Physical Sciences and Mathematics Commons^™

Fresnel Diffraction Effects In Misfocused Vision, James A. Lock

Physics Faculty Publications

If a narrow line stimulus on an opposite contrast background is observed with appropriately misfocused vision, the stimulus appears as a number of alternating bright and dark fringes. A numerical calculation of this effect was performed. As a result it was found that the banding phenomenon is a Fresnel diffraction effect depending on the details of both the narrow line stimulus and the eye pupil.

Fourier Transform Of The Product Of N One-Center Hydrogenic Orbitals, Jack C. Straton

Physics Faculty Publications and Presentations

Integrating the radial part of the Fourier transform of the product of N hydrogenic orbitals results in an associated Legendre function that can be reduced to a finite series of elementary functions. This transform is found to depend on a polynomial in the wave vector k divided by a binomial in k² raised to a power that is the sum of principle quantum numbers. This form facilitates the analytical reduction of integrals arising from orthogonalization corrections in atomic processes. Transforms for the product of orbital pairs (1s,1s) through (1s,3d) are given …

Transport Anisotropy And Percolation In The Two-Dimensional Random-Hopping Model, Kalyan P. Kundu, Paul Ernest Parris, Philip W. Phillips

Physics Faculty Research & Creative Works

We consider hopping transport on an anisotropic two-dimensional square lattice. The displacements parallel to one axis are governed by uniform, nearest-neighbor hopping rates c, while the displacements parallel to the other axis are governed by static but spatially fluctuating rates w_n. Adapting a new class of generating functions recently introduced for the random-trapping problem, we are able to obtain expressions for the mean-square displacement in the fluctuating direction through an exact decoupling of the effects due to displacements in the uniform direction. The resulting expressions for the low-frequency diffusion coefficient D(ε) are exact in the limits c →0 …

Recoil Ions From Close 20-Kev H+ Collisions With O2, Co, Co2, And Ne, Akio Itoh, M. Eugene Rudd

M. Eugene Rudd Publications

Recoil ions ejected at 70° from 20-keV proton collisions with O₂, CO, CO₂, and Ne were analyzed by an electrostatic analyzer. For the molecular targets, only singly ionized ions of oxygen or carbon were detected while in the spectrum of neon ions, Ne⁺ and Ne²⁺ were both observed. The absence of O₂⁺, CO⁺, and CO₂⁺ is due to the fact that the recoil ions detected in this experiment result only from very close collisions with one of the atoms in the molecule resulting in dissociation. A possible …

Antireflection Of An Absorbing Substrate By An Absorbing Thin Film At Normal Incidence, R. M.A. Azzam, E. Bu-Habib, J. Casset, G. Chassaing, P. Gravier

Electrical Engineering Faculty Publications

An absorbing substrate of complex refractive index n₂ - jk₂ at wavelength λ can be coated by an absorbing thin film of complex refractive index n₁ - jk₁ and thickness d to achieve zero reflection at normal incidence. For given n₂,k₂ multiple solutions (n₁,k₁,d/λ) are found that correspond to infinitely many distinct antireflection layers. This is demonstrated for a Si substrate at two wavelengths (6328 and 4420 Å). The response of these absorbing antireflection layers to changes of the angle of incidence from 0 …

Composition Range Of Binary Amorphous Alloys, Sy_Hwang Liou, C.L. Chien

Sy-Hwang Liou Publications

We have studied a number of binary metal-metal and metalloid alloy systems made by a single vapor-quench method under very consistent conditions. In each case, amorphous alloys are found in one continuous composition range (x_{min≤x≤xmax}) regardless of the number of eutectic points in the equilibrium phase diagrams. It is found that the atomic size difference is the single most important factor in the quantitative determination of the composition range.

Demountable Piezoelectric Transducer Holder For Use At Low Temperatures, Matthew J. Moelter, M. B. Manning, C. Ebaum

Physics

We present a design for a piezoelectric transducer holder for use at low temperatures, which is easily constructed and assembled. Improved acoustic signals with "ringing" eliminated were reliably obtained. The standard problems of demountability, electrical integrity, and leak tightness in the presence of liquid helium at moderate pressures were resolved.

Equivalence Of Donor And Acceptor Fits Of Temperature-Dependent Carrier-Concentration Data, David C. Look, J. R. Sizelove

Physics Faculty Publications

It is shown that the usual charge-balance analysis of temperature-dependent carrier-concentration data cannot distinguish between the donor and acceptor behavior of a center which is emitting carriers to a particular band, even though the statistics are different in the two cases. Other data, such as mobility or analytical results are needed to make the distinction.

