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Articles 35701 - 35730 of 36522

Full-Text Articles in Physical Sciences and Mathematics

Mössbauer Effect In Fe-Doped Kmgf3, J. Chappert, J. R. Regnard, Richard B. Frankel, A. Misetich, N. A. Blum Mar 1971

Mössbauer Effect In Fe-Doped Kmgf3, J. Chappert, J. R. Regnard, Richard B. Frankel, A. Misetich, N. A. Blum

Physics

An iron-doped KMgF3 single crystal has been studied with the Mössbauer technique. The two charge states, Fe2+ and Fe3+, are observed. Below 12 °K an Fe2+ quadrupole doublet appears. Using Ham strain model we calculate that the first excited spin-orbit level lies ~ 120 cm-1 above the Γ5g ground state.

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Low-Lying Even-Parity Resonances In Ki:Ag+, Roger D. Kirby Mar 1971

Low-Lying Even-Parity Resonances In Ki:Ag+, Roger D. Kirby

Roger Kirby Publications

Lattice resonances of Eg symmetry (16.35 cm-1) and A1g symmetry (25 cm-1) have been found in KI:Ag+ using far-infrared spectroscopic techniques. The two even-parity modes are found to be anharmonically coupled to the T1u- symmetry resonant mode at 17.3 cm-1, giving rise to the combination bands observed at 30 and 44.4 cm-1.

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Isomeric Shift Of The 83 Kev Transition In 153Eu, E. Ansaldo, L. Grodzins, Richard B. Frankel Feb 1971

Isomeric Shift Of The 83 Kev Transition In 153Eu, E. Ansaldo, L. Grodzins, Richard B. Frankel

Physics

No abstract provided.

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Far-Infrared Properties Of Lattice Resonant Modes. V. Second-Order Stark Effect, B.P. Clayman, Roger D. Kirby, A. J. Sievers Feb 1971

Far-Infrared Properties Of Lattice Resonant Modes. V. Second-Order Stark Effect, B.P. Clayman, Roger D. Kirby, A. J. Sievers

Roger Kirby Publications

Small electric-field-induced frequency shifts have been observed for resonant modes associated with three defect systems. For NaI: Clˉ, the shifts have been used to measure the quartic anharmonic terms of the interionic potential of the impurity ion. For KBr: Li+, the quartic anharmonic terms are found to be very small, and an harmonic potential which includes a central barrier with the barrier height less than the zero-point energy of the oscillator is required to explain the experimental results. For NaCl: Cu+, only an "on-center" resonant-mode configuration is consistent with the experimental results.

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Simulation Of Particle Tracks In Emulsion, Thomas E. Furtak, Robert Katz Feb 1971

Simulation Of Particle Tracks In Emulsion, Thomas E. Furtak, Robert Katz

Robert Katz Publications

Micrographs of energetic particles in nuclear emulsion are simulated by computing the spatial distribution of developed grains with the δ-ray theory of track structure, and representing the developed grains by points of light on an IBM 2250 visual display unit. The simulated tracks display many of the features of actual track structure and serve as a visual comparison between experiment and theory,

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Dielectric Polarization And Alignment And The Structure Of Polar Fluids, John D. Ramshaw, D. W. Schaefer, John S. Waugh, J. M. Deutsch Feb 1971

Dielectric Polarization And Alignment And The Structure Of Polar Fluids, John D. Ramshaw, D. W. Schaefer, John S. Waugh, J. M. Deutsch

Physics Faculty Publications and Presentations

An analysis is made of the information about the structure of dense polar fluids which resides in the dielectric constant, the Kerr constant, and the nuclear magnetic resonance (NMR) quadratic electric field effect. The inadequacy of the "local-field" model for liquids is discussed. The existence of a nonzero molecular hyperpolarizability is shown to destroy an equivalence which would otherwise exist between the Kerr and NMR experiments, and can easily account for apparent discrepancies between the reported Kerr and NMR data for nitrobenzene and nitromethane. A method is presented for removing dielectric boundary effects from statistical averages, so that the averages …

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Lamb-Mössbauer Factor Of Sodium Ferrocyanide, Daniel L. Decker, L. E. Lortz Feb 1971

Lamb-Mössbauer Factor Of Sodium Ferrocyanide, Daniel L. Decker, L. E. Lortz

Faculty Publications

Using a set of commercially prepared sodium ferrocyanide absorbers enriched to 91.2% Fe57 the Lamb-Mössbauer factor was measured to be 0.28±0.03. The thickness of Fe57 for these absorbers was measured using x-ray absorption techniques and was found to be considerably smaller than that advertised by the manufacturer even after correcting for the size of the ferrocyanide particles in the absorbers.

