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1983

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Articles 1 - 30 of 89

Full-Text Articles in Physics

Pseudo-Brewster And Second-Brewster Angles Of An Absorbing Substrate Coated By A Transparent Thin Film, R. M.A. Azzam, T F. Thonn Dec 1983

Pseudo-Brewster And Second-Brewster Angles Of An Absorbing Substrate Coated By A Transparent Thin Film, R. M.A. Azzam, T F. Thonn

Electrical Engineering Faculty Publications

The pseudo-Brewster angle of minimum reflectance for the p polarization, the corresponding angle for thes polarization, and the second-Brewster angle of minimum ratio of the p and s reflectances are all determined as functions of the thickness of a transparent film coating an absorbing substrate by numerical solution of the exact equations that govern such angles of the form Re(Z′/Z) = 0, where Z = Rp, Rs, or ρ represent the complex amplitude-reflection coefficients for the p and s polarizations and their ratio (ρ =Rp/Rs), respectively, and Z′ is the angle-of-incidence derivative of Z ...


Low-Mass Solitons From Fractional Charges In Quantum Chromodynamics, A. P. Balachandran, V. Parameswaran Nair, N. Panchapakesan, S. G. Rajeev Dec 1983

Low-Mass Solitons From Fractional Charges In Quantum Chromodynamics, A. P. Balachandran, V. Parameswaran Nair, N. Panchapakesan, S. G. Rajeev

Publications and Research

Slansky, Goldman, and Shaw have proposed a model to account for the observation of fractionally charged states. We show that in this model, there are expected to be several low-mass solitons (four being in the mass range ∼20-60 MeV) associated with the third homotopy group π3(SU(3)/SO(3))=Z4, besides a low-mass (∼30 MeV) Z2 monopole. Confirmation of these levels and hence of the model has important implications for Cabrera's results on the magnetic monopole. An efficient algorithm for the calculation of π3(G/H) for a general Lie group G and a subgroup ...


Cross Sections For Ionizaton Of Gases By 5-4000-Kev Protons And For Electron Capture By 5-150-Kev Protons, M. Eugene Rudd, R. D. Dubois, L. H. Toburen, C. A. Ratcliffe, T. V. Goffe Dec 1983

Cross Sections For Ionizaton Of Gases By 5-4000-Kev Protons And For Electron Capture By 5-150-Kev Protons, M. Eugene Rudd, R. D. Dubois, L. H. Toburen, C. A. Ratcliffe, T. V. Goffe

M. Eugene Rudd Publications

Using the parallel-plate-capacitor method and a capacitance manometer to determine pressures, total cross sections for the production of positive and negative charges were measured for 5-4000- keV-proton impact on He, Ne, Ar, Kr, Hz, N2, CO, 02, CH4, and C02. From these, ionization and electron-capture cross sections were obtained and fitted to semi-empirical equations describing the energy dependence in terms of a few parameters. At high energies very good agreement is obtained in the comparison of the ionization cross sections to earlier proton- and electron-impact measurements and with theoretical treatments where they are available, but discrepancies ...


Isotope Effect And Momentum-Transfer Scaling In The Elastic-Scattering Differential Cross Sections For Hydrogen-Isotope Collision Systems, Eduard P. Rille, Jerry Peacher, Denver G. Seely, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park Dec 1983

Isotope Effect And Momentum-Transfer Scaling In The Elastic-Scattering Differential Cross Sections For Hydrogen-Isotope Collision Systems, Eduard P. Rille, Jerry Peacher, Denver G. Seely, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park

Physics Faculty Research & Creative Works

A projectile-dependent isotope effect was found for the elastic-scattering differential cross sections in the hydrogen-isotope collision systems. All four differential cross sections lie on a common curve if they are divided by the square of the reduced mass and plotted against momentum transfer. The experimental results are in satisfactory agreement with a simple Glauber-approximation calculation.


Mst Radar Data-Base Management, Vincent B. Wickwar Dec 1983

Mst Radar Data-Base Management, Vincent B. Wickwar

All Physics Faculty Publications

No abstract provided.


