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Excitation Of Morphology-Dependent Resonances And Van De Hulst's Localization Principle, James A. Lock

Physics Faculty Publications

When a laser beam scatters from a microparticle whose shape deviates from that of a sphere, a number of partial waves of the incident beam couple to a given partial wave of the scattered and interior fields. As a result, partial-wave coupling caused by small surface irregularities of a liquid droplet provides the mechanism for exciting low-radial-order morphology-dependent resonances. (C) 1999 Optical Society of America.

Reviews Of Atomic Audit: The Costs And Consequences Of Us Nuclear Weapons Since 1940 By Stephen Schwartz; And Killing Detente: The Right Attacks The Cia By Anne Cahn, David W. Hafemeister

Physics

Science aims to link cause and effect for natural phenomena. Linking cause and effect for historical events is often more difficult since historical events cannot be tested by rerunning history with varied parameters. Despite the difficulty, it is worthwhile to review the causes behind the magnitude of the U.S. nuclear buildup. Two critical questions should guide this analysis: How much of the $5.8 trillion (1996 dollars) that the U.S spent to build 70,000 nuclear warheads, deployed on 75,000 missiles and 8600 bombers, was too much? And, was the effectiveness of the Soviet military exaggerated with false predictions? These two books …

Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans

Theses and Dissertations

Multiplexed Compton Scatter Tomography (MCST) is explored as a method of nondestructively generating cross-sectional images of a sample's electron density. MCST is viable when access is available to only one side of the sample because it registers scattered gamma radiation. Multiplexing in scattered photon energy and in detector position allows simultaneous interrogation of many voxels with comparatively wide collimation. Primary components include a radioisotope source, fan beam collimators, and energy-discriminating detectors. The application of MCST to inspecting aluminum airframes for corrosion is considered. This application requires source gammas near 100 keV where the scattered gamma energy is severely broadened by …

Performance Of Sinusoidally Deformed Hydrophone Line Arrays, Deanna M. Caveny, Donald R. Del Balzo, James H. Leclere, George E. Ioup

Physics Faculty Publications

It is well known that array deformations can distort beam patterns and introduce bearing errors if the beamformer assumes linearity. It is also known that deformed arrays can resolve left–right ambiguities, provided the shape is known. In this work, these two effects are studied for undamped and damped sinusoidally deformed arrays with small deformation amplitudes in the horizontal (x,y) plane only. By use of fixed arc-length separations along the array, the hydrophone (x,y) coordinates are determined numerically and the error in assuming equal x spacing is summarized for a sample array. Array-response …

Periodicity And Disorder, Simeon D. Simeonov

Dissertations

We have studied four examples of periodicity and disorder in nature and the phenomena associated with them.

In the first chapter of the dissertation we present an introduction to this work.

In the second chapter, the photonic band structures of two types of zinc blend structures are computed using the plane wave expansion method. Both structures are formed from an array of dielectric spheres in a vacuum background. In a first type zinc blend structure the spheres have the same size but different dielectric constants. In a second type of structure we keep the dielectric contrast of the spheres the …

In Situ Measurement Of The Aerosol Size Distribution In Stratospheric Solid Rocket Motor Exhaust Plumes, Martin N. Ross, Philip D. Whitefield, Donald E. Hagen, Alfred R. Hopkins

Chemistry Faculty Research & Creative Works

The concentration and size distribution of aerosol in the stratospheric exhaust plumes of two Space Shuttle rockets and one Titan IV rocket were measured using a two component aerosol sampling system carried aboard a WB‐57F aircraft. Aerosol size distribution in the 0.01 µm to 4 µm diameter size range was measured using a two component sampling system. The measured distributions display a trimodal form with modes near 0.005 µm, 0.09 µm, and 2.03 µm and are used to infer the relative mass fractionation among the three modes. While the smallest mode has been estimated to contain as much as 10% …

