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2009

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Articles 1 - 30 of 907

Full-Text Articles in Physics

Differential Cross Sections And Spin Density Matrix Elements For The Reaction Γp→Pω, M. Williams, Gerard P. Gilfoyle, Et. Al. Dec 2009

Differential Cross Sections And Spin Density Matrix Elements For The Reaction Γp→Pω, M. Williams, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

High-statistics differential cross sections and spin-density matrix elements for the reaction γp → pω have been measured using the CEBAF large acceptance spectrometer (CLAS) at Jefferson Lab for center-of-mass (c.m.) energies from threshold up to 2.84 GeV. Results are reported in 112 10-MeV wide c.m. energy bins, each subdivided into cos θωc.m. bins of width 0.1. These are the most precise and extensive ω photoproduction measurements to date. A number of prominent structures are clearly present in the data. Many of these have not previously been observed due to limited statistics in earlier measurements.

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Partial Wave Analysis Of The Reaction Γp→Pω And The Search For Nucleon Resonances, M. Williams, Gerard P. Gilfoyle, Et. Al. Dec 2009

Partial Wave Analysis Of The Reaction Γp→Pω And The Search For Nucleon Resonances, M. Williams, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

An event-based partial wave analysis (PWA) of the reaction γp → pω has been performed on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world’s first high-precision spin-density matrix element measurements, available to the event-based PWA through the decay distribution of ω → π +π −π0. The data confirm the dominance of the t-channel π0 exchange amplitude in the forward direction. The dominant resonance contributions are consistent with the previously identified states F15(1680) and …

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Equalization Of Loudspeakers And Enclosed Sound Fields, Xi Chen Dec 2009

Equalization Of Loudspeakers And Enclosed Sound Fields, Xi Chen

Theses and Dissertations

Equalization of loudspeakers and enclosed sound fields has been a topic of considerable interest for decades. Confusion has often arisen among audio professionals regarding the feasibility of simultaneously equalizing a loudspeaker and the enclosed field (i.e., the “room”) it excites. Because of frustrations encountered in such efforts, some have advocated abandoning simultaneous equalization altogether. This dissertation discusses the drawbacks of this approach as well as traditional in situ equalization methods. It demonstrates that many problems with traditional equalization stem from the use of measured acoustic pressure at a discrete point in a sound field as the system output. The dissertation …

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A High-Yield Synthesis Of Chalcopyrite Cuins2 Nanoparticles With Exceptional Size Control, Aaron Thurber, Alex Punnoose Dec 2009

A High-Yield Synthesis Of Chalcopyrite Cuins2 Nanoparticles With Exceptional Size Control, Aaron Thurber, Alex Punnoose

Physics Faculty Publications and Presentations

We report high-yield and efficient size-controlled syntheses of Chalcopyrite CuInS2 nanoparticles by decomposing molecular single source precursors (SSPs) via microwave irradiation in the presence of 1,2-ethanedithiol at reaction temperatures as low as 100◦C and times as short as 30 minutes. The nanoparticles sizes were 1.8nm to 10.8 nm as reaction temperatures were varied from 100◦C to 200◦C with the bandgaps from 2.71 eV to 1.28 eV with good size control and high yields (64%–95%). The resulting nanoparticles were analyzed by XRD, UV-Vis, ICP-OES, XPS, SEM, EDS, and HRTEM. Titration studies by 1H NMR using SSP 1 with 1,2-ethanedithiol …

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Single Ionization Of Ne, Ar And Kr By Proton Impact: Single Differential Distributions In Energy And Angle, Sebastian Otranto, J. E. Miraglia, Ronald E. Olson Dec 2009

Single Ionization Of Ne, Ar And Kr By Proton Impact: Single Differential Distributions In Energy And Angle, Sebastian Otranto, J. E. Miraglia, Ronald E. Olson

Physics Faculty Research & Creative Works

Synopsis in this work we present a theoretical study of singly differential cross sections in energy and angle for the single ionization of neon, argon and krypton by proton impact. Theoretical results obtained by means of the Continuum Distorted Wave-Eikonal initial state (CDW-EIS) model are compared to those provided by the First-Born Approximation (FBA) and the classical trajectory Monte Carlo (CTMC) method as well as to experimental data from several laboratories. We note in particular for argon, that the CDW-EIS model does not reproduce the experimental data as accurately as expected, while the CTMC instead is in very good agreement.

