Digital Commons Network^™

The Blazhko Effect Of The Rr Lyrae Star Gv Andromedae, Kevin M. Lee, Edward G. Schmidt, Shawn T. Langan

Edward Schmidt Publications

We have obtained 462 new V and R observations of the RR Lyrae star GV Andromedae. Our data set is consistent with a primary period of 0.528092 days; however, the light curve of GV And cannot be well described by a single period. We conclude that GV And demonstrates the Blazhko effect with a Blazhko period of approximately 32 days.

Effect Of Implanted Metal Impurities On Superconducting Tungsten Films, Betty A. Young, T. Saab, Blas Cabrera, A. J. Miller, P. L. Brink, J. P. Castle

Physics

The superconducting transition temperature of more than 30 thin-film tungsten samples was measured using a dilution refrigerator. The samples were fabricated using a 99.999% pure tungsten target and a dc magnetron sputtering system. Individual films were then doped with metal impurity ions using an accurate ion implantation technique. The effect of the metal–ion doping on the superconducting transition temperature was measured for samples with superconducting transitions in the range of 40–150 mK. Magnetic dopant species including Ni, Co, and Fe resulted in suppressed values of the tungsten T_c. The suppression was linear with increasing dopant concentration, for concentrations …

Depth-Dependent Investigation Of Defects And Impurity Doping In Gan/Sapphire Using Scanning Electron Microscopy And Cathodoluminescence Spectroscopy, X. L. Sun, S. H. Goss, L. J. Brillson, David C. Look, Richard J. Molnar

Physics Faculty Publications

Cathodoluminescence (CL) imaging and temperature-dependent cathodoluminescence spectroscopy (CLS) have been used to probe the spatial distribution and energies of electronic defects near GaN/Al₂O₃ interfaces grown by hydride vapor phase epitaxy (HVPE). Cross sectional secondary electron microscopy imaging, CLS, and CL imaging show systematic variations in defect emissions with a wide range of HVPE GaN/sapphire electronic properties. These data, along with electrochemical capacitance–voltage profiling and secondary ion mass spectrometry provide a consistent picture of near-interface doping by O out-diffusion from Al₂O₃ into GaN over hundreds of nanometers. Low-temperature CL spectra exhibit a new donor level …

The Role Of Bandgap In The Secondary Electron Emission Of Small Bandgap Semiconductors: Studies Of Graphitic Carbon, Neal E. Nickles

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The question of whether the small bandgaps of semiconductors play a significant role in their secondary electron emission properties is investigated by studying evaporated graphitic amorphous carbon, which has a roughly 0.5 eV bandgap, in comparison with microcrystalline graphite, which has zero bandgap. The graphitic amorphous carbon is found to have a 30% increase in its maximum secondary electron yield over that of two microcrystalline graphite samples with comparable secondary electron yields: highly oriented pyrolytic graphite and colloidal graphite. The potentially confounding influence of the vacuum level has been isolated through the measurement of the photoelectron onset energy of the …

Orbital Ordering In Paramagnetic Lamno₃ And Kcuf₃, Julia E. Medvedeva, Michael A. Korotin, Vladimir I. Anisimov, Arthur J. Freeman

Physics Faculty Research & Creative Works

Ab initio studies of the stability of orbital ordering, its coupling to magnetic structure and its possible origins (electron-phonon and/or electron-electron interactions) are reported for two perovskite systems, LaMnO₃ and KCuF₃. We present an average spin state calculational scheme that allowed us to treat a paramagnetic state and to succesfully describe the experimental magnetic or orbital phase diagram of both LaMnO₃ and KCuF₃ in crystal structures when the Jahn-Teller distortions are neglected. Hence, we conclude that the orbital ordering in both compounds is purely electronic in origin.

Measurement Of B-Meson Lifetimes Using Fully Reconstructed B Decays Produced, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present an improved measurement of b-meson lifetimes using fully reconstructed B-decays produced in pp̅ collisions at √s =1.8 TeV, using 114 pb^-1 of data collected at the Collider Detector at Fermilab. We obtain τ (B⁺)=1.636±0.058(stat) ±0.025(syst) ps, τ (B⁰)=1.497±0.073(stat) ±0.032(syst) ps and for the lifetime ratio τ (B⁺)/(B⁰)=1.093±0.066(stat) ±0.028(syst).

Search For Single-Top-Quark Production In Pp̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We search for standard model single-top-quark production in the W-gluon fusion and W* channels using 106 pb^-1 of data from pp̅ collisions at √s =1.8 TeV collected with the Collider Detector at Fermilab. We set an upper limit at 95% confidence level (C.L.) on the combined W-gluon fusion and W* single-top cross section of 14 pb, roughly six times larger than the standard model prediction. Separate 95% C.L. upper limits in the W-gluon fusion and W* channels are also determined and are found to be 13 and 18 pb, respectively.

