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Time-Dependent Ionization Equilibrium And Line Radiation Under Flarelike Conditions, Menas Kafatos, W. H. Tucker

Mathematics, Physics, and Computer Science Faculty Articles and Research

The results of calculations for time-dependent ionization equilibrium and line emission are presented and compared with the values obtained under the assumption that steady-state conditions prevail. In the models considered, it is assumed that the electron density is constant (=10^3 cm^-3) and that the temperature increases by a factor of 10 from 3 x 10^6 K on timescales ranging from 100 to 300 s and decays back to 3 x 10^6 K on a timescale ranging from 600 to 1400 s. Ions of oxygen and silicon are considered, and it is found that the spectrum is softer during the rise …

Collisional Excitation Of N+ At 50 Kev, D. H. Crandall, G. York, V. Pol, John T. Park

Physics Faculty Research & Creative Works

The excitation spectrum of N+ has been observed by examining the energy lost by a 50- keV N+ beam passing through a He target. The spectrum exhibits dramatic features with large cross sections. Determination of the approximate ratio of metastable to ground-state ions in the primary ion beam has permitted measurement of excitation cross sections from both ground-state and metastable N+ ions colliding with He target atoms. © 1972 The American Physical Society.

Some Bonding Aspects Of Cobalt Ions In Phosphate Glasses, Tewfik Boutros Absi

Archived Theses and Dissertations

No abstract provided.

Observation Of A Broad Resonance In The 23S Excitation Of Helium By Electron Impact, G. B. Crooks, R. D. Dubois, D. E. Golden, M. Eugene Rudd

M. Eugene Rudd Publications

We have observed a broad P-wave resonance at about 50 eV primary energy in the angular distribution of electrons scattered after excitation of the 2³S state of helium. The resonance has a width of about 15 eV and affects the differential excitation cross section by more than 3 orders of magnitude. It is suggested that this resonance is associated with the temporary formation of triply excited states of the negative helium ion.

Detection Of Energetic Heavy Ions, Robert Katz, S. C. Sharma, Mehdi Homayoonfar

Robert Katz Publications

The delta-ray theory of track structure, applied earlier to such 1-or-more hit detection systems as the inactivation of dry enzymes and viruses, the NaI(Tl) scintillation counter, and nuclear emulsion, is extended to the silver activated phosphate glass dosimeter, the LiF thermoluminescent dosimeter, the creation of free radicals in solid biological substances, solid and liquid organic scintillators, and the ferrous sulfate (Fricke) dosimeter. The response of these systems to both gamma-rays and heavy ions is characterized by two parameters: 1) D_γ³⁷, the dose of gamma-rays at which 37% of the sensitive elements remain unaffected by the radiation, and …

Ionization Mechanisms In Cesium, Yu Bong Hahn

Doctoral Dissertations

"Autoionizing states in Cs between 12 and 20 eV have been studied by electron impact. The retarding-potential-difference(RPD) method was used to obtain an electron beam with energy spread of about 0.1 eV. To determine the threshold energies, inelastically scattered electrons were analyzed by the trapped-electron method. We have been able to identify about 20 levels, and the agreement with spectroscopic data is excellent. A peak appearing at 12.80 eV is probably due to the quartet states observed by Feldman and Novick"--Abstract, page 2. "The structure in the electron impact ionization cross section in cesium can be partially accounted for by …

Time Resolved Measurements Of Droplet Growth In A Wilson Cloud Chamber, Michael Anthony Vietti

Doctoral Dissertations

"The growth rates of water drops in a Wilson expansion cloud chamber are measured with air, argon and helium as the carrier gas, in the size range of .5 to 10 microns. The drops growing in the supersaturated chamber exhibit oscillations in the scattered intensity as predicted by Mie theory. Scattered intensity is measured at 30 degrees to the He-Ne laser beam. Supersaturation ratios during growth range from S =1.2 to S = 3.5 for all three gases. The initial temperature is measured and the pressure is monitored continuously so that droplet growth theory can be compared with experiment. Three …

An Inexpensive Electrical Vacuum Feedthrough, D. R. Kastelein, Richard A. Anderson, Kaare J. Nygaard

Physics Faculty Research & Creative Works

No abstract provided.

