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The Weakly Coupled Polaron, Kou-Ying Yang Moravan

Graduate Dissertations and Theses

The Green's Function technique has been used to investigate the properties of weakly coupled longitudinal optical polarons. By taking into consideration the contribution of the multi-phonon and the phonon-cross-exchange diagrams in the self-energy, a vertex correction has been made to the lowest order diagram. The real part and the imaginary part of the self-energy are obtained. The dispersion relationship obtained by this approximation gives the ground state energy which is lower than the upper bound obtained from the variational method. Also, the spectral weight function for several momentum values has been calculated. It shows that the quasi-particle description is good …

Nuclear Charge Distribution Of ¹⁸¹Ta, David Edward Mcloughlin

Graduate Dissertations and Theses

The energies of the x rays emitted by the muonic atom of ¹⁸¹Ta were measured by a Ge(Li) solid state detector. From the clustering of these gamma rays it was possible to identify the transitions of the muonic atom which produced them. When a form is chosen for the nuclear charge distribution, a theoretical spectrum can be calculated…The parameters ��, c, and t can then be chosen to make the calculated spectrum coincide for the 3D-2P, and 2P-1S transitions with the observed spectrum.

The first part of the calculation was performed in the following way. The monopole part of …

Nuclear Charge Distribution Of Tm¹⁶⁹, Eugene Clark Deci

Graduate Dissertations and Theses

The distribution of electrical charge in the nucleus of Tm¹⁶⁹ was determined by measurement of the energies of the X rays of muonic atoms of Tm¹⁶⁹.

The values of the energies of the K X rays and the L X rays were calculated from a model assuming an anisotropic Fermi distribution of charge, and compared to the treasured values. The assumed distribution is a function of three parameters; a half radius, a surface thickness, and a measure of the anisotropy.

The values of the parameters were varied to find the values that gave the best agreement with …

Laser Scattering Measurements Of Droplet Growth In Binary Mixtures. Ii. H2o And Argon H2o And Helium, M. A. Viettit, Burton Schuster

Physics Faculty Research & Creative Works

Water droplet growth rates in a Wilson cloud chamber were measured in Ar-H2O and He-H2O media. These rates were determined in the size range 0.45-10.0 u.m by detection of oscillations in the intensity of polarized light from a He-Ne laser source scattered at 30° by the droplet population. Pressure and initial temperature were measured in the chamber for use in the computation of three droplet growth theories for comparison to experiment. Experiments were conducted in supersaturations ranging from 1.04 to 3.45.

Note On The Poisson Distribution, I. Adawi

Physics Faculty Research & Creative Works

No abstract provided.

Gaas Laser Experiments For The Undergraduate Laboratory, R. E. Robert, Daniel J. Jones, Kaare J. Nygaard

Physics Faculty Research & Creative Works

No abstract provided.

Chemical Shift Parameters For Shallow Donors In Semiconductors, Edward Boyd Hale

Physics Faculty Research & Creative Works

A model for a shallow donor impurity in a semiconductor is used to calculate two relationships and several conditions involving the chemical shift parameters. The model is based on the standard effective mass form for the donor electron wave function, the existence of a potential in the chemical cell which may be real, pseudo, or rather general in nature, and a few somewhat restrictive approximations. The parameters, Δ, δ and Λ are theoretically calculated and are shown to be related if the approximations are valid. These parameters determine the 1S multiplet level structure and it is shown how properties of …

Production Of Metastable Ions In Cesium-Atom-Electron Collisions, Kaare J. Nygaard, Yu Bong Hahn

Physics Faculty Research & Creative Works

The structure in the total electron-impact ionization cross section in cesium can be partially accounted for by the mechanisms of autoionization and excitation ionization of 5p electrons. For electron energies above 17 eV a large fraction of the ions are metastable and can de detected by Auger emission from a metal surface. The experiment was performed in a cesium-atom-electron crossed-beam apparatus, and the metastable ions were counted with a channel electron multiplier. The metastable-ion count rate was a factor of 100 higher than that due to photons from atomic and ionic transitions. We have measured the over-all excitation function for …

Total Electron Impact Ionization Cross Section In Rubidium From Threshold To 250 Ev, Kaare J. Nygaard, Yu Bong Hahn

