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Electron Doubly Differential Cross Section For 0.5-Mev H--He Detachment Collisions, Chang-Hwan Park, Anthony F. Starace, Joseph Macek Mar 1985

Electron Doubly Differential Cross Section For 0.5-Mev H--He Detachment Collisions, Chang-Hwan Park, Anthony F. Starace, Joseph Macek

Anthony F. Starace Publications

A comprehensive theoretical treatment is presented for the electron detachment cross section, differential in both electron momentum and direction, for collisions of 0.5-MeV H- projectiles on He targets. Our calculation, which assumes that the residual H atom is left in the 1s state, employs the usual first Born approximation as well as the closure approximation (in order to sum over all He target final states). Electron correlations within the H- system are treated in detail within the framework of the adiabatic hyperspherical coordinate approximation. In particular, for the first time for this collision process, angular correlations are included. The …

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Antireflecting And Polarizing Transparent Bilayer Coatings On Absorbing Substrates At Oblique Incidence, R. M.A. Azzam, Karim Javily Feb 1985

Antireflecting And Polarizing Transparent Bilayer Coatings On Absorbing Substrates At Oblique Incidence, R. M.A. Azzam, Karim Javily

Electrical Engineering Faculty Publications

The condition of zero reflection of p- and s-polarized light by a transparent bilayer on an absorbing substrate is derived in the form |gν(ø,Ni)| ≤ 1, where gν is a function of the angle of incidence ø, the refractive indices Ni(i = 0,1,2,3) of the system, and the polarization state ν (= p or s). As an application, the air-Si3N4-SiO2-Si system is considered at two laser wavelengths λ = 6328 and 3250 Å. The thicknesses of the two films of the bilayer and the …

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Single-Layer Antireflection Coatings On Absorbing Substrates For The Parallel And Perpendicular Polarizations At Oblique Incidence, R. M.A. Azzam Feb 1985

Single-Layer Antireflection Coatings On Absorbing Substrates For The Parallel And Perpendicular Polarizations At Oblique Incidence, R. M.A. Azzam

Electrical Engineering Faculty Publications

Explicit equations are derived that determine the refractive index of a single layer that suppresses the reflection of p- or s-polarized light from the planar interface between a transparent and an absorbing medium at any given angle of incidence. The required layer thickness and the system reflectance for the orthogonal unextinguished polarization also follow explicitly. This generalizes earlier work that was limited to normal incidence or to oblique incidence at dielectric—dielectric interfaces. Specific examples are given of p- and s-antireflection layers on Si and Al substrates at λ = 6328 Å at various angles of incidence.

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Measurement Of The Real-To-Imaginary Ratio Of The P̅ P Forward-Scattering Amplitudes, R. Debbe, William J. Fickinger, R. Marino, D. K. Robinson Feb 1985

Measurement Of The Real-To-Imaginary Ratio Of The P̅ P Forward-Scattering Amplitudes, R. Debbe, William J. Fickinger, R. Marino, D. K. Robinson

Faculty Scholarship

We have measured the ratio of the real to the imaginary parts of the pÌ… p forward-scattering amplitude in the incident-momentum range 360 to 650 MeV/c. These results are in good agreement with predictions of the Paris nucleon-antinucleon potential model which include spin-flip effects.

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The Hydrogen Line Spectra Of Narrow-Line Radio Galaxies, Gary J. Ferland, Donald E. Osterbrock Feb 1985

The Hydrogen Line Spectra Of Narrow-Line Radio Galaxies, Gary J. Ferland, Donald E. Osterbrock

Physics and Astronomy Faculty Publications

We report the results of the first detection of Lyα in a narrow-line radio galaxy. Nearly simultaneous optical and UV observations of 3C 192 and 3C 223 allow the measurement of both Balmer and Lyman decrements. These line ratios are approximate functions of the interstellar reddening and of a parameter which is proportional to the amount of H I collisional excitation present. The reddening of 3C 192 is slightly larger than that due to our Galaxy, although 3C 223 may have a larger value. Both galaxies have intrinsic Balmer and Lyman decrements which are significantly steeper than case B, …

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Extinction Of The P And S Polarizations Of A Wave On Reflection At The Same Angle From A Transparent Film On An Absorbing Substrate: Applications To Parallel-Mirror Crossed Polarizers And A Novel Integrated Polarimeter, R. M.A. Azzam Feb 1985