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Theory Of Relativistic Magnetic Dipole Transitions: Lifetime Of The Metastable 2s3 State Of The Heliumlike Ions, Gordon W. F. Drake Jan 1971

Theory Of Relativistic Magnetic Dipole Transitions: Lifetime Of The Metastable 2s3 State Of The Heliumlike Ions, Gordon W. F. Drake

Physics Publications

It has recently been established that the radiative lifetime of the metastable 2S3 state of helium and the heliumlike ions is determined by single-photon magnetic dipole (M1) transitions to the ground state, rather than the two-photon process proposed by Breit and Teller. The theory of nl-n′l M1 transitions with n ′ is developed in the Pauli approximation and extended to two-electron systems. Terms arising from relativistic energy corrections and finite-wavelength effects are included. The results for hydrogenic systems are shown to be identical to those obtained in the relativistic four-component Dirac formulation. The coefficients in the Z-1 perturbation expansion of …

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Mossbauer Study Of An Intramolecular Antiferromagnet, R. Lechan, C. R. Abeledo, R. B. Frankel Jan 1971

Mossbauer Study Of An Intramolecular Antiferromagnet, R. Lechan, C. R. Abeledo, R. B. Frankel

Physics

Mossbauer measurements at 4.2 ≤T ≤ 22 K and OsHosBO kOe are + reported in (Fe Salen Cl)2, a molecular complex containing two coupled Fe3+ ions bridged by oxygen atoms. At 4.2 K only the ground state with effective spin S = 0 is appreciably populated. Analysis of the magnetic field and temperature dependence of the magnetic hyperfine field yields an exchange constant J= -6.7 cm>sup>-1 and a hyperfine field of -192 kOe per unit spin at each Fe3+ nucleus.

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A Variable Coeficient Of Restitution Experiment On A Linear Air Track, R. Gruebel, James C. Dennis, L. Choate Jan 1971

A Variable Coeficient Of Restitution Experiment On A Linear Air Track, R. Gruebel, James C. Dennis, L. Choate

Faculty Publications

A system consisting of two pendula attached to an air cart is mathematically analyzed, and the coefficient of restitution is shown to pass through a deep minimum. The solution to the small angle equation of motion is transcendental and provides an exercise in graphical methods for the beginning mechanics student.

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Small Momentum Transfer Structure Factor Of Quantum Liquids, Robert Hallock Jan 1971

Small Momentum Transfer Structure Factor Of Quantum Liquids, Robert Hallock

Robert Hallock

The liquid structure factor of 3He has been determined in the momentum-transfer range 0.2 to 1.0 Å-1. At temperatures near 0.4 K there is evidence for a gentle change of slope of the structure factor in the region near 0.35 Å-1 Comparison with the work on helium-4 suggests that the observed behavior is a general feature of the two fluids.

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An Inexpensive Target Cell For The Study Of Liquids And Gases By X-Ray Scattering, Robert Hallock Jan 1971

An Inexpensive Target Cell For The Study Of Liquids And Gases By X-Ray Scattering, Robert Hallock

Robert Hallock

No abstract provided.

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The Impulse And Doublet, Richard C. Heyser Jan 1971

The Impulse And Doublet, Richard C. Heyser

Unpublished Writings

The basic problem to which this paper is directed is that of characterization of the acoustic field perceived by an observer and due to a loudspeaker situation in a room. Before immediately jumping into an apparent solution and presenting the results of a set of measurements it is essential to present the considerations leading to that measurment...First, there are at least two ways of characterizing the same acoustic signal if we restrict our attention to a well defined set of parameters...Secondly, since both characterizations define the same thing it must be possible to translate information without loss from one domain …

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Recent Meetings-Nebraska Section, Robert Fuller Jan 1971

Recent Meetings-Nebraska Section, Robert Fuller

Robert G. Fuller Publications

The fall meeting of the Nebraska Section of the AAPT was held 31 October 1970 at the University of Nebraska in Lincoln. The sessions were chaired by Professor Clyde Sachtleben, Hastings College.

