Physics Commons^™

Heisenberg Theory Of Ferromagnetism: Constant Coupling Revisited, Harry A. Brown

Physics Faculty Research & Creative Works

The Heinsenberg theory of ferromagnetism has been treated by many types of approximations; one of the more successful is known as constant coupling. The literature constants several different ways of arriving at results like those of the constant-coupling approximation, but proofs that they are indeed equivalent are lacking in some cases. It is shown that two of these methods are equivalent for spin 1/2 and explicitly demonstrated that both yield exactly the constant-coupling results, though simpler in use and concept than the latter. Finally, it is shown that one of the two methods yields the same Curie temperatures as constant …

Surface Electromagnetic Waves With Damping. Ii. Anisotropic Media, G. S. Kovener, Ralph William Alexander, I. L. Tyler, Robert John Bell

Physics Faculty Research & Creative Works

The Technique of Plotting the Attenuated-Total-Reflection (ATR) Reflectance as a Function of Both Frequency and Incident Angle using a Three-Dimensional Plot is Applied to Surface Electromagnetic Waves (SEW) in a Uniaxial Material, MnF2. It is Shown that Dispersion Curves Calculated Without Absorption Do Not Completely Describe the ATR Reflectivity. Experimental Data Confirming the Reflectance Surface Features Are Presented. Also, Additional Minima in the Reflectance Surface Not Associated with SEW Are Discussed. © 1977 the American Physical Society.

Interaction Of Electric And Magnetic Charges, I. Adawi

Physics Faculty Research & Creative Works

It is shown classically that in a head-on collision between an electric and a magnetic charge a repulsive polarization force of the form r-5 results (where r is the distance between the charges), if one (both) charge(s) is (are) assigned a finite spherical size. This force leads to a minimum distance of approach and prevents one particle from going through the other, and thus guards against the violation of the conservation of angular momentum. This polarization force is a manifestation of the diamagnetism (diaelectricity) of extended electric (magnetic) charges. © 1977 The American Physical Society.

Light Emission From Atom Beam - Plasma Interactions, Kaare J. Nygaard

Physics Faculty Research & Creative Works

A beam of atoms penetrating a plasma can be considered a line source of contaminants. Atoms excited by the plasma electrons yield information about the spatially resolved electron density and temperature. The light intensity as a function of time and position along the beam can be conveniently observed with an optical multichannel analyzer Since the beam atoms are different from the plasma constituents, the method does not suffer from self-absorption. Copyright © 1977 by The Institute of Electrical and Electronics Engineers, Inc.

Final-State Effects In Carbon Auger Spectra Of Transition-Metal Carbides, M. A. Smith, L. L. Levenson

Physics Faculty Research & Creative Works

The carbon Auger spectra of TiC, VC, and Cr₃C₂ are measured with a resolution of 1.2 eV. Background subtraction is performed, and a deconvolution technique is used to remove energy-dependent broadening from the spectra. An analysis of the data in terms of density-of-states calculations, x-ray emission work, and x-ray photoelectron data shows that final-state effects dominate the Auger spectra. For all of the carbides three peaks are identified as spectral terms resulting directly from final-state hole interactions. Other peaks appearing in the Auger spectra can be identified without final-state considerations. © 1977 The American Physical Society.

Valence-Band Information From The Auger Kvv Spectrum Of Graphite, M. A. Smith, L. L. Levenson

Physics Faculty Research & Creative Works

The Auger KVV and x-ray photoelectron valence-band spectra of atomically clean, well-ordered graphite are measured. After background subtraction is performed and a deconvolution technique is used to remove energy-dependent features from the Auger data, the transition density function is calculated for the graphite valence band. A comparison is made with other experimental work and with a density-of-states calculation. It is found that the transition density closely resembles the density of states if localized hole effects are considered. © 1977 The American Physical Society.

Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Functional-Derivative Approach, John D. Ramshaw

Physics Faculty Publications and Presentations

In a previous article [J. Chem. Phys. 57, 2684 (1972)] sufficient conditions were established for the existence of the dielectric constant ɛ in rigid-dipole fluids. One of these conditions was an unrealistic restriction on the angular dependence of the direct correlation function c (12) at short range. Here it is shown that this restriction can be removed without altering the previous conclusions. Consequently, ɛ rigorously exists if c (12) depends only upon relative positions and orientations of molecules 1 and 2, and becomes asymptotic to -φd(12)/kT at long range, where φd(12) is the dipole-dipole potential. The development is based upon …

Measurement Of Radiative Muon Capture In Calcium, Richard Dennis Hart

Dissertations, Theses, and Masters Projects

No abstract provided.