Extinction Of The P And S Polarizations Of A Wave On Reflection At The Same Angle From A Transparent Film On An Absorbing Substrate: Applications To Parallel-Mirror Crossed Polarizers And A Novel Integrated Polarimeter, R. M.A. Azzam

Electrical Engineering Faculty Publications

The p- and s-polarized components of light can be suppressed on reflection at the same angle of incidence from an absorbing substrate coated by a transparent thin film if the wave is refracted in the film at 45° and the constraint Re[(ε2 - α)/(l -α)]1/2 = α + | ε2 - α| is satisfied, where 2α and ε2 are the ratios of dielectric constants of the film and substrate, respectively, to that of the ambient. For high-reflectance metal substrates (|ε2| » 1), α≈ 1, the ratio of film to ambient refractive index …

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Example Of A Group Action Determined Phase Transition, Jeffrey W. Felix, Dorian M. Hatch Feb 1985

Example Of A Group Action Determined Phase Transition, Jeffrey W. Felix, Dorian M. Hatch

Faculty Publications

The principles of the group action approach to structural phase transitions are outlined. It is assumed that all properties of the transition are determined by the action of a single physically irreducible represention of the space group of the more symmetric phase. We determine the isotropy groups using the image space of the representation. The free energy minima are determined to fourth order and to all orders using the results of Gufan and then compared. This theory is applied to Calcite (Roverline3c) to determine all possible continuous commensurate phase transitions.

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Schottky-Barrier Profiling Techniques In Semiconductors - Gate Current And Parasitic Resistance Effects, David C. Look Jan 1985

Schottky-Barrier Profiling Techniques In Semiconductors - Gate Current And Parasitic Resistance Effects, David C. Look

Physics Faculty Publications

The theory for obtaining mobility and carrier concentration profiles by the Hall-effect, magnetoresistance, and capacitance-conductance methods is developed in the relaxation-time approximation. This theory is then applied to semiconductors in which a Schottky barrier is used to control a depletion region. Particular emphasis is given to field-effect transistor structures which are ideally suited for geometric magnetoresistance measurements. A unique feature of the present model is the correction for finite gate (Schottky-barrier) current, which can be very important under forward-gate-bias conditions. The ability to use forward-bias makes the near-surface region more accessible. Also, parasitic resistance effects are treated. We apply these …

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Qcd Vacuum As A Chromomagnetic Superconductor: Microscopic Physics, V. Parameswaran Nair, C. Rosenzweig Jan 1985

Qcd Vacuum As A Chromomagnetic Superconductor: Microscopic Physics, V. Parameswaran Nair, C. Rosenzweig

Publications and Research

The compactness of the QCD gauge group leads to the existence of chromomagnetic monopole configurations. The interactions of these monopoles are studied using electric-magnetic duality as a guide. It is shown that the gluon-monopole interaction acquires an extra minus sign which tends to destabilize the monopole configurations. A model is presented which exploits this observation. We present a scenario where the monopoles condense, giving chromomagnetic superconductivity, via a first-order phase transition at a scale where the electric and magnetic charges are equal, i.e., α = 1/2 . In this vacuum medium gluons propagate like 1/k4 which is now seen …

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New Shubnikov-De Haas Effects In A Two-Dimensional Electron-Hole System, S. Washburn, Richard A. Webb, E. E. Mendez, L. L. Chang, L. Esaki Jan 1985

New Shubnikov-De Haas Effects In A Two-Dimensional Electron-Hole System, S. Washburn, Richard A. Webb, E. E. Mendez, L. L. Chang, L. Esaki

Faculty Publications

We report the temperature dependence of the Shubnikov–de Haas oscillations from a two-dimensional electron-hole system in GaSb-InAs-GaSb quantum wells at very low temperatures. The samples are double heterostructures containing separate electron and hole layers. The oscillations arising from the electron layer behave regularly with temperature. Additional oscillations, characterized by strong temperature dependence, and relatively large peak widths are believed to arise from the presence of hole layers.

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Solution Of The Kondo Problem By Diagrammatic Methods, S. E. Barnes Jan 1985

Solution Of The Kondo Problem By Diagrammatic Methods, S. E. Barnes

Physics Articles and Papers

A self-consistent parquet approximation is shown to give exact results for the Kondo problem in the scaling limit.