Development And Testing Of An Ac Micro Hollow Cathode Simulator, Thomas E. Caldwell

Electrical & Computer Engineering Theses & Dissertations

The use of AC source plasma discharge devices in applications such as material processing and film deposition has increased in recent years due to improvements in discharge efficiency made possible by devices such as the micro hollow cathode. Designing hollow cathodes for specific applications requires an understanding of the processes that govern the discharge. Simulation is an inexpensive tool for understanding hollow cathode operation and optimizing the device for specific applications. This thesis describes the development of an AC micro hollow cathode simulator. It details the theoretical models used in the simulation and presents the results of test cases intended …

Virtual Compton Scattering Processes In Quantum Chromodynamics, Igor V. Musatov

Physics Theses & Dissertations

Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual Parton distributions for the case when long-distance information is accumulated in nonforward matrix elements [special characters omitted] of quark and gluon light-cone operators. We consider different aspects of the investigation of the virtual Compton amplitude in the QCD on two examples: the spin dependent observables in the forward virtual Compton process (measured in the experiments on deep inelastic scattering) and the γγ* transition form factor. Then we discuss in detail evolution equations for non-forward parton distributions [special characters omitted] The …

Binary Nucleation Kinetics. Iv. Directional Properties And Cluster Concentrations At The Saddle Point, Gerald Wilemski

Physics Faculty Research & Creative Works

Using a new approach, Stauffer's expression for the rate of steady state binary nucleation and Trinkaus's expression for the steady state cluster concentrations f are derived directly from the diffusion equation that governs the evolution of f in composition space. The behavior of φ (≡f/N, where N is the equilibrium cluster concentration) is explored since this function provides a characterization of the nucleating binary system that, to lowest order, is independent of the actual composition of the mother phase. The angle ω that describes the direction of ▽ φ at the saddle point differs, in general, from the angle φ …

Fiber-Optic Coupled Lidar Receiver System To Measure Stratospheric Ozone, David Brent Harper

Electrical & Computer Engineering Theses & Dissertations

A fiber-optic coupled lidar receiver system was constructed to determine ozone concentrations in the stratosphere. The system was used to make ground-based measurements of lidar returns from a UV DIAL system. A fiber-optic cable was used to couple the light from the receiver telescope to the light detector. Photon counting was implemented as the light detection technique. This technique allowed detection of 301 and 311 nm lidar returns up to 27.5 and 32.5 km respectively. A software application was developed to control the photon counting system and perform real-time data analysis of measured lidar returns. DIAL measurements of stratospheric ozone …

State To State Ne-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane

Peer Reviewed Articles

Measurements of state-to-state integral cross sections for rotational excitation of CO by collisions with Ne are reported. The measurements were performed in crossed molecular beams with resonance enhanced multiphoton detection at collision energies of 711 and 797 cm^-1. The cross sections display strong interference structure, with a propensity for odd Δj below Δj=10. Predictions of the ab initio potential surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)] and the new ab initio surface of McBane and Cybulski [J. Chem. Phys. 110, 11734 (1999), preceding paper] are compared to the …

An Ab Initio Potential Energy Surface For The Ne-Co, George C. Mcbane, Slawomir M. Cybulski

Peer Reviewed Articles

A new ab initio two-dimensional potential energy surface for the Ne-CO interaction is described. The surface was obtained by the supermolecule method at the CCSD(T) level of theory. It is compared with several experimental data sets and with the symmetry-adapted perturbation theory (SAPT) surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)]. The new surface gives modestly better predictions of experimental results that depend on close approach of Ne to CO, but does not describe the ground state geometry as well as the SAPT surface.

The Cleo-Iii Rich Detector And Beam Test Results, Raymond Mountain, J.C. Wang, Marina Artuso, R. Ayad

Physics - All Scholarship

We are constructing a Ring Imaging Cherenkov detector (RICH) for the CLEO III upgrade for precision charged hadron identification. The RICH uses plane and sawtooth LiF crystals as radiators, MWPCs as photon detectors with TEA as the photo-sensitive material, and low-noise Viking readout electronics. Results of a beam test of the first two out of total 30 sectors are presented.

