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Articles 1 - 30 of 112
Full-Text Articles in Physics
Bowen Fluoresence And He Ii Lines In Active Galaxies And Gaseous Nebulae, Hagai Netzer, Moshe Elitzur, Gary J. Ferland
Bowen Fluoresence And He Ii Lines In Active Galaxies And Gaseous Nebulae, Hagai Netzer, Moshe Elitzur, Gary J. Ferland
Physics and Astronomy Faculty Publications
We have calculated the intensity of He II and the O III and N III Bowen lines under a variety of astrophysical conditions. Our line-transfer method is based on the escape probability formalism and is especially suitable for combining line fluorescence and photoionization calculations in a simple, straightforward way. It reproduces the results of the more sophisticated line-transfer calculations quite accurately and is much better for producing realistic ionization and thermal structures. An extensive grid of models is presented and discussed, with special emphasis on the case of active galactic nuclei (AGNs). Many O III and N III Bowen lines …
Total Refraction At Oblique Incidence By A Transparent Bilayer Coating On A High-Index Transparent Or Absorbing Substrate, R. M.A. Azzam, Karim Javily
Total Refraction At Oblique Incidence By A Transparent Bilayer Coating On A High-Index Transparent Or Absorbing Substrate, R. M.A. Azzam, Karim Javily
Electrical Engineering Faculty Publications
Transparent bilayer coatings that produce total refraction (TR) of obliquely incident monochromatic light into an underlying substrate are considered. When the substrate is transparent, it is shown that TR takes place without any accompanying change of polarization. Totally refracting bilayers are realizable in the IR where high-refractive-index substrates are available. This is illustrated by a BaF2–ZnSe bilayer on a Ge substrate at a 10.6-μm (CO2-laser) wavelength and 45° angle of incidence. Limited changes of the angle of incidence, wavelength, and refractive indices and thicknesses of the two films of the bilayer are introduced, and their effects …
Helium-4 Solid-Liquid Interface Mobility And Ultrasonic Energy Absorption Mechanisms, M. B. Manning, Matthew J. Moelter, C. Elbaum
Helium-4 Solid-Liquid Interface Mobility And Ultrasonic Energy Absorption Mechanisms, M. B. Manning, Matthew J. Moelter, C. Elbaum
Physics
The first measurements of acoustic reflection, together with acoustic transmission at the solid-liquid interface of 4He, are used to determine the total relative acoustic energy absorption at the interface as a function of temperature. Based on these results, a new mechanism for the temperature dependence of the kinetics of growth and interface mobility is proposed.
Magnetic Transitions And Scaling Behavior In Gd-Rich Glasses , M.J. O'Shea, David J. Sellmyer
Magnetic Transitions And Scaling Behavior In Gd-Rich Glasses , M.J. O'Shea, David J. Sellmyer
David Sellmyer Publications
The magnetic properties of amorphous alloys with composition GdxLa72-xGa18B10 have been investigated using ac-susceptibilty and dc-magnetization techniques in the temperature range 4.2–300 K. This system shows double-transition behavior for x≳67 and paramagnetic–spin-glass transition behavior for x<67. Time-dependent magnetization effects are present in the spin-glass phase and these effects vanish in finite fields, in qualitative agreement with mean-field theory. The magnetic isotherms around both the paramagnetic-ferromagnetic and ferromagnetic–spin-glass transitions scale according to the scaling hypothesis, and these results are discussed in some detail. A magnetic phase diagram for this system is obtained from the transition temperatures determined from scaling.
Investigation Of Electronic Holography Using Spice Computer Simulation Experiments, Monish Ranjan Chatterjee
Investigation Of Electronic Holography Using Spice Computer Simulation Experiments, Monish Ranjan Chatterjee
Electrical and Computer Engineering Faculty Publications
Using SPICE experiments, it has been possible to verify most of the important aspects of electronic holography. The generation and properties of dynamic echoes under different types of nonlinearities have been extensively tested, and some new information has been garnered in the process. The case of pulse and generalized memory echoes has also been tested, and the results have been fairly satisfactory. Most of all, the simplicity with which the intriguing concept of memory echoes has translated into the circuit implementation on SPICE, and the closeness of the results to predicted behavior have been somewhat of a pleasant surprise.
