Physical Sciences and Mathematics Commons^™

An Assessment Of The Transmission Electron Microscope For The Study Of Aerosol-Gas Interactions: Direct Observations Of Sodium Chloride Hydration Phenomena, Antony David Clarke

Dissertations and Theses

An experimental study of solid-gas interactions was made for sodium chloride particles, using a specially fabricated environmental chamber in a transmission electron microscope. It was found that under suitable conditions the hydration and dehydration of these particles could be directly observed and quantitatively measured. Measurements of growth were obtained with a time resolution of one-thirtieth of a second for particles having diameters ranging from 0.02 μm to 1.0 μm.

Representation Of Ab Initio Energy Surfaces By Analytic Functions, R.L. Vance, Gordon A. Gallup

Gordon Gallup Publications

A method for the analytical representation of ab initio energy surface results is described. For a three-atom surface, the potential function is written as a sum of atomic, two-body, and three-body terms. This allows an easy fitting of the whole surface, including the dissociated and united atom limits. The theory is applied to an H₃ surface of limited accuracy calculated for these purposes. Comparisons are made, where possible, with more accurate calculations. Extensions to surfaces involving four or more atoms are also discussed.

Angular Differential Cross Sections For 25-, 50-, And 100-Kev-Proton Excitation Of Helium To The N=2 Level, John T. Park, Jacob M. George, Jerry Peacher, Judith E. Aldag

Physics Faculty Research & Creative Works

Differential cross sections for 25-, 50-, and 100-keV-proton excitation of helium to the n=2 level have been determined for center-of-mass scattering angles from 0 to 1.2 mrad. The cross sections were obtained from an analysis of the angular distribution of the scattered protons which had lost an energy corresponding to the excitation of the helium target to its n=2 level. The differential cross section is very sharply peaked in the forward direction and decreases by a factor of 45 in 1.0 mrad at 25 keV and by a factor of 650 in 1.0 mrad at 100 keV. The data are …

Measurements Of Orbit-Lattice Coupling Of Er And Dy Impurities In Ag And Al Hosts, S. A. Dodds, Jeff Sanny

Physics Faculty Works

The magnetic resonance of dilute Dy and Er impurities has been observed in thin polycrystalline Al and Ag films on two different substrates. The films are deposited at room temperature, and the measurements are made at liquid-helium temperatures. During cooling, the difference in thermal contraction between film and substrate produces an effectively uniaxial strain in the film. This results in an anisotropic g value, which we have used to obtain lower limits on the orbit-lattice coupling coefficient for these systems. We find values for V ( Γ _3g, 2 ) from 600 to 2000 cm ^{− 1} , somewhat …

Theory Of Near-Adiabatic Collisions. Ii. Scattering Coordinate Method, W. R. Thorson, John B. Delos

Arts & Sciences Articles

A rigorously correct and fully quantum-mechanical theory of slow atomic collisions is presented, which removes the formal defects and spurious nonadiabatic couplings of perturbed-stationary-states theory, and arrives at coupled equations for the heavy-particle motion which are the same as those obtained in the preceding paper by the electron translation factor formulation. Here, however, the theory is formulated in terms of suitably defined scattering coordinates, and electron translation factors do not appear. A unified physical interpretation of both approaches can thereby be made, and smaller terms in the coupled equations, describing corrections of order mμ to electronic binding energies and to …

Theory Of Near-Adiabatic Collisions. I. Electron-Translation-Factor Method, W. R. Thorson, John B. Delos

Arts & Sciences Articles

The theory of near-adiabatic collisions is formulated in a fully quantum-mechanical form, correctly taking into account the role of electron translation factors (ETF's). A general form for the ETF, using switching functions, is given for systems which are electrically either asymmetric or symmetric (with or without mass asymmetry). The main result is that the close-coupled scattering equations obtained in the perturbed-stationary-states theory must be replaced by equations of identical form, but having modified nonadiabatic coupling matrices. In general, the corrections involved are substantial; their nature, and effect on coupling matrices, is discussed, and conditions when they are likely to …

Infrared Spectral Detectivity Of Cr‐Doped Gaas, David C. Look

Physics Faculty Publications

The room‐temperature spectral detectivity of Cr‐doped GaAs has been examined in the impurity excitation region out to 1.7 μ, a range which includes the wavelengths of several important lasers as well as low‐loss optical fibers. The results include values of D∗ greater than 10¹¹ cm Hz^1/2/W in the photoconductive mode, and 10¹⁰ cm Hz^1/2/W in the photomagnetoelectric mode. Small carrier lifetimes, ∼10⁻⁸ sec, offer the potential of high‐speed operation; however, the measured response times are much larger, ∼10⁻³–10⁻² sec, because of very high input impedances. Formulas are presented to …

