Physics Commons^™

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.

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 …

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.

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.

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

Masters Theses

No abstract provided.

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. …

New Method For Generating Density Expansions, John D. Ramshaw

Physics Faculty Publications and Presentations

The calculus of finite differences is used to develop a new method for expressing the thermodynamic limit of a reasonably arbitrary statistical?mechanical average as a power series in the number density ?. The method is simple, straightforward, and purely analytic: it involves no intermediate expansion in powers of the activity and it avoids the use of graph theory. Moreover, the method is developed independently of the prescription for computing the statistical average, a fact which lends to the results an especially wide range of applicability. In particular, these results may be used in classical or quantum statistical mechanics, for intermolecular …

Lasing Conditions Of Elemental Sulfur In A Gas Discharge, David E. Egbert

Theses and Dissertations

The partial pressures from heated sulfur crystals and helium, and sulfur and nitrogen required for ionic sulfur laser action in a gas discharge were determined. Previous work with sulfur lasers is reviewed and population inversion mechanisms are presented for the ionic sulfur laser lines. Possible excitation mechanisms are presented for both electron and ion or atomic collision excitation. Transition diagrams for all the known ionic sulfur laser transitions and an approximate potential energy curve for the diatomic sulfur molecule are presented. Laser action was achieved only when a spark gap pulser was used with a laser tube especially designed to …

X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve Ii. Sodium, Keith H. Brown, J. Dean Barnett

Faculty Publications

Coherent x-ray diffraction patterns for liquid Na have been extracted from measured patterns at 0.5, 7.5, 17, and 43 kbar along the melting curve. The experimentally determined liquid structure factor and resulting radial distribution function are given at each pressure. The position of the principal x-ray intensity peak is reproducible to within 0.5% and shows shifts of the order of 12%. The resulting nearest neighbor distance in the radial distribution function also shifts 12% but is reproducible only to approximately 2%. The distribution functions obtained at points along the melting curve suggest a simple dimensional compression or scaling; however, a …

X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve. I. Methods And Techniques, Keith H. Brown, J. Dean Barnett

Faculty Publications

A technique using the tetrahedral anvil high-pressure x-ray system has been developed to extract coherent x-ray intensity patterns of liquids near melting from measured scattering curves in the presence of high-background counts. Radial distribution functions for liquids along the melting curve to pressures of at least 50 kbar can be obtained. At each pressure scattering curves are recorded for the liquid and solid on opposite sides of the melting curve and a subtraction is made to eliminate background and incoherent scattering. Theoretical estimates of the thermal diffuse scattering from the solid are added to the appropriately corrected difference patterns to …

Measurements Of The Mössbauer Fraction In Chromium, B. Frederick Brace Jr.

Dissertations and Theses

Precision measurements of the Mossbauer fraction of Fe57 in chromium were made using the black absorber technique over a range of temperatures from 78K to 792K. Because of uncertainty in corrections at high temperatures, only the data collected from 78K to 600K was used in analyzing the results.

The f values were analyzed in terms of a Debye approximmation. This analysis of the data yielded a theoretical fit which was based on two adjustable parameters (a Debye temperature of 438K and an anharmonicity parameter of 2 x 10^-4K^-1).

The f measurements were also analyzed using a …

Raman Scattering From Zns Polytypes, J. Schneider, Roger D. Kirby

Roger Kirby Publications

The Raman spectra of the 2H and 4H structures of ZnS have been measured between room temperature and 60 K, and compared with the spectra from zinc blende ZnS. The observed phonons in each case are in good agreement with those expected from the known structural differences.

Frenkel Defects In Alkali Halides, Paul Schulze, John Hardy

John R. Hardy Papers

The method of lattice statics and the deformation dipole model have been applied to Frenkel defects in ionic crystals. For isolated interstitials, all short-ranged repulsive and Coulomb-defect host-lattice ion forces were evaluated at the relaxed configuration. The zero-order Coulomb force was allowed to act on the remainder of the host-lattice ions past first neighbors. We have calculated Frenkel-pair formation energies, ionic displacements, and ionic polarizations in the twelve Na, K, Rb halides. Our results show over all that, in ionic crystals of the rocksalt structure, Schottky defect pairs are more likely to be present than Frenkel defect pairs.

Mössbauer Studies Of Electrostatic Hyperfine Interactions In 238U, 236U, And 234U, Joyce Anne Monard

Doctoral Dissertations

The nuclear gamma resonance (NGR) for ²³⁸U, ²³⁶U, and ²³⁴U in the compound (UO₂) Rb (NO₃)₃ has been established at 4.2°K following the alpha decay of PuO₂ sources. The ratios of the electric quadrupole moments of these isotopes have been determined and the electric field gradient at the uranium site has been calculated from the data. The isomer shift in ²³⁴U has been measured for both PuO₂ and PuA1₄ sources and the change in nuclear radius between the excited and the ground state has been calculated.

