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Variational Methods For High-Order Multiphoton Processes, Bo Gao, Cheng Pan, Chih-Ray Liu, Anthony F. Starace

Anthony F. Starace Publications

Methods for applying the variationally stable procedure for N th-order perturbative transition matrix elements of Gao and Starace [Phys. Rev. Lett. 61, 404 (1988); Phys. Rev. A 39, 4550 (1989)] to multiphoton processes involving systems other than atomic H are presented. Three specific cases are discussed: one-electron ions or atoms in which the electron-ion interaction is described by a central potential; two-electron ions or atoms in which the electronic states are described by the adiabatic hyperspherical representation; and closed-shell ions or atoms in which the electronic states are described by the multiconfiguration Hartree-Fock representation. Applications are made to the dynamic …

Nonlocal Effects In Dissociative Electron Attachment To H2, D E. Atems, J M. Wadehra

Physics and Astronomy Faculty Research Publications

Electron scattering by diatomic molecules involving the formation of a single resonance is treated within the configuration-interaction formalism. A technique is presented for solving the resulting nonlocal integro-differential equation for the nuclear motion in the resonant state. This technique is applied to the scattering of electrons by molecular hydrogen (and its isotopes) via the formation of X^2 Σ^+_u resonance, using a semiempirical model for the resonant state. Numerical cross sections for dissociative attachment, to H_2, of electrons with energies below 5 eV are presented and compared both with available experimental data and with those obtained using the local approximation for …

Energy Deposition Of Energetic Silicon Atoms Within A Silicon Lattice, P. Zecher, D. Wang, J. Rapaport, C. Jeff Martoff, Betty A. Young

Physics

The energy dependence of the ionization produced in silicon by recoiling silicon atoms was measured in the 4–54-keV energy interval. It is found that the fraction of the recoil energy that is dissipated as ionization follows an E^1/2 dependence which agrees well with the predictions of the theory of Lindhard et al. [Mat. Fys. Medd. 33, 10 (1963)].

Polymerization On The Diamond Hierarchical Lattice: The Migdal-Kadanoff Renormalization-Group Scheme, Miron Kaufman, J. E. Touma

Physics Faculty Publications

The thermodynamics of the equilibrium polymerization model (grand-canonical ensemble of self-avoiding walks) in two dimensions is worked out by means of the Migdal-Kadanoff renormalization-group technique. This method involves renormalization-group flows in an eight-dimensional parameter space. At the critical point the number of relevant fields (positive exponents) is four. The leading exponent value differs by less than 1% from the (presumed) exact value. The results are exact for the polymerization problem defined on the diamond hierarchical lattice. Some results are peculiar to this lattice and are not expected to hold for Bravais lattices. For instance, the polymerized phase (infinite polymerization index) …

Chiral Phase Transition For Su(N) Gauge Theories Via An Effective Lagrangian Approach, Joseph Schechter, Francesco Sannino

Physics - All Scholarship

We study the chiral phase transition for vector-like SU(N) gauge theories as a function of the number of quark flavors N_f by making use of an anomaly-induced effective potential. We modify an effective potential of a previous work, suggested for N_f < N, and apply it to larger values of N_f where the phase transition is expected to occur. The new effective potential depends explicitly on the full \beta-function and the anomalous dimension \gamma of the quark mass operator. By using this potential we argue that chiral symmetry is restored for \gamma <1. A perturbative computation of \gamma then leads to an estimate of the critical value N_f^c for the transition.

Analytic Variational Method For Hamiltonian Lattice Gauge Theory In 3+ 1 Dimensions, Ming C. Huang, Mohammad W. Katoot

Aerospace, Physics, and Space Science Faculty Publications

We present an analytic d in 3 + 1 dimensions for Hamiltonian lattice gauge theory. This method is based on Batrouni's mean-plaquette method and space integration. The Abelianized Bianchi identities are used and a detailed study of the number of identities that are needed and the validity of this approximation is given. The we use is the product of single-plaquette wave functions. The guage group we consider here is SU(2), but the method is valid for any gauge theory. We apply this method to calculate the 0++ glueball mass, and, in addition, the results of the string tension (scaling is …