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Theoretical & Experimental (E,2e) Studies For Electron Impact Ionization Of Argon Measured In The Perpendicular Plane, Ola Al-Hagan, Christian Kaiser, Andrew Murray, Don H. Madison Dec 2009

Theoretical & Experimental (E,2e) Studies For Electron Impact Ionization Of Argon Measured In The Perpendicular Plane, Ola Al-Hagan, Christian Kaiser, Andrew Murray, Don H. Madison

Physics Faculty Research & Creative Works

FDCS for electron impact ionization of the Argon atom with equal energy outgoing electrons ranging from 1 eV to 25 eV are studied in the perpendicular plane.

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Theoretical Fully Differential Cross Sections For Transfer-Excitation Collisions, A. L. Harris, Jerry Peacher, Michael Schulz, Don H. Madison Dec 2009

Theoretical Fully Differential Cross Sections For Transfer-Excitation Collisions, A. L. Harris, Jerry Peacher, Michael Schulz, Don H. Madison

Physics Faculty Research & Creative Works

Synopsis Transfer-excitation calculations from a full four-body theoretical model will be compared with experiment.

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Double Differential Projectile Angular Distributions For Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, A. C. Laforge, K. Egodapitiya, J. S. Alexander, A. Hasan, Michael Schulz Dec 2009

Double Differential Projectile Angular Distributions For Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, A. C. Laforge, K. Egodapitiya, J. S. Alexander, A. Hasan, Michael Schulz

Physics Faculty Research & Creative Works

Synopsis Doubly differential cross sections (DDCSp) for single ionization of atomic hydrogen by 75-keV proton impact as a function of the projectile scattering angle and energy loss have been measured.

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New Double Ionization Channel Uncovered In Four-Particle Dalitz Plots, Michael Schulz, M. F. Ciappina, T. Kirchner, D. Fischer, R. Moshammer, J. Ullrich Dec 2009

New Double Ionization Channel Uncovered In Four-Particle Dalitz Plots, Michael Schulz, M. F. Ciappina, T. Kirchner, D. Fischer, R. Moshammer, J. Ullrich

Physics Faculty Research & Creative Works

Synopsis Double ionization in 6 MeV p + He collisions was analyzed in terms of 4-particle Dalitz plots.

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Minima In The Triple Differential Cross Sections For The Electron-Impact Ionization Of Helium, J. Colgan, C. Kaiser, A. J. Murray, O. Al-Hagan, Don H. Madison, M. S. Pindzola Dec 2009

Minima In The Triple Differential Cross Sections For The Electron-Impact Ionization Of Helium, J. Colgan, C. Kaiser, A. J. Murray, O. Al-Hagan, Don H. Madison, M. S. Pindzola

Physics Faculty Research & Creative Works

We examine unusual minima found in the triple differential cross sections for the electron-impact ionization of helium for configurations where the incident electron is out-of-plane with respect to the plane in which the outgoing electrons are detected. the position of the experimentally determined minima are confirmed by time-dependent close-coupling calculations. an analysis is made of the origin of the minima in the cross section, where it is found they are due to deep destructive interference between the partial-wave amplitudes which contribute to the differential cross section.

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Longitudinal Recoil Ion Momentum Distributions For Proton-Argon Ionizing Collisions At Intermediate Energies, S. Otranto, Ronald E. Olson Dec 2009

Longitudinal Recoil Ion Momentum Distributions For Proton-Argon Ionizing Collisions At Intermediate Energies, S. Otranto, Ronald E. Olson

Physics Faculty Research & Creative Works

Synopsis Proton-argon ionizing collisions at intermediate energies are studied by means of the classical trajectory Monte Carlo method (CTMC). in particular, we focus on the longitudinal and transverse recoil momentum distributions for the process. We compare the profile of the longitudinal momentum distribution at the abrupt rise region corresponding to the electron capture to the continuum (ECC) processes, with those obtained for simpler targets like H and He. Selected subsets of the data show that the recoiling multielectronic ion plays a major role in the low energy electron emission, influencing the angular asymmetry of the electronic emission.