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Thermal Expansivity And Refractive Index Determinations For Some Hydrosol Systems And Their Similarity To Properties Ascribed To "Anomalous" Water, Gerald Wayne Chappue Jan 1971

Thermal Expansivity And Refractive Index Determinations For Some Hydrosol Systems And Their Similarity To Properties Ascribed To "Anomalous" Water, Gerald Wayne Chappue

Masters Theses

"The characteristic thermal expansion and refractive index of aqueous dispersions of SiO₂ and NaOH were determined for samples contained in quartz micro-capillaries. Comparison is made with the expansivity and refractive properties of anomalous water or polywater as reported by other investigators. The similarity between the properties and behavior of various hydrosol systems and those ascribed to anomalous water is cited as a serious challenge to the hypothesized existence of an allotropic modification of water"--Abstract, page ii.

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Calculation Of Anisotropic Hyperfine Constants For Lattice Nuclei Near A Shallow Donor, Edward B. (Boyd) Hale, Robert Lee Mieher Jan 1971

Calculation Of Anisotropic Hyperfine Constants For Lattice Nuclei Near A Shallow Donor, Edward B. (Boyd) Hale, Robert Lee Mieher

Physics Faculty Research & Creative Works

A method is presented for calculating the magnetic anisotropic (dipolar) hyperfine constants for lattice nuclei near a shallow-donor impurity. The method assumes that the wave function of the donor electron can be expressed in an effective-mass form, i.e., a slowly varying envelope function times conduction-band Bloch functions. For each dipolar hyperfine constant, two separate calculations are performed. One calculation is for a local region about the lattice nucleus of interest. The greatest part of the interaction occurs in this region (about 85 ± 10%). The second calculation is for the more distant region. The dipolar constants in the distant region …

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Excitation Of The 2s State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation - Angular Distributions, W. Neil Shelton, E. S. Leherissey, Don H. Madison Jan 1971

Excitation Of The 2s State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation - Angular Distributions, W. Neil Shelton, E. S. Leherissey, Don H. Madison

Physics Faculty Research & Creative Works

The excitation of ground-state hydrogen atoms to the 2s state by the impact of electrons with energies of 1 to 50 Ry (13.6 to 680.3 eV) has been calculated in the distorted-wave approximation with exchange included. The angular distributions of the scattered electrons at 1 and 4 Ry are compared with those derived from the close-coupling calculations by Burke, Schey, and Smith, and are compared with four different plane-wave theories at all energies calculated. Taking the close-coupling results as a standard, it is found that the distorted-wave angular distributions represent an improvement over those of the plane-wave theories.

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Angular And Energy Distribution Of Cross Sections For Electron Production By 50-300-Kev-Proton Impacts On N2, O2, Ne, And Ar, J. B. Crooks, M. Eugene Rudd Jan 1971

Angular And Energy Distribution Of Cross Sections For Electron Production By 50-300-Kev-Proton Impacts On N2, O2, Ne, And Ar, J. B. Crooks, M. Eugene Rudd

M. Eugene Rudd Publications

Cross sections differential in angle and ejection energy for electron production by proton impact on nitrogen, oxygen, neon, and argon have been measured using electrostatic analysis and counting of individual electrons. The range of proton energies was 50-300 keV, the angles ranged from 10° to 160°, and the electron energies were measured from 1.5 to 1057 eV. Integrations over angle and/or electron energy yielded singly differential and total electron production cross sections. Our total cross sections for oxygen fall halfway between previous data of deHeer et al. and Hooper et al., but our argon cross sections agree better with deHeer …

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Observation Of Quadrupole Splitting Of B-12 In A Single Crystal, R. L. Williams Jr., Richard C. Haskell, Leon Madansky Jan 1971

Observation Of Quadrupole Splitting Of B-12 In A Single Crystal, R. L. Williams Jr., Richard C. Haskell, Leon Madansky

All HMC Faculty Publications and Research

The quadrupole coupling of B-12 implanted in Be-9 has been observed using a single crystal of Be. One sees a narrow resonance line, the location of which depends in the normal way on the orientation of the crystalline c-axis with respect to the external magnetic field direction. The coupling constant is given by e2qQ/h = 54.9(6) kHz. This is consistent with our previous measurement using a Be foil. Using the field gradient at Be-9 lattice sites, calculated by Pomerantz and Das, one finds Q(B-12) = about 34.6 mb.