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Radial Distribution Of Dose And Cross-Sections For The Inactivation Of Dry Enzymes And Viruses, Zhang Chunxiang, D. E. Dunn, Robert Katz Jan 1985

Radial Distribution Of Dose And Cross-Sections For The Inactivation Of Dry Enzymes And Viruses, Zhang Chunxiang, D. E. Dunn, Robert Katz

Robert Katz Publications

A new semi-empirical algorithm for the radial distribution of dose is compared with available data. The algorithm is used to calculate the inactivation cross section for dry enzymes and viruses using an extended target model of a 1-hit detector. Agreement with data is at about the 15% level, approximating the precision of the data itself.

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The Rotated Diffraction Grating: A Laboratory Experiment, James A. Lock Jan 1985

The Rotated Diffraction Grating: A Laboratory Experiment, James A. Lock

Physics Faculty Publications

No abstract provided.

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Theoretical Study Of Anomalously High F Region Peak Altitudes In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk Jan 1985

Theoretical Study Of Anomalously High F Region Peak Altitudes In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

During the last solar maximum period several observations of anomalously high F region peak altitudes have been made by the high latitude incoherent scatter radars. The observations indicate that there are several distinctive features associated with these high hmF2 ionospheric profiles: (1) they are observed near midnight with the plasma flowing out of the polar cap, (2) NmF2 ranges from 105 to 106 cm−3, (3) hmF2 ranges from 400 to 500 km, (4) below 300 km the profile is devoid of ionization, and (5) the observations are for solar maximum conditions. …

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A Theoretical Study Of The Global F Region For June Solstice, Summer Maximum, And Low Magnetic Activity, Jan Josef Sojka, Robert W. Schunk Jan 1985

A Theoretical Study Of The Global F Region For June Solstice, Summer Maximum, And Low Magnetic Activity, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

We constructed a time-dependent, three-dimensional, multi-ion numerical model of the global ionosphere at F region altitudes. The model takes account of all the processes included in the existing regional models of the ionosphere. The inputs needed for our global model are the neutral temperature, composition, and wind; the magnetospheric and equatorial electric field distributions; the auroral precipitation pattern; the solar EUV spectrum; and a magnetic field model. The model produces ion (NO+, O2+, N2+, N+, O+, He+) density distributions as a function of time. For our …

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Mossbauer Spectroscopy Of Iron Biomineralization Products In Magnetotactic Bacteria, Richard B. Frankel, Georgia C. Papaefthymiou, Richard P. Blakemore Jan 1985

Mossbauer Spectroscopy Of Iron Biomineralization Products In Magnetotactic Bacteria, Richard B. Frankel, Georgia C. Papaefthymiou, Richard P. Blakemore

Physics

No abstract provided.

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Refilling Of Geosynchronous Flux Tubes As Observed At The Equator By Geos 2, Jan Josef Sojka, G. L. Wrenn Jan 1985

Refilling Of Geosynchronous Flux Tubes As Observed At The Equator By Geos 2, Jan Josef Sojka, G. L. Wrenn

All Physics Faculty Publications

During periods of extended quiet geomagnetic activity the geosynchronous satellite orbit lies inside the plasmasphere. Five such periods were observed by the GEOS 2 satellite. During the initial 48 hours of such periods the equatorial plasma flux tube density increases at 30 to 50 cm−3/day. However, on reaching ∼100 cm−3 the refilling rate decreases, and refilling is limited. Only when the density reaches ∼100 cm−3 do the plasma characteristics and fluctuations appear to be plasmaspheric and the flow predominantly corotational. The “hot outer zone” of the plasmasphere is highly structured in density and temperature when viewed …

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Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Thermal Stress Analysis, A. Ballantyne, H.A. Hyman, Clive L. Dym, R.C. Southworth Jan 1985

Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Thermal Stress Analysis, A. Ballantyne, H.A. Hyman, Clive L. Dym, R.C. Southworth

All HMC Faculty Publications and Research

This paper examines the effects of thermal loading and time history upon the thermal stresses developed in lithographic mask structures as would be expected under irradiation by intense soft x rays. The objective of this work was to examine the phenomenology of the interaction and to evaluate the limits placed upon mask dosage. The mechanics of mask failure are examined in terms of single pulse and cumulative, or fatigue, effects. A number of prototypical mask structures are investigated, which show that the application of intense pulsed sources to x‐ray lithography does not reduce the potential utility of the techique. However, …