Variational Treatment Of A Harmonic Oscillator Coupled To A Dissipative Heat Bath, Paul Ernest Parris, Robert J. Silbey

Physics Faculty Research & Creative Works

We consider the problem of a single quantum oscillator coupled linearly to a heat bath of independent harmonic modes. An exact solution is presented for the system-oscillator observables of interest. The exact results are then used to evaluate the utility of a variational approach to the problem that has proven useful recently in elucidating the dynamics of dissipatively coupled systems. We find that the variational approach does provide a good description for most, but not all, observables of interest. Both the exact and the variational treatment demonstrate the important role played by the low-frequency bath modes in determining qualitative features …

Kobayashi-Maskawa Angles And Su(3) Breaking In Hyperon Beta-Decay, Jf Donoghue, Br Holstein, Sw Klimt

Barry R Holstein

The determination of the Kobayashi-Maskawa matrix element Vus from hyperon β decays has long had a hidden uncertainty due to the almost universal assumption of SU(3) invariance in Cabibbo-type fits, especially since the data definitely indicate the presence of SU(3) breaking. We have reanalyzed the hyperon-decay data using the pattern of symmetry breaking predicted by the quark model including the center-of-mass correction. We find that the SU(3)-broken picture is far superior to the assumption of perfect SU(3), and provides a good fit to experiment. The sensitivity of Vus to the breaking is not large and we find Vus=0.220+/-0.001+/-0.003 (the errors …

Implications Of Atmospheric Test Fallout Data For Nuclear Winter, George H. Baker

George H Baker

Atmospheric test fallout data have been used to determine admissible dust particle size distributions for nuclear winter and nuclear fallout studies. The research was originally motivated by extreme differences noted in the magnitude and longevity of dust effects predicted by particle size distributions routinely used in fallout predictions versus those used for nuclear winter studies. Three different sets of historical data have been analyzed:

1. Stratospheric burden of Strontium-90 and Tungsten-185, 1954-1967 (97 contributing events) 2. Continental U.S Strontium-90 fallout through 1958 (75 contributing events) 3. Local Fallout from selected Nevada tests (16 events)

The contribution of dust to possible …

Optically Phased Laser Transmitter, Janet S. Fender, Salvatore J. Cusumano, Robert R. Butts, Christopher R. Dehainaut

AFIT Patents

An apparatus and technique are described for phasing the outputs of a multiplier telescope array used as a laser transmitter. The technique uses samples of the transmitted beams to control optical path lengths through the separate telescopes so that the beams add coherently at the receiver. The phasing concept is applicable both to systems which provide inputs to the multiple telescopes by dividing a single laser beam and to systems in which the inputs to the telescopes and multiple, phase-locked laser beams. The approach is also compatible with single line and multi-line lasers, and it does not entail stringent alignment …

Atomic Hydrogen In A Uniform Magnetic Field: Low-Lying Energy Levels For Fields Above 109 G, Chih-Ray Liu, Anthony F. Starace

Anthony F. Starace Publications

The energies and wave functions of the 1s, 2s, 2p(m_l = 0), and 2p(m_l = ±1) levels of hydrogen in a uniform magnetic field B (10⁹ G ≤ B ≤ 10¹² G) are calculated in two cylindrical adiabatic approximations, each of which includes the influence of the Coulomb field on the radial motion of the electron. For the lowest levels of each symmetry [i.e., the 1s, 2p(m_l = 0) and 2p(m_l = ±1) levels] our calculations provide rigorously both upper and lower bounds on …

Stability-Instability Transitions In Hamiltonian Systems Of N Dimensions, Foek T. Hioe, Z Deng

Physics Faculty/Staff Publications

We show analytically that for a class of simple periodic motions in a general Hamiltonian system of n dimensions, if C is a parameter of the system and Cz one of its generally many critical values at which the motion undergoes a stability-instability transition, the behavior of the largest Lyapunov exponent p as C approaches Ce from the unstable region is given by µ, =constX |~ C—C_p |^β where β= 1/2, independent of the transition point, type of transitions, or the dimensionality of the system. We present numerical results for a three-dimensional Harniltonian system which exhibits three types …

Erratum: Spontaneous Two-Photon Decay Rates In Hydrogenlike And Heliumlike Ions (Physical Review A (1987) 35, 7, (3168)), Gordon W. F. Drake

Physics Publications

No abstract provided.