Model Fe(Iii) Porphyrin Systems: Axial Ligation In Oxidized Cytochrome P-450.S, G. C. Papaefthymiou, Richard B. Frankel, S. Foner, S. C. Tang, S. Koch, R. H. Holm

Physics

In an effort to develop useful experimental criteria to distinguish among the viable axial ligation possibilities of O, N, and S coordination in oxidized cytochrome P-450. S (substrate-bound, high-spin), syntheticmodel compounds with O-(Fe(PPIXDME) (OEt) and Fe(PPIXDME) (OC₆H₄NO₂)) and S-(Fe(PPIXDME) (S₆H₄NO₂) and Fe(OEP) (SPh)) donor axial ligands were prepared and studied by Mössbauer spectroscopy. Ferric hemoglobin and myoglobin were used as model compounds with N-axial coordination. The isomer shifts (δ) and quadrupole splittings (ΔE_Q) observed are typical of high-spin Fe(III) porphyrins and are comparable with results …

Synthetic Analogs Of The Active Sites Of Oxidized And Reduced Rubredoxin, Richard B. Frankel, G. C. Papaefthymiou, R. W. Lane, R. H. Holm

Physics

The bischelate monoanion [Fe((SCH₂)₂C₆H₄)₂]^1- contains an unconstrained, near-tetrahedral Fe(III)-S₄ coordination unit (similar to the Fe-S₄ coordinationunit occurring in rubredoxin proteins) and exhibits the Fe(III)/Fe(II) redox couple. Mossbauer parameters at 77 K are isomer shift δ = 0.13 mm/s (relative to iron metal) and electric quadrupole splitting ΔE_Q = 0.57 mm/s. Application of an external magnetic field parallel to the direction of observation at 4.2 K induces a saturation magnetic hyperfine field of - 380 kOe. Upon reduction to the dianion [Fe((SCH₂)₂C …

Experiments On The Attenuation Of Third Sound In Saturated Superfluid Helium Films, Robert Hallock, K. L. Telschow, R. K. Galkiewicz

Robert Hallock

Upper limits of the attenuation of third sound in saturated superfluid 4He films have been measured in three separate experiments. Our observations at frequencies from 0.1 to 200 Hz indicate that the attenuation in these thick films is substantially lower than would be inferred from the only previous experiment done on saturated films. We observe the third-sound velocity to have the temperature dependence predicted by Bergman.

Review Of Quantum States Of Atoms, Molecules And Solids, M. Eugene Rudd

M. Eugene Rudd Publications

The subjects of atomic, molecular and solid-state physics have only rarely been treated at an advanced level in a single volume. The notable exception, of course, is John C. Slater’s Quantum Theory of Matter. In the present book the three authors, Michael Morrison, Thomas Estle and Neal Lane, stress the unity among these fields by ernphasizing the concept of electronic quantum states in atoms, diatomic molecules and crystalline solids. Such a combination should be of basic interest to students in a variety of scientific fields and also form the basis for more advanced work in those three subjects themselves. …

Ultraviolet Stimulated Thermoluminescent Response Characteristics Of Aluminum Oxide, Edward Ryan Iii

Masters Theses & Specialist Projects

This investigation has demonstrated that some aluminum oxide crystals have high sensitivity and are well suited for detecting and measuring ultraviolet radiation rates significantly less than .01 µW/cm².

The thermoluminescent glow curve, linearity of response, and fading of the crystals were determined. An action spectrum was performed to determine the relative sensitivities of several crystals in a range of wavelengths from 230 nm to 546 nm.

The sensitivity of the crystals was found to decrease as a function of exposure. \n explanation for the decrease in sensitivity due to the presence of high temperature traps is presented.

This …

Ultraviolet Stimulated Thermoluminescent Response Characteristics Of Aluminum Oxide, Edward Ryan

Masters Theses & Specialist Projects

This investigation has demonstrated that some aluminum oxide crystals have high sensitivity and are well suited for detecting and measuring ultraviolet radiation rates significantly less than 0.1 pW/cm2. The thermoluminescent glow curve, linearity of response, and fading of the crystals were determined. An action spectrum was performed to determine the relative sensitivities of several crystals in a range of wavelengths from 230 nm to 546 nm. The sensitivity of the crystals was found to decrease as a function of exposure. An explanation for the decrease in sensitivity due to the presence of high temperature traps is presented. This investigation has …

Energy Dependence Of Amorphizing Implant Dose In Silicon, John R. Dennis, Edward Boyd Hale

Physics Faculty Research & Creative Works

The radiation-induced transformation from crystalline to amorphous silicon was studied using ion implantation. The ion energy was varied from 20 to 180 keV for Li+, N+, Ne+, Ar+, and Kr +. The energy dependence of the critical amorphizing dose was determined by electron spin resonance. Comparison of the data with theoretical calculations of the energy density deposited into atomic processes showed good agreement. This energy-dependent agreement gave evidence that energy density is important to the transformation at both low and high implantation temperatures.