Eikonal Approximation For Coupled Equations For Multichannel Scattering, Rung T. Ling, Joseph C.Y. Chen, Jerry Peacher, Kenneth M. Watson

Physics Faculty Research & Creative Works

It is well known that the Glauber approximation for scattering amplitudes is obtained by applying the eikonal approximation to the Fourier transform of the transition operator. The eikonal approximation can also be applied to the coupled equations of scattering obtained by the expansion of the state function in terms of a suitable set of functions. The scattering amplitude can thus be obtained by solving the set of eikonal coupled equations. The latter approach is analyzed for a special class of channel-coupling potentials. The first-order approximation to the derived eikonal coupled equations is the eikonal Born approximation. Numerical illustrations in this …

Nuclear-Magnetic-Resonance Study Of Co2+ In Cds, David C. Look, Donald R. Locker

Physics Faculty Publications

Nuclear spin-lattice relaxation times, T₁, have been measured over a temperature range T=(1.1-300) °K and frequency range ν=2-15 MHz in a single crystal of CdS doped with 13-ppm cobalt. Minima in T₁ vs T are observed, and absolute values of the effective electron relaxation time, τ_e, may be calculated at the temperatures of the minima, e.g., at 14 °K, τ_e=8.0×10^-8 sec. At low temperatures, T≲5 °K, τ_e is dominated by a resonant Orbach process involving the two ground-state Kramers doublets (S=±3/2 and S=±1/2) which, according to our measurements, are split by …

Semiclassical Theory Of Inelastic Collisions Ii. Momentum Space Formulation, John B. Delos, Walter R. Thorson

Arts & Sciences Articles

The time-dependent equations of the classical picture of inelastic collisions (classical-trajectory equations) are derived using the momentum-space semiclassical approximation. Thereby it is shown that the classical-trajectory equations remain valid in the vicinity of classical turning points provided that (a) the momentum-space semiclassical approximation is valid, (b) the trajectories for elastic scattering in the various internal states differ only slightly, and (c) the slopes of the elastic scattering potentials have the same sign. A brief review of the existing derivations of the classical-trajectory equations is given, and the general conditions for their validity are discussed.

A Study Of The (3He, N) Reaction At 25 Mev, Mark Bentley Greenfield

Doctoral Dissertations

Energy spectra of neutrons from the ¹²C (³He, n)140; ²⁷A1(³He, n)²⁹P; ²⁸Si(³He, n)³⁰S; and ^58,60,62Ni(³He, n)^60,62,64Zn reactions have been measured at 25 MeV incident ³He energy using time-of-flight techniques. An overall energy resolution of about 1 percent for detection of 10-35 MeV neutrons provided accurate determinations of level excitations. Differential cross sections were extracted for many two particle states with up to 10 MeV excitation in the residual nuclei. By varying the beam incident angle and leaving the flight path somewhat …

Hydrostatic Pressure Effects On The Epr Spectrum Of V2+: A1203 And Cr3+: A120, Charles J. Wilcox

Masters Theses

No abstract provided.

Calculations Of Nuclear Structure Using Isospin Formalism, Roger A. Cook

Masters Theses

No abstract provided.

Studies Of The Potential Curve Crossing Problem Ii. General Theory And A Model For Close Crossings, John B. Delos, W. R. Thorson

Arts & Sciences Articles

A unified formal treatment of the two-state potential-curve-crossing problem in atomic collision theory is presented, and the case of close crossings analyzed in detail. A complete solution for this case, including necessary computations, is given using a suitable generalization of the linear model originally suggested by Landau, Zener, and Stueckelberg. Our solution is based upon a hierarchy of approximations concerned with (i) choice of a discrete basis set for electronic coordinates, (ii) semiclassical treatment of the nuclear motion, (iii) an appropriate model for the two-state electronic Hamiltonian, and (iv) a complete solution to that model.

Semiclassical Theory Of Inelastic Collisions I. Classical Picture And Semiclassical, John B. Delos, W. R. Thorson, Stephen Knudson

Arts & Sciences Articles

This series of papers is concerned with the derivation of the equations of the classical picture of atomic collisions, iℏddtdi(t)=Σjhij(t)dj(t), which describe the "time" dependence of electronic-quantum-state amplitudes as the nuclei move along a classical trajectory. These equations are derived in two ways. In the first formulation, which coincides with the intuitive classical picture of the collision, the nuclear part of the wave function is treated as a superposition of narrow wave packets, each traveling along a classical trajectory. In the second formulation, a semiclassical approach is used. The validity and meaning of the two formulations are discussed and compared.

14th Annual Rocky Mountain Spectroscopy Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 14th annual meeting of the Rocky Mountain Spectroscopy Conference, sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 31 - August 1, 1972.

X-Ray Irradiation Apparatus In Which An X-Ray Source Is Energized Upon The Recording Of Irradiation Dosage Data, George S. Hurst, Norbert Thennard, Karl A. Schneider

Physics and Astronomy Faculty Patents

Apparatus for use in examining or treating patients with X-radiation or the like requires the making of a permanent record of the radiation applied. The operation of the radiation source is controlled in dependence upon the making of the record and the to radiation, or dose exposure is limited to a predetermined amount. A method is disclosed for safeguarding the patient and for producing a tangible record of the dose to which the patient is subjected.

Reducing Uncertainty, Richard C. Heyser

Unpublished Writings

Intended for audio engineers, Richard C. Heyser meant for this paper to bring attention to the misapplication of the theoretical concept, the Uncertainty Principle. Heyser argues that this concept has been "freely applied without regard to the errors which may result due to lack of understanding of its derivation."

Development Of The Oso-6 High-Energy Neutron Detector And Correlation Of Measured Solar Neutron Fluxes To Solar Flares, Frederick Young

Physics & Astronomy ETDs

In an attempt to understand certain of the high energy processes that occur in the solar and terrestrial atmospheres and the interplanetary medium a detector of 20 to 160 MeV neutrons had been designed and constructed for inclusion in the NASA Orbiting Solar Observatory, Satellite OSO-G, which was launched into a near circular orbit at approximately 500 km altitude in August 1969. Both the angle of incidence and the energy of the neutron are determined by a telescopic arrangement of four scintillation plastic counters (Pilot B; hydrogen to carbon ratio 1:1) which generates proton recoils and provides pulse heights for …