Since …
Polarization Asymmetry In The Photodisintegration Of The Deuteron, M. P. De Pascale, G. Giordano, G. Matone, D. Babusci, R. Bernabei, Oleksa-Myron Bilaniuk, L. Casano, S. D'Angelo, M. Mattioli, P. Picozza, D. Prosperi, C. Schaerf, S. Frullani, B. Girolami
Polarization Asymmetry In The Photodisintegration Of The Deuteron, M. P. De Pascale, G. Giordano, G. Matone, D. Babusci, R. Bernabei, Oleksa-Myron Bilaniuk, L. Casano, S. D'Angelo, M. Mattioli, P. Picozza, D. Prosperi, C. Schaerf, S. Frullani, B. Girolami
Physics & Astronomy Faculty Works
The reaction ²(γ,p)n has been studied using a monochromatic and polarized gamma ray beam at energies E(γ)=19.8, 29.0, 38.6, and 60.8 MeV. The beam of an intensity ∼4×10⁵ γ/sec was obtained by Compton back scattering of mode-locked laser light off electron bunches in the Adone storage ring. Photoneutron yields were measured at nine neutron angles thetan≃15, 30, 45, 60, 90, 120, 135, 150, and 165 deg in the center of mass (c.m.) for E(γ)=19.8, 29.0, and 38.6 MeV, and at thetan≃30, 60, 90, 120, and 150 deg c.m. for E(γ)=60.8 MeV. The polarization independent component Iₒ(theta) of the differential cross …
Use Of The Fock Expansion For 1State Wave Functions Of Two-Electron Atoms And Ions, James M. Feagin, Joseph Macek, Anthony F. Starace
Use Of The Fock Expansion For 1State Wave Functions Of Two-Electron Atoms And Ions, James M. Feagin, Joseph Macek, Anthony F. Starace
Anthony F. Starace Publications
The exact representation of a two-electron wave function near the origin is the Fock expansion, i.e., a double summation over powers of R and of lnR [where R≡(r12+r22)1/2] with coefficients dependent on the five remaining angular variables. Using a representation of hyperspherical harmonics, we present here the first numerical solution of the equations for the Fock coefficients. We present also a general procedure for matching a linear combination of Fock-series solutions onto a basis of adiabatic hyperspherical functions at a matching radius R0. This matching procedure ensures …
A Chronology Of Energy Conservation And Production, David W. Hafemeister
A Chronology Of Energy Conservation And Production, David W. Hafemeister
Physics
No abstract provided.
Physics Of Some Environmental Aspects Of Energy, David W. Hafemeister
Physics Of Some Environmental Aspects Of Energy, David W. Hafemeister
Physics
Approximate numerical estimates are carried out on the following environmental effects from energy production and conservation: (1) The greenhouse effect caused by increased CO2 in the atmosphere; (2) Loss of coolant accidents in nuclear reactors; (3) Increased radon concentrations in buildings with very low air infiltration rates; (4) Acid rain from the combustion of fossil fuels; and (5) Explosions of liquified natural gas (LNG).
Energy Conservation In Large Buildings, A. Rosenfeld, David W. Hafemeister
Energy Conservation In Large Buildings, A. Rosenfeld, David W. Hafemeister
Physics
As energy prices rise, newly energy aware designers use better tools and technology to create energy efficient buildings. Thus the U.S. office stock (average age 20 years) uses 250 kBTU/ft2 of resource energy, but the guzzler of 1972 uses 500 (up × 2), and the 1986 ASHRAE standards call for 100–125 (less than 25% of their 1972 ancestors). Surprisingly, the first real cost of these efficient buildings has not risen since 1972. Scaling laws are used to calculate heat gains and losses of buildings to obtain the ΔT(free) which can be as large as 15–30 °C (30–60 °F) for …
Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Donald Umstadter Publications
Clayton et al. Respond: The authors of the Comment are quite correct when they point out that the ruby-laser scattering system used in our study can only respond to beat-excited density fluctuations with ky = k2, where the CO2 (ruby) beam propagates in the z (y) direction.
