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Articles 1  30 of 89
FullText Articles in Physics
PseudoBrewster And SecondBrewster Angles Of An Absorbing Substrate Coated By A Transparent Thin Film, R. M.A. Azzam, T F. Thonn
PseudoBrewster And SecondBrewster Angles Of An Absorbing Substrate Coated By A Transparent Thin Film, R. M.A. Azzam, T F. Thonn
Electrical Engineering Faculty Publications
The pseudoBrewster angle of minimum reflectance for the p polarization, the corresponding angle for thes polarization, and the secondBrewster 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 = R_{p}, R_{s}, or ρ represent the complex amplitudereflection coefficients for the p and s polarizations and their ratio (ρ =R_{p}/R_{s}), respectively, and Z′ is the angleofincidence derivative of Z ...
LowMass Solitons From Fractional Charges In Quantum Chromodynamics, A. P. Balachandran, V. Parameswaran Nair, N. Panchapakesan, S. G. Rajeev
LowMass 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 lowmass solitons (four being in the mass range ∼2060 MeV) associated with the third homotopy group π_{3}(SU(3)/SO(3))=Z_{4}, besides a lowmass (∼30 MeV) Z_{2} 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 54000Kev Protons And For Electron Capture By 5150Kev Protons, M. Eugene Rudd, R. D. Dubois, L. H. Toburen, C. A. Ratcliffe, T. V. Goffe
Cross Sections For Ionizaton Of Gases By 54000Kev Protons And For Electron Capture By 5150Kev Protons, M. Eugene Rudd, R. D. Dubois, L. H. Toburen, C. A. Ratcliffe, T. V. Goffe
M. Eugene Rudd Publications
Using the parallelplatecapacitor method and a capacitance manometer to determine pressures, total cross sections for the production of positive and negative charges were measured for 54000 keVproton impact on He, Ne, Ar, Kr, Hz, N_{2}, CO, 0_{2}, CH_{4}, and C0_{2}. From these, ionization and electroncapture cross sections were obtained and fitted to semiempirical 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 electronimpact measurements and with theoretical treatments where they are available, but discrepancies ...
Isotope Effect And MomentumTransfer Scaling In The ElasticScattering Differential Cross Sections For HydrogenIsotope Collision Systems, Eduard P. Rille, Jerry Peacher, Denver G. Seely, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park
Isotope Effect And MomentumTransfer Scaling In The ElasticScattering Differential Cross Sections For HydrogenIsotope 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 projectiledependent isotope effect was found for the elasticscattering differential cross sections in the hydrogenisotope 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 Glauberapproximation calculation.
Mst Radar DataBase Management, Vincent B. Wickwar
Mst Radar DataBase Management, Vincent B. Wickwar
All Physics Faculty Publications
No abstract provided.
Magnetic Phase Transition, Aggregate Formation, And Electrical Conductivity In Fecl_{3}Doped Polyacetylene, E. K. Sichel, M. F. Rubner, J. Georger, Jr., G. C. Papaefthymiou, S. Offer, Richard B. Frankel
Magnetic Phase Transition, Aggregate Formation, And Electrical Conductivity In Fecl3Doped Polyacetylene, E. K. Sichel, M. F. Rubner, J. Georger, Jr., G. C. Papaefthymiou, S. Offer, Richard B. Frankel
Physics
Both Fe^{3+} and Fe^{2+} ions occur in FeCl_{3}doped polyacetylene. At low dopant levels (2+ and Fe^{3+} ions are paramagnetic down to 4.2 K. At dopant levels >0.01 mole fraction, there is evidence from Mössbauer spectroscopy that Fe^{2+} 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
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 flavorchanging processes by monopoles. The role of the axial anomaly is clarified. A general currentalgebraic argument which clarifies the nature of flavor violation is also given.
IonicConfigurationInteraction Effects On Xe 5SSubshell Photoionization Processes, Göran Wendin, Anthony F. Starace
IonicConfigurationInteraction Effects On Xe 5SSubshell Photoionization Processes, Göran Wendin, Anthony F. Starace
Anthony F. Starace Publications
Recent measurements of the 5ssubshell photoelectron angular distribution of xenon have found larger values for the asymmetry parameter β in the region of the 5ssubshell crosssection minimum than predicted by relativistic randomphaseapproximation calculations. Finalstate 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
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 highenergy (~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 Kshell ionization process is completely insensitive to the polarization of the incident beam.
Composition Of The Critical Nucleus In Multicomponent Vapor Nucleation, Gerald Wilemski
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
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 endtoend 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.
Fe_{3}O_{4} Precipitation In Magnetotactic Bacteria, Richard B. Frankel, Georgia C. Papaefthymiou, Richard P. Blakemore, Wendy O'Brien
Fe3O4 Precipitation In Magnetotactic Bacteria, Richard B. Frankel, Georgia C. Papaefthymiou, Richard P. Blakemore, Wendy O'Brien
Physics
Using Mössbauer resonance spectroscopy of ^{57}Fe, we have determined the nature and distribution of major iron compounds in the magnetotactic bacterium Aquaspirillum magnetotacticum. In addition to magnetite (Fe_{3}O_{4}), cells contained a lowdensity hydrous ferric oxide, a highdensity 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 ^{57}Fe indicated that Fe_{3}O_{4} precipitation resulted from partial reduction of the highdensity 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
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 excitedstate populations and optical emission in ways which allow a relatively low density gas to closely mimic the highdensity 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
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 _{Φ}_{B2}, at which the ratio R_{p}/R_{s} of intensity reflectances R_{p} and R_{s} for the parallel (p) and the perpendicular (s) polarizations of a dielectricconductor 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= sin^{2}_{Φ}_{B2}. An equivalent quartic equation in u is also derived that can be solved exactly and explicitly to determine _{Φ}_{B2} in terms of ∊.
Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, Partha P. Banerjee, Adrianus Korpel, Karl E. Lonngren
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.
FieldTheoretic Approach To Biconnectedness In Percolating Systems, A. Brooks Harris
FieldTheoretic Approach To Biconnectedness In Percolating Systems, A. Brooks Harris
Department of Physics Papers
A general method is given whereby mconnectedness 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
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 shortrange 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
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 flavorchanging processes.
Magnetic Field Behavior Of A JosephsonJunction Array: TwoDimensional Flux Transport On A Periodic Substrate, Richard A. Webb, Richard F. Voss, G. Grinstein, P. M. Horn
Magnetic Field Behavior Of A JosephsonJunction Array: TwoDimensional 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 KosterlitzThouless transition involving the unbinding of defects in the flux lattice.
Atomic Photoionization, Anthony F. Starace
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 photonatom 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 Nelectron 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 particlehole 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
Electrical Engineering Faculty Publications
Measurements of the polarization states (represented by complex numbers X_{r} and X_{t}, 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 N_{1} independently of film thickness or input polarization. If α = X_{r}/X_{t}, we find that α = r_{s} + r_{s}^{1}, where r_{s} is Fresnel’s complex reflection coefficient of the ambientfilm interface for the s polarization at 45° incidence. From α, r ...
Low Compensation VaporPhase Epitaxial GalliumArsenide, P. C. Colter, David C. Look, D. C. Reynolds
Low Compensation VaporPhase Epitaxial GalliumArsenide, 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/H_{2}/AsCl_{3} method. One of these samples has been studied extensively by electrical measurements and shows an acceptor concentration of (2.0 ± 0.7)X10^{13} cm^{3} , and a compensation rate of N_{A}/N_{D} = 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
Hole Transport In Pure And Doped Gaas, H. J. Lee, David C. Look
Physics Faculty Publications
We have used a twoband model (heavy and light holes) to calculate the transport properties ofptype GaAs. The scattering mechanisms included are acousticmode deformation potential, acousticmode piezoelectric potential, polar and nonpolarmode 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 opticalmode scattering, for which a relaxation time cannot be defined, was calculated by using the numerical method of Fletcher and Butcher. The acoustic deformationpotential parameter and the coupling coefficient for interband scattering were calculated by fitting the theory to Hallmobility data for both pure ...
CenterOfMass Properties Of Composite Systems Subject To NonLinear External Interactions, James A. Lock
CenterOfMass Properties Of Composite Systems Subject To NonLinear 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 centerofmass coordinates. For this case, the details of internal state of the composite affect its centerofmass properties. The extent of this internal state influence is examined for an exactly soluble onedimensional model system.
Unification Of ErnstEquation Backlund Transformations Using A Modified WahlquistEstabrook Technique; WahlquistEstabrook, B. Kent Harrison
Unification Of ErnstEquation Backlund Transformations Using A Modified WahlquistEstabrook Technique; WahlquistEstabrook, B. Kent Harrison
Faculty Publications
The three known Backlund transformations for the Ernst equation are derived using a modification of the WahlquistEstabrook 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 ErnstMaxwell equations can be found by the same method. Promising generalizations are mentioned.
Order Of Phase Transitions In A Field Theory, V. Parameswaran Nair
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. Firstorder phase transitions in gauge theories are related to the asymptotic freedom of the Φ^{3} 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 ParallelPolarized Light At Interfaces Between Transparent And Absorbing Media, R. M.A. Azzam
Maximum Minimum Reflectance Of ParallelPolarized Light At Interfaces Between Transparent And Absorbing Media, R. M.A. Azzam
Electrical Engineering Faculty Publications
The pseudoBrewster angle Ø_{p}B, of minimum reflectance R_{pm} 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 = sin^{2}ø_{p}B. It is shown that, for a given value of the normalincidence amplitude reflectance r, there is an associated normalincidence phase shift, δ = δ_{mm}, that leads to maximum minimum parallel reflectance, R_{pmm}. We determine δ_{mm}, R_{pmm}, ø_{p}B_{mm} as functions ...
Study Of Prenucleation Ion Clusters: Correlation Between Ion Mobility Spectra And Size Distributions, SungHo Suck Salk, Donald E. Hagen, James L. Kassner
Study Of Prenucleation Ion Clusters: Correlation Between Ion Mobility Spectra And Size Distributions, SungHo 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 ionwater 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
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.
SecondOrder Phase Transitions, Inflationary Universe, And Formation Of Galaxies, V. Parameswaran Nair
SecondOrder Phase Transitions, Inflationary Universe, And Formation Of Galaxies, V. Parameswaran Nair
Publications and Research
At the critical point of a secondorder 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 twopoint 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.