Magnetic-Field-Induced Intensity Revivals In Harmonic Generation, Dejan B. Miloševic, Anthony F. Starace

Anthony F. Starace Publications

We demonstrate control of high harmonic generation by a linearly polarized laser field using a uniform static magnetic field parallel to the laser polarization. We predict that particular values of the magnetic field can increase harmonic intensities by orders of magnitude. Classical orbit calculations show that these magnetic-field-induced intensity revivals occur when the return time for laser-driven motion of the electron back to the origin is a multiple of the cyclotron period for motion perpendicular to the laser polarization direction.

Temperature Dependence Of Stark Width Of The 463.054 Nm Nii Spectral Line, Vladimir Milosavljevic, Ruzica Konjevic, Stevan Djenize

Articles

Stark width of the 463.054 nm singly ionized nitrogen spectral line, that belong to transition, have been measured in a linear pulsed, low pressure, arc discharge. The working gas was helium-nitrogen-oxygen mixture. Electron densities of 0.7510²³ to 1.4510²³ were determined in the electron temperature range between 30000 K - 38000 K. The measured values have been compared with our calculated data, using the modified semiempirical approximation. On the basis of the agreement among experimental and theoretical Stark width data, the isolated 463.054 nm NII spectral line can be recommended as convenient spectral line for plasma diagnostics.

Renormalized Effective Qcd Hamiltonian: Gluonic Sector, David G. Robertson, E.S. Swanson, A.P. Szczepaniak, C.R. Ji, S.R. Cotanch

Physics Faculty Scholarship

Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which generates an effective Hamiltonian for the gluon sector. The formulation is in the Coulomb gauge where the QCD Hamiltonian is renormalizable and the Gribov problem can be resolved. We utilize elements of the Głazek and Wilson regularization method but now introduce a continuous cut-off procedure which eliminates non-local counterterms. The effective Hamiltonian is then derived to second order in the strong coupling constant. The resulting renormalized Hamiltonian provides a realistic starting point for approximate many-body calculations of hadronic properties for systems with explicit gluon degrees of freedom.

Search For New Particles Decaying To Bb̅ In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have used 87 pb^-1 of data collected with the collider detector at Fermilab to search for new particles decaying to bb̅. We present model-independent upper limits on the cross section for narrow resonances which exclude the color-octet technirho in the mass interval 350 < M < 440 GeV/c². In addition, we exclude top-gluons, predicted in models of top-color-assisted technicolor, of width Γ= 0.3M in the mass range 280 < M < 670 GeV/c², of width Γ= 0.5M in the mass range 340 < M < 640 GeV/c², and of width Γ= 0.7M in the mass range 375 < M < 560 GeV/c².

Mirroring Behavior Of Partial Photodetachment And Photoionization Cross Sections In The Neighborhood Of A Resonance, Chien-Nan Liu, Anthony F. Starace

Anthony F. Starace Publications

Partial photodetachment and photoionization cross sections corresponding to highly excited residual atoms or ions are shown analytically to mirror one another in the neighborhood of a resonance. More precisely, any two groupings of partial cross sections are shown here to have components whose variations with energy near a resonance are equal in magnitude and opposite in direction. This work extends an analysis of Starace [Phys. Rev. A 16, 231 (1977)] for the behavior of partial cross sections near a resonance to the case when the ρ2 parameter of Fano and Cooper [Phys. Rev. 137, A1364 (1965)] tends to zero.