Magnetic Phase Transition, Aggregate Formation, And Electrical Conductivity In Fecl3-Doped Polyacetylene, E. K. Sichel, M. F. Rubner, J. Georger, Jr., G. C. Papaefthymiou, S. Offer, Richard B. Frankel Dec 1983

Magnetic Phase Transition, Aggregate Formation, And Electrical Conductivity In Fecl3-Doped Polyacetylene, E. K. Sichel, M. F. Rubner, J. Georger, Jr., G. C. Papaefthymiou, S. Offer, Richard B. Frankel

Physics

Both Fe3+ and Fe2+ ions occur in FeCl3-doped polyacetylene. At low dopant levels (2+ and Fe3+ ions are paramagnetic down to 4.2 K. At dopant levels >0.01 mole fraction, there is evidence from Mössbauer spectroscopy that Fe2+ ions associate into aggregates which are magnetically ordered below 25 K. Aggregate formation appears to correlate with high electrical conductivity.


Breakdown Of Flavor Conservation In A Monopole Background, V. Parameswaran Nair Nov 1983

Breakdown Of Flavor Conservation In A Monopole Background, V. Parameswaran Nair

Publications and Research

We give a simple derivation of the catalysis of baryon decay and other flavor-changing processes by monopoles. The role of the axial anomaly is clarified. A general current-algebraic argument which clarifies the nature of flavor violation is also given.


Ionic-Configuration-Interaction Effects On Xe 5S-Subshell Photoionization Processes, Göran Wendin, Anthony F. Starace Nov 1983

Ionic-Configuration-Interaction Effects On Xe 5S-Subshell Photoionization Processes, Göran Wendin, Anthony F. Starace

Anthony F. Starace Publications

Recent measurements of the 5s-subshell photoelectron angular distribution of xenon have found larger values for the asymmetry parameter β in the region of the 5s-subshell cross-section minimum than predicted by relativistic random-phase-approximation calculations. Final-state ionic configuration interaction is adduced as a possible explanation for this and other discrepancies.


Ionization Of Heavy Atoms By Polarized Relativistic Protons, P.T. Leung, M. L. Rustgi Oct 1983

Ionization Of Heavy Atoms By Polarized Relativistic Protons, P.T. Leung, M. L. Rustgi

Physics Faculty Publications and Presentations

The effect due to the polarization of the incident high-energy (~GeV) proton beam on the ionization cross section of heavy atoms is investigated. In particular, with the use of Darwin wave functions for the atomic electron, the effect for hydrogenlike atoms is worked out. A numerical illustration shows that the polarization effect is completely insignificant. The authors also conclude that the K-shell ionization process is completely insensitive to the polarization of the incident beam.


Composition Of The Critical Nucleus In Multicomponent Vapor Nucleation, Gerald Wilemski Oct 1983

Composition Of The Critical Nucleus In Multicomponent Vapor Nucleation, Gerald Wilemski

Physics Faculty Research & Creative Works

No abstract provided.


Resistance Of Random Walks, Jayanth R. Banavar, A. Brooks Harris, Joel Koplik Sep 1983

Resistance Of Random Walks, Jayanth R. Banavar, A. Brooks Harris, Joel Koplik

Department of Physics Papers

Unrestricted lattice random walks in which a unit conductor is placed along each bond traversed are considered. The mean end-to-end resistance is studied as a function of the number of steps in the walk and the spatial dimension. A critical scaling law is found whose exponent is consistently given by four different calculational schemes.


Fe3O4 Precipitation In Magnetotactic Bacteria, Richard B. Frankel, Georgia C. Papaefthymiou, Richard P. Blakemore, Wendy O'Brien Sep 1983

Fe3O4 Precipitation In Magnetotactic Bacteria, Richard B. Frankel, Georgia C. Papaefthymiou, Richard P. Blakemore, Wendy O'Brien

Physics

Using Mössbauer resonance spectroscopy of 57Fe, we have determined the nature and distribution of major iron compounds in the magnetotactic bacterium Aquaspirillum magnetotacticum. In addition to magnetite (Fe3O4), cells contained a low-density hydrous ferric oxide, a high-density hydrous ferric oxide (ferrihydrite), and ferrous iron. Analysis at different temperatures of whole cells harvested early and late in growth, of mutant cells unable to synthesize magnetite, and of cell fractions enriched in 57Fe indicated that Fe3O4 precipitation resulted from partial reduction of the high-density hydrous ferric oxide precursor.