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Triply Differential Measurements For 200 Ev E⁺-And E--Ar Collisions, O. G. De Lucio, Robert D. Dubois Dec 2009

Triply Differential Measurements For 200 Ev E⁺-And E--Ar Collisions, O. G. De Lucio, Robert D. Dubois

Physics Faculty Research & Creative Works

Triply differential single ionization yields for projectile scattering and electron emission are presented for 200 eV positron and electron impact ionization of argon. the projectile scattering and the electron emission are observed to be different for positron and electron impact.

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Exploring Differences Of Atomic And Molecular Ionization By Electron Impact, X. Ren, A. Senftleben, T. Pflüger, A. Dorn, I. Bray, D. V. Fursa, J. Colgan, M. S. Pindzola, O. Al-Hagan, Don H. Madison, J. Ullrich Dec 2009

Exploring Differences Of Atomic And Molecular Ionization By Electron Impact, X. Ren, A. Senftleben, T. Pflüger, A. Dorn, I. Bray, D. V. Fursa, J. Colgan, M. S. Pindzola, O. Al-Hagan, Don H. Madison, J. Ullrich

Physics Faculty Research & Creative Works

Electron impact single ionization of helium and the hydrogen molecule is studied at equivalent electron kinematics to explore the differences of atomic and molecular ionization. Fully differential cross sections (FDCS) were obtained covering the whole solid angle in order to critically test theoretical calculations.

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Classical Modeling Of Non-Sequential Double Ionization: Recollision, Time-Delayed Ionization, Drift, And Possible Reattachment, Stanley L. Haan, Z. S. Smith, K. N. Shomsky, P. W. Plantinga Dec 2009

Classical Modeling Of Non-Sequential Double Ionization: Recollision, Time-Delayed Ionization, Drift, And Possible Reattachment, Stanley L. Haan, Z. S. Smith, K. N. Shomsky, P. W. Plantinga

University Faculty Publications and Creative Works

We employ 3d classical ensembles to study Non-Sequential Double Ionization (NSDI) of atoms by strong laser fields at visible and infrared wavelengths. We consider in particular the wavelength dependence of final electron drift directions and the net momentum spectra parallel to the laser polarization. We find that as the wavelength is increased the spectrum transitions from a singlet to a doublet, then to a triplet, and finally back to a doublet. We also show that electrons that escape the central potential-energy well during the pulse may nonetheless be bound to the nucleus after laser turnoff.

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Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom Dec 2009

Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom

University Faculty Publications and Creative Works

Photoassociation spectra for purely long-range (PLR) krypton molecules are both computed and measured. The photoassociation laser is tuned just red of the 5s[3/2]2-5p[5/2]2 transition at 810.6 nm, over a frequency range in which fourteen different PLR potential wells support hundreds of vibrational bound states. In the experiment, laser light is directed into a cloud of magneto-optically trapped 84Kr atoms, and the emission of both ultraviolet photons and ions is monitored. Peaks in these signals are observed for laser frequencies within 200 MHz of the atomic resonance. Ongoing work is aimed at improving the experimental signal and understanding the degree of …

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Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom Dec 2009

Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom

University Faculty Publications and Creative Works

Photoassociation spectra for purely long-range (PLR) krypton molecules are both computed and measured. The photoassociation laser is tuned just red of the 5s[3/2]2-5p[5/2]2 transition at 810.6 nm, over a frequency range in which fourteen different PLR potential wells support hundreds of vibrational bound states. In the experiment, laser light is directed into a cloud of magneto-optically trapped 84Kr atoms, and the emission of both ultraviolet photons and ions is monitored. Peaks in these signals are observed for laser frequencies within 200 MHz of the atomic resonance. Ongoing work is aimed at improving the experimental signal and understanding the degree of …

