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Articles 34711 - 34740 of 36535

Full-Text Articles in Physical Sciences and Mathematics

Book Review: The Theory Of Atomic Structure And Spectra By Robert D. Cowan, Anthony F. Starace Apr 1982

Book Review: The Theory Of Atomic Structure And Spectra By Robert D. Cowan, Anthony F. Starace

Anthony F. Starace Publications

The field of atomic spectroscopy is currently experiencing a resurgence of interest owing on the one hand to its applications in astrophysics, plasma physics, and other fields and on the other hand to the development of new experimental tools to probe atomic structures. One example of the latter is the use of tunable lasers to study highly excited atoms in the presence of strong external electric and magnetic fields. Another is the use of synchrotron radiation to probe with increasing detail the inner shell structure of rare earth, actinide, and other heavy atoms.

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Photoelectron Angular Distributions: Energy Dependence For S Subshells, Steven T. Manson, Anthony F. Starace Apr 1982

Photoelectron Angular Distributions: Energy Dependence For S Subshells, Steven T. Manson, Anthony F. Starace

Anthony F. Starace Publications

An overview of the theory of photoelectron angular distributions for atoms is presented. Its features, which are embodied in a single asymmetry parameter β in the electric dipole approximation, are examined within the framework of the angular momentum transfer formulation. The β parameter is in principle always energy dependent. Within the LS coupling approximation, however, there are instances, each representing a multitude of particular photoionization processes, in which β is an analytically determined constant. The energy dependence of the β parameters in such instances is due entirely to spin-orbit and other relativistic interactions. The study of the energy dependence of …

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Fe Hyperfine Fields In Fe3-XVXSi Alloys, T. J. Burch, C. A. Weiler, K. Raj, J. I. Budnick, V. Niculescu, G. C. Papaefthymiou, Richard B. Frankel Apr 1982

Fe Hyperfine Fields In Fe3-XVXSi Alloys, T. J. Burch, C. A. Weiler, K. Raj, J. I. Budnick, V. Niculescu, G. C. Papaefthymiou, Richard B. Frankel

Physics

The Mössbauer spectra of Fe in Fe3-xVxSi alloys for 0≤x≤1 shows that V occupies almost exclusively one of two Fe sites (the B site). As x increases the spectra of Fe on the other site (the A, C site) becomes increasingly complex as the number of their V 1st neighbors increases. Simulated Mössbauer spectra were calculated using moments obtained by a simple model from bulk magnetization and V NMR data. This model assumes a decrease in Fe(A, C) moments as the number of their Fe 1st neighbors decreases. Comparison of the Fe(B) field of the alloy …

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Four-Color And Hβ Photometry Of The Galactic Cluster M25, Edward G. Schmidt Apr 1982

Four-Color And Hβ Photometry Of The Galactic Cluster M25, Edward G. Schmidt

Edward Schmidt Publications

Four-color and Hβ photometry has been obtained for 39 stars in the field of the galactic cluster M25. The membership of the individual stars is discussed. From 27 stars which are considered likely members we obtain a mean distance modulus of 8.76 and a mean color excess of E(b – y) = 0.341.

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Intermediate-Band Photometry Of The Open Cluster Ngc 3114, Edward G. Schmidt Apr 1982

Intermediate-Band Photometry Of The Open Cluster Ngc 3114, Edward G. Schmidt

Edward Schmidt Publications

Four-color and Hβ photometry has been obtained of 33 stars in the southern galactic cluster NGC 3114. This cluster contains many interesting stars including blue stragglers, red giants, and stars with spectral peculiarities. The distance modulus was found to be V0 – Mv = 10.26 which corresponds to 1130 pc. The color excess is E(b – y) = 0m.060. The cluster appears to be slightly older than the Pleiades. There are two extreme blue stragglers and six additional stars which might be considered milder cases of the same phenomenon. The distance moduli of …

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Random-Phase Approximation To One-Body Transition Matrix Elements For Open-Shell Atoms, Anthony F. Starace, Siamak Shahabi Apr 1982

Random-Phase Approximation To One-Body Transition Matrix Elements For Open-Shell Atoms, Anthony F. Starace, Siamak Shahabi