Stimulated Emission And The Flat Balmer Decrements Of Cataclysmic Variable Stars, Moshe Elitzur, Gary J. Ferland, W. G. Mathews, G. A. Shields Sep 1983

Stimulated Emission And The Flat Balmer Decrements Of Cataclysmic Variable Stars, Moshe Elitzur, Gary J. Ferland, W. G. Mathews, G. A. Shields

Physics and Astronomy Faculty Publications

Balmer emission lines from cataclysmic variables often have nearly equal intensities rather than the rapid decrement predicted by simple nebular theory. Traditionally, this has been interpreted in terms of local thermodynamic equilibrium emission from a dense gas with small volume located just above the accretion disk. In this Letter we show that the intense radiation field within a close binary system can affect excited-state populations and optical emission in ways which allow a relatively low density gas to closely mimic the high-density situation. In at least one case, the old nova V603 Aql, the emitting gas has a low density ...


Explicit Equations For The Second Brewster Angle Of An Interface Between A Transparent And An Absorbing Medium, R. M.A. Azzam Sep 1983

Explicit Equations For The Second Brewster Angle Of An Interface Between A Transparent And An Absorbing Medium, R. M.A. Azzam

Electrical Engineering Faculty Publications

The second Brewster angle ΦB2, at which the ratio Rp/Rs of intensity reflectances Rp and Rs for the parallel (p) and the perpendicular (s) polarizations of a dielectric-conductor interface reaches a minimum, is determined by Im[(u - ∊)(u - ∊)2/(u - 2∊)2] = 0, where ∊ is the complex ratio of dielectric constants of the media of refraction and incidence, ∊ = ∊/(∊ + 1), and u= sin2ΦB2. An equivalent quartic equation in u is also derived that can be solved exactly and explicitly to determine ΦB2 in terms of ∊.


Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, Partha P. Banerjee, Adrianus Korpel, Karl E. Lonngren Sep 1983

Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, Partha P. Banerjee, Adrianus Korpel, Karl E. Lonngren

Electrical and Computer Engineering Faculty Publications

Self‐refraction effects have been observed during the propagation of deep‐water capillary‐gravity waves. The observations are shown to be in qualitative agreement with the theory of self‐focusing and defocusing in a cubically nonlinear medium in the presence of diffraction.


Field-Theoretic Approach To Biconnectedness In Percolating Systems, A. Brooks Harris Sep 1983

Field-Theoretic Approach To Biconnectedness In Percolating Systems, A. Brooks Harris

Department of Physics Papers

A general method is given whereby m-connectedness correlation functions can be studied in the percolation problem. The method for m=1 involves calculating the kth power of the correlation function ⟨σ(x)σ(x′)⟩ for a randomly dilute Ising model at nonzero temperature and subsequently averaging over configurations. The final step is to take the limit k→0. This method is tested by reproducing the standard results for the percolation problem from an extension of the calculation of Stephen and Grest. For m>1 an additional "color" index is introduced and a Hamiltonian is constructed in which different colors ...


Pretransitional Effects In The Isotropic Phase Of A Lyotropic Nematic Liquid Crystal, Satyendra Kumar, J. D. Litster, Charles Rosenblatt Sep 1983

Pretransitional Effects In The Isotropic Phase Of A Lyotropic Nematic Liquid Crystal, Satyendra Kumar, J. D. Litster, Charles Rosenblatt

Physics Publications

We report quantitative observations of the pretransitional fluctuations in short-range nematic order and the divergence of the magnetic birefringence in the isotropic phase of a lyotropic liquid crystal. The results are analyzed to obtain the anisotropy of the diamagnetic susceptibility and the coefficients in a Landau expansion of the free energy.


Catalysis Of Flavor Nonconservation By Monopoles, V. Parameswaran Nair Aug 1983

Catalysis Of Flavor Nonconservation By Monopoles, V. Parameswaran Nair

Publications and Research

A simple argument based on current algebra is given to show how monopoles can lead to baryon decay and other flavor-changing processes.


Magnetic Field Behavior Of A Josephson-Junction Array: Two-Dimensional Flux Transport On A Periodic Substrate, Richard A. Webb, Richard F. Voss, G. Grinstein, P. M. Horn Aug 1983

Magnetic Field Behavior Of A Josephson-Junction Array: Two-Dimensional Flux Transport On A Periodic Substrate, Richard A. Webb, Richard F. Voss, G. Grinstein, P. M. Horn

Faculty Publications

This Letter reports measurements down to 3 mK of the magnetic field dependence of the resistance and critical current of a weakly coupled periodic array of Josephson junctions. Below 700 mK the resistance is an oscillatory function of field. The temperature dependence of the resistance for integral numbers of flux quanta per cell suggests the existence of a Kosterlitz-Thouless transition involving the unbinding of defects in the flux lattice.