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Measurement Of Nuclear Magnetic Dipole Moment Of Li-8 By Implantation In Metal Foils, Richard C. Haskell, R. L. Williams Jr., Leon Madansky Jan 1971

Measurement Of Nuclear Magnetic Dipole Moment Of Li-8 By Implantation In Metal Foils, Richard C. Haskell, R. L. Williams Jr., Leon Madansky

All HMC Faculty Publications and Research

Polarized 8Li nuclei have been produced through the 7Li(d,p) reaction using the 3.5-MeV Van de Graaff accelerator at Brookhaven National Laboratory. The observed polarization was a slowly-varying function of deuteron energy over the range 1.3-2.9 MeV, reaching a maximum of about +1.6%. The recoiling nuclei were stopped in Au, Pt and Pd foils and the effective dipole moments were measured by a resonant depolarization method. The results were 1.65362(22)µN, 1.65288(20)µN and 1.65270(30)µN respectively. These are consistent with the work of Connor, who found µ(8Li) =1.6530(8)µN in a LiF crystal. An upper limit for the 8Li quadrupole moment will also be …

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Comparison Of Experimental And Theoretical Values Of Cross Sections For Electron Production By Proton Impact, M. Eugene Rudd, D. Gregoire, J. B. Crooks Jan 1971

Comparison Of Experimental And Theoretical Values Of Cross Sections For Electron Production By Proton Impact, M. Eugene Rudd, D. Gregoire, J. B. Crooks

M. Eugene Rudd Publications

Angle and energy distributions of electrons ejected from single- and multishell atoms by 50-to 300-keV protons are compared with various theoretical treatments. Partial cross sections for each subshell are calculated by scaling according to the number of electrons and the binding energy and then are added. The Born approximation fails at large and at small angles but yields fair agreement at intermediate angles. The treatments of Salin and of Macek, which take account of the influence of the projectile after the collision, yield much improved agreement at small angles. The binary-encounter model is used to calculate cross sections which are …

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Collision Cross Sections For The Excitation Of The Schumann-Runge Dissociation Continuum In Molecular Oxygen By 20-110-Kev Protons, John T. Park, F. D. Schowengerdt, D. R. Schoonover Jan 1971

Collision Cross Sections For The Excitation Of The Schumann-Runge Dissociation Continuum In Molecular Oxygen By 20-110-Kev Protons, John T. Park, F. D. Schowengerdt, D. R. Schoonover

Physics Faculty Research & Creative Works

Absolute cross sections for the excitation of the Schumann-Runge dissociation continuum of molecular oxygen have been obtained from inelastic energy-loss spectra induced by 20-110-keV protons incident on gaseous targets of molecular oxygen. Apparent differential energy loss cross sections, ionization cross sections, and total inelastic cross sections are also obtained from the energy-loss spectra. The proton energy-loss spectra have an energy resolution of about 2 eV. The energy location of the first peak in the energy-loss spectra of O2 is in general agreement with the findings of photo absorption and electron energy-loss-spectra measurements. The cross section for the Schumann-Runge dissociation continuum …

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Local Magnetic Moments And The Mossbauer Effect, Richard B. Frankel, Brian B. Schwartz Jan 1971

Local Magnetic Moments And The Mossbauer Effect, Richard B. Frankel, Brian B. Schwartz

Physics

No abstract provided.

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X-Ray And Mössbauer Spectroscopy Studies Of The Silicon-Antimony And Bismuth-Antimony Alloys, James Ralph Teague Jan 1971

X-Ray And Mössbauer Spectroscopy Studies Of The Silicon-Antimony And Bismuth-Antimony Alloys, James Ralph Teague

Doctoral Dissertations

"X-ray and Mossbauer spectroscopy were used to investigate two antimony alloys, Bi-Sb and Si-Sb, showing semiconductorsemimetallic transitions or vice versa, depending on the antimony concentration in the host lattice. Resistivity and density measurements were found to be helpful in the analysis of the results. X-ray studies for dislocation-free antimony-doped silicon showed that the lattice constant of the alloy increased as the antimony concentration increased from 10¹⁸ to 10¹⁹ Sb atoms/cc. Rather good agreement was found between theoretical and experimental changes in lattice constant for dislocation-free silicon. Mössbauer studies showed that the isomer shift decreased linearly with increasing antimony concentration, which …

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Second- And Third-Order Elastic Constants Of Aluminum And Lead, Tetsuro Suzuki Jan 1971