Computer Model Of A Fast Toroidal Plasma Compression, With Application To The Topolotron, H. Mark Nelson, Keith H. Brown, Charles A. Hart

Faculty Publications

The method is developed for a comuputer sequence which models a fast toroidal theta or screw pinch for a highly conducting axially symmetric plasma. The computer sequence takes into account the self-inductances of the plasma and the external conductors which drive the compression as well as the mutual inductance which electromagnetically couples the two. The computer sequence is divided into three phases: a snowplow compression phase, an adiabatic compression phase, and a crowbarred circuit phase. The computer sequence is applied to a topolotron and an example is given of a magnetohydrodynamic equilibrium geometry for which the plasma surface possesses an …

Electron Transmission Studies Of The Negative Ion States Of Substituted Benzenes In The Gas Phase, Kenneth D. Jordan, J.A. Michejda, Paul Burrow

Paul Burrow Publications

Temporary negative ions of benzene, aniline, phenol, anisole, fluoro-, chloro-, and bromobenzene, formed in the gas phase by capture of electrons into the low-lying π* orbitals, are studied by means of electron transmission spectroscopy. The electron affinities are determined and their relative values are interpreted in terms of resonance and inductive effects.

Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation, Ralph V. Calhoun, Don H. Madison, W. Neil Shelton

Physics Faculty Research & Creative Works

The differential cross sections for excitation of the n=2 state of atomic hydrogen by the impact of electrons with energies of 54, 100, 136, and 200 eV are calculated in the distorted-wave approximation with exchange included. Cross sections for excitation of the 2s_1/2, 2p_1/2, and 2p_3/2 states are calculated and summed to give the n=2 differential cross sections. The results of this calculation are compared with previous theoretical calculations and with recent absolute experimental data.

Abstract: Mössbauer Spectroscopy Of Pdh Fe Alloys, M. Weber, C. R. Abeledo, Richard B. Frankel, Brian B. Schwartz

Physics

Large changes in the electron susceptibility of PdH alloys have been observed with increasing H concentration, with important consequences for the magnetic and superconducting properties of these alloys. (1) To observe the effect of the changing spin susceptibility, we have studied PdH Fe alloys with 2, 1 and < 0.1 at. % Fe by Mössbauer spectroscopy in external magnetic fields. Mydosh (2) has reported spin glass behavior in the high Fe concentration alloys and Kondo phenomena in the dilute Fe alloys. For hydrogen-metal ratios < 0.5, α and β phases, with low and high hydrogen content respectively, coexist. For temperatures below T_c of the α phase but above T_c of the β phase, we observe a superposition of a six line spectrum and a single line corresponding to the α and β phases respectively. (3) In an applied field, the β phase magnetizes and both phases have hyperfine fields which extrapolate to …

Mössbauer And Nmr Studies Of Site Substitution And Magnetic Structure Of Fe3-XMnXSi Alloys, K. Raj, V. Niculescu, T. J. Burch, J. I. Budnick, Richard B. Frankel

Physics

The NMR measurements in Fe_3−xMn_xSi alloys show increasingly complex spectra for x > 0.75 due to overlapping signals from Fe, Si and Mn nuclei in various sites. Mössbauer experiments were undertaken to identify the Fe⁵⁷ resonances. The combined NMR and Mössbauer results have been used to elucidate the site substitution and magnetic structure of these alloys for (0 < x < 1.75).

A Comparison Of The Rough Sphere Rotational Diffusion Model With Experimental Results For Liquid Methyl Iodide, Dane R. Jones, Scott L. Whittenburg, C. H. Wang

Chemistry and Biochemistry Faculty Publications

No abstract available.

Electronic And Magnetic Properties Of Amorphous And Crystalline Zr40Cu60-XFeX Alloys, F.R. Szofran, G.R. Gruzalski, John W. Weymouth, David J. Sellmyer, B.C. Giessen

David Sellmyer Publications

Electronic states and localized magnetic moments and their interactions were studied in amorphous and crystalline Zr₄₀Cu_60-xFe_x alloys for 0≤x≤12. Electrical resistivity, magnetic susceptibility, and high-field magnetization measurements were performed. In the dilute crystalline alloys Curie-Weiss behavior is seen in the susceptibility and is associated with localized moments (μ_eff≈3μ_B) on the iron atoms. At higher iron concentrations ferromagnetism is observed. Curie-Weiss behavior also is seen in the susceptibility of the dilute (0eff≈0.7μ_B). There is some evidence that the local environment of the Fe atoms is important and may depend …

Calculated Temperature Of Grid Lateral Wires In Microwave Power Triodes, Jewell Tucker

Masters Theses & Specialist Projects

In microwave power triodes the grid drive power causes grid lateral wire heating. This development calculates the temperature of the wire as a function of the drive power, physical dimensions and characteristics of the wire material, for the following boundary conditions:

I. Constant grid drive, grid lateral wire of infinite length not connected to a heat sink.

II. Same as I except the wire is of finite length brazed to a grid frame.

III. The grid excitation in the form of pulses, and the grid lateral wire of finite length brazed to a grid frame.

the equations were verified experimentally …

Behavior Of A Manganin Coil At Elevated Temperatures And Pressures, Jonathan D. Weiss, Daniel L. Decker, H. B. Vanfleet

Faculty Publications

We have determined the temperature dependence in the first-order pressure coefficient of a manganin coil to be dBetaB/dT= (4.2±0.8) ×10^-7 (kbar degrees C)^-1 in the equation R (T,P) =R (T,0)(1+BetaP+GammaP2), where R (T,P) is the coil resistance at temperature T and pressure P. The measurements were performed by simultaneously measuring the coil resistance and temperature at the transitions of mercury and bismuth, which were observed by differential thermal analysis.

Supralinearity Of Thermoluminescent Dosimeters, Leif Larsson, Robert Katz

Robert Katz Publications

The supralinear response of thermoluminescent dosimeters (TLDs) after irradiation with gamma- or beta-rays can be decomposed by use of the cumulative Poisson distribution into a sum of 1-or-more and 2-or-more hit components, suggesting the coexistence of both types of trap structures. Following the response of other 1-hit detectors, and of biological cells to energetic heavy ions, we expect and find that the supralinear response tends to disappear with alpha particle, and with neutron irradiation, and that the supralinear, or 2-hit, component tends to be more responsive to high LET (Linear Energy Transfer) radiations. Since the response of biological cells to …

The Quantum Defect Theory Approach, Anthony F. Starace

Anthony F. Starace Publications

The Quantum Defect Theory (QDT) is a method of using the analytically known properties of excited electrons moving in a pure Coulomb field to describe atomic photoabsorption and electron-ion scattering processes in terms of a few parameters. These parameters may be determined either from experimental data or from ab initio theoretical calculations. In addition, they are usually nearly independent of energy in the threshold energy region (i.e., within a few eV of the atomic ionization threshold). Thus the determination of these parameters at any single energy suffices to predict the variation with energy of numerous atomic properties in the threshold …

18th Annual Rocky Mountain Spectroscopy Conference

Rocky Mountain Conference on Magnetic Resonance

Final program and abstracts from the 18th 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 2-3, 1976.

Cross Sections For Excitation Of Atomic Hydrogen To The N=2, 3, And 4 States By 15-200-Kev Protons, John T. Park, Judith E. Aldag, Jacob M. George, Jerry Peacher

Physics Faculty Research & Creative Works

Cross sections for the processes H⁺+H(1 s)H⁺+H*(n = 2, 3, 4) have been extracted from the energy-loss spectra of 15- to 200-keV protons by using a spectrum-fitting technique. Absolute cross sections have been obtained by normalization of the spectra to the theoretical cross section through the use of the Born approximation at 200 keV. The cross-section curves are very similar in shape with maxima at 60 keV. The results have been compared with available theoretical calculations. The n = 2 and n = 3 cross-section measurements are in very good agreement in curve shape with Glauber-approximation …

Electrical Conductivity Of Thin Lecithin-Cholesterol Membranes Due To 2,4-D, 2,4-Db, 2,4,5-T And 2,4-Dcp, Malkanthi Paulis

Dissertations and Theses

The effect of the following pesticides on DC electrical conductivity of lecithin-cholesterol membranes has been studied: endothall, paraquat, diquat, 2,4-D, 2,4-DB, 2,4,5-T, 2,4-DCP. It has been found that the ions of endothall, paraquat and diquat are essentially membrane impermeable and that they do not bind to the membrane surface. In contrast, 2,4-D, 2,4-DB, 2,4,5-T and 2,4-DCP induce electrical conductivity in lecithincholesterol membranes and in addition they also cause an increase in the nonactin-K⁺ membrane conductivity.

The compounds 2,4-D, 2,4-DB, 2,4,5-T and 2,4-DCP basically behave as class II uncouplers. The kinetic scheme of charge transfer across the membrane, based on …

Frequency-Mixing Detection (Fmd) Of Polarization-Modulated Light, R. M.A. Azzam

Electrical Engineering Faculty Publications

When a light beam whose polarization and intensity are weakly modulated at a frequency ω_m passes through a periodic analyzer of frequency ω_a(<ω_m) and the transmitted flux is linearly detected, the resulting total signal S_t consists of two components: (i) a periodic baseband signal S_bb with harmonics of frequencies nω_a (n = 0,1,2,…) and (ii) an amplitude-modulated-carrier signal δS_mc with center (carrier) frequency ω_m and sideband frequencies at ω_m ± nω_a(n = 1,2,…). In this paper we show that the average polarization of the beam is determined …