Calculated Yields And Slowing-Down Spectra For Electrons In Liquid Water: Implications For Electron And Photon Rbe, R. N. Hamm, H. A. Wright, Robert Katz, J. E. Turner, R. H. Ritchie

Robert Katz Publications

Detailed Monte Carlo calculations have been carried out of slowing-down spectra and yields for a number of end-points for electrons in liquid water. These investigations were made to study differences in physical effects of different low-LET radiations and implications for RBE. Initial electron energies from 1 keV to 1 MeV were used, and all secondary electrons were followed in the computations until their energies fell below 10 eV. Though there are substantial differences in the slowing-down spectra at energies near and above the K-shell ionization potential of oxygen, the energy spectrum of electrons at lower energies is found to be …

Existence Of The Dielectric Constant In Fluids Of Nonlinear Rigid Polar Molecules, John D. Ramshaw

Physics Faculty Publications and Presentations

The existence of the dielectric constant epsilon is investigated for fluids composed of nonlinear rigid polar molecules. The investigation is performed using the functional-derivative approach previously employed to establish sufficient conditions for the existence of epsilon in fluids of linear (axially symmetric) molecules. It is shown that these same conditions are sufficient for nonlinear molecules of arbitrary symmetry. An expression for epsilon in terms of the direct correlation function emerges automatically from the development. This expression, which involves the inversion of a 3 x 3 matrix, is a slight generalization of one obtained earlier by Hoye and Stell using an …

Magnetic Properties Of Linear Chain Systems: Metamagnetism Of Single Crystal Co(Pyridine)2Cl2, S. Foner, Richard B. Frankel, W. M. Reiff, H. Wong, Gary J. Long

Physics

The metamagnetic behavior of the low temperature properties of single crystal Co(pyridine)₂Cl₂ is discussed. At 1.25 K oriented single crystals exhibit a two‐step metamagnetic transition at applied fields ∼0.8 and 1.6 kG along the b‐axis, a single transition at ∼0.7 kG for applied fields along the a^∗ axis, and a single transition at ∼4.2 kG for an applied field along the c axis. Just above the transition fields a moment of 2μ_B/Co atom is measured for B₀ parallel to the a^∗ axis or b axis, and 0.4μ_B/Co atom is …

Angular Differential Cross Sections For Excitation Of Atomic Hydrogen By 25-, 50-, And 100-Kev Protons, John T. Park, Judith E. Aldag, Jerry Peacher, Jacob M. George

Physics Faculty Research & Creative Works

Angular differential cross sections for the process H⁺ + H(1s ) → H⁺ (θ ) + H ( n = 2 ) are presented for 25-, 50-, and 100-keV protons incident on atomic hydrogen. The experimental results are in fair agreement with Glauber-approximation calculations.

Kinetics Of Oxidation Of Bismuth And Bismuth Based Alloys In Air Between 500 And 530 (Degree) K, Magda Ishak Ahmed Waly El-Guindy

Archived Theses and Dissertations

No abstract provided.

Emp Analysis Of An Fm Communications Radio With A Long Wire Antenna, George H. Baker Iii, Werner J. Stark

George H Baker

A Norton equivalent circuit is developed for a long-wire antenna used with a VHF man-pack FM radio exposed to an incident electromagnetic pulse (EMP). The required short-circuit current and antenna impedance are computed by use of a transmission-line model for the antenna, and the computations are compared with measurements of the short-circuit current and antenna impedance. The comparison shows that the transmission-line model for the antenna is adequate for performing a vulnerability analysis of the radio. A network model is developed for a portion of the radio and is used as the load in the Norton equivalent circuit. Load currents …

Electron Drift Velocities In Helium-Fluorine Gas Mixtures, Kaare J. Nygaard, John L. Fletcher, Scott R. Hunter, Stephen R. Foltyn

Physics Faculty Research & Creative Works

Using a simple time-of-flight technique, we have measured the electron drift velocity in helium with 0.1-1% fluorine additive. Our results in a 0.1% mixture are in close agreement with data in pure helium. The measured drift velocity increases with increasing fluorine concentration. © 1978, American Institute of Physics. All rights reserved.