Search For Lepton-Flavor Violation In E+P Collisions At Desy Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

A search has been made for lepton-flavor-violating interactions of the type e+p→lX, where l denotes a μ or τ with high transverse momentum, at a center-of-mass energy √s of 300 GeV with an integrated luminosity of 47.7 pb-1 using the ZEUS detector at HERA. No evidence was found for lepton-flavor violation and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below √s, limits are set on λeq1βlq, where λeq1 is the coupling of the LQ to an electron and a first-generation quark q1 and βlq is the branching ration of the LQ to l …

Comparision Of Measured Convection Velocities With Calcuulations Based On Electric Potential Model, Daniel E. Britton

Honors Capstone Projects and Theses

No abstract provided.

Projectile And Target Ionization In Mev U⁻¹ Collisions Of Xe Ions With N2, Ronald E. Olson, R. L. Watson, V. Horvat, K. E. Zaharakis

Physics Faculty Research & Creative Works

Experimental cross sections are presented for single and multiple electron stripping from Xe¹⁸⁺ projectiles in collisions with N₂ at energies 2.0-9.3 MeV u^-1. The data are compared to 2-30 MeV u^-1 n-body classical trajectory Monte Carlo calculations that explicitly include electrons on both centres. Two-centre electron-electron (e-e) and electron-screened nuclear interactions contribute to the ionization reactions. The computations are in reasonable accord for the total stripping cross section but underestimate the higher stages of multiple electron loss. An energy deposition model gives improved agreement with experiment. The energy dependence of the total stripping cross section …

Measurement Of The Photon-Proton Total Cross Section At A Center-Of-Mass Energy Of 209 Gev At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

The photon-proton total cross section has been measured in the process e+ p → e+ γp → e+ X with the ZEUS detector at HERA. Events were collected with photon virtuality Q2 < 0.02 GeV2 and average γp center-of-mass energy Wγp = 209 GeV in a dedicated run, designed to control systematic effects, with an integrated luminosity of 49 nb-1. The measured total cross section is σtotγp = 174 ± 1 (stat.) ± 13 (syst.) μb. The energy dependence of the cross section is compatible with parameterizations of high-energy pp and pap data. © 2002 Elsevier Science B.V. All rights reserved.

Charged Jet Evolution And The Underlying Event In Proton-Antiproton Collisions At 1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

The growth and development of ‘‘charged particle jets’’ produced in proton-antiproton collisions at 1.8 TeV are studied over a transverse momentum range from 0.5 GeV/c to 50 GeV/c. A variety of leading (highest transverse momentum) charged jet observables are compared with the QCD Monte Carlo models HERWIG, ISAJET, and PYTHIA. The models describe fairly well the multiplicity distribution of charged particles within the leading charged jet, the size of the leading charged jet, the radial distribution of charged particles and transverse momentum around the leading charged jet direction, and the momentum distribution of charged particles within the …

Γ Production And Polarization In Pp̅ Collisions At √S= 1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on measurements of the ϒ(1S), ϒ(2S), and ϒ(3S) differential cross sections (d²σ/dp_Tdy)|y|pp̅ collisions at √s = 1.8 TeV using a sample of 77±3 pb^-1 collected by the collider detector at Fermilab. The three resonances were reconstructed through the decay ϒ→μ⁺μ^-. The measured angular distribution of the muons in the ϒ(1S) rest frame is consistent with unpolarized meson production.

De Haas-Van Alphen Oscillations In The Quasi-Two-Dimensional Organic Conductor Κ-(Et)2cu(Ncs)2: The Magnetic Breakdown Approach, V. M. Gvozdikov, Yuriy V. Pershin Dr, E. Steep, A. G. M. Jansen, P. Wyder

Faculty Publications

We present both experimental data and an analytic theory for the de Haas–van Alphen ~dHvA! effect in the two-dimensional organic single-crystal conductor k -(ET)2Cu(NCS)2. We show that the magnetization oscillation pattern and the fast Fourier transform (FFT) spectrum of our measurements are well described theoretically within the coherent magnetic breakdown (MB) model for a two-dimensional Fermi surface consisting of two open sheets and closed pockets connected by magnetic breakdown centers. The spectrum of Landau quantized energy levels changes substantially due to the MB. Landau bands develop whose bandwidth and relative distance between them oscillate in inverse magnetic field. These oscillations …

Diffractive Dijet Production At √S= 630 And 1800 Gev At The Fermilab Tevatron, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a measurement of the diffractive structure function F_jj^D of the antiproton obtained from a study of dijet events produced in association with a leading antiproton in p̅p collisions at √s =630 GeV at the Fermilab Tevatron. The ratio of F_jj^D at √s =630 GeV to F_jj^D obtained from a similar measurement at √s =1800 GeV is compared with expectations from QCD factorization and other theoretical predictions. We also report a measurement of the ξ(x-Pomeron) and β(x of parton in Pomeron) dependence of F_jj^D at √s =1800 GeV. In the region …