Anthony F. Starace Publications

A graphical procedure is presented for evaluating each term in the equation satisfied by the first-order transition matrix for an arbitrary (open-shell) atom. For those terms involving the interaction of excited virtual pairs of electrons with the ionic core, we introduce the approximation that there is no exchange of orbital or spin angular momentum with the ionic core. This approximation is shown to lead to the random-phase approximation (RPA) equations in the closed-shell-atom case; we use it to define the RPA for open-shell atoms. The single equation satisfied by the first-order transition matrix is used to obtain a set of …

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Light Scattering Determination Of Magnetic Moments Of Magnetotactic Bacteria (Invited), Charles Rosenblatt, F. F. Torres De Araujo, Richard B. Frankel Mar 1982

Light Scattering Determination Of Magnetic Moments Of Magnetotactic Bacteria (Invited), Charles Rosenblatt, F. F. Torres De Araujo, Richard B. Frankel

Physics

Light scattering is used to determine the average lengths and magnetic moments of magnetotactic bacteria in culture. The results are consistent with estimates made from electron micrographs.

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Giant Coercivities And Chemical Short-Range Order In Pr-Ga-Fe Metallic Glasses, S.G. Cornelison, David J. Sellmyer, J.G. Zhao, Z.D. Chen Mar 1982

Giant Coercivities And Chemical Short-Range Order In Pr-Ga-Fe Metallic Glasses, S.G. Cornelison, David J. Sellmyer, J.G. Zhao, Z.D. Chen

David Sellmyer Publications

Results of magnetic, Mössbauer, and structural studies are presented for (Pr80Ga20)100-xFex metallic glasses, where 0≤x≤30. For x≥20 two magnetic transitions are observed and the structural studies indicate the presence of a phase separation into at least two glassy phases, one being Fe-rich and the other Fe-deficient. Coercivities above 60 kOe are observed and the results are discussed in terms of a model involving the magnetic properties of the two phases. Journal of Applied Physics is copyrighted by The American Institute of Physics.

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Are Vpd3 And Nbpd3 Itinerant Ferromagnets?, W.L. Burmester, David J. Sellmyer Mar 1982

Are Vpd3 And Nbpd3 Itinerant Ferromagnets?, W.L. Burmester, David J. Sellmyer

David Sellmyer Publications

Low-field magnetic susceptibility and high-field magnetization results are reported for polycrystalline samples of NbPd3, VPd3, and iron doped VPd3. Recent self-consistent, spin-polarized band calculations have predicted that the pure compounds are itinerant ferromagnets. Down to 1.6 K there is no evidence for either magnetic ordering or exchange enhancement in VPd3 and NbPd3. The Fe-doped alloys exhibit transitions at low temperatures to a magnetic cluster-glass state. Journal of Applied Physics is copyrighted by The American Institute of Physics.

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Magnetic, Mössbauer, And Resistivity Studies Of Amorphous Fe74Zr26 And Fe81Hf19 Alloys, C. L. Chien, K. M. Unruh, A. Levy, Sy_Hwang Liou, J. P. Stokes, R.J. Gambino, K. Fukamichi Mar 1982

Magnetic, Mössbauer, And Resistivity Studies Of Amorphous Fe74Zr26 And Fe81Hf19 Alloys, C. L. Chien, K. M. Unruh, A. Levy, Sy_Hwang Liou, J. P. Stokes, R.J. Gambino, K. Fukamichi

Sy-Hwang Liou Publications

Amorphous metal-metal samples of Fe74Zr26 and Fe81Hf19 have been studied by bulk magnetic, Mössbauer spectroscopy and resistivity measurements. The values of Tc have been determined to be 285 K and 295 K for Fe74Zr26 and Fe81Hf19, respectively. Both the magnetic isotherms and Mössbauer measurements indicate that these samples are ferromagnetics. The isomer shifts and the quadrupole interactions are much smaller than those of amorphous Fe-metalloid systems. The P(H) are broad and extend to small H values. Negative temperature coefficients of the resistivity are observed at low …

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Comparison Of Bethe's Formula For Magnetic-Moment Transitions In Atoms With The Generalized Rosenbluth's Equation, P.T. Leung, M. L. Rustgi, J. E. Turner Mar 1982

Comparison Of Bethe's Formula For Magnetic-Moment Transitions In Atoms With The Generalized Rosenbluth's Equation, P.T. Leung, M. L. Rustgi, J. E. Turner

Physics Faculty Publications and Presentations

An error in an old but often quoted paper by Bethe (1935) on the cross section for an atomic transition caused by the magnetic moment of the projectile is corrected by comparing it with the generalized Rosenbluth's formula (1950).