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Electron Impact Ionization And Fragmentation Of C2h2, A. C.F. Santos, Robert D. Dubois, E. C. Montenegro Dec 2009

Electron Impact Ionization And Fragmentation Of C2h2, A. C.F. Santos, Robert D. Dubois, E. C. Montenegro

Physics Faculty Research & Creative Works

Ionization and fragmentation of C2H2 resulting from 750 eV electron impact is measured as a function of electron loss. Electron losses up to 400 eV are investigated. the interaction kinematics are investigated by measuring ejected electron-C2H2+ ion-scattered projectile coincidences and generating triply and doubly differential yields for the electron emission and projectile scattering respectively.

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Fully Differential Cross Sections For The Single Ionization Of Argon By Positron Impact At Intermediate Energies, Sebastian Otranto, Ronald E. Olson Dec 2009

Fully Differential Cross Sections For The Single Ionization Of Argon By Positron Impact At Intermediate Energies, Sebastian Otranto, Ronald E. Olson

Physics Faculty Research & Creative Works

In this work, we present theoretical fully differential cross sections (FDCS) for the single ionization of argon by positron impact obtained by means of the CDW-EIS model. the impact energies considered are 113.5 eV and 200 eV. the obtained angular distributions for 2eV and 5 eV emitted electrons are compared to those obtained for electron impact under the same energetic configuration. in particular, we show that the shape of the binary structure evolves from a single peak to a two-peak structure as the projectile scattering angle is increased. Similar conclusions apply for the usually termed recoil peak structure.

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1st And 2nd Order Contributions To The Double Ionization Of Argon Resulting From Positron And Electron Impact, Robert D. Dubois, O. G. De Lucio, J. Gavin Dec 2009

1st And 2nd Order Contributions To The Double Ionization Of Argon Resulting From Positron And Electron Impact, Robert D. Dubois, O. G. De Lucio, J. Gavin

Physics Faculty Research & Creative Works

Angular dependences for electron emission resulting from single and double ionization of argon are presented for 200, 500, and 1000 eV positron and electron impact. from these data, double to single ionization ratios are determined as a function of the emission direction. at each impact energy, these ratios have different angular dependences positive and negative particle impact. the positron and electron induced ratios are analyzed to provide information about how first- and second-order double ionization mechanisms interfere and contribute to the differential electron emission.

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Single And Multiple Projectile Electron-Loss And Capture Of Low Charge States Of Oxygen Beams Colliding With The Methane Molecule, A. C.F. Santos, M. M. Sant'anna, W. Wolff, G. M. Sigaud, E. C. Montenegro, Robert D. Dubois Dec 2009

Single And Multiple Projectile Electron-Loss And Capture Of Low Charge States Of Oxygen Beams Colliding With The Methane Molecule, A. C.F. Santos, M. M. Sant'anna, W. Wolff, G. M. Sigaud, E. C. Montenegro, Robert D. Dubois

Physics Faculty Research & Creative Works

The projectile electron loss and capture are important ionization components collision channels in dressed ion-atom and ion-molecule collisions. They play important roles in several processes connected to the penetration of neutral and charged projectiles in gases, in radiation damage and upper atmospheric physics. in this work, cross sections for total single and multiple electron loss and capture of O-, Oo, O+, O2+ projectiles impinging on the methane molecule were measured in the 15 keV ≤ E ≤ 1000 keV energy range. in addition, an extended version of the free-collision model was employed for the calculation …

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Carbon Coated Tellurium For Optical Data Storage, Jonathan D. Abbott Dec 2009

Carbon Coated Tellurium For Optical Data Storage, Jonathan D. Abbott

Theses and Dissertations

A highly durable optical disk has been developed for data archiving. This optical disk uses tellurium as the write layer and carbon as a dielectric and oxidation prevention layer. The sandwich style CTeC film was deposited on polycarbonate and silicon substrates by plasma sputtering. These films were then characterized with SEM, TEM, EELS, ellipsometry, ToF-SIMS, etc, and were tested for writability and longevity. Results show the films were uniform in physical structure, are stable, and able to form permanent pits. Data was written to a disk and successfully read back in a commercial DVD drive.