Atomic Photoionization, Anthony F. Starace Aug 1983

Atomic Photoionization, Anthony F. Starace

Anthony F. Starace Publications

We present here a brief overview of the theory of atomic photoionization. The main aim is to describe current theoretical understanding of the dynamics of the photon-atom collision process. In particular the discussion focuses on those kinds of electron correlation that have been found to be most important for photoionization processes. The general theoretical formulation of the interaction between an incident photon and an N-electron atom is presented first. This is followed by a description of those quantitative and qualitative features of the photoionization cross section that can be understood within a central potential model. The particle-hole type of electron ...


Simple And Direct Determination Of Complex Refractive Index And Thickness Of Unsupported Or Embedded Thin Films By Combined Reflection And Transmission Ellipsometry At 45° Angle Of Incidence, R. M.A. Azzam Aug 1983

Simple And Direct Determination Of Complex Refractive Index And Thickness Of Unsupported Or Embedded Thin Films By Combined Reflection And Transmission Ellipsometry At 45° Angle Of Incidence, R. M.A. Azzam

Electrical Engineering Faculty Publications

Measurements of the polarization states (represented by complex numbers Xr and Xt, respectively) of light reflected and transmitted by an unsupported or embedded thin film, for totally polarized light (with nonzero p and s components) incident at 45°, permit simple, direct, and explicit determination of the film's complex refractive index N1 independently of film thickness or input polarization. If α = Xr/Xt, we find that α = rs + rs-1, where rs is Fresnel’s complex reflection coefficient of the ambient-film interface for the s polarization at 45° incidence. From α, r ...


Low Compensation Vapor-Phase Epitaxial Gallium-Arsenide, P. C. Colter, David C. Look, D. C. Reynolds Aug 1983

Low Compensation Vapor-Phase Epitaxial Gallium-Arsenide, P. C. Colter, David C. Look, D. C. Reynolds

Physics Faculty Publications

Vapor phase epitaxial gallium arsenide (GaAs) layers, with lower compensation ratios than any reported heretofore, have been reproducibly grown by the Ga/H2/AsCl3 method. One of these samples has been studied extensively by electrical measurements and shows an acceptor concentration of (2.0 ± 0.7)X1013 cm-3 , and a compensation rate of NA/ND = 0.06 ± 0.02. These numbers are supported by magnetophotothermal spectroscopy and photoluminescence measurements. The preparation involves growth on [211A] substrates, and a pregrowth bakeout of the Ga source, which results in a significantly lower Zn acceptor concentration in ...


Hole Transport In Pure And Doped Gaas, H. J. Lee, David C. Look Aug 1983

Hole Transport In Pure And Doped Gaas, H. J. Lee, David C. Look

Physics Faculty Publications

We have used a two-band model (heavy and light holes) to calculate the transport properties ofp-type GaAs. The scattering mechanisms included are acoustic-mode deformation potential, acoustic-mode piezoelectric potential, polar- and nonpolar-mode deformation potential, ionized impurity, and space charge. Interband scattering is included explicitly for the optical phonons and phenomenologically for the acoustic phonons. The intraband polar optical-mode scattering, for which a relaxation time cannot be defined, was calculated by using the numerical method of Fletcher and Butcher. The acoustic deformation-potential parameter and the coupling coefficient for interband scattering were calculated by fitting the theory to Hall-mobility data for both pure ...


Center-Of-Mass Properties Of Composite Systems Subject To Non-Linear External Interactions, James A. Lock Aug 1983

Center-Of-Mass Properties Of Composite Systems Subject To Non-Linear External Interactions, James A. Lock

Physics Faculty Publications

If two bound nonrelativistic quantum particles are each subject to a nonlinear external potential, their Schrödinger equation does not separate in relative and center-of-mass coordinates. For this case, the details of internal state of the composite affect its center-of-mass properties. The extent of this internal state influence is examined for an exactly soluble one-dimensional model system.


