Physical Sciences and Mathematics Commons^™

Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, Don H. Madison

Physics Faculty Research & Creative Works

Absolute values of doubly differential cross sections are obtained for electron production in helium by 5- to 100-keV proton impact. The measured values along with earlier data at higher energies are compared with theoretical plane-wave Born-approximation functions obtained from a Hartree-Fock potential. Not only is good agreement obtained at high impact energies (above 300 keV), but fairly good agreement is found at low energies (below about 20 keV). For electrons ejected in the backward hemisphere, unexpectedly poor agreement is noted at intermediate energies where the measured cross sections dip to 50% of the calculated values in some cases. Singly differential …

Modulated Generalized Ellipsometry, R. M.A. Azzam

Electrical Engineering Faculty Publications

We extend ellipsometry to the direct measurement of small perturbations of the Jones matrix of any linear nondepolarizing optical sample (system) subjected to a modulating stimulus such as temperature, stress, or electric or magnetic field. The methodology of this technique, to be called Modulated Generalized Ellipsometry (MGE), is presented. First an ellipsometer with arbitrary polarizing and analyzing optics is assumed, and subsequently the discussion is specialized to a conventional ellipsometer having either the polarizer-sample-analyzer (PSA) or the polarizer-compensator-sample-analyzer (PCSA) arrangement. MGE provides the tool for the systematic study of thermo-optical, piezo-optical, electro-optical, magneto-optical, and other allied effects for both isotropic …

Observation Of Vibrationally Excited Nitrogen With A Simplified Electron Transmission Apparatus, J.A. Michejda, Paul Burrow

Paul Burrow Publications

A simple electron transmission apparatus is used to observe vibrationally excited N₂ in the first two vibrational levels. The method is based on the pronounced peaks appearing in the total electron scattering cross section in the range of energy 2–4 eV. Because of the wide spacing between these peaks, good energy resolution is not required and measurements can be performed without an electron monochromator.

Reply To “Comments On ‘Theoretical Study Of Impurity-Induced First-Order Raman Spectra For The Alkali Halides’”, John R. Hardy, Arnold Karo

John R. Hardy Papers

This is a reply to the preceding comment by Page on the relative merits of the breathing-shell and deformation-dipole models for predicting defect-activated first-order Raman spectra. We show that when both models are parametrized in the same fashion the agreement between theory and experiment is comparable.

Metamagnetism In Single Crystal Γ-Co(Pyridine)2Cl2, S. Foner, Richard B. Frankel, W. M. Reiff, H. Wong, Gary J. Long

Physics

Small (≤1 mg) single crystals of γ-Co(pyr)₂Cl₂ have been grown and measurements of magnetic moment vs applied field H and temperature have been made for 0≤H≤54 kG and 1.25 K≤T≤4.2 K. At 1.25 K, metamagnetic transitions are observed along the a-axis at ~700 G; along the b-axis at both ~800 and ~1500 G; and along the c-axis at ~4 kG. The low field susceptibilities show a maximum at T≃3.4 K for each orientation. Magnetic saturation is not achieved at 54 kG; about 2.5 µ_B is achieved along the a*- or b-axes, whereas a lower moment is …

Hyperfine Interactions In Antiferromagnetic Eute Using The Te-125 Mossbauer Resonance, N. A. Blum, Richard B. Frankel

Physics

Europium telluride crystallizes in the NaCl structure and is antiferromagnetic with a Néel temperature TN of 9.6 K. We have used the 35.5 keV Møssbauer transition in Te-125 to examine the nature of the spontaneous magnetic moment which has been observed in conducting samples below TN. At 80 K the Mössbauer resonance spectrum consisted of a single absorption line comparable in width with the spectrum of nonmagnetic cubic ZnTe, indicating the absence of a significant quadrupole splitting at this temperature. At 4.2 K the line-width increased by a factor of 1.5, which is equivalent to a single magnetic hyperfine field …

Debye–Hückel Theory For Rigid‐Dipole Fluids, John D. Ramshaw

Physics Faculty Publications and Presentations

The dipolar analog of classical linearized Debye–Hückel theory is formulated for a finite fluid system of arbitrary shape composed of rigid polar molecules. In contrast to the ionic case, the dipolar Debye–Hückel (DDH) theory is nonunique due to an inherent arbitrariness in the choice of a local field E*. This nonuniqueness is expressed in terms of a parameter ϑ related to the ellipticity of the spheroidal cavity used to define E*. The theory then leads to an expression for the direct correlation function c (ϑ) as a function of ϑ. Only the short‐range part of c (ϑ) depends upon ϑ; …