Ionization Cross Sections For 10-300-Kev/U And Electron-Capture Cross Sections For 5- 150-Kev/U 3He2+ Ions In Gases, M. Eugene Rudd, T. V. Goffe, A. Itoh
Ionization Cross Sections For 10-300-Kev/U And Electron-Capture Cross Sections For 5- 150-Kev/U 3He2+ Ions In Gases, M. Eugene Rudd, T. V. Goffe, A. Itoh
M. Eugene Rudd Publications
Cross sections for production of positive and negative charge for 10-300-keV/u He2+ ions on He, Ne, Ar, Kr, H2, N2, CO, O2, CH4, N2O, and C02 were measured by the transverse-field method. Single- and double-electron-capture cross sections at 5-150 keV/u for the same targets were measured by the method of deflection of different charge-state components of the beam after passing through a known length of target gas. A secondary-emission detector was used to detect the neutral component of the beam. A small least-squares adjustment of the cross sections …
Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Y-K. Kim, D. H. Madison, J. W. Gallagher
Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Y-K. Kim, D. H. Madison, J. W. Gallagher
M. Eugene Rudd Publications
Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given.
The Temporary Capture Of Light By A Dielectric Film, James A. Lock
The Temporary Capture Of Light By A Dielectric Film, James A. Lock
Physics Faculty Publications
When a wave packet of light passes through a dielectric film it is found that at a transmission maximum, the group velocity of the light wave packet within the film attains its minimum value. Similarly, at a transmission minimum, it is found that the group velocity of the light wave packet within the film attains its maximum value. The measurability of this effect is also discussed.
Investigation Of The Appropriateness Of Sensitized Luminescence To Determine Exciton Motion Parameters In Pure Molecular Crystals, Vasudev M. Kenkre, Paul Ernest Parris, Dankward B. Schmid
Investigation Of The Appropriateness Of Sensitized Luminescence To Determine Exciton Motion Parameters In Pure Molecular Crystals, Vasudev M. Kenkre, Paul Ernest Parris, Dankward B. Schmid
Physics Faculty Research & Creative Works
A wealth of experimental data has been collected over the years regarding the sensitized luminescence of molecular crystals. Indeed, such observations have played a primary role in attempts to characterize the dynamical aspects of exciton transport in these materials. Nonetheless, as has been noted previously, serious questions of interpretation remain concerning the relationship between primary experimental observables and microscopic parameters which govern exciton transport and capture. In the past these questions have led to an uncertainty, not always acknowledged, in the values of exciton diffusion constants reported in the literature. On the other hand, careful analysis of some recent experiments …
Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Yongki Kim, Don H. Madison, Jean W. Gallagher
Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Yongki Kim, Don H. Madison, Jean W. Gallagher
Physics Faculty Research & Creative Works
Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given.
Temperature Dependence Of The Normal-Metal Aharonov-Bohm Effect, S. Washburn, C. P. Umbach, R. B. Laibowitz, Richard A. Webb
Temperature Dependence Of The Normal-Metal Aharonov-Bohm Effect, S. Washburn, C. P. Umbach, R. B. Laibowitz, Richard A. Webb
Faculty Publications
The amplitude of h/e periodic oscillations in the magnetoresistance of very small normal-metal (Au) rings, as well as the harmonic h/2e, have been studied as a function of temperature. The amplitudes depend on the temperature T roughly as T-1/2, as expected from the averaging of conduction channels in the absence of inelastic scattering, but may not be entirely consistent with this model. At the lowest T, the size of the fluctuations in the conductance is about ΔG∼e2/h, as predicted recently.