Unification Of Ernst-Equation Backlund Transformations Using A Modified Wahlquist-Estabrook Technique; Wahlquist-Estabrook, B. Kent Harrison Aug 1983

Unification Of Ernst-Equation Backlund Transformations Using A Modified Wahlquist-Estabrook Technique; Wahlquist-Estabrook, B. Kent Harrison

Faculty Publications

The three known Backlund transformations for the Ernst equation are derived using a modification of the Wahlquist-Estabrook prolongation procedure. The modification requires that the equation to be studied be cast into a set of differential forms and their exterior derivatives, such that all coefficients are constant (a "CC ideal''). Analysis of the resulting equations produces 16 solutions composed of the three basic transformations combined with identity and other essentially trivial transformations. The group structure of the transformations is discussed. A Backlund transformation (already known) for the Ernst-Maxwell equations can be found by the same method. Promising generalizations are mentioned.


Order Of Phase Transitions In A Field Theory, V. Parameswaran Nair Jul 1983

Order Of Phase Transitions In A Field Theory, V. Parameswaran Nair

Publications and Research

The relation between the gauge or global nature of a symmetry being broken and the order of the associated phase transition is clarified. First-order phase transitions in gauge theories are related to the asymptotic freedom of the Φ3 interaction in six dimensions. Spontaneous violation of lepton number in the standard electroweak theory provides a nontrivial illustration of our results.


Maximum Minimum Reflectance Of Parallel-Polarized Light At Interfaces Between Transparent And Absorbing Media, R. M.A. Azzam Jul 1983

Maximum Minimum Reflectance Of Parallel-Polarized Light At Interfaces Between Transparent And Absorbing Media, R. M.A. Azzam

Electrical Engineering Faculty Publications

The pseudo-Brewster angle ØpB, of minimum reflectance Rpm for the parallel (p) polarization, of an interface between a transparent and an absorbing medium is determined by Im{(∊ - u)[1 - (1 + ∊-1)u]2} = 0, where ∊ is the complex ratio of dielectric constants of the media and u = sin2øpB. It is shown that, for a given value of the normal-incidence amplitude reflectance |r|, there is an associated normal-incidence phase shift, δ = δmm, that leads to maximum minimum parallel reflectance, Rpmm. We determine δmm, Rpmm, øpBmm as functions ...


Study Of Prenucleation Ion Clusters: Correlation Between Ion Mobility Spectra And Size Distributions, Sung-Ho Suck Salk, Donald E. Hagen, James L. Kassner Jul 1983

Study Of Prenucleation Ion Clusters: Correlation Between Ion Mobility Spectra And Size Distributions, Sung-Ho Suck Salk, Donald E. Hagen, James L. Kassner

Physics Faculty Research & Creative Works

Additional studies regarding our earlier electrothermodynamic theory are presented. Comparisons to recent expansion cloud chamber ion mobility measurements are made, indicating general agreement with observations. This theory predicts more stable and ordered structure for prenucleation ion-water cluster systems than accounted for by the classical Thomson's theory. In the limiting case of the dielectric constant ε = 1, our monopole electrostatic energy term contributed by the foreign ion center precisely converges to that of Thomson. Predicted ion cluster size distributions are found to correlate well with ion cluster size spectra obtained from the ion mobility measurements of hydrated ion clusters and ...


Dissociative Attachment In Hcl, Dcl, And F2, J. N. Bardsley, J. M. Wadehra Jun 1983

Dissociative Attachment In Hcl, Dcl, And F2, J. N. Bardsley, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

Resonant scattering models, using nonlocal decay widths, are developed for dissociative attachment of slow electrons to diatomic molecules. Cross sections are obtained for HCl and DCl in several initial rotational and vibrational states, and the dependence of the average attachment cross section upon the rotational and vibrational temperature is examined. For F_2 the cross section for ground state molecules agrees well with experiment above 0.2 eV but shows no zero energy peak. The attachment cross section is higher for vibrationally excited molecules, but the enhancement is much less than that found in H_2 and HCl.


Second-Order Phase Transitions, Inflationary Universe, And Formation Of Galaxies, V. Parameswaran Nair Jun 1983

Second-Order Phase Transitions, Inflationary Universe, And Formation Of Galaxies, V. Parameswaran Nair

Publications and Research

At the critical point of a second-order phase transition, statistical fluctuations are correlated and enhanced in amplitude. We explore this phenomenon in the early universe as a possible mechanism for the formation of galaxies. In an inflationary universe, such dynamical effects on galactic scales are consistent with the constraints imposed by the horizon. Spontaneous breakdown of lepton number provides a model where these ideas are realized. The two-point correlation function for density fluctuations is calculated and agrees with the observed correlation for galaxies. An estimate of the density contrast is shown to be of the required magnitude.