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Reevaluating The Cosmological Origin Of Dark Matter, Scott Watson Dec 2009

Reevaluating The Cosmological Origin Of Dark Matter, Scott Watson

Physics - All Scholarship

The origin of dark matter as a thermal relic offers a compelling way in which the early universe was initially populated by dark matter. Alternative explanations typically appear exotic compared to the simplicity of thermal production. However, recent observations and progress from theory suggest that it may be necessary to be more critical. This is important because ongoing searches probing the microscopic properties of dark matter typically rely on the assumption of dark matter as a single, unique, thermal relic. On general grounds I will argue that non-thermal production of dark matter seems to be a robust prediction of physics …

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Measured Optical Constants Of Copper From 10 Nm To 35 Nm, David D. Allred, Nicole Brimhall, Nicholas Herrick, Justin Peatross, R. Steven Turley, Michael Ware Dec 2009

Measured Optical Constants Of Copper From 10 Nm To 35 Nm, David D. Allred, Nicole Brimhall, Nicholas Herrick, Justin Peatross, R. Steven Turley, Michael Ware

Faculty Publications

We use laser high-order harmonics and a polarization-ratioreflectance technique to determine the optical constants of copper and oxidized copper in the wavelength range 10-35 nm. This measurement resolves previously conflicting data sets, where disagreement on optical constants of copper in the extreme ultraviolet most likely arises from inadvertent oxidation of samples before measurement.

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Fractal Location And Anomalous Diffusion Dynamics For Oil Wells From The Ky Geological Survey, Keith Andrew, Karla M. Andrew, Kevin A. Andrew Dec 2009

Fractal Location And Anomalous Diffusion Dynamics For Oil Wells From The Ky Geological Survey, Keith Andrew, Karla M. Andrew, Kevin A. Andrew

Physics & Astronomy Faculty Publications

Utilizing data available from the Kentucky Geonet (KYGeonet.ky.gov) the fossil fuel mining locations created by the Kentucky Geological Survey geo-locating oil and gas wells are mapped using ESRI ArcGIS in Kentucky single plain 1602 ft projection. This data was then exported into a spreadsheet showing latitude and longitude for each point to be used for modeling at different scales to determine the fractal dimension of the set. Following the porosity and diffusivity studies of Tarafdar and Roy[1] we extract fractal dimensions of the fossil fuel mining locations and search for evidence of scaling laws for the set of deposits. The …

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Disordered, Quasicrystalline And Crystalline Phases Of Densely Packed Tetrahedra, Rolfe G. Petschek Dec 2009

Disordered, Quasicrystalline And Crystalline Phases Of Densely Packed Tetrahedra, Rolfe G. Petschek

Faculty Scholarship

All hard, convex shapes are conjectured by Ulam to pack more densely than spheres, which have a maximum packing fraction of Ø /18 0.7405. Simple lattice packings of many shapes easily surpass this packing fraction. For regular tetrahedra, this conjecture was shown to be true only very recently; an ordered arrangement was obtained via geometric construction with Ø= 0.7786 (ref. 4), which was subsequently compressed numerically to Ø= 0.7820 (ref. 5), while compressing with different initial conditions led to Ø= 0.8230 (ref. 6). Here we show that tetrahedra pack even more densely, and in a completely unexpected way. Following a …

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Analysis Of Expedient Field Decontamination Methods For The Xmx/2l-Mil High-Volume Aerosol Sampler, Brandon C. Laroche Dec 2009

Analysis Of Expedient Field Decontamination Methods For The Xmx/2l-Mil High-Volume Aerosol Sampler, Brandon C. Laroche