Photoluminescence Studies In Znxcd1-Xte Single Crystals, David D. Allred, Jesus González-Hernández, Elías López-Cruz, Worth P. Allred

Faculty Publications

The crystalline quality of ZnxCd1-xTe single crystals prepared by a modified Bridgman method with 0≤x≤0.05 has been analyzed using photoluminescence. The spectrum of a typical sample is dominated by lines originating from the recombination of free and bound excitons. Lines due to free excitons in their ground and first excited states are observed in both the pure CdTe and the mixed crystals. Excitons bound to Dc vacancies are observed in the pure CdTe crystal but not in the mixed crystal. Weaker and broader features appearing at energies below the exciton emission range were associated with transitions involving free-to-bound and bound-to-bound …

Hydrogen Adsorption On The Β N-Covered W(100) Surface: An Infrared Study Of The W–Hstretch, D. Mark Riffe, A. J. Sievers

All Physics Faculty Publications

The adsorption of hydrogen on the c(2×2) β-N-covered W(100) surface has been studied with infrared and thermal-desorption spectroscopies. A new dipole-active vibrational absorption due to chemisorbed hydrogen has been discovered. Its center frequency (1738 cm^-1 for minimal H₂ adsorption), isotopic dependence (1252 cm^-1 for D₂ adsorption and the existence of both lines for HD adsorption), absorption strength versus β-N coverage, and effective dynamic charge e^*/ε_∞≥0.12e lead to the assignment of the W-H stretch associated with a top-bonded H species. The vibration has been studied in detail on the highly ordered surface characterized …

Size‐Inconsistency Effects In Molecular Properties For States With Valence‐Rydberg Mixing: The Low‐Lying Π→Π∗ States Of Ethylene And Butadiene, Robert J. Cave

All HMC Faculty Publications and Research

Ab initio results for the low‐lying 1B1u states of ethylene are used to discuss size‐inconsistency effects on calculated molecular properties for states where valence‐Rydberg mixing is important. Results for the expectation value of x2, x being the coordinate perpendicular to the plane of the molecule, are presented from quasidegenerate variational perturbation theory and multireference configuration‐interaction calculations. These results are compared with values from previous studies. It is argued that size inconsistency in configuration‐interaction studies can have a significant effect on estimated molecular properties. Calculations on several low‐lying states of butadiene are also reported where similar size‐inconsistency effects are found.

Surface And Interface Free-Carrier Depletion In Gaas Molecular Beam Epitaxial Layers: Demonstration Of High Interface Charge, David C. Look, C. E. Stutz, K. R. Evans

Physics Faculty Publications

Molecular beam epitaxial GaAs layers of electron concentration 1.69×10¹⁷ cm⁻³, and various thicknesses d=0.25, 0.50, 1.00, and 2.00 μm, have been grown on semi‐insulating GaAs substrates and characterized by the Hall effect and capacitance‐voltage (C‐V) techniques. A plot of sheet Hall concentration n_s vs d gives accurate values of (N_D−N_A) and (w_s+w_i), the sum of the surface and interface free‐carrier depletion widths, respectively. The C‐V measurements verify the value of N_D−N_{A …}

Eta' To Eta Pi Pi Decay As A Probe Of A Possible Lowest-Lying Scalar Nonet, Joseph Schechter, Amir H. Fariborz

Physics - All Scholarship

We study the eta' to eta pi pi decay within an effective chiral Lagrangian approach in which the lowest lying scalar meson candidates sigma(560) and kappa(900) together with the f0(980) and a0(980) are combined into a possible nonet. We show that there exists a unique choice of the free parameters of this model which, in addition to fitting the pi pi and pi K scattering amplitudes, well describes the experimental measurements for the partial decay width of eta' to eta pi pi and the energy dependence of this decay. As a by-product, we estimate the a0(980) width to be 70 …

Corrugation In The Nitrogen-Graphite Potential Probed By Inelastic Neutron Scattering, F. Y. Hansen, L. W. Bruch, H. Taub, V. L. Frank, H. J. Lauter, John R. Dennison

All Physics Faculty Publications

Inelastic neutron spectra of the commensurate √3 ×3 herringbone monolayer phase of nitrogen physisorbed on the graphite (002) surface at low temperature have been compared with lattice dynamics calculations of the polycrystalline-averaged one-phonon coherent neutron cross section. The observed zone-center energy gap of ∼0.4 THz in the acoustic-phonon branches is a factor of 2 larger than calculated from central atom-atom potentials. We conclude that current models of the corrugation in the adatom substrate potential greatly underestimate the lateral restoring forces in this relatively simple molecular film.