Multiple Rainbows From Single Drops Of Water And Other Liquids, Jearl D. Walker

Physics Faculty Publications

The scattering of light by spherical drops and the theory of rainbows are reviewed in detail to predict the angular positions of rainbows from single drops. The angular positions of the first 13 rainbows of water, observed from a drop suspended in a student spectrometer, were compared to these theoretical positions. Since the rainbows were dependent on the refractive index, the positions shifted with drops of other fluids having other refractive indices. Light corn syrup yielded 11 rainbows, including the 17th-order one. The light emerging from the drops was white except for the multicolors of the rainbows and the faint …

Photoinization Cross Sections For Atomic Chlorine Using An Open-Shell Random-Phase Approximation, Anthony F. Starace, Lloyd Armstrong Jr.

Anthony F. Starace Publications

The use of the random-phase approximation with exchange (RPAE) for calculating partial and total photoionization cross sections and photoelectron angular distributions for open-shell atoms is examined for atomic chlorine. Whereas the RPAE corrections in argon (Z=18) are large, we find those in chlorine (Z=17) to be much smaller due to geometric factors. Hartree-Fock calculations with and without core relaxation are also presented. Sizable deviations from the close-coupling results of Conneely are found.

Intermetallic Reactions In Vacuum-Deposited Nickel And Gold Films On (111) Silicon Single Crystals, K. H. Yoon, Gordon Lewis, L. L. Levenson

Materials Science and Engineering Faculty Research & Creative Works

Pure nickel and gold thin films were vacuum-deposited on (111) silicon single crystals. When Ni/Au/Si or Au/Ni/Si samples were heated to about 550° in situ, hexagonal or deformed hexagonal shaped crystallites were formed on the silicon substrates. The composition of these crystallites was determined by using x-ray diffraction, scanning electron microscopy and scanning Auger microprobe methods. The crystallites were identified as NiSi2. The crystal-lites on the (111) silicon plane parallel to the surface appeared as regular hexagons while the inclined crystal-lites resembled trapezia. The results of Auger spectra and in-depth composition profiles for Ni, Au, and Si showed that the …

Hall-Effect Measurements In Cd-Implanted Gaas, B. K. Shin, David C. Look, Y. S. Park, J. E. Ehret

Physics Faculty Publications

Cadmium ions were implanted in GaAs crystals at 135 keV to doses ranging from 10¹² to 10¹⁶ ion/cm² at room temperature. Sheet‐resistivity and Hall‐effect measurements were carried out as a function of temperature, 4.2–300°K, after annealings at 700, 800, or 900°C in an Ar ambient. The sample surfaces were protected with pyrolytically deposited Si₃N₄. Significant p‐type conduction was observed when samples with doses ≳10¹³cm⁻² were annealed at ≳700°C. For doses below 10¹⁴ cm⁻² nearly complete electrical activity was attained after an 800–900°C anneal. The Cd profiles were …

Evidence Favoring Nonevolutionary Cepheid Masses, Norman R. Simon, Edward G. Schmidt

Edward Schmidt Publications

It is suggested that the bumps on the velocity curves of nonlinear Cepheid models may be understood as the consequence of a resonance between the fundamental and the second overtone modes of the pulsating star. Thus the presence of bumps can be inferred from linear calculations. The region of the observational instability strip containing bumps is compared with the location of the calculated resonances. As was the case for the nonlinear calculations, we find that masses considerably less than evolutionary values are required to bring agreement between the observations and the theory.

The Effect Of A Magnetic Field On The Leclanché Cell, Walter Edward Socha

Dissertations and Theses

The effect of a magnetic field on an electrochemical system, the Leclanche cell, was investigated. Experiments show that there is an increase power output and charge passed when a cell is discharged in an applied magnetic field.

Possible explanations for the effect and descriptions of attempts to verify these explanations are presented.

"Nuclear Power: Its Role In Our Future", Betsy Macinness, Dave Ferg, Rudi Nussbaum, Tom Davis, Sandra Kiefer

Special Collections: Oregon Public Speakers

No abstract provided.