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Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Dynamic Response, Clive L. Dym, A. Ballantyne Jan 1985

Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Dynamic Response, Clive L. Dym, A. Ballantyne

All HMC Faculty Publications and Research

This paper addresses the issue of the dynamic response of thin lithographic mask structures to thermally induced stress fields. In particular, the impact of repetitively pulsed x‐ray sources are examined: the short duration (1–100 nsec) pulses induce large step changes in mask temperatures, which can, in turn, induce a dynamic response. The impact of conductive cooling of the mask is to reduce the repetitively pulsed problem to a series of isolated nearly identical thermal impulses of duration approximately equal to the cooling time. The importance of self‐weight and prestress is examined, and an analysis of the nonlinear dynamic response to …

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Motion Of A Plane Front During Crystallization, Alexander Umantsev Jan 1985

Motion Of A Plane Front During Crystallization, Alexander Umantsev

Chemistry and Physics Faculty Working Papers

Many authors have studied the growth rates of crystals with a plane front. It is known that, if the advance of the boundary is determined by deviation of its state from equilibrium, then various regimes can be realized in the system, depending on the external conditions. 1,2 However, they have not yet been obtained as different solutions of a single problem. In our work, the integral equation representing normal growth of a crystal is solved by means of an asymptotic expansion by the method of Laplace. In the second part we construct an algorithm for obtaining numerical solutions to the …

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Cross Sections For Ionization Of Water Vapor By 7-4000-Kev Protons, M. Eugene Rudd, T. V. Goffe, R. D. Dubois, L. H. Toburen Jan 1985

Cross Sections For Ionization Of Water Vapor By 7-4000-Kev Protons, M. Eugene Rudd, T. V. Goffe, R. D. Dubois, L. H. Toburen

M. Eugene Rudd Publications

Cross sections for production of electrons and positive ions by proton impact on water vapor have been measured from 7-4000 keV by the transverse-field method.

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The Production Of Highly Unidirectional Lower-Hybrid Waves, R. Mcwilliams, M. Okubo, R. C. Platt, D. P. Sheehan Jan 1985

The Production Of Highly Unidirectional Lower-Hybrid Waves, R. Mcwilliams, M. Okubo, R. C. Platt, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

The development of a highly unidirectional lower-hybrid wave source would improve the electron current drive efficiency in tokamaks. Lower-hybrid waves launched from a phased wave array are shown to be reflected from a grid placed in a cold, low-density plasma. The antenna-grid combination results in highly unidirectional lower-hybrid waves.

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Effect Of The Interplanetary Magnetic Field Y Component On The High‐Latitude Nightside Convection, O. De La Beaujardiere, Vincent B. Wickwar, J D. Kelly, J H. King Jan 1985

Effect Of The Interplanetary Magnetic Field Y Component On The High‐Latitude Nightside Convection, O. De La Beaujardiere, Vincent B. Wickwar, J D. Kelly, J H. King

All Physics Faculty Publications

Sondrestrom radar observations reveal that the dawn‐dusk (By) component of the interplanetary magnetic field (IMF) strongly influences the nightside polar convection. This effect is quite complex. The convection for one orientation of By is not the mirror image of the other orientation. A positive By (i.e., pointing toward dusk) seems to organize the velocities such that, at all local times, they are predominantly westward within the radar field‐of‐view (≃68°‐to‐82° invariant latitude). Between dusk and midnight, on one such occasion, sunward flow is observed within the polar cap. In the midnight and dawn sectors, when By …

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Universal Time Dependence Of Nighttime F Region Densities At High Latitudes, O De La Beaujardiere, Vincent B. Wickwar, G Caudal, J Holt, J D. Craven, L A. Frank, L Brace, D Evans, J D. Winningham, R A. Heelis Jan 1985

Universal Time Dependence Of Nighttime F Region Densities At High Latitudes, O De La Beaujardiere, Vincent B. Wickwar, G Caudal, J Holt, J D. Craven, L A. Frank, L Brace, D Evans, J D. Winningham, R A. Heelis

All Physics Faculty Publications

Coordinated EISCAT, Chatanika, and Millstone Hill incoherent scatter radar observations have revealed that in the auroral zone, the nighttime F region densities vary substantially with the longitude of the observing site: EISCAT’s densities are the largest and Millstone Hill’s are the lowest. The nighttime F region densities measured by the individual radars are not uniform: the regions where the densities are maximum are the so-called “blobs” or “patches” that have been reported previously. The observations are consistent with the hypothesis that the nighttime densities are produced in significant amounts not by particle precipitation, but by solar EUV radiation, and that …