Surface And Interface Free-Carrier Depletion In Gaas Molecular-Beam Epitaxial Layers: Demonstration Of High Interface Charge, David C. Look, C. E. Stutz, K. R. Evans

Physics Faculty Publications

Molecular beam epitaxial GaAs layers of electron concentration 1.69×10¹⁷ cm⁻³, and various thicknesses d=0.25, 0.50, 1.00, and 2.00 μm, have been grown on semi‐insulating GaAs substrates and characterized by the Hall effect and capacitance‐voltage (C‐V) techniques. A plot of sheet Hall concentration n_s vs d gives accurate values of (N_D−N_A) and (w_s+w_i), the sum of the surface and interface free‐carrier depletion widths, respectively. The C‐V measurements verify the value of N_D−N_{A …}

Quantum Measurement And Geometry, James Thomas Wheeler

All Physics Faculty Publications

A model for the interpretation of spacetime as a Weyl geometry is proposed, based on the hypothesis that a system moves on any given path with a probability which is inversely proportional to the resulting change in length of the system. The results of physical measurements are calculated as the product of Weyl-conjugate gauge-dependent probabilities for the detection of conjugate objects. Each probability, expressed as a Wiener integral, is the Green's function for a diffusion equation. If the line integral of the Weyl field equals the action functional divided by ℏ this equation provides the stochastic equivalent of the Schrödinger …

Perturbations Of Gravitational Instantons, Charles G. Torre

Aerospace, Physics, and Space Science Faculty Publications

Ashtekar's spinorial formulation of general relativity is used to study perturbations of gravitational instantons corresponding to finite-action solutions of the Euclidean Einstein equations (with a nonzero cosmological constant) possessing an anti-self-dual Weyl curvature tensor. It is shown that, with an appropriate "on-shell" form of infinitesimal gauge transformations, the space of solutions to the can be described in terms of an elliptic complex; the cohomology of the complex defines gauge-inequivalent perturbations. Using this elliptic complex we prove that there are no nontrivial solutions to the linearized instanton equation on conformally anti-self-dual Einstein spaces with a positive cosmological constant. Thus, the space …

Improved Resolution Of A 6m Torodial Grating Monochromator, G. K. Wertheim, J. E. Rowe, D. Mark Riffe, N. V. Smith

All Physics Faculty Publications

We report a modification of the AT&T Bell Laboratories 6m toroidal grating monochromator at the National Synchrotron Light Source at Brookhaven National Laboratory which provides greatly improved resolution at midrange without the use of a movable exit slit. This modification is based on detailed ray tracing calculation, using the precedures developed by Haber, Howells, and McKinney and Howells, modified to include the holographic correction terms to the focusing equations. To maintain the optimum resolution requires an exit slit assembly movable over a distance of ∼20 cm. However, we show that an additional fixed slit 16.8 cm closer to the grating …

Molecular View Of The Interfacial Adhesion In Aluminum‐Silicon Carbide Metal‐Matrix Composites, B. K. Rao, Puru Jena

Physics Publications

The binding energies, electron charge transfer,bond lengths, and core level shifts of Al‐Al, Al‐Si, Al‐C, and Si‐C dimers have been calculated self‐consistently using the linear combination of atomic orbitals‐molecular orbital theory. The exchange interactions are treated using the unrestricted Hartree–Fock theory and correlation corrections are included through the Möller–Plesset perturbation scheme up to fourth order. The results are used to understand the nature and strength of bonding at the interface of Al and SiC crystals. The strong bonding of Al‐C dimers compared to Al‐Al and Al‐Si is shown to be responsible for the aluminumcarbide formation at the interface. The charge …

Differential, Partial Cross Sections For Electron Excitation Of The Sodium 3p State, Xianming Han, G. W. Schwinn, A. Gallagher

Scholarship and Professional Work - LAS

Using a powerful laser-based experimental method, the cross section for electron excitation of Na(3S) atoms to the Na(3P) state has been decomposed into partial components with respect to changes in the spin and angular momentum of the atomic electron, and these partial cross sections are further reduced to their differential character with respect to the electron scattering angle. Partial, differential cross sections are reported for electron collision energies from threshold 2.1 to 3.6 eV, and compared to available calculations.

