Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

Physics

Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 32341 - 32370 of 34091

Full-Text Articles in Entire DC Network

Reaction ⁶Li(P, Δ⁺⁺)⁶He At 1.04 Gev And The Δ−N Interaction, T. Hennino, D. Bachelier, Oleksa-Myron Bilaniuk, J. L. Boyard, J. C. Jourdain, M. Roy-Stephen, P. Radvanyi, M. Bedjidian, E. Descroix, P. Foessel, S. Gardien, J. Y. Grossiord, A. Guichard, M. Gusakow, R. Haroutunian, M. Jacquin, J. R. Pizzi, A. Garin Apr 1982

Reaction ⁶Li(P, Δ⁺⁺)⁶He At 1.04 Gev And The Δ−N Interaction, T. Hennino, D. Bachelier, Oleksa-Myron Bilaniuk, J. L. Boyard, J. C. Jourdain, M. Roy-Stephen, P. Radvanyi, M. Bedjidian, E. Descroix, P. Foessel, S. Gardien, J. Y. Grossiord, A. Guichard, M. Gusakow, R. Haroutunian, M. Jacquin, J. R. Pizzi, A. Garin

Physics & Astronomy Faculty Works

The reaction ⁶Li(p, Δ⁺⁺)⁶He has been studied at 1.04 GeV for transferred momenta ranging from 0.11 to 0.35 (GeV/c)2. An exponential decrease of the cross section is observed. A Glauber-type calculation is presented. The possibility of extracting information on σ(ΔN) and α(ΔN) is discussed.

Go to article

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.

Go to article

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 …

Go to article

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 …

Go to article

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.

Go to article

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 …

Go to article

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 …

Go to article

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.

Go to article

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.

Go to article

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).

Go to article

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 …

Go to article

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.

Go to article

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.

Go to article

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 …

Go to article

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 …

Go to article

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

Go to article

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 …

Go to article

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.

Go to article

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.

Go to article

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.

Go to article

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 …

Go to article

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).

Go to article

Predicted Diurnal Variations Of Electron Density For Three High-Latitude Incoherent Scatter Radars, Jan Josef Sojka, Robert W. Schunk Jan 1982

Predicted Diurnal Variations Of Electron Density For Three High-Latitude Incoherent Scatter Radars, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

We have used a high‐latitude ionospheric model to predict the diurnal variations of electron density that should be observed by the EISCAT, Chatanika and Millstone Hill incoherent scatter facilities. Our calculations were for a strong convection model without substorms. Our results provide an indication of the quantitative differences in measured electron density that are expected when the three radars probe the high‐latitude ionosphere simultaneously. The differences are significant and vary with altitude, latitude, local time, and season, and are associated with the UT dependence of the high‐latitude ionosphere which results from the displacement between the geomagnetic and geographic poles.

Go to article

Observations Of The Diurnal Dependence Of The High-Latitude F Region Ion Density By Dmsp Satellites, Jan Josef Sojka, W. John Raitt, Robert W. Schunk, F. J. Rich, R. C. Sagalyn Jan 1982

Observations Of The Diurnal Dependence Of The High-Latitude F Region Ion Density By Dmsp Satellites, Jan Josef Sojka, W. John Raitt, Robert W. Schunk, F. J. Rich, R. C. Sagalyn

All Physics Faculty Publications

Data from the DMSP F2 and F4 satellites for the period December 5-10, 1979, have been used to study the diurnal dependence of the high-latitude ion density at 800-km altitude. A 24-hour periodicity in the minimum orbital density (MOD) during a crossing of the high-latitude region is observed in both the winter and summer hemispheres. The phase of the variation in MOD is such that it has a minimum during the 24-hour period between 0700 and 0900 UT. Both the long term variation of the high-latitude ion density on a time scale of days, and the orbit by orbit variations …

Go to article

The Light Curves Of Rr Lyrae Field Stars, Norman R. Simon, Terry J. Teays Jan 1982

The Light Curves Of Rr Lyrae Field Stars, Norman R. Simon, Terry J. Teays

Department of Physics and Astronomy: Faculty Publications

Fourier decompositions have been made of the light curves of a large sample of RR Lyrae field stars. The coefficients have been tabulated. Following the scheme of an earlier investigation of classical Cepheids, certain combinations of the low-order coefficients - φ21, R21, and φ31 - are plotted against period. The Bailey-type c pulsators stand out from the type ab stars, particularly on the R21 plot which is found to be a more sensitive discriminator of Bailey type than is the traditionally employed amplitude-period diagram. We compare the RR Lyrae plots of φ21, …

Go to article

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.

Go to article

Cyclotron Resonance Effects On Stochastic Acceleration Of Light Ionospheric Ions, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka Jan 1982

Cyclotron Resonance Effects On Stochastic Acceleration Of Light Ionospheric Ions, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

Numerical studies on the interaction of electrostatic hydrogen cyclotron (EHC) waves with light ionospheric ions, such as He+, show that when the wave number ratio k⊥/kll ≤ 10 resonant effects are important in the stochastic heating of the ions. When k⊥/kll > 10 an appreciable acceleration occurs even though the cyclotron‐resonant effects are absent. As the parallel wave number increases, causing k⊥/kll to decrease (< 10), the number of accelerated ions and the perpendicular and parallel energization increase.

Go to article

Ionospheric Hot Spot At High Latitudes, Robert W. Schunk, Jan Josef Sojka Jan 1982

Ionospheric Hot Spot At High Latitudes, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

A hot spot (or spots) can occur in the high‐latitude ionsophere depending on the plasma convection pattern. The hot spot corresponds to a small magnetic local time‐magnetic latitude region of elevated ion temperatures located near the dusk and/or dawn meridians. For asymmetric convection electric field patterns, with enhanced flow in either the dusk or dawn sector of the polar cap, a single hot spot should occur in association with the strong convection cell. However, on geomagnetically disturbed days, two strong convection cells can occur, and hence, two hot spots should exist. The hot spot should be detectable when the electric …

Go to article

Seasonal Variations Of The High-Latitude F Region For Strong Convection, Jan Josef Sojka, Robert W. Schunk, W. John Raitt Jan 1982

Seasonal Variations Of The High-Latitude F Region For Strong Convection, Jan Josef Sojka, Robert W. Schunk, W. John Raitt

All Physics Faculty Publications

We combined a plasma convection model with an ionospheric-atmospheric composition model in order to study the seasonal variations of the high-latitude F region for strong convection. Our numerical study produced time-dependent, three-dimensional, ion density distributions for the ions NO+, O2 +, N2 +, O+, N+, and He+. We covered the high-latitude ionosphere above 42°N magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day. From our study we found the following: (1) For strong convection, the high-latitude ionosphere exhibits a significant UT variation both during winter and summer. (2) In general, the …

Go to article

Ion Temperature Variations In The Daytime High-Latitude F Region, Robert W. Schunk, Jan Josef Sojka Jan 1982

Ion Temperature Variations In The Daytime High-Latitude F Region, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

We improved our high-latitude ionospheric model by including thermal conduction and diffusion-thermal heat flow terms in the ion energy equation so that we could study the ion temperature variations in the daytime high-latitude F layer in a region poleward of the auroral oval for steady state conditions at local noon. From our study we found that (1) The variation of Ti with solar cycle, season, and geomagnetic activity closely follows the Tn variation. The general trend is for higher temperatures in summer than in winter, at solar maximum than at solar minimum, and for active magnetic conditions than for quiet …

Go to article

First Prev Next Last