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Constant-Psi Constant-Delta Contour Maps: Applications To Ellipsometry And To Reflection-Type Optical Devices, A.-R. M. Zaghloul, R. M.A. Azzam Feb 1982

Constant-Psi Constant-Delta Contour Maps: Applications To Ellipsometry And To Reflection-Type Optical Devices, A.-R. M. Zaghloul, R. M.A. Azzam

Electrical Engineering Faculty Publications

Constant-psi constant-delta contour maps in the reduced angle-of-incidence-film-thickness plane that are useful in ellipsometry and in design of reflection-type optical devices are discussed. As a specific example, a contour map is given for the SiO2-Si film-substrate system at the 6328-Å He-Ne laser wavelength.

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Review Of Atoms And Molecules By M. Weissbluth, Anthony F. Starace Feb 1982

Review Of Atoms And Molecules By M. Weissbluth, Anthony F. Starace

Anthony F. Starace Publications

The advent of high-powered lasers and of dedicated synchrotron light sources and the needs of research in such areas as astrophysics and fusion have led to a resurgence of interest in atomic and molecular physics. Concurrently, there have been significant advances in atomic and molecular theory, not only in the ability to make more reliable numerical predictions but also in the detailed understanding of the dynamics of atomic and molecular collisions. The nonspecialist or beginning graduate student who must read the scientific journals to learn of these advances often finds that the requisite basic knowledge is extensive. Mitchel Weissbluth, whose …

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Structure-Factor Measurements In 4he As A Function Of Density, Robert Hallock, H. N. Robkoff Feb 1982

Structure-Factor Measurements In 4he As A Function Of Density, Robert Hallock, H. N. Robkoff

Robert Hallock

Measurements of the structure factor S(k) for 4He are reported as a function of pressure at 1.67, 2.20, and 4.24 K from saturated vapor pressure to 25 atm. The liquid structure factor is seen to sharpen and increase in amplitude with an increase in pressure at each of the temperatures studied. Comparison is made to previous results obtained by the technique of neutron scattering as well as to the theoretical predictions of Chang and Campbell and of Whitlock et al. The pair correlation function g(r) is obtained from the liquid structure factor by means of a Fourier transform, and comparison …

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Magneto-Hall And Magnetoresistance Coefficients In Semiconductors With Mixed Conductivity, David C. Look Feb 1982

Magneto-Hall And Magnetoresistance Coefficients In Semiconductors With Mixed Conductivity, David C. Look

Physics Faculty Publications

Magneto-Hall and magnetoresistance formulas, correct to order B2, are derived for the case in which both single-carrier and mixed-carrier effects are important. Also, a new magneto-Hall coefficient Is Presented: β=‹π4›‹π›/‹π2›3 - 1. Values of β for various scattering mechanisms are calculated and compared with experiment

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The Chromospheres Of Classical Cepheids. I. Low Resolution Iue Spectra, Edward G. Schmidt, Sidney B. Parsons Feb 1982

The Chromospheres Of Classical Cepheids. I. Low Resolution Iue Spectra, Edward G. Schmidt, Sidney B. Parsons

Edward Schmidt Publications

We have undertaken a program to study the behavior of chromospheres in classical Cepheids using both ground-based and satellite-based observations. Five stars, δ Cep, η Aql, β Dor, ζ Gem, and l Car, have been included, and where possible the various types of data have been obtained simultaneously. The first part of this investigation concerns low dispersion spectra from the IUE satellite. Fine error sensor (FES) magnitudes are presented for the five Cepheids and, in the case of one, η Aql, are used to re-discuss the period. The "artificial viscosity dip" predicted by some theoretical calculations may be present in …

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Polarization Of Fluorescence Radiation Subsequent To Inner-Shell Photoionization: Ls-Coupling Formulas, Anthony F. Starace Feb 1982

Polarization Of Fluorescence Radiation Subsequent To Inner-Shell Photoionization: Ls-Coupling Formulas, Anthony F. Starace