Parity Nonconservation In Neutron Resonances In 133cs, E I. Sharapov, J D. Bowman, Bret E. Crawford, P P J. Delheij, T Haseyama, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Spatial parity nonconservation (PNC) has been studied in the compound-nuclear states of ¹³⁴Cs by measuring the helicity dependence of the neutron total cross section. Transmission measurements on a thick ¹³³Cs target were performed by the time-of-flight method at the Manuel Lujan Neutron Scattering Center with a longitudinally polarized neutron beam in the energy range from 5 to 400 eV. A total of 28 new p-wave resonances were found, their neutron widths determined, and the PNC longitudinal asymmetries of the resonance cross sections measured. The value obtained for the root-mean-square PNC element M=(0.06_-0.02^+0.25) meV in ^{133 …}

Megamaser Disks In Active Galactic Nuclei, John F. Kartje, Arieh Königl, Moshe Elitzur

Physics and Astronomy Faculty Publications

Recent spectroscopic and VLBI-imaging observations of bright extragalactic H₂O maser sources have revealed that the megamaser emission often originates in thin circumnuclear disks near the centers of active galactic nuclei (AGNs). Using general radiative and kinematic considerations and taking account of the observed flux variability, we argue that the maser emission regions are clumpy, a conclusion that is independent of the detailed mechanism (X-ray heating, shocks, etc.) driving the collisionally pumped masers. We examine scenarios in which the clumps represent discrete gas condensations (i.e., clouds) and do not merely correspond to velocity irregularities in the disk. We show …

Residual Native Shallow Donor In Zno, David C. Look, Joseph W. Hemsky, J. R. Sizelove

Physics Faculty Publications

High-energy electron irradiation in ZnO produces shallow donors at about E_C-30meV. Because the production rate is much higher for Zn-face (0001) than O-face (0001̅ ) irradiation, the donor is identified as a Zn-sublattice defect, most likely the interstitial Zn_I or a Zn_I-related complex. The donor energy is quite close to that of the unirradiated sample, and of other samples discussed in the literature, strongly suggesting that Zn_I (and not V_O) is the dominant native shallow donor in ZnO. An exceptionally high displacement threshold energy (∼1.6MeV) is quantitatively explained in terms of a …

Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts

Theses and Dissertations

The Multiplexed Compton Scatter Tomograph (MCST) uses single back-scattered photons to image electron density in aluminum. A source of error in this imaging technique is the presence of multiple scatters. This thesis studies the double scatter spectrum as an approximation of the multiple scatter spectrum. A deterministic code called Monte Carlo Double Scatter (MOCADS) was developed to investigate the double scatter spectrum. The code includes calculations of the Rayleigh scatter, Compton scatter, Doppler broadening effects of the spectrum, and polarization effects following the Compton scatter. The Doppler broadening portion of the code was validated by a deterministic code called Scatgram. …

Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil

Theses and Dissertations

This laboratory thesis investigated the applicability of reflectance spectroscopy as a tool to measure desorption rates by directly observing the change in trichloroethylene bound to surface sites. Diffuse reflectance spectroscopy holds the promise of being a faster technique with minimal sample preparation time. Reflectance spectroscopy's dependence on the surface of the sample is its greatest advantage, as well as its greatest disadvantage. Both high and low resolution scans were made of different soil samples contaminated by trichloroethylene. After the technique of spectral subtraction was used, potential TCE signals were observed from the dolomitic limestone sample. Unfortunately, due to the low …

Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath

Theses and Dissertations

Electrical characterization has been performed on ion-implanted p-type 4H-SiC to assess the activation efficiency and implantation-related damage recrystallization with the intention of developing an implantation/annealing scheme. Low doped (Na - Nd = 5x10¹⁵cm³ epitaxial p-type layers grown by MOCVD were implanted with Al or B at doses ranging from 1x10¹³ to 1x10¹⁴/cm² at room temperature or 500°C. The electrical technique of Temperature Dependent Hall Effect (TDHE) indicated that Al and B act as shallow acceptors 4H-SiC with ionization energies of ~252 and ~285 meV, respectively. The highest activation efficiency for Al and B …

Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday

Theses and Dissertations

Initial efforts to characterize the scattering dynamics of B + H₂ focus on computing scattering matrix elements for the fine structure transition B (²P_1/2) --> B (²P_3/2) in collisions with H₂, allowing for rotational excitation. Using a new application of the time dependent Channel Packet Method (CPM), reactant and product wave packets are prepared in the asymptotic limit on the B (²P_1/2) and B (²P_3/2) surfaces. They are propagated using the split operator method together wit a unitary transformation between the …

Band Structure Anisotropy In Semiconductor Quantum Wells, Steven J. Novotny

Theses and Dissertations

The focus of this research is an investigation of energy band anisotropy in simple quantum well structures. This anisotropy results from the asymmetry of the periodic potential within the crystal lattice. For sufficiently high doping levels, band structure anisotropy is expected to play an important role in the evaluation of the electronic and optical properties of the quantum well structures. The analysis uses a model based on a 6x6 Luttinger-Kohn k.p approach for bulk material valence band structure together with the Envelope Function Approximation. The model is used to analyze Si/SiGe, AlGaAs/GaAs, and GaAs/InGaAs quantum wells for the 001 and …

Laser Beam Combining And Cleanup Via Stimulated Brillouin Scattering In Multi-Mode Optical Fibers, Blake C. Rodgers

Theses and Dissertations

The main objective of this thesis was to demonstrate the feasibility of combining and cleaning up multiple laser beams via Stimulated Brillouin Scattering (SBS) in a multi-mode optical fiber. Beam combining via SBS in an optical fiber is of interest because of the low SBS threshold power in an optical fiber allowing low power diode laser beams to be combined into one high power beam. SBS theory and some of the important historical results are described briefly. The experimental results clearly indicate that SBS in multi-mode optical fiber can indeed combine laser beams and clean up the beams at the …

A Continuous Wave Atomic Bromine Laser Produced By Photolysis Of Iodine Monobromide, Brian A. Smith

Theses and Dissertations

An apparatus to generate continuous wave (CW) lasing at 2.714 µm by Br(²P_1/2) atoms produced from photodissociation of IBr was designed, constructed and tested. A frequency doubled Nd:YAG laser firing 8 ns, 850 mJ pulses at 532 nm was used to photodissociate static IBr vapor inside a flow nozzle. The CaF₂ windows on either side of the nozzle proved to have a damage threshold below the threshold for lasing. Pulsed lasing in static mode was not observed. Therefore, CW lasing in flow mode, using an Ar⁺ laser at 488 nm, could not be investigated.

Numerical Solutions To The Two Dimensional Boltzmann Equation, Christopher G. Smithtro

Theses and Dissertations

A strict kinetic, two-dimensional model of the electron kinetics within a glow discharge positive column is developed. The problem is solved in cylindrical geometry using the standard two-term Legendre expansion of the electron velocity distribution function. The model establishes a steady state solution, such that the net ionization rate is exactly balanced by the wall loss. In addition to a thorough analytic development, we present the numerical techniques used to solve the resulting elliptic partial differential equation, including an efficient method to treat sparse banded matrices. The model is validated against published results, local and nonlocal kinetic approximations, and a …

Space Charge Structure Of A Glow Discharge In The Presence Of A Longitudinal Inhomogeneity, Frank A. Tersigni

Theses and Dissertations

A survey of space charge structures arising due to inhomogeneities in glow discharges was conducted. Space charge structures associated with tube geometries, the cathode sheath, striations, and shockwaves were examined. Space charge effects on the Electron Energy Distribution Function (EEDF) were explored for a geometric inhomogeneity using an approximate nonlocal solution to the one dimensional Boltzmann equation after Godyak. The approximate solution partially captured qualitative aspects of space charge effects on the EEDF. Simplification of collisional effects and adaptation of an approximate electric field restricted quantitative comparisons with experimental data. It is recommended that any future analysis of space charge …