Theses and Dissertations

The XMX/2L-MIL is a high volume air sampler used by the Air Force Bioenvironmental Engineering community to collect biological aerosols. Without a verified decontamination technique, however, the XMX cannot be used effectively. The objective of this study was to evaluate several proposed methods for expedient field decontamination of the XMX. This study centered on the inactivation of Bacillus atrophaeus spores and vegetative Erwinia herbicola organisms from the XMX inner canister. The goals in this investigation were twofold: 1) to verify the antimicrobial efficacy of a 10% bleach solution and 2) to determine if wiping the components with a bleach-soaked paper …

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Midwave Infrared Imaging Fourier Transform Spectrometry Of Combustion Plumes, Kenneth C. Bradley Dec 2009

Midwave Infrared Imaging Fourier Transform Spectrometry Of Combustion Plumes, Kenneth C. Bradley

Theses and Dissertations

A midwave infrared (MWIR) imaging Fourier transform spectrometer (IFTS) was used to successfully capture and analyze hyperspectral imagery of combustion plumes. Jet engine exhaust data from a small turbojet engine burning diesel fuel at a flow rate of 300 cm3/min was collected at 1 cm−1 resolution from a side-plume vantage point on a 200x64 pixel window at a range of 11.2 meters. Spectral features of water, CO, and CO2 were present, and showed spatial variability within the plume structure. An array of thermocouple probes was positioned within the plume to aid in temperature analysis. A single-temperature …

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Viscosity Dependent Liquid Slip At Molecularly Smooth Hydrophobic Surfaces, Sean P. Mcbride, Bruce M. Law Dec 2009

Viscosity Dependent Liquid Slip At Molecularly Smooth Hydrophobic Surfaces, Sean P. Mcbride, Bruce M. Law

Physics Faculty Research

Colloidal probe atomic force microscopy is used to study the slip behavior of 18 Newtonian liquids from two homologous series, the n-alkanes and n-alcohols, at molecularly smooth hydrophobic n-hexadecyltrichlorosilane coated surfaces. We find that the slip behavior is governed by the bulk viscosity η of the liquid, specifically, the slip length b∼ηx with x∼0.33. Additionally, the slip length was found to be shear rate independent, validating the use of Vinogradova slip theory in this work.

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Patterning-Induced Surface Chirality And Modulation Of Director Twist In A Nematic Cell, Yoonseuk Choi, Timothy J. Atherton, Sameh Ferjani, Rolfe G. Petschek, Charles Rosenblatt Dec 2009

Patterning-Induced Surface Chirality And Modulation Of Director Twist In A Nematic Cell, Yoonseuk Choi, Timothy J. Atherton, Sameh Ferjani, Rolfe G. Petschek, Charles Rosenblatt

Faculty Scholarship

A substrate coated with a polyimide alignment layer is scribed bidirectionally with the stylus of an atomic force microscope to create an easy axis for liquid-crystal orientation. The resulting noncentrosymmetric topography breaks two-dimensional inversion symmetry and results in a spatial amplitude modulation of an imposed twisted nematic state. This is observed optically as spatially periodic light and dark stripes. When the alignment layer is scribed unidirectionally the centrosymmetric topography maintains inversion symmetry, and no stripes are observed. The appearance of the twist modulation is consistent with a chiral term in the free energy.

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Partially Coherent Standard And Elegant Laguerre-Gaussian Beams Of All Orders, Fei Wang, Yangjian Cai, Olga Korotkova Dec 2009

Partially Coherent Standard And Elegant Laguerre-Gaussian Beams Of All Orders, Fei Wang, Yangjian Cai, Olga Korotkova

Physics Articles and Papers

Partially coherent standard and elegant Laguerre-Gaussian (LG) beams of all orders are introduced as a natural extension of coherent standard and elegant LG beams to the stochastic domain. By expanding the LG modes into a finite sum of Hermite-Gaussian modes, the analytical formulae are obtained for the cross-spectral densities of partially coherent standard and elegant LG beams in the source plane and after passing through paraxial ABCD optical system, based on the generalized Collins integral formula. A comparative study of the propagation properties of the partially coherent standard and elegant LG beams in free space is carried out via a …

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