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Optical Properties Of Natural Minerals In The Far-Infrared, Larry Lavern Long Jan 1985

Optical Properties Of Natural Minerals In The Far-Infrared, Larry Lavern Long

Doctoral Dissertations

"The reflectivity of natural mineral powders were measured in the far infrared. The complex indices of refraction were then determined by Kramers-Kronig analysis or dispersive analysis. The samples were constructed by pressing the powdered sample into a 13 mm diameter pellet. A few of the samples that were measured were kaolin, illite, and montmorillonite, clay samples that could not be obtained in large single crystals. For calcite and gypsum crystals a comparison between the single crystal measurements and powder measurements was done to determine the effect of sample preparation on the measured spectra"-- Abstract, p. ii

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Advances In Verification Technology, David W. Hafemeister Jan 1985

Advances In Verification Technology, David W. Hafemeister

Physics

The alleged limits of verification techniques have been used to justify lack of action at the negotiating table, but advances in computer science and optics should help dispel doubts about the verifiability of treaties

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The Vibrational Distribution Of N2+ In The Terrestrial Ionosphere, Jane L. Fox, Alexander Dalgarno Jan 1985

The Vibrational Distribution Of N2+ In The Terrestrial Ionosphere, Jane L. Fox, Alexander Dalgarno

Physics Faculty Publications

The densities and vibrational distributions of N2+ in the X²Σg+, A²Πu, and B²Σu+ states in the daytime terrestrial ionosphere are computed for both low and high solar activity. Altitude profiles of the relative populations of the vibrational levels of N2+X²Σg+ are presented. The fraction of vibrationally excited N2+ varies from 5% at 100 km to 50% at 450 km. Several models are examined in which loss of N2+(v) is enhanced for v > 0 and in …

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Analysis Of Solar Collector Surface To Air Flow Thermal Transfer Using Solid State Sensors And Microcomputer Interfacing, Rudolph J. Eichenberger Jan 1985

Analysis Of Solar Collector Surface To Air Flow Thermal Transfer Using Solid State Sensors And Microcomputer Interfacing, Rudolph J. Eichenberger

Journal of the Arkansas Academy of Science

No abstract provided.

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Low-Dimensional Chaotic Attractors For An Unstable, Inhomogeneously Broadened, Single-Mode Laser, Alfonso M. Albano, J. Abounadi, T. H. Chyba, C. E. Searle, S. Yong, R. S. Gioggia, N. B. Abraham Jan 1985

Low-Dimensional Chaotic Attractors For An Unstable, Inhomogeneously Broadened, Single-Mode Laser, Alfonso M. Albano, J. Abounadi, T. H. Chyba, C. E. Searle, S. Yong, R. S. Gioggia, N. B. Abraham

Physics Faculty Research and Scholarship

Quantitative characterization of the intensity pulsations from an inhomogeneously broadened laser confirm that observed irregular pulsing has its origins in deterministic chaos corresponding to motion on a strange attractor of low fractal dimensionality. The pointwise information dimension and the Grassberger-Procaccia K2 (estimators from below of the fractal dimensionality of the attractor and the Kolmogorov entropy, respectively) have been determined for digitized time series from parameter regions identified qualitatively by power spectra as representing periodic, period-doubled, quasi-periodic, and chaotic behavior. Some amount of chaos seems present for almost all operating conditions.

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Laser-Assisted Charge-Transfer Collisions: K++Na, Y. P. Hsu, M. Kimura, Ronald E. Olson Jan 1985

Laser-Assisted Charge-Transfer Collisions: K++Na, Y. P. Hsu, M. Kimura, Ronald E. Olson

Physics Faculty Research & Creative Works

A theory has been formulated to characterize charge-transfer collisions in the presence of an external laser field. The molecular-state-expansion method is used to describe the scattering process within the impact-parameter formalism. Electron translation factors are included in the molecular-state expansion so that the scattering wave function satisfies the correct boundary conditions. The theory is applied to the process K++NaK+Na+. In addition, we have made a detailed analysis of laser-assisted charge transfer for low-energy collisions. In this case, a Landau-Zener formula can be derived which shows that the cross section increases with decreasing incident energy. In general the laser coupling is …

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