A Variation-Perturbation Method For Atomic And Molecular Interactions. I. Theory, Gordon A. Gallup, J. Gerratt
A Variation-Perturbation Method For Atomic And Molecular Interactions. I. Theory, Gordon A. Gallup, J. Gerratt
Gordon Gallup Publications
We have developed a variation-perturbation procedure for calculating intermolecular forces. It is based on the valence bond method of constructing wave functions and involves a number of interlocking techniques and approximations that are justified by the small size of the interaction potential relative to the total energy. In this article we give an outline of the theory of our technique. We have used this procedure to determine the potential between a Ne atom and a rigid HF molecule. The results of this calculation are given in the next article. The Journal of Chemical Physics is copyrighted by The American Institute …
Angular Differential Cross Sections For The Excitation Of 1¹S Helium To The 2¹S And 2¹P States By 25- To 100-Kev-Proton Impact, Thomas J. Kvale, Denver G. Seely, D. M. Blankenship, E. Redd, Timothy Gay, Mineo Kimura, Eduard P. Rille, Jerry Peacher, John T. Park
Angular Differential Cross Sections For The Excitation Of 1¹S Helium To The 2¹S And 2¹P States By 25- To 100-Kev-Proton Impact, Thomas J. Kvale, Denver G. Seely, D. M. Blankenship, E. Redd, Timothy Gay, Mineo Kimura, Eduard P. Rille, Jerry Peacher, John T. Park
Physics Faculty Research & Creative Works
Angular differential cross sections for the proton-impact excitation of ground-state helium (11S) to the 21S and 21P states have been measured for the first time in the energy range 25 to 100 keV with use of the energy-loss technique. The data indicate that, for very small scattering angles, at 25 keV the 21S differential cross section is greater than the 21P differential cross section. For impact energies greater than 50 keV, the 21P differential cross section clearly dominates over the 21S cross section in the very …
A Variation-Perturbation Method For Atomic And Molecular Interactions. Ii. The Interaction Potential And Van Der Waals Molecule For Ne–Hf, Gordon A. Gallup, J. Gerratt
A Variation-Perturbation Method For Atomic And Molecular Interactions. Ii. The Interaction Potential And Van Der Waals Molecule For Ne–Hf, Gordon A. Gallup, J. Gerratt
Gordon Gallup Publications
A recently developed variation-perturbation theory for calculating intermolecular forces has been applied to the Ne–HF system for fixed H–F distances. The maximum well depth is 0.49 kJ/mol (41 cm-1) for a linear configuration with the H between the Ne and F and the Ne–H distance approximately 5.5 bohr. A secondary minimum of depth 0.24 kJ/mol (20 cm-1) was found for the other linear configuration at a Ne–F distance of about 7.0 bohr. A saddle point, about 0.20 kJ/mol (17 cm-1) deep, for the T-shaped configuration is present also at about 7.0 bohr. The potential …
Angular Differential Cross Sections For The Excitation Of 11S Helium To The 21S And 21P States By 25- To 100-Kev-Proton Impact, T. J. Kvale, D. G. Seely, D. M. Blakenship, E. Redd, Timothy J. Gay, M. Kimura, E. Rille, J. L. Peacher, J. T. Park
Angular Differential Cross Sections For The Excitation Of 11S Helium To The 21S And 21P States By 25- To 100-Kev-Proton Impact, T. J. Kvale, D. G. Seely, D. M. Blakenship, E. Redd, Timothy J. Gay, M. Kimura, E. Rille, J. L. Peacher, J. T. Park
Timothy J. Gay Publications
Angular differential cross sections for the proton-impact excitation of ground-state helium (11S) to the 21S and 21P states have been measured for the first time in the energy range 25 to 100 keV with use of the energy-loss technique. The data indicate that, for very small scattering angles, at 25 keV the 21S differential cross section is greater than the 21P differential cross section. For impact energies greater than 50 keV, the 21P differential cross section clearly dominates over the 21S cross section in the very small scattering …
Time-Dependent Magnetic Structures Of The Superconducting Mixed Ternary System Ho(Rh₁₋ₓirₓ)₄B₄, Steven E. Lambert, M. Brian Maple, Oran Allan Pringle, Herbert A. Mook
Time-Dependent Magnetic Structures Of The Superconducting Mixed Ternary System Ho(Rh₁₋ₓirₓ)₄B₄, Steven E. Lambert, M. Brian Maple, Oran Allan Pringle, Herbert A. Mook
Physics Faculty Research & Creative Works
Magnetic structures have been determined by netron diffraction for several compositions in the superconducting mixed ternary system Ho(Rh1-xIrx)4B4. Two features previously reported to occur in the heat capacity for some compositions are shown to correspond to successive magnetic transitions. For x=0.30 and 0.45, neutron diffraction peaks for the lowest temperature structure develop over a timescale of many hours. The results are discussed in terms of magnetic frustration.