The Eikonal Distorted Wave Born Approximation For The Excitation Of Hydrogen By Impact With Hydrogen And Helium In The Intermediate Energy Range, Richard Homer Shields

Doctoral Dissertations

"An eikonal approximation is applied to atom-atom scattering in the intermediate energy range. The theory and the form of the eikonal approximation are reviewed. Also a brief survey of previous theoretical methods for all energy ranges is included.

In particular, the differential and total cross sections for the excitation of hydrogen to the 2s and 2p states by impact on hydrogen and helium atoms have been calculated using the eikonal distorted wave Born approximation (DWBA) for the incident energy range of 2.25-100 keV. The eikonal DWBA differential cross sections are compared to the differential cross sections given by the first …

Radiative And Predissociative Lifetimes Of The A²Σ⁺ State Of Oh, Robert Allen Sutherland

Doctoral Dissertations

"Lifetime measurements have been made on the A²Σ⁺ state of OH by the delayed coincidence technique in conjunction with an interrupted rf discharge through water vapor. Lifetimes are reported for rotational states up to K = 29 and K = 20 in the v = 0 and v = 1 vibrational levels respectively and on the unresolved levels of v =2. A predissociation, previously predicted from relative intensity measurements, resulting from a curve crossing by the repulsive 4 Σˉ state, was observed for the rotational states above K = 23 of v = 0, for those above K = 14 …

Diffusiophoretic Forces Between Juxtaposed Atmospheric Particles, Allen L. Williams

Doctoral Dissertations

"The role of diffusiophoretics and Stefan flow in droplet growth by accretion and in-cloud scavenging is examined. A calculation is made for the diffusive forces between two juxtaposed spheres one or both of which are undergoing diffusional growth and the influence of the diffusive force on the trajectories of two spheres, assumed to obey the creeping flow equations is found. The results are: a) the diffusiophoretic force between two water droplets is zero. b) the diffusiophoretic force between a spherical ice particle and a water droplet, although non-zero, is too small to appreciably influence the fall trajectories. c) the diffusiophoretic …

Gas-To-Particle Conversions Of So₂-No₂-H₂O-Air Gas Mixtures Under Specific Uv Irradiation, James Leonard Fowler

Masters Theses

"In these series of experiments, mixtures of sulfur dioxide and nitrogen dioxide were irradiated in an absorption cell with monochromatic radiation found in the tropospheric region of the atmosphere. The irradiated mixtures were then introduced into a Wilson type cloud chamber to investigate the effects of these specific wavelength induced gas to particle conversions on nucleation. Results showed that sulfur dioxide could not be the sole agent for the formation of condensation nuclei. A mixture of sulfur dioxide and nitrogen dioxide irradiated at 3660 angstroms produced copious droplet formation identifying nitrogen dioxide as an integral reactant in nuclei production"--Abstract, page …

Geophysical Institute Annual Report 1971-72, Geophysical Institute

GI Reports

The 1971-72 Geophysical Institute Annual Report presents an overview of the year’s scientific research achievements across the Institute’s disciplines, alongside operational summaries covering finances, administrative changes, and other key activities.

Shubnikov-De Haas Effect And Magnetic Breakdown In Be , David J. Sellmyer, I.S. Goldstein, B.L. Averbach

David Sellmyer Publications

Magnetic breakdown in the basal plane of Be was investigated in fields up to 150 kG. Geometrical aspects of the open orbits caused by breakdown are discussed. An estimate of 30 kG for the characteristic breakdown field is obtained by applying the theory of Falicov et al. Shubnikov-de Haas frequency measurements are reported for the central-cigar cross section. These measurements are relevant to a recent conjecture that the Onsager-Lifshitz quantization scheme may be violated in the presence of magnetic breakdown.

A Study Of Isospin Mixing In 16O Near 18 Mev Exitation Energy, Li-Yun Kuo

Masters Theses

No abstract provided.

Average Solid Angle For Detection Of Photon Pair Positron Annihilations, Albert S. Ferrari

Masters Theses

No abstract provided.