Anthony F. Starace Publications

The polarization and angular distribution of fluorescence radiation subsequent to inner-shell photoionization in atoms are presented here in the important special case that dynamic amplitudes are calculated in LS coupling taking full account of anisotropic electron-ion interactions. The resulting formulas require for their evaluation no more dynamical information than is usually obtained in an LS-coupling calculation of the photoionization cross section. Exact geometrical relationships which are obscured in more general treatments become apparent in an LS-coupling formulation. Thus it is shown that in LS coupling the fluorescence resulting from photoionization of an s subshell in an atom having …

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Conductance In Restricted-Dimensionality Accumulation Layers, A. B. Fowler, A. Hartstein, Richard A. Webb Jan 1982

Conductance In Restricted-Dimensionality Accumulation Layers, A. B. Fowler, A. Hartstein, Richard A. Webb

Faculty Publications

Conductance has been studied in metal-oxide-silicon field-effect transistor accumulation-layer samples in which it is possible to constrict the channel to small dimensions both perpendicular to the surface and perpendicular to the channel. A temperature-dependent conductance σ=σ0exp[-(T0/T)n] is observed, where n=1/2 for small channel widths and n=1/3 for larger channel widths. It is believed that this behavior arises from a transition from one-dimensional to two-dimensional variable-range hopping in the sample.

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Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw Jan 1982

Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw

Physics Faculty Publications and Presentations

Classical statistical mechanical description of dielectric fluids is further discussed. Dipole moment correlations of polarizable molecules are discussed.

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Relativistic Sum Rules And Integral Properties Of The Dirac Equation, S. P. Goldman, Gordon W. F. Drake Jan 1982

Relativistic Sum Rules And Integral Properties Of The Dirac Equation, S. P. Goldman, Gordon W. F. Drake

Physics Publications

Relativistic generalizations are derived for the well-known nonrelativistic electric-dipole oscillator-strength sum rules. The relativistic sum rules include both positive- and negative-energy states. The derivations are valid for a Dirac electron in an arbitrary local potential. We also present a number of simple integral properties related to the relativistic virial theorem which are useful in the calculation of matrix elements. © 1982 The American Physical Society.

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E1-E1 Damping Interference In The Electric Field Quenching Of Spin-Polarized He+2s12 Ions, A. Van Wijngaarden, R. Helbing, J. Patel, Gordon W. F. Drake Jan 1982

E1-E1 Damping Interference In The Electric Field Quenching Of Spin-Polarized He+2s12 Ions, A. Van Wijngaarden, R. Helbing, J. Patel, Gordon W. F. Drake

Physics Publications

When a beam of spin-polarized metastable He+2s12 ions is quenched by an electric field E, the emitted radiation intensity contains an asymmetry term proportional to (kE)(P'k×E) where P' is the spin-polarization vector and k is the direction of observation. The resulting asymmetry is nearly proportional to the level width of the 2p12 state in He+. The experiment provides the first observation of the asymmetry. The measured asymmetry is (0.007 69±0.000 10) in agreement with the theoretical value 0.007 618 and corresponds to a lifetime 2p=(0.988±0.013)×10-10 sec. © 1982 The American Physical Society.

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Measurements Of An E 1-M 1 Interference Effect In The Electric-Field Quenching Of Spin-Polarized He+2s12 Ions, A. Van Wijngaarden, Gordon W. F. Drake Jan 1982

Measurements Of An E 1-M 1 Interference Effect In The Electric-Field Quenching Of Spin-Polarized He+2s12 Ions, A. Van Wijngaarden, Gordon W. F. Drake

Physics Publications

When a beam of spin-polarized metastable He+2s12 ions is quenched by an electric field E, the emitted radiation intensity contains an asymmetry term which is proportional to kE ×P, where P is the spin-polarization vector and k is the direction of observation. The effect is due to interference between spontaneous magnetic-dipole (M 1) and induced electric-dipole (E 1) decay modes to the ground state. At |E|=38.14 V/cm, the measured asymmetry is (0.3230.085) × 10-3 in agreement with the theoretical value 0.3443 × 10-3. The experiment provides the first measurement of the relativistic M 1 matrix element for the 2s12-1s12 transition …