Efficient Ci Calculations Utilizing The Symmetric Group, Gordon A. Gallup, J.M. Norbeck

Gordon Gallup Publications

Gallup has recently given a solution to the problem of determining an orthogonal representation matrix for an arbitrary permutation of the symmetric group in terms of sandwich representations. In this paper it is shown how this provides a means for the precalculation and storage of the necessary distinct coefficients needed in the construction of the various Hamiltonian matrix elements of an orthogonal orbital CI calculation. This method has the advantage over those published previously in that the spin degeneracy problem is handled more efficiently. It is shown that this procedure can be utilized with both the "construction and storage" algorithms …

Raman Spectrum Of Gadolinium Molybdate At 80°K, B.N. Ganguly, Frank G. Ullman, Roger D. Kirby, John R. Hardy

Roger Kirby Publications

Lines that overlap from thermal broadening in the room-temperature Raman spectrum of gadolinium molybdate are resolved in the 80°K spectrum. A total of 126 of the possible 201 lines have been resolved. Symmetry assignments are derived from considerations of both point symmetry and polariton dispersion, supported by separate measurements of A1(TO) and A1(LO) spectra. The splitting of the unstable 47 cm-1 room-temperature A1(TO) line into a doublet at 44.5 and 51.5 cm-1, observed previously only in ir absorption, is also observed in these spectra. On heating, the 44.5-cm-1 line remains fixed in frequency whereas the 51.5-cm-1 line broadens and shifts …

(R - I) Colors Of Cepheids And Yellow Supergiants In Open Clusters, Edward G. Schmidt

Edward Schmidt Publications

(R - I ) and (b - y) observations of nine Cepheids which are members of open clusters, 14 field Cepheids, and 34 nonvariable yellow giants in or near open clusters are presented. Colorcolor relations for the Cepheids are found to differ significantly from star to star. Additionally, the nonvariables may differ from the Cepheid color-color relation. Pulsational masses are determined for the Cepheids using both (R - I) and (B - V) colors as temperature indicators. For some of the shorter period stars the (R - I) masses agree with evolutionary masses, which is not the …

Quantum Beats In The Electric-Field Quenching Of Metastable Hydrogen, A. Van Wijngaarden, E Goh, Gordon W. F. Drake, P. S. Farago

Physics Publications

The strong field-induced quantum beats observed in beam-foil studies of Ly- alpha radiation are obtained in a conventional metastable-hydrogen quenching experiment. The phase relation between the Stark shifted 2s 1/2- 2p 1/2 Lamb-shift oscillations and the much more rapid 2s 1-2p 3/2 fine-structure oscillations depends on the detailed way in which the quenching field is switched on. Apart from a phaseshift, the results agree with a non-perturbative theoretical calculation which assumes that the field is applied suddenly. Various frequency components of the time-dependent radiation intensity are identified with specific hyperfine transitions or groups of transitions. No adjustable parameters are used …

Relativistic Corrections To Spin-Forbidden Electric-Dipole Transitions, Gordon W. F. Drake

Physics Publications

Theoretical results for spin-forbidden electric-dipole transitions have recently been questioned on the grounds that relativistic corrections to the transition operator were not included. It is shown here that these corrections are automatically included when the transition operator is expressed in the dipole length form. The above criticism of previous dipole-length calculations is therefore unfounded. The 1s2p 3P1-1s21S0 and 1s2p 3P1-1s2s 1S0 transitions of helium are discussed as specific numerical examples.

Calculated Anisotropies For The Quenching Radiation In The Hydrogen Isoelectronic Sequence, Gordon W. F. Drake, C. P. Lin

Physics Publications

Accurate values of the Lamb shift can be derived from measurements of the anisotropy in the angular distribution of the radiation accompanying the electric field induced 2s-1s transition of hydrogen. Calculations of the anisotropy, including relativistic and hyperfine structure corrections, are presented for the hydrogenic ions up to S15+. The data enable the calculation of the Lamb shift from a measured value of the anisotropy. © 1976 The American Physical Society.

Proton Spin Relaxation In Dilute Methane Gas: A Symmetrized Theory And Its Experimental Verification, Peter A. Beckmann, M. Bloom, I. Ozier

Physics Faculty Research and Scholarship

Nuclear spin relaxation in low density methane gas is investigated theoretically and experimentally. A theory is developed in which full account is taken of the tetrahedral symmetry of the molecule. For a nuclear Larmor frequency of 30 MHz, the time evolution of the nonequilibrium magnetization is measured as a function of density between approximately 0.005 and 17 amagats at temperatures of 110, 150, and 295 K. In all cases, exponential relaxation is observed. By using the theory in conjunction with the known spin rotation constants and rotational energy levels of CH₄, the measured values of the relaxation rate …

Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, D. H. Madison

M. Eugene Rudd Publications

Absolute values of doubly differential cross sections are obtained for electron production in helium by 5- to 100-keV proton impact. The measured values along with earlier data at higher energies are compared with theoretical plane-wave Born-approximation functions obtained from a Hartree-Fock potential. Not only is good agreement obtained at high impact energies (above 300 keV), but fairly good agreement is found at low energies (below about 20 keV). For electrons ejected in the backward hemisphere, unexpectedly poor agreement is noted at intermediate energies where the measured cross sections dip to 50% of the calculated values in some cases. Singly differential …