Even-Parity Lattice Resonances And Anharmonicity In Ki: Ag+, Roger D. Kirby

Roger Kirby Publications

We report here the observation of four impurity-induced lattice resonances in KI:Ag+. In addition to the well-known T1u symmetry resonant mode at 17.3 cm-1, we have observed two even-parity resonant modes of A1g and Eg symmetries at 25 and 16.35 cm-1, respectively, and a T1u symmetry gap mode at 86.2 cm-1. The two even-parity modes were detected using far-infrared spectroscopic techniques with the sample in an external electric field. The field induces a strong mixing of the modes of opposite parity and results in large field-induced shifts. The Eg symmetry resonance has also been seen in the Raman spectrum of …

Thermionic Space Charge Oscillations, William Carl

Masters Theses & Specialist Projects

Thermionic electrons emitted into a potential well will produce radiation, the frequency of which is determined by the transit time of the electrons. This paper investigates the case where radiation is produced by a vacuum tube in which two Pierce guns face each other, one acting as the emitter, the other acting as a reflector. Symmetry and the focusing of the electron beam by the Pierce guns make it possible to make an accurate determination of the electron transit time. Measurements showed that the period of the oscillation was 1.5 times the period required for an electron to traverse the …

Mössbauer-Effect Studies Of The Phase Transitions In Antiferroelectric Pbzro₃ And Ferroelectric Pbti₀.₀₂Zr₀.₈O₃, James P. Canner, C. M. Yagnik, Robert Gerson, William Joseph James

Physics Faculty Research & Creative Works

The Mössbauer spectra were studied for the antiferroelectric compound PbZrO₃ and for the closely related ferroelectric PbTi_0.2Zr_0.8O₃. In both cases, a substitution of 5-mol% BiFeO₃ was made to permit the Mössbauer measurements. Little difference was found in the isomer shift in these compounds, whether they were in the ferroelectric, antiferroelectric, or cubic state, indicating that the bonding character is not affected by the transitions among the states. There was a pronounced and approximately equivalent dip in the recoil-free fraction at the Curie points of both the antiferroelectric and ferroelectric materials, associated with …

Cellular Inactivation By Heavy Ions, Neutrons, And Pions, Robert Katz, S. C. Sharma, M. Hamayoonfar

Robert Katz Publications

The delta-ray theory of the inactivation of cells by energetic heavy ions describes cellular survival after heavy ion bombardment through a two-component survival model, in which 4 operational parameters (E₀,m₀, σ₀, and κ) describe the response of a particular cellular variety in a particular ambient condition, for an arbitrary radiation environment. The quantities m and E₀ are the extrapolation number and extrapolated D-37 dose of the survival curve after gamma-ray irradiation. The quantities σ₀ and κ are found from the initial slope of survival curves after irradiation with ions of different LET, …

Nuclear-Magnetic-Resonance Studies Of The Semiconductor-To-Metal Transition In Chlorine-Doped Cadmium Sulfide, Frank D. Adams, David C. Look, Carlton L. Brown, Donald R. Locker

Physics Faculty Publications

Spin-lattice relaxation times (T₁) and Knight shifts were measured for Cd¹¹³ nuclei in 12 CdS crystals doped with various amounts of chlorine. Hall coefficients were measured in order to estimate conduction-electron concentrations. Data were obtained for all samples at 300 °K and for some highly doped samples at 77, 4.2, and 2.13 °K. Metallic properties were observed in all samples having electron concentrations n>2×10¹⁸ cm^-3. At 300 °K, we find 1/T₁∝n for nonmetallic samples and 1/T₁∝n^2/3 when samples are metallic. The latter proportionality continues to hold at lower …

Comment On Electron Scattering In The Image Potential Well, Pavel Smejtek, M. Silver

Physics Faculty Publications and Presentations

Comments are made on the model of electron injection into SiO₂ proposed by Berglund and Powell. Their assumptions on electron scattering, disregarding the change of the escape cone with the distance from the emitter, lead to serious underestimation of the injected current. Two alternative models of electron injection, based solely on elastic scattering are discussed and do not predict the experimental results. We suggest that observed field dependence of the injected current into SiO₂ indicates that energy relaxation associated with the injected electrons is responsible for the voltage dependence of the current.