Theoretical Intensity-Dependent Response Of Nonlinear Periodic Structures, Paul A. Gohman, Gust Bambakidis, Robert J. Spry

Physics Faculty Publications

We have modeled the response of a nonlinear periodic structure by means of the Abelés 2×2 matrix method. Our structure differs from the usual rejection‐band filter designs, in that we have chosen the filter elements to be index matched in the absence of radiation, providing a rejection band that both grows and shifts as a function of incident intensity. The intensity output function of the model not only directly demonstrates optical bistability, but also limiting, switching, self‐pulsing, and chaos.

Rotational Symmetries Of Nuclear States: Spin Determinations In Advanced Laboratory, Wilfred J. Braithwaite

Journal of the Arkansas Academy of Science

An advanced laboratory experiment is described which shows the connection between the rotational symmetries of nuclear states and the assignments of spins to discrete nuclear states. Standard angular correlation methods were used to study the two sequential gamma ray transitions in each ⁶⁰Ni nucleus, populated by unobserved beta decays from a weak radioactive ⁶⁰Co source. The chosen electronics and detectors were inexpensive and easy to operate. This experiment was extended to introduce students to real-world data acquisition, using finite-geometry detectors, which resulted in enormously larger coincident data rates.

Review Of Hall Effect And Magnetoresistance Measurements In Gaas Materials And Devices, David C. Look

Physics Faculty Publications

The use of magnetic fields in the electrical characterization of semiconductor materials is familiar to everyone in the form of Hall‐effect measurements. However, there is another magnetic‐field‐based phenomenon, magnetoresistance (MR), which is highly useful but not nearly so familiar to the majority of workers. One of the unique features of MR measurements is their applicability to common device structures, in particular, field‐effect transistors (FETs) and contact‐resistance patterns. We will show how channel mobility information can be extracted from the MR data in metal‐semiconductor FETs (MESFETs) and modulation‐doped heterostructure FETs (MODFETs), and also how the material under ohmic contacts can be …

Reduced Form For The General-State Multicenter Integral From An Integro-Differential Transform, Jack C. Straton

Physics Faculty Publications and Presentations

In a previous paper Gaussian transforms were utilized to obtain the analytically reduced form for the class of multicenter integrals containing a product of hydrogenic orbitals for s states, Yukawa or Coulomb potentials, and plane waves. In the present paper a related transformation is developed for nonspherical functions, leading to the reduced form for multicenter integrals that include hydrogenic orbitals representing states of arbitrary angular momentum.

High-Velocity Limits For The Ratio Of Double To Single Ionisation Of Helium By Projectiles With Electrons, Y. D. Wang, Jack C. Straton, James H. Mcguire, R. D. Dubois

Physics Faculty Publications and Presentations

The ratio of total double to total single ionisation cross sections, R, by high velocity projectiles containing electrons is examined in the first Born approximation. For ionisation of helium by H+, H0 and He0 impact, it is found that t filt H+ < filt Ho < filt Heo . Connection with Bohr's free-collision model for collisions with projectile electrons is given.

Optimization And Thermodynamic Performance Measures Of A Class Of Finite Time Thermodynamic Cycles, Joseph D. Walters

Dissertations and Theses

Modifications to the quasistatic Carnot cycle are developed in order to formulate improved theoretical bounds on the thermal efficiency of certain refrigeration cycles that produce finite cooling power. The modified refrigeration cycle is based on the idealized endoreversible finite time cycle. Two of the four cycle branches are reversible adiabats, and the other two are the high and low temperature branches along which finite heat fluxes couple the refrigeration cycle with external heat reservoirs.