Improved Anisotropy Measurement Of The Lamb Shift In He+, J. Patel, A. Van Wijngaarden, Gordon W. F. Drake

Physics Publications

An improved anisotropy measurement of the Lamb shift is obtained by means of a new method for the high-precision measurement of light intensities. The photon-counting techniques used in our previous work [Phys. Rev. A 20, 1299 (1979)] are replaced by the direct measurement of photoelectron currents with high-precision electrometers. Our new value for the Lamb shift in He+ is 14 041.91.5 MHz. This agrees with the earlier microwave resonance measurement of Lipworth and Novick [Phys. Rev. 108, 1434 (1957)], but lies clearly below the more recent measurement by Narasimham and Strombotne [Phys. Rev. A 4, 14 (1971)]. © 1987 The …

Non-Abelian Bosonization: Current Correlation Functions, Lowell S. Brown, Rafael I. Nepomechie

Physics Articles and Papers

We demonstrate that, in 1+1 dimensions, the effective action produced by massless fermions moving in external gauge potentials is identical with that produced by a suitably defined σ model which includes a Wess-Zumino term. Hence the current correlation functions of the fermion and boson theories are identical.

Non-Abelian Bosonization: Stress-Energy Correlation Functions, Lowell S. Brown, Gary J. Goldberg, Chaiho P. Rim, Rafael I. Nepomechie

Physics Articles and Papers

We demonstrate that, in 1+1 dimensions, the effective action produced by massless fermions moving in external gravitational and gauge fields is identical with that produced by a suitably defined σ model which includes a Wess-Zumino term. This equivalence holds provided that the two models have the same conformal anomaly, a condition that we investigate in detail.

Electron Paramagnetic Resonance Of Gd3+ Ions In The Superconductor Gdba2Cu3OX, F. Mehran, S. E. Barnes, C. C. Tsuei, T. R. Mcguire

Physics Articles and Papers

EPR from Gd³⁺ ions in the high-T_c≃90 K superconductor GdBa₂Cu₃O_x is reported. The temperature dependence of the linewidth and intensity of the Gd³⁺ ions in the vicinity of T_c are related to the corresponding characteristics of the Cu²⁺ ions.

Paramagnetic Resonance Of Cu2+ Ions In The Superconductor Y0.2Ba0.8CuoX, F. Mehran, S. E. Barnes, T. R. Mcguire, W. J. Gallagher, R. L. Sandstrom, T. R. Dinger, D. A. Chance

Physics Articles and Papers

A strong paramagnetic resonance signal characteristic of Cu²⁺ ions in ‖x²-y²〉 states is observed in the high-T_c≊90 K superconductor Y_0.2Ba_0.8CuO_x. The line intensity of the ioniclike signal shows a deviation from Curie behavior at T≳T_c. It is speculated that the phase that is responsible for the signal is an example of an Anderson lattice with an unusually high Kondo temperature.

Observation Of Al2O3: Cr3+ Magnetic Resonance Via Solitons In Long Josephson Junctions, F. Mehran, S. E. Barnes, C. C. Chi, R. L. Sandstrom, C. P. Umbach

Physics Articles and Papers

We have detected the zero-field electron-spin resonance signal of Al₂O₃ with ∼1000 ppm Cr³⁺ using an edge Josephson junction. The sample comprises the substrate upon which the junction was fabricated and the coupling to the electron-spin resonance is via the solitons which exist in these "long" devices.

The Aperiodic Crystal Picture And Free Energy Barriers In Glasses, Randall W. Hall, Peter G. Wolynes

Collected Faculty and Staff Scholarship

The aperiodic crystal picture associates the glass transition with freezing into a nonperiodic structure. Dynamics in the glassy state involves activated jumps between different aperiodic free energy minima. Activation barriers may be estimated through the use of freezing theory and the theory of dense solids. The results resemble, but are distinct from, free volume theory. Reasonable fits to experimental data are obtained.