Low-Energy Electron Scattering From Mg, Zn, Cd And Hg: Shape Resonances And Electron Affinities, Paul Burrow, J.A. Michejda, J. Comer

Paul Burrow Publications

Measurements of electron scattering at low energy from Mg, Zn, Cd and Hg have been carried out using the electron transmission method. A large shape resonance is observed for each element which we identify with the (ns²np)²P ground state of the negative ion. The electron affinities in eV are found to be Mg(–0.15), Zn(–0.49), Cd(–0,33) and Hg(–0.63) with an error of ±0.03 eV. The results are compared with the available theoretical predictions.

Photoconductivity In Bone And Tendon, Robert G. Fuller, A. A. Marino, R. O. Becker

Robert G. Fuller Publications

Ultraviolet light can be used to stimulate electrical current flow in bone and tendon. This stimulated photocurrent is directional. In tendon the photocurrent parallel to the fibrils is greater than the photocurrent perpendicular to the fibrils. In bone, the longitudinal photocurrent is less than the transverse photocurrent.

Thomson's Monopoles, I. Adawi

Physics Faculty Research & Creative Works

The angular momentum L of the electromagnetic field due to an electric point charge e, and a magnetic point charge (pole) g, is calculated by several methods to obtain J. J. Thomson's result that L = eg/c, and L is directed along the line joining the electric monopole to the magnetic monopole. The relation to Dirac's monopoles is discussed, and particle size is considered. © 1991, American Association of Physics Teachers. All rights reserved.

Radiative Lifetimes And Alignment Depolarization Cross Sections For Ybi And Ii By The Hanle Effect In A Flowing Helium System, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

The radiative lifetimes of the 17992-,25068-,28857-, 37414-, 40564-, and 44017-cm-1 neutral levels and the 30392-cm-1 ion level of Yb have been measured by the Hanle method in a fast-flowing He system. The lifetimes (in units of 10-9 sec) were found to be 820(20), 5.12(0.12), 14.4(0.4), 77.4(6.0), 9.32(0.6), 39.1(3.5), and 5.8(0.6), respectively. In a flowing system with He as a buffer gas the alignment depolarization cross sections with Yb were obtained and are reported here for the first time. They are (in units of 10-15 cm2) 5.0(1.0), 5.9(1.0), 5.9(1.2), 17.9(2.0), 28.2(3.0), 5.16(4.0), and 7.2(2.5), respectively. © 1976 The American Physical Society.

Numerical Simulation Of A Widely Used Cloud Nucleus Counter., Darryl J. Alofs, J. C. Carstens

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Performance of the Conventional Horizontal Plate Thermal Diffusion Chamber as a Cloud Nucleus Counter Was Studied. Numerical Calculations Were Performed in Order to Follow the Simultaneous Drop Growth and Sedimentation in the Spatially and Temporally Nonuniform Supersaturation Field. the Effect of Nuclei Distribution and Smallest Detectable Drop Size Were Investigated. the Results Indicate Order of Magnitude Uncertainty in the Count at 0. 1% Supersaturation, and a Factor of 2 Uncertainty at 1. 0% Supersaturation.

Simplified Rbe-Dose Calculations For Mixed Radiation Fields, Robert Katz, B. G. Fullerton Jr., R. A. Roth, S. C. Sharma

Robert Katz Publications

A problem for radiobiology, radiation protection and treatment planning is the calculation of RBE as a function of the delivered dose when this dose is a result of a mixture of low and high LET radiations, as for neutron and pion beams. Track structure theory (Katz and Sharma, 1975) has recently been used to produce an algorithm for calculating survival, RBE, and OER as a function of dose in such environments. This simple formulation is based on the concept of irradiation equivalence (Katz et al., 1972) through which the effect of a mixed radiation environment is calculated as if it …

Four-Color And Hβ Photometry Of The Galactic Cluster Ngc 6633, Edward G. Schmidt

Edward Schmidt Publications

Photometric measurements of stars in the intermediate-age galactic cluster NGC 6633 are presented. From these data the color excess is found to vary slightly across the cluster with an average of E_{b – y} = 0^m.124. The distance modulus is found to be 7^m.711 and the turnoff occurs at about (b – y)₀ = 0^m.l. The cluster is slightly metal poor.

Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen

Physics Faculty Research & Creative Works

No abstract provided.