Physics Faculty Research & Creative Works

A study of ionization in rubidium has been made in a crossed atom-electron beam apparatus. At an electron energy of about 10 eV there is a maximum in the cross section corresponding to the maximum probability for removal of the 5s valence electron. At 16.5 eV we have observed a new peak that is caused by the mechanism of autoionization. For energies below 30 eV there is a good agreement, both in shape and magnitude, between the present measurements and the empirical formula of Lotz. The over-all uncertainty in the measurements is ± 12% which is mostly accounted for by …

Molecular Beam Measurements Of Total Collision Cross Sections Of H 22o, William R. Snow, J. T. Dowell, J. G. Chevrenak, H. E. Berek

Physics Faculty Research & Creative Works

The total cross section for H22O-H22O scattering is measured with a supersonic nozzle beam system. The primary beam has a narrow velocity distribution, and the velocity is varied by control of the nozzle temperature. Velocities are determined by time-of-flight techniques. Cross sections obtained are averages over a Maxwellian distribution of the target molecules. Data at three velocities are presented. The cross sections for H2O are surprisingly small, for example, 3.07 x10-14 cm2 at 1x105 cm/sec, indicating little contribution from the dipole-dipole interaction.

Absolute Differential Elastic- And Inelastic-Scattering Cross Sections In 25-140 Kev He+ + He Collisions, Victor Pol, Walter Kauppila, John T. Park

Physics Faculty Research & Creative Works

Data obtained as energy-loss spectra at angles from 0 to 7.3x10-3 rad (c.m.) with typical energy-loss resolution of 0.7 eV and angular resolution of 2x10-3 rad (c.m.) were used to calculate average differential cross sections dσdΩav for elastic scattering, direct excitation of the individual He(n=2) states, and direct excitation of the He+(n=2) states. The total cross section for excitation of the He(n=2) states obtained by integrating the differential cross sections was found to be 20x10-18 cm2 at 25 keV (lab) decreasing to 7x10-18 cm2 at 140 keV. At incident lab energies below 100 keV the He(2S2) and He(2P3) states dominate …

On The Effect Of Cesium In Photoionization Laser Plasmas, Kaare J. Nygaard

Physics Faculty Research & Creative Works

A number of photoionization mechanisms and how they can be used to generate large-volume laser plasmas are discussed. Reaction rates for two-step photoionization of the cesium atoms as well as formation of molecular ions (Cs2+) are estimated. The necessary cross-section data were obtained from related research in thermionic energy converters. © 1973, IEEE. All rights reserved.

Penning Ionization Of Zn And Cd By Noble-Gas Metastable Atoms, L. A. Riseberg, William F. Parks, Laird D. Schearer

Physics Faculty Research & Creative Works

The Penning-ionization cross sections for He, Ne, Ar, and Kr metastable atoms with Zn and Cd have been measured in a pulsed afterglow. Within the framework of existing theories we have determined those parameters which are of importance in collisions of this type. We find that our data are internally consistent if the cross sections are proportional to the cube of the "hard-sphere" radii and the effects of selection rules are included. A theoretical basis for this dependence is suggested. © 1973 The American Physical Society.

General Theory Of Diffusion-Controlled Reactions, Gerald Wilemski, Marshall Fixman

Physics Faculty Research & Creative Works

A formal mathematical description of diffusion-controlled bimolecular reactions is presented. The theory is completely general with respect to the kinds of reaction processes that may be considered. Besides the presentation of the general formalism, the paper also contains several examples illustrating the application of the theory to a simple many-particule system for simple catalytic bimolecular reactions, including fluorescence quenching. The manner in which approximate solutions may be obtained is also outlined.

Possible Applications Of Surface Electromagnetic Waves To Measure Absorption Coefficients, Ralph William Alexander, Robert John Bell, C. A. Ward, James Roger Weaver, I. L. Tyler, B. Fischer

Physics Faculty Research & Creative Works

We Show that Surface Electromagnetic Waves Can Probably Be Used to Measure the Absorption Coefficients of Materials overlaying Metals. the Proposed Experimental Method is Illustrated in the Infrared Frequency Range using Water, Teflon, and Polyethylene as Sample Materials.