Second- And Third-Order Elastic Constants Of Aluminum And Lead, Tetsuro Suzuki

Physics Faculty Research & Creative Works

The second- and third-order elastic constants of Al and Pb are calculated as the second and third derivatives of the binding energy with respect to the finite deformation parameter. The binding energy is derived from a local pseudopotential by use of second-order perturbation theory. It is shown that the binding energy satisfied not only the diagonal equilibrium condition, but also the off-diagonal equilibrium condition, i.e., the first derivative of the binding energy with respect to a volume change as well as with respect to shear deformations is zero. Accordingly, the present method of calculation is based on a stable lattice …

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Magnetostriction And Magnetic Breakdown In Cadmium, J. M. Carter, Don M. Sparlin Jan 1971

Magnetostriction And Magnetic Breakdown In Cadmium, J. M. Carter, Don M. Sparlin

Physics Faculty Research & Creative Works

Studies of the monotonic magnetostriction of cadmium at 4.2 °K in applied magnetic fields to 70 kG have shown that the angular variation of an extremal point Hm is proportional to secθ. The magnitude of Hm is in close agreement with the onset of a breakdown orbit γ13 observed for the applied field within 35 °of the c axis. The range of observation of Hm coincides with the range of the orbit γ. © 1971 The American Physical Society.

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Electron-Impact Excitation Of Auto-Ionizing Levels In Cesium, Yu Bong Hahn, Kaare J. Nygaard Jan 1971

Electron-Impact Excitation Of Auto-Ionizing Levels In Cesium, Yu Bong Hahn, Kaare J. Nygaard

Physics Faculty Research & Creative Works

Auto-ionizing states in Cs between 12 and 20 eV have been studied by electron impact. The retarding-potential-difference method was used to obtain an electron beam with energy spread of about 0.1 eV. To determine the threshold energies, inelastically scattered electrons were analyzed by the trapped-electron method. We have been able to identify about 20 levels, and the agreement with spectroscopic data is excellent. A peak appearing at 12.80 eV is probably due to the quartet states observed by Feldman and Novick. © 1971 The American Physical Society.

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Absolute Excitation Cross Sections Of He+ In 20-100-Kev He+-He Collisions Using Energy-Loss Spectrometry, D. R. Schoonover, John T. Park Jan 1971

Absolute Excitation Cross Sections Of He+ In 20-100-Kev He+-He Collisions Using Energy-Loss Spectrometry, D. R. Schoonover, John T. Park

Physics Faculty Research & Creative Works

Application of positive-ion energy-loss spectrometry has been extended to include experimental determination of absolute excitation cross sections of ground-state helium ions. Helium ion-atom collisions were studied for impact energies ranging between 20-100 keV, in 10-keV intervals. The data were taken with an apparatus resolution between 0.6-0.8 eV full width at half-maximum (FWHM). Cross sections for transitions from ground state to the second and third principal quantum levels of the ion plotted as a function of impact energy were still rapidly increasing at 100 keV. The cross sections at this energy were (1.64 ± 0.28) x 10-18 cm2 for He+(1s122)→He+ (n=2) …

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Properties Of The Interstitial In The Diamond-Type Lattice, G D. Watkins, R P. Messmer, C Weigel, David Peak, J W. Corbett Jan 1971

Properties Of The Interstitial In The Diamond-Type Lattice, G D. Watkins, R P. Messmer, C Weigel, David Peak, J W. Corbett

All Physics Faculty Publications

Linear combination of atomic orbital—molecular orbital cluster calculations using extended Hückel theory suggest that the interstitial carbon atom in diamond prefers an "interstitialcy" configuration. The predicted minimum-energy configuration changes with charge state, providing a possible example of the Bourgoin mechanism for "athermal" migration of the interstitial in the presence of ionizing radiation.

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Photoionization Of Photoexcited Cesium, Robert E. Hebner Jan 1971

Photoionization Of Photoexcited Cesium, Robert E. Hebner

Doctoral Dissertations

"A new method for obtaining the cross section for photoionization of photoexcited cesium is presented. The salient feature of this experiment is to use three crossed beams, i.e., two light beams intersecting a beam of cesium atoms. The cross section is determined by counting the ions produced by the two step process: Cs (6S) + h[upsilon]₁ --> Cs (6P) ; Cs (6P) + [upsilon]₂ --> Cs⁺ + e⁻ The relative cross section for the second step has been obtained from threshold (5060 Å) to 2500 Å. The excitation light source used in obtaining this cross section was a rf resonance …

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