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Travelling-Wave Sub-Doppler Excited Molecule Energy Transfer Spectroscopy, Khalid Iqbal, Shannon G. Lieb, J. W. Bevan Jan 1982

Travelling-Wave Sub-Doppler Excited Molecule Energy Transfer Spectroscopy, Khalid Iqbal, Shannon G. Lieb, J. W. Bevan

Scholarship and Professional Work - LAS

A general formulation of traveling‐wave sub‐Doppler excited molecule energy transferspectroscopy is presented. The line profile analysis is applied to that determined experimentally for the R(22) ν3 HCN transition. Pn the noise equivalent power of the detector is demonstrated to be ⩽10−12 W. Finally, the technique is applied to resolve the KsR(7) ν1 transition head in NH3.

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Magnetotactic Bacteria, Richard B. Frankel Jan 1982

Magnetotactic Bacteria, Richard B. Frankel

Physics

No abstract provided.

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Classroom Demonstration Of Sunspots, Thomas O. Callaway, Harry D. Downing, Glen T. Clayton Jan 1982

Classroom Demonstration Of Sunspots, Thomas O. Callaway, Harry D. Downing, Glen T. Clayton

Faculty Publications

No abstract provided.

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Physical Science Workshop Course For Elementary Teachers, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway Jan 1982

Physical Science Workshop Course For Elementary Teachers, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway

Faculty Publications

Science for elementary school grades K-6 varies somewhat in content from one textbook series to another, but it is fairly common that 40-60% of the material covered is directly related to physics. These texts suggest that certain learning activities such as experiments, demonstrations, and observations be carried out by the teacher and the class. Often the apparatus for a learning activity is to be constructed from simple, readily available materials. The typical elementary school teacher has had little experience in performing experiments and is often frustrated in his/her attempts at carrying out the suggested learning activity. To meet this need …

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Thermodynamic Model For Tricritical Mixtures With Application To Ammonium, Miron Kaufman, Robert B. Griffiths Jan 1982

Thermodynamic Model For Tricritical Mixtures With Application To Ammonium, Miron Kaufman, Robert B. Griffiths

Miron Kaufman

Procedures are developed for using composition data in the three-phase region and variations of meniscus heights to determine the parameters needed to relate a classical thermodynamic model for fluid mixtures near tricritical points to actual experiments. In the case of the mixture ammonium sulfate + water + ethanol + benzene the result is a reasonably good fit to a variety of data, including light scattering measurements of intensity and correlation length. There is some evidence for deviations from the classical theory, but it is not unambiguous.

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Infinite Susceptibility At High Temperatures In The Migdal-Kadanoff Scheme, Miron Kaufman, Robert B. Griffiths Jan 1982

Infinite Susceptibility At High Temperatures In The Migdal-Kadanoff Scheme, Miron Kaufman, Robert B. Griffiths

Miron Kaufman

The Migdal-Kadanoff real-space renormalisation group scheme applied to the Ising and classical XY (and probably other) ferromagnetic models yields an infinite susceptibility at all temperatures above the critical temperature for a hypercubic lattice of dimension d > 2.

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The Etc And Instantaneous Intensity, Richard C. Heyser Jan 1982

The Etc And Instantaneous Intensity, Richard C. Heyser

Unpublished Writings

Richard C. Heyser explains how to measure the energy-time response of an acoustic signal by expressing the energy density in a logarithmic form, which he cales the Energy-Time Curve (ETC).

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The Electronic Controls Used In A Search For Fractional Charges In Mercury Drops, William Walters, David C. Joyce, Peter C. Abrams, K. R. Koburn, Betty A. Young Jan 1982

The Electronic Controls Used In A Search For Fractional Charges In Mercury Drops, William Walters, David C. Joyce, Peter C. Abrams, K. R. Koburn, Betty A. Young

Physics

At San Francisco State University, we have developed an Automatic Millikan Device (AMI)) for measuring the charge on small drops of Mercury. The device uses a standard atomic physics laboratory Millikan chamber, a piezoelectric driven ink-jet glass dropper, and a laser-photomultiplier system for tracking the motion of the drop. This paper describes the electronic control and error detection system used with the AMO. Signals from this system are sent to a microprocessor which controls the experiment. To this date (Dec 7, 1981), we have measured 175 micrograms of Hg and found no fractional charges in 1.05 x 1020 nucleons.

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