Magnetoresistance Method To Determine Gaas And Alxga1-Xas Mobilities In Alxga1-Xas/Gaas Modulation-Doped Field-Effect Transistor Structures, David C. Look, George B. Norris, W. Kopp, T. Henderson, H. Morkoç
Magnetoresistance Method To Determine Gaas And Alxga1-Xas Mobilities In Alxga1-Xas/Gaas Modulation-Doped Field-Effect Transistor Structures, David C. Look, George B. Norris, W. Kopp, T. Henderson, H. Morkoç
Physics Faculty Publications
Charge carrier mobilities are conveniently measured in simple, homostructure field-effect transistors (FET's) by means of the geometric magnetoresistance (GMR) technique. Heterostructure FET's, however, are more complicated because of multiple conducting regions, as well as multiple conducting bands within a given region. We apply a multilayer GMR mobility model to a frequently used heterostructure FET design, namely, the Al0.3Ga0.7As conduction band. In the particular MODFET structure studied here, the lowest GaAs subband mobility ranges from 5.7X103 cm2/Vs at threshold to 6.9X103 cm2/Vs at saturation while Al0.3Ga0.7As mobility …
Emerging Technologies For Verification Of Arms Control Treaties, David W. Hafemeister
Emerging Technologies For Verification Of Arms Control Treaties, David W. Hafemeister
Physics
Progress in the technical means of monitoring to verify compliance to arms control treaties is discussed in the following areas: Real-time surveillance with charge-coupled devices in the visible and infrared; image enhancement with digital 1 image processing and with adaptive optics; imaging with radars based on satellites and on the ground; seismic monitoring with high frequency discrimination and with unattended in-country seismic stations; and nuclear weapons test monitoring with the global positioning satellite system.
Theoretical And Experimental Capacitance-Voltage Behavior Of Al0.3ga0.7as Gaas Modulation-Doped Heterojunctions - Relation Of Conduction-Band Discontinuity To Donor Energy, George B. Norris, David C. Look, W. Kopp, J. Klem, H. Morkoç
Theoretical And Experimental Capacitance-Voltage Behavior Of Al0.3ga0.7as Gaas Modulation-Doped Heterojunctions - Relation Of Conduction-Band Discontinuity To Donor Energy, George B. Norris, David C. Look, W. Kopp, J. Klem, H. Morkoç
Physics Faculty Publications
For the first time, we show that the capacitance-voltage behavior of modulation-doped heterojunctions may be accurately described by a first-principles theory that includes selfconsistent quantum two-dimensional (2-D) electron subbands in the GaAs, numerical solution of Poisson's equation for band bending and space charge in the (Al,Ga) As, and series resistance in the 2-D channel and heterointerface. The excellent agreement found between the theory and measurements on selected high-quality Al0.3Ga0.7 As/GaAs heterojunctions allows accurate determination of the maximum 2-D carrier concentration. From this, we find a strong relationship between the conduction-band discontinuity and donor binding energy, giving offsets. …
Birefringence Measurements Of The Uniaxial-Stress Dependence Of The Incommensurate Phase Transition In K2Seo4, D. P. Billesbach, F. G. Ullman, John R. Hardy
Birefringence Measurements Of The Uniaxial-Stress Dependence Of The Incommensurate Phase Transition In K2Seo4, D. P. Billesbach, F. G. Ullman, John R. Hardy
John R. Hardy Papers