This finite time model has been used to obtain the following results: First, the performance of a finite time Carnot refrigeration cycle (FTCRC) is examined. In …

Cross Section, Robert Katz

Robert Katz Publications

In radiobiology the term cross section is used in ways that depart from its original physical meaning. Some of these conceptual extensions represent significant distortions of the original concept. These distortions lead to the misinterpretation of experimental findings.

Undergraduate Elementary Education Students’ Concepts Of Light, Deborah Lynn Orr

Dissertations and Theses @ UNI

The purpose of the study was to describe some ideas that future elementary school teachers have about light and shadows. Twenty-five freshmen and sophomores in elementary education were interviewed using the Interview-About-Instances technique developed by Osborne and Gilbert. Students were asked to explain specific instances of sources and non-sources of light, the distance light travels, and the role of light in vision. Students defined the word "shadow" and predicted where shadows could be in particular situations. The results of this study indicate that many students lack factual information or have misconceptions concerning light propagation. Fifty-six percent of the students in …

A Study Of The Hydration Properties Of Selected Laser Dye Aerosols Including Continuous-Flow Parallel Plate And Alternating-Gradient Thermal Diffusion Cloud Chamber Measurements In The High Supersaturation Regime, Donald E. Hagen, Max B. Trueblood, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Hydration Behavior of Aerosols made Up of Various Fluorescent Dyes when Exposed to Water Saturation or Supersaturated Conditions Has Been Studied. Critical Supersaturation Spectra Are Reported. the Dyes Are Found to Behave as High Molecular Weight Ionic Compounds that Obey Kohler Theory. their Relevant Kohler Parameters Are Measured. This Study Makes Use of and Compares Results from the Isothermal Hazecontinuous-Flowand Alternating-Gradient Thermal Diffusion Cloud Chambers. the Ability of the Continuous-Flow Thermal Diffusion Chamber to Operate Correctly at High Supersaturations is Shown. © 1990 Elsevier Science Publishing Co., Inc.

Oxidation-Reduction Behavior Of Undoped And Sr-Doped Lamno3: Defect Structure, Electrical Conductivity, And Thermoelectric Power, J. H. Kuo, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

Seebeck coefficient and electrical conductivity measurements were performed for undoped and Sr-doped LaMnO₃ as a function of temperature and oxygen partial pressure. The results of electrical conductivity showed typical p-type behavior. As reduction proceeded, the electrical conductivity of these LaMnO₃-based perovskites decreased with P 1 4O₂. The analysis of the electrical conductivity data was performed by extending the defect model from a previous thermogravimetric (TG) study. The measured Seebeck coefficients were found to be positive except for the most reducing conditions when the decomposition into multiple phases occurred. The Heikes formula was adopted to interpret …

State-Selective Capture In Collisions Between Ions And Ground- And Excited-State Alkali-Metal Atoms, J. Pascale, Ronald E. Olson, C. O. Reinhold

Physics Faculty Research & Creative Works

Total cross sections for state-selective electron capture in collisions between ions and alkali-metal atoms have been calculated by means of a three-body classical-trajectory Monte Carlo (CTMC) method using model potentials to describe the electron ionic-core interactions. Calculations have been performed for Na⁺-Na(28d) collisions and for N⁵⁺ and Ar⁸⁺-Cs(6s) collisions. The collision velocity range corresponds to 0.5vp/ve2, where vp is the projectile velocity in the laboratory frame and ve is the initial orbital velocity of the electron bound to the alkali-metal core. In the case of Na₊+Na(28d) collisions, calculations of the final n,l,m distributions …

Experimental And Theoretical Study Of The Electron Spectra In 66.7350-Kev/U C++He Collisions, L. H. Toburen, R. (Robert) D. Dubois, C. O. Reinhold, D. R. Schultz, Ronald E. Olson

Physics Faculty Research & Creative Works

Measurements of the differential and total cross sections for production of free electrons are reported for collisions of 66.7350-keV/u C+ ions with He. The experimental data are compared with theoretical calculations that include electron emission from both target and projectile using the classical-trajectory Monte Carlo method and the independent-electron approximation. Good agreement is observed between theory and experiment, and structures appearing in the electron spectra can be explained in terms of either, or both, target and projectile ionization. © 1990 The American Physical Society.