward Ellis Fitchard

Physics Theses & Dissertations

In this thesis a theoretical study is made of excitation of hydrogenic atom by charged particles such as protons or electrons. The approximation to the cross section for an inelastic scattering process is obtained under the following radically simplifying assumptions. The projectile is represented in its initial and final state by plane waves. All distortions are neglected whether they originate in an inelastic process or an elastic deflections of the charged particle by the nucleus. The perturbation of the atomic orbits between which the projectile induces transitions is neglected. Nonrelativistic hydrogenic wave functions are used for the electronic states. In …

Ionic Polishing Of Fused Silica And Glass, Raymond Wilson

Raymond Wilson

Entropy Of The Mixed State Of Some Low-Κ Type-Ii Superconductors, Don Carlos Hopkins, R. R. Rice, J. M. Carter, J. D. Hayes

Physics Faculty Research & Creative Works

The entropy of the mixed state of type-II superconductors with low κ(∼1) is studied for the alloys Pb_0.96Tl_0.04 and In_0.88Sn_0.12. The current theories are reviewed for approximations valid near Hc1 and near Hc2. The experiments show for the most reversible sample (Pb_0.96Tl_0.04) that (SB)_T of the mixed state depends only on temperature, and that (ST)_B increases linearly with B from its value for the superconducting state until it drops discontinuously to its normal state value at H_c2. There is no abrupt increase in the specific …

A Heavy-Ion Energy Loss Spectrometer, John T. Park, F. D. Schowengerdt

Physics Faculty Research & Creative Works

A high-resolution system for the measurement of the energy loss spectra of 20-250 keV heavy ions incident on gas targets is described. The high resolution is obtained by decelerating the ion beam to a low, well-defined energy before performing the energy analysis. The energy loss spectrum is determined by changing the accelerator energy to compensate for energy lost in collisions with the gas atoms. The system is arranged so that normal fluctuations in the accelerator's power supply do not affect the energy resolution. The resolving power of the system is 2.5x104. The primary proton beam has a detected WHM of …

Some New Approaches To Shallow Impurity States, Wayne E. Tefft, Robert John Bell, Harold V. Romero

Physics Faculty Research & Creative Works

A variational calculation of shallow surface impurity states including image-charge and anisotropic mass effects was performed using two different sets of orthogonal functions. The first set was obtained by varying the Bohr radius in the hydrogenic functions, separately for each state. In the second set the Bohr radius was allowed to become anisotropic, and the elements were separately treated as variational parameters. In each case it was shown that with certain restrictions on the variational parameters the set remained complete and orthogonal. General expressions for the energy eigenvalues for both the bulk and surface problem obtained from the first set …

Charge-Transfer Cross Sections For Negative Ions On Atomic And Molecular Targets, W. (William) R. Snow, R. D. Rundel, R. Geballe

Physics Faculty Research & Creative Works

Charge-transfer cross sections for H^- on O, O₂, and NO₂; O^- on H, O, H₂, O₂, and NO₂; and C^- on H and O have been measured over an energy range of 0.5 to 4 keV using a modulated crossed-beam apparatus. The experimental cross sections are compared with theories of resonant and non-resonant charge transfer based on a two-state approximation. For the reactions H^-+O O^-+H, the cross sections are found to be consistent with detailed balancing. The effect of electron detachment on charge-transfer …