Production And Decay Of Double L Vacancies In Argon And Phosphorus, M. Eugene Rudd, B. Fastrup, P. Dahl, F. D. Schowengerdt

M. Eugene Rudd Publications

Measurements have been made at two laboratories which indicate that the structure reported at 450-550eV in the electron spectrum from Ar⁺-Ar collisions by Ogurtsov, Flaks, and Avakyan is spurious. It is argued that the double L vacancies which they invoke to explain the structure are more likely to decay by the two-step Auger process L ²→LM²→M⁴ than by the one-step process L²→M³ suggested by these authors. Evidence supporting this is found in our electron spectra from P⁺-Ar collisions, where it is known from energy-loss and charge-state measurements that double …

Hall Effect Measurements Of The Net Ionic Mobility In Nacl, Nabr And Nai, Suman Kumar Hukku

Doctoral Dissertations

"Ac Hall effect measurements of the net ionic mobility, µ_H, in "pure" NaCl, NaBr and Nal were made over their intrinsic temperature ranges extending up to about 250⁰ C below the crystal melting point. A well characterized detector system was employed which provided a mobility sensitivity ≥ 2 x 10^-4 cm² · V^-1 · s^-1. Complementary electrical conductivity, σ, data was also collected. The charge transport was assumed to be due to Schottky defects and both cation and anion contributions were considered. The high temperature anion contribution to mobility was clearly demonstrated by …

Model Correction For The Formation Of Amorphous Silicon By Ion Implantation, John Robert Dennis

Masters Theses

"ESR has been used to study the formation of an amorphous layer in silicon by ion implantation. The room temperature implants were done at 20 keV with low dose rates. The critical dose was determined as a function of ion mass for six different ion species. Our experimental heavy ion results agree with those found by other ESR investigators at higher energy, but are not the same for light ions. However, our light and heavy ion results agree with electron microscope measurements for low energy implants. An energy-independent model for the formation of amorphous silicon by ion implantation has …

Electron Transmission Spectroscopy In Atomic Hydrogen, L. Sanche, Paul Burrow

Paul Burrow Publications

An electron transmission experiment is used to study the resonances in the total scattering cross section of atomic hydrogen below the threshold of the first excited state. The three lowest resonances, designated ¹S, ³P, and ¹D, are observed and their energies and decay widths are found to be in good agreement with the values predicted theoretically using close coupling with correlation.

Effects Of Pressure On The Rotational Phase Transitions And Dielectric Properties Of Solid Cyclopentanol, David Nason Glidden

Physics & Astronomy ETDs

The dielectric constant and loss for solid cyclopentanol have been measured at hydrostatic pressures up to 2.5 Kbar for frequencies of 1 KHz to 5 MHz from 258 °K to 200 °K. Activation parameters have been calculated from the experimental data. In addition, activation parameters have also been calcuated from a fluctuation-barrier model for dipole reorientation and compare favorably with the experimental quantities. The dielectric constant shows that the phase transition from form I, with sperically symetric orientational freedom, to form II, with restricted orientational freedom, is readily brought about at these pressures. This phase transition was elucidated by an …

First Measurements Of Earth Albedo Neutrons In Space, James R. Place

Physics & Astronomy ETDs

NASA satellite OSO-6 carried as part of its payload a proton recoil telescope capable of detecting neutrons between 40 and 200 MeV with directional discrimination. Sixteen months of data from this instrument were analyzed with a view to determining properties of the earth albedo neutron flux above the atmosphere.

The variation of albedo neutron flux with geomagnetic latitude was found to be 1:4 between 0° and 40°. The angular distribution shows that about 40% fewer neutrons come upward from directly beneath the satellite compared to the number coming from a direction tangential to the top of the atmosphere. These results …

The Analysis Of Three Narrow Resonances Observed In Protons On Oxygen-16, Benjamin Y. J. Tan

Masters Theses

No abstract provided.

System For Data Acquisition From High Voltage Terminals, George W. York, John T. Park, James J. Miskinis, David H. Crandall, Victor Pol

Physics Faculty Research & Creative Works

An inexpensive data acquisition system has been designed to provide high voltage isolation for data acquisition in analog, digital, and pulse modes. The telemetry system uses GaAs light sources, fiber optics, and phototransistors to accomplish the data transmission. Prewired logic boards have been adapted to accomplish the timing and logic functions. Seven decades of digital data are transmitted error free, pulse data can be transmitted at rates up to 1 MHz, and analog data are transmitted with 0.05% full scale accuracy. © 1972 The American Institute of Physics.