Measurement Of Currents In Lake Mead With The Deep Water Isotopic Current Analyzer (Dwica), J. J. Sartoris, D. A. Hoffman, Bureau Of Reclamation

Publications (WR)

In Nov 1967, a Deep Water Isotopic Current Analyzer (DWICA) was used to study current patterns in the Boulder Basin of Lake Mead to determine if low-quality water from Las Vegas Bay might enter the Southern Nevada Water Project intake on Saddle Island. Secondary objectives were to study the general current patterns in Boulder Basin and the effect of power discharges at Hoover Dam on these currents. Results of current measurements at 3 stations in Boulder Basin are given. Observations indicate a definite possibility that low-quality water from Las Vegas Bay might enter the water intake on Saddle Island. Current …

Evidence For The Existence Of Two Stable Sites For Cobalt Impurity Atoms In Aluminum, Arun Venkatachar

Dissertations and Theses

Using Fe⁵⁷Mössbauer spectroscopy, two alternative sites occupied by cobalt (10^-4 at. % ) impurity atoms in aluminum have been isolated. The substitutional site A is the stable position after annealing the sample above 840 K, followed by a rapid quench. The impurity atoms in site A are characterized by a single line Mössbauer spectrum (indicative of a cubic environment), a room-temperature f = 0.502 (r. m. s. displ. 0.071 A) and an I. S. (reI. to Fe) = -0.421 mm/sec. For anneals below 770 K the cobalt atoms migrate to site B, which is characterized by a …

Application Of The Method Of Lattice Statics To Vacancies In Aluminum, Larry Boyer, John R. Hardy

John R. Hardy Papers

In this paper the method of lattice statics is applied to the calculation of the atomic displacements about a vacancy in aluminum using a fifth-neighbor force-constant model for the dynamical matrix and the vacancy-host lattice interaction. The strain-field interaction energy between two vacancies is similarly calculated. The main object of this work is to demonstrate the important modifications of earlier results, obtained for a first- and second-neighbor force-constant model, when one uses the fifth-neighbor model designed to give a significantly better fit to the measured phonon dispersion curves. In particular it is demonstrated that the displacements about the vacancy continue …

13th Annual Rocky Mountain Spectroscopy Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 13th annual meeting of the Rocky Mountain Spectroscopy Conference, hosted by the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 9-10, 1971.

Energy Calibration Of The Western Michigan University Model En Tandem Accelerator, Michael Joseph Parrott

Masters Theses

No abstract provided.

Elastic Scattering Of Alpha Particles From 12C, Hsi-Chiu Liu

Masters Theses

No abstract provided.

On The Molecular Theory Of Dielectric Polarization In Rigid‐Dipole Fluids, John D. Ramshaw

Physics Faculty Publications and Presentations

A molecular theory is developed for the polarization P(r) produced by a weak position‐dependent external electric field E₀(r) in a finite fluid system, of arbitrary shape, composed of rigid polar molecules. The theory differs from earlier work in that no assumption is made concerning the form of the electrostatic constitutive relation. [The usual assumption in this regard is that P(r) = (ε–1) E(r) / 4π, where E(r) is the total Maxwell electric field. The “dielectric constant” ε is well defined only if the relation between P(r) and E(r) …

An Application Of Spectroscopic Techniques To The Measurement Of Electron Density And Temperature In A Brush Cathode Plasma, Ramabhai M. Patel

Physics Theses & Dissertations

A brief review of the Langmuir probe, microwave and spectroscopic techniques most commonly used to make measurements .of plasma electron temperature and density is presented. Of these various methods, certain spectroscopic methods are applied to the measurements of electron density and temperature in a helium brush cathode plasma. The density measurement is based on the manner in which a series of Stark broadened spectral lines merges into an apparent continuum before the normal series limit is reached. This approach met with only limited success in that the density could be determined only by extrapolating the data obtained. Primarily because of …