Energy And Angular Distribution Of Neutrons From Proton-Proton Inelastic Scattering At 800 Mev, Ted Dean Rupp

Physics & Astronomy ETDs

The neutron energy spectra from the reaction p + p → n + p + π⁺ for an incident proton energy of 800 MeV was measured for all phase space. ++ The channels were dominated by △⁺⁺. (1232) resonance and had a total cross section of 16 ± 1.5 mb. Also, the data demonstrated the dominance of Sand P waves. The experimental results were compared to isobar, phase space and a one pion exchange model. The isobar and phase space models failed to predict the experimental results; however, the one pion exchange model fit the data for …

Polynomial And Rational Fraction Representations Of A Diatomic Molecular Potential, Paul R. Findley

Physics & Astronomy ETDs

A method is presented for approximating a diatomic molecular vibrational potential by fitting to modified forms of the potential. Power's numerical Born-Oppenheimer potential for the H₂⁺ electronic ground state is the potential used in this thesis. The modification procedure is to multiply the potential by various powers of the internuclear separation. This removes the troublesome Coulomb pole at zero internuclear separation. Graphs of the modified forms are presented. Polynomials were fitted directly to the potential, to the modified forms, and to the pure electronic energy. Comparisons are made among the various representations of the potential obtained from the …

Generalized Ellipsometry Based On Azimuth Measurements Alone, R. M.A. Azzam

Electrical Engineering Faculty Publications

We investigate the azimuth response function, θ_o = f(θ_i), of a linear nondepolarizing optical system S, whereθ_i and θ_o, are the azimuths (orientations) of the generally elliptic vibrations of totally polarized light at the input and output of S. We find that the azimuth response function depends on five of the six parameters that specify the normalized circular Jones matrix of the optical system. Thus the entire polarization response of an optical system can be nearly completely reconstructed from its azimuth response alone. Five input-output azimuth measurements (θ_ik, θ_ok), k …

Simulation Of Mechanical Rotation By Optical Rotation: Application To The Design Of A New Fourier Photopolarimeter, R. M.A. Azzam

Electrical Engineering Faculty Publications

The mechanical rotation of an optical element around the axis of a beam of polarized light can be easily simulated by using the phenomenon of optical rotation. Because optical rotation can be magnetically or electrically induced, virtually any kind of mechanical rotation can be mimicked. This interesting principle is applied to the design of a new Fourier photopolarimeter that uses an oscillating-azimuth retarder (OAR). The OAR consists of a quarter-wave plate surrounded by two ac-excited Faraday cells that produce equal and opposite sinusoidal optical rotations. Analysis of the operation of this polarimeter of no moving parts proves its ability to …

Generalization Of The Form Of The T Matrix Operator Of Non-Relativistic Scattering Theory, Francis Leone

Masters Theses

No abstract provided.

Theoretical Thermodynamic Functions For Krypton Gas, A-Hamid Aidinejad

Masters Theses

No abstract provided.

Tip-Angle-Dependent Magnetic Relaxation In Superfluid 3he, Richard A. Webb

Faculty Publications

Using a pulsed superconducting-quantum-interference-device (SQUID) NMR technique, relaxation of the longitudinal magnetization in superfluid ³He has been measured in magnetic fields of 31, 102, 180, and 306 Oe in the pressure range 16-26 bar. It is observed that in both superfluid phases there is a temperature-dependent, well-defined spin-tipping angle, θc, for which the relaxation of the magnetization changes from an exponential to a nonexponential behavior.

Negative Ion Resonances In The Fluorobenzenes And Biphenyl, John Ronald Frazier

Doctoral Dissertations

Conclusion: In the present work a new experimental device was built, tested, and applied to the study of NIR's of a basic series of organic molecules. The importance of this work is threefold:

1. It has demonstrated that such a device can yield accurate values of electron affinities and vertical attachment energies.

2. A complete series of fluorine-substituted benzene derivatives has been studied to yield their electron affinities and/or vertical attachment energies. This has provided new insights concerning the negative ion states of these molecules.

3. Solid samples (with sufficient vapor pressures) can be studied with the present device to …

Mössbauer Spectroscopy Of Iron Deposits In Thalassemic Heart Tissue, G. C. Papaefthymiou, K. S. Kaufman, Richard B. Frankel, A. Rosenthal

Physics

No abstract provided.

Magnetic Ordering And Local Random Anisotropy In Dilute Magnetic Glasses, G.R. Gruzalski, J.D. Patterson, David J. Sellmyer

David Sellmyer Publications

Magnetic susceptibility and high-field magnetization measurements are presented for amorphous Zr₄₀Cu_60-xM_x (M denoting Fe, Mn, Gd, and Tb) and Nb₅₀Ni_50-xFe_x, with x ranging from zero to about ten. The alloys for M=Gd, Tb, and Fe develop low-temperature ordered states that are characterized as spin glass like, whereas the Mn alloy exhibits no evidence of order down to 1.3 K. The magnetic properties of these alloys are discussed in terms of local random anisotropy, fluctuations in the interimpurity exchange interactions, extremely short electron-mean-free paths, antiferromagnetic interactions between the …