The uniaxial-stress dependence of the incommensurate-phase-transition temperature (at 130 K) in K2SeO4 was measured along all three crystal axes by observation of the anomalies in the birefringence caused by the structure change. The results for the c-axis-stress dependence (- 17.0±0.2 K/kbar) agree with previous studies of other workers. This experiment has also provided the first direct measurements of the a-axis- and b-axis-stress dependences (+ 3.1 ±0.2 K/kbar and +7.7± 0.2 K/kbar, respectively). Also, a value of -6.2±0.3 K/kbar was calculated from these data for the dependence of the transition temperature on hydrostatic pressure. This …
Cross Sections For Ionization Of Gases By 10-2000-Kev He+ Ions And For Electron Capture And Loss By 5-350-Kev He+ Ions, M. Eugene Rudd, T. V. Goff, A. Itoh, R. D. Dubois
Cross Sections For Ionization Of Gases By 10-2000-Kev He+ Ions And For Electron Capture And Loss By 5-350-Kev He+ Ions, M. Eugene Rudd, T. V. Goff, A. Itoh, R. D. Dubois
M. Eugene Rudd Publications
Cross sections for production of positive and negative charge for 10-2000-keV He+ ions on He, Ne, Ar, Kr, H2, N2, CO, O2, CH4, and CO2 were measured by the transverse-field method. Electron-capture and -loss cross sections for 5-350-keV He+ ions on the same targets were measured by the method of beam deflection of various charge states after passing through a known length of target gas. Secondary-emission detectors were used to detect neutral, singly charged, and doubly charged beam components. The equation σ+- σ- = σ10 …
Thindown In Radiobiology, Robert Katz, D. E. Dunn, G. L. Sinclair
Thindown In Radiobiology, Robert Katz, D. E. Dunn, G. L. Sinclair
Robert Katz Publications
A new expression for the radial dose distribution, tested against available data, and yielding good agreement with enzyme and virus cross sections, is used to calculate cellular inactivation cross sections from track theory models and parameters. We use a cellular model and radiosensitivity parameters, fitted to HILAC data 15 years ago, to represent mammalian cells irradiated at the UNILAC. The observed branching with Z and the decline in cellular action cross sections with an increase in ion LET are attributed to thindown; that is, to the limits imposed by the maximum radial penetration of delta rays. Target size and structure …
Low Temperature Tunneling Dynamics In Condensed Media, Paul Ernest Parris, Robert J. Silbey
Low Temperature Tunneling Dynamics In Condensed Media, Paul Ernest Parris, Robert J. Silbey
Physics Faculty Research & Creative Works
There has been considerable interest recently in the low temperature dynamics of condensed phase tunneling phenomena. In this paper we consider the interplay between quasiparticle transport and vibrational relaxation; the former taking place via tunneling in a double well potential, and the latter occurring due to interactions of the tunneling system with a harmonic bath. Taking the system-bath interactions to be linear in the bath coordinates, and explicitly allowing for a vibrationally excited well, we present a unified treatment of the weak and strong coupling regimes and obtain reduced equations of motion for the tunneling particle position operator. Solutions are …
Angle-Resolved Photoemission From Bromine Chemisorbed On Ni(100), Peter A. Dowben, Y. Sakisaka, T.N. Rhodin
Angle-Resolved Photoemission From Bromine Chemisorbed On Ni(100), Peter A. Dowben, Y. Sakisaka, T.N. Rhodin
Peter Dowben Publications
Molecular bromine dissociatively adsorbs to form a chemisorbed overlayer on Ni(100). The bromine induced 4px,y and 4pz orbitals have been identified at Γ̅ with binding energies of 6.6 ± 0.2 eV and 5.3 ± 0.2 eV below the Fermi energy, respectively. The relative ionization cross-section variations of the two bromine levels 4px and 4pz are observed to differ with changing photon energy.