Channeltron Gain In Magnetic Fields, Yu Bong Hahn, Robert E. Hebner, Daniel R. Kastelein, Kaare J. Nygaard

Physics Faculty Research & Creative Works

The gain and total count rate of electron channel multipliers depend strongly on applied magnetic fields. We report experimental results for Channeltrons operated in magnetic fields of up to 300 G, and find that the applied voltage must be increased to about 4000 V to maintain a sufficiently high gain. Slightly higher count rates are observed if the magnetic field is parallel to the plane of the Channeltron, as compared to perpendicular to that plane. © 1972 The American Institute of Physics.

The Design And Construction Of An Electron Lens For Use In A Low Energy Electron Diffraction System, Rodney S. Krieger

Masters Theses

No abstract provided.

Irradiation Equivalence, Robert Katz, S. C. Sharma, M. Homayoonfar

Robert Katz Publications

Recent analyses of track structure show that the parameters describing a radiation field are not separable from those describing a detecting system; that is, it is impossible to write an expression describing the effect of irradiation as a product of 2 factors, one of which contains only parameters describing the detecting system, while the other contains parameters describing only the radiation field. From this perspective it is difficult to understand the use of a “quality factor,” applicable to all biological substances and given as a function of the “effective LET,” for the conversion of rads to rems. One cannot define, …

Decay Of Multiple Spin Echoes In Dipolar Solids, C. H. Wang, John D. Ramshaw

Physics Faculty Publications and Presentations

In this paper we derive a general expression describing the evolution of the transverse nuclear-spin magnetization for the Ostroff-Waugh multiple-spin-echo experiment in dipolar solids. Our approach consists of expressing the formula for the magnetization at even echoes in a form resembling an ordinary time-correlation function, and then evaluating this quantity by means of Zwanzig's projection-operator technique. For long times, we show that under certain conditions the echo envelope decays exponentially, in agreement with experiment. A general expression is obtained for the time constant T^* associated with the decay. This result may be used to generate an expansion of 1T …

Magnetic And Thermometric Properties Of Na3[Ce(C7h3no4)3] ·15h2o In The Millikelvin Range, Richard A. Webb, J. C. Wheatley

Faculty Publications

Measurements of the 16-Hz susceptibility of a powdered Na₃[Ce(C₇H₃NO₄)₃] · 15H₂O (CDP) sample, in the shape of a right-circular cylinder with diameter equal to height, have been made as a function of the Johnson noise temperature T_J of a resistor in the range 2 to 20 mK. Pure liquid ³He was used for thermal contact between the CDP and the noise thermometer in a demagnetization cell. The results are compared with similar data for cerium magnesium nitrate (CMN). CDP appears, like CMN, to have an anomalously …

Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Direct Correlation Function, John D. Ramshaw

Physics Faculty Publications and Presentations

The question of whether the dielectric constant ε exists (is well defined) for a finite fluid system of rigid dipolar molecules is reconsidered and reformulated. It is found that this question can most simply be expressed in terms of the behavior of the position‐ and orientation‐dependent direct correlation function c(r₁,ω₁; r₂, ω₂). It is shown that ε exists if c satisfies the following two conditions: (a) c~–φ/kT for |r₁–r₂|>σ, where φ is the dipole‐dipole potential and σ is a length which is large microscopically but small macroscopically. …

Light Scattering From Mammalian Cells., Albert Brunsting

Physics & Astronomy ETDs

Light scattering intensity functions for concentrically coated spheres (core diameter 7 mu and total sphere diameter 10 mu, approximately) have been computed. The coated spheres model many types of nearly spherical mammalian cells whose nuclei have a low relative refractive index (~1.05) and cytoplasm with a slightly lower relative refractive index (~1.03). Studies are made on the relationships between the scattering coefficients for nonadsorbing, spherically symmetric scatterers. The physical origin of these coefficients is examined for absorbing scatterers. Diffraction accounts for most of the light scattered in the forwards lobe, whereas at larger angles the coated sphere scattering patterns are …