Magnetic Properties Of The Rare-Earth Intermetallics RGa2, T.H. Tsai, J.A. Gerber, John W. Weymouth, David J. Sellmyer

David Sellmyer Publications

The magnetic susceptibility (χ) of polycrystalline samples of RGa₂, R=Ce, Pr, Nd, Gd, Tb, Dy, Ho, and Er, has been measured at low field, from 1.5 K to 300 K. The magnetization of these samples also has been measured up to 80 kOe at low temperatures. Antiferromagnetic behavior was observed for all the samples with Neel temperatures (T_N) ranging from about 4.1 K for CeGa₂ to about 14.8 K for TbGa₂. Curie-Weiss fits to the high-temperature χ (T) data led to effective moments in good agreement with those expected for …

Magnetic Ordering In Amorphous Nd-Co, Gd-Co And Er-Co Alloys, J.A. Gerber, D.J. Miller, David J. Sellmyer

David Sellmyer Publications

Previous studies of magnetism in amorphous rare earth–transition metal alloys have emphasized alloys rich in transition metal. We report here results on three rare earth rich amorphous alloys: Nd₆₄Co₃₆, Gd₆₅Co₃₅, and Er₆₅Co₃₅. Low field susceptibility, χ, was measured for T in the range 4.2 K≤T≤300 K and magnetization was measured for 1.3≤T≤200 K and applied fields, H, of 0≤H≤80 kOe. Curie-Weiss fits were made to high temperature χ (T) data to determine average effective moments and Weiss temperatures. Hysteresis …

Ferromagnetic And Spin-Glass Ordering In Fe-Doped AuXPd1-X Alloys, E.R. Domb, David J. Sellmyer, T.M. Quick, R.J. Borg

David Sellmyer Publications

Ferromagnetic and spin-glass ordering has been studied in (Au_xPd_1-x)_1-cFe_c alloys for 0<~x<~1 and 0<~c≲0.06. Magnetic susceptibility, high-field magnetization, and Mössbauer measurements have been performed between liquid-helium and room temperature. For small x, the alloys are strongly exchange enhanced. Assuming that the local-moment-conduction-electron exchange coupling J is independent of x, and employing the Takahashi-Shimizu-Doniach-Wohlfarth theory, we obtain J=0.12 eV from the saturation moment versus host susceptibility data. The theory, however, fails to describe the interimpurity coupling that leads to magnetic order in the Pd-rich alloys. A simple phenomenological model, based on the ferromagnetic coupling of all the giant polarization clouds except those that are "isolated," gives qualitative agreement with the …

Isospin Forbidden And Allowed Reactions 16O(Α,Α0)160 And 160(Α,Γ)20Ne, Daniel J. Steck

Physics Faculty Publications

Six ²⁰Ne levels have been investigated in detail via the ¹⁶O+α channel between 6.9≤E_α≤10.2 MeV. Level parameters for states at E_x(²⁰Ne)=10.264±0.008, 11.077±0.008, 11.259±0.008, 11.552±0.008,12.237±0.008, and 12.390±0.008 MeV have been extracted from γ decay properties and phase shift analysis of the elastic scattering. With the exception of the 11.552 and 12.39 MeV states, these levels display primarily TT=0 states, several other weak γ decaying resonances were observed at 11.97 ± 0.04, 12.05 ± 0.04, and 12.49 ± 0.02 MeV but were not studied in detail. Charge dependent matrix elements (4-120 …

Deuterium Lamb Shift Via Quenching-Radiation Anisotropy Measurements, A. Van Wijngaarden, Gordon W. F. Drake

Physics Publications

The Lamb shift of a hydrogenic ion can be deduced from the anisotropy in the angular distribution of the 2s12-1s12 electric field quenching radiation. The accuracy of our previous anisotropy measurement for deuterium is improved to about ± 150 ppm. The derived Lamb shift is (1059.36±0.16) MHz. The sources of error are carefully analyzed and the prospects for further improvements in the accuracy are discussed. © 1978 The American Physical Society.

Angular Integrals And Radial Recurrence Relations For Two-Electron Matrix Elements In Hylleraas Coordinates, Gordon W. F. Drake

Physics Publications

General formulas are obtained for the reduction of a wide class of two-electron matrix elements in Hylleraas coordinates to finite sums of radial integrals for states of arbitrary angular momentum. Multipole transition integrals and the Breit interaction are treated as special cases. A number of recurrence relations are derived for radial integrals containing PL(cosθ) (where cosθ=r^1•r^2) in terms of radial integrals containing lower-order Legendre polynomials. The results are well suited to computer implementation. © 1978 The American Physical Society.