Electronic Structure, Photoemission, And Magnetism In Gd2Co And Er2Co Glasses, Sitaram Jaswal, David J. Sellmyer, M. Engelhardt, Z. Zhao, A.J. Arko, K. Xie

David Sellmyer Publications

The electronic and magnetic structures of amorphous Gd₂Co and Er₂Co are studied by ultraviolet and x-ray photoemission measurements and band calculations. The spectra for both glasses show a band of Co 3d levels centered at a binding energy E_B of about -1.0 eV and peaks arising from 4f levels at E_B=-8.4 eV and E_Bapeq2-5–9 eV for Gd and Er, respectively. Magnetization data have shown that a-Gd₂Co possesses a ferrimagnetic structure with a small Co moment. The linear-muffin-tin-orbital method is used to perform self-consistent, spin-polarized calculations in …

Electron Transmission Study Of The Temporary Negative Ion States Of Selected Benzenoid And Conjugated Aromatic Hydrocarbons, Paul Burrow, J.A. Michejda, K.D. Jordan

Paul Burrow Publications

Electron transmission spectroscopy is utilized to determine the vertical electron affinities and to characterize the temporary anion states of a series of alternant hydrocarbons including benzene, naphthalene, anthracene, tetracene, styrene, and cis- and trans-stilbene. The vibrational structure present in the low lying resonances is interpreted in light of the charge distributions of the temporarily occupied orbitals. The energies of the anion states are compared with the predictions of PPP, PPP-CI, and HAM calculations, the pairing theorem and with the results from optical absorption measurements on the ground state anions in rigid glasses.

The Further Geometry Of Grain Boundaries In Hexagonal Close-Packed Metals, Fu-Rong Chen, Alexander H. King

Alexander H. King

A technique is given for finding partial DSC vectors appropriate to crystals with more than one atom per lattice site. The DSC lattice is made up of vectors that represent displacements of one crystal with respect to the other that leave the boundary structure shifted, but not complete. A new, rapid method for finding the step vectors associated with perfect DSC dislocations is described. Partial DSC vectors and step vectors for perfect DSC dislocations in hexagonal close-packed crystals are determined. The availability of reactions between lattice partial dislocations and grain boundaries in hexagonal close-packed crystals is also assessed.

Interaction Between Magnetic And Compositional Order In Ni‐Rich Ni C Fe1−C Alloys (Invited), J. B. Staunton, Duane D. Johnson, B. L. Gyorffy

Duane D. Johnson

We have developed a first‐principles electronic theory of concentration fluctuations in spin polarized binary alloys. It is a mean field theory of the state of compositional order and it is based on the local spin density (LSD) approximation for describing the electrons. The usual averages over the statistical mechanical ensemble are carried out with the aid of the self‐consistent Korringe–Kohn–Rostoker coherent‐potential approximation (SCF‐KKR‐CPA). To illustrate the main consequences of the theory we study the compositional short‐range order in the Ni c Fe1−c alloy system. We find that the ordering energy is almost entirely of magnetic origin.

Fluctuating Hydrodynamics In A Dilute Gas, Alejandro Garcia, G. Lie, E. Clementi

Faculty Publications

Hydrodynamic fluctuations in a dilute gas subjected to a constant heat flux are studied by both a computer simulation and the Landau-Lifshitz formalism. The latter explicitly incorporates the boundary conditions of the finite system, thus permitting quantitative comparison with the former. Good agreement is demonstrated.

Hydrodynamic Fluctuations In A Fluid Under Constant Shear, Alejandro Garcia, M. Malek Mansour, G. Lie, E. Clementi, M. Mareschal

Faculty Publications

No abstract provided.

Electrical Characterization Of Ion Implantation Into Gaas, David C. Look

Physics Faculty Publications

Recent advances in the characterization of ion‐implanted samples have included whole wafer mapping (topography) and depth profiling techniques. We review several methods for mapping electrical parameters, including the dark‐spot resistance (DSR), and the microwave photoconductance techniques. In addition, we suggest a new photo‐Hall technique which would allow mobility and carrier‐concentration mapping as well as that of resistivity . Finally, we review methods for obtaining ρ, μ, and depth profiles, with particular emphasis on the application of the magnetoresistance techniques in actual field‐effect transistor structures.

Fluctuating Hydrodynamics In A Dilute Gas, Alejandro Garcia, G. Lie, E. Clementi

Alejandro Garcia

Hydrodynamic fluctuations in a dilute gas subjected to a constant heat flux are studied by both a computer simulation and the Landau-Lifshitz formalism. The latter explicitly incorporates the boundary conditions of the finite system, thus permitting quantitative comparison with the former. Good agreement is demonstrated.