Soft And Hard Interactions In Pp̅ Collisions At √S =1800 And 630 Gev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a study of pp̅ collisions at √s =1800 and 630 GeV collected using a minimum bias trigger by the CDF experiment in which the data set is divided into two classes corresponding to “soft” and “hard” interactions. For each subsample, the analysis includes measurements of the multiplicity, transverse momentum (p_T) spectrum, and the average p_T and event-by-event p_T dispersion as a function of multiplicity. A comparison of results shows distinct differences in the behavior of the two samples as a function of the center of mass (c.m.) energy. We find evidence that the …

High-Mass Dijet Cross Sections In Photoproduction At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

Dijet differential cross sections for the reaction e+ p → e+ + jet + jet + X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb-. The cross sections are given for photon-proton centre-of-mass energies in the range 134 < W < 277 GeV. The differential cross sections as a function of the dijet mass, MJJ, and of the dijet angular variables have been measured for 47 < MJJ < 160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75 < MJJ < 100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of σ e+p→e+Z0X < 5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV. © 2002 Elsevier Science B.V. All rights reserved.

Structure And Magnetic Properties Of Ferromagnetic Nanowires In Self-Assembled Arrays, H. Zeng, Ralph Skomski, L. Menon, Yi Liu, Supriyo Bandyopadhyay, David J. Sellmyer

David Sellmyer Publications

Static and dynamic aspects of the magnetization reversal in nanowire arrays are investigated. The arrays have been produced by electrodeposition of ferromagnetic metals (Fe, Co, and Ni) into porous anodic alumina templates, with diameters as small as 5 nm. The crystal structures of the nanowires are bcc (Fe) and fcc (Ni) and a mixture of fcc and hcp (Co), with grain sizes of a few nanometers. Magnetic properties as a function of temperature are investigated. The temperature dependence of coercivity can be understood in terms of thermal activation over an energy barrier with a 3/2-power dependence on the field. Coercivity …

Visual And Lidar Observations Ofnoctilucent Clouds Above Logan, Utah, At 41.7°N, Vincent B. Wickwar, Michael J. Taylor, Joshua P. Herron, B. A. Martineau

All Physics Faculty Publications

Noctilucent clouds (NLCs) were observed from a midlatitude site (Logan, Utah) on the evenings of 22 and 23 June 1999 mountain daylight time. On both nights the clouds were seen for approximately an hour by experienced observers, and they were photographed. The NLC was also observed on the second evening for approximately an hour in the zenith with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory, which is operated by the Center for Atmospheric and Space Sciences on the campus of Utah State University. These observations enabled several of the properties of the cloud to be determined. They were within …

A Compact Method For Optical Induction Of Proximal Probe Heating And Elongation, Andres H. La Rosa, Hans D. Hallen

Physics Faculty Publications and Presentations

A tapered, metal-coated, optical fiber probe will elongate when heated by light input through a fiber. The induced motion can be used for data storage or nanostructuring of a surface. The elongation produced by this alignment-free system is measured with force feedback in a near-field scanning optical microscope (NSOM). The input light intensity controls the elongation magnitude, which ranges from a few nanometers to more than 100 nm. A 0.5-mW input energy yields ~20 nm of probe elongation. The elongation quantified here can create artifacts in any experiment using pulsed laser light with a NSOM or an atomic force microscope.

Development Of A Data Acquisition And Analysis System, Michael V. Mores '02

Honors Projects

Plasma is the fourth and least understood state of matter. A more complete understanding of this state of matter has numerous practical applications, including fusion energy, space travel, materials synthesis, and thin film deposition. As such, there is an obvious motivation to study this state. To do this, we have constructed a radio-frequency plasma device at Illinois Wesleyan University. I have developed a data acquisition using LabVIEW software that can digitize eight analog signals, saving the data to disk for later analysis. I have also written analysis software using LabVIEW to extract meaningful information from Langmuir Probe Trace.

Design And Construction Of A Radio Frequency Plasma Device, Matthew Highland '02

Honors Projects

We have constructed a radio frequency plasma device to study a wide range of phenomena including, power coupling between the plasma and the antenna and wave propagation. Our system includes a high vacuum chamber with mechanical and diffusion pumps, a radio frequency source magnetic field coils and a matching network.

Local Versus Nonlocal Order-Parameter Field Theories For Quantum Phase Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

General conditions are formulated that allow us to determine which quantum phase transitions in itinerant electron systems can be described by a local Landau-Ginzburg-Wilson (LGW) theory solely in terms of the order parameter. A crucial question is the degree to which the order parameter fluctuations couple to other soft modes. Three general classes of zero-wave-number order parameters, in the particle-hole spin-singlet and spin-triplet channels and in the particle-particle channel, respectively, are considered. It is shown that the particle-hole spin-singlet class does allow for a local LGW theory, while the other two classes do not. The implications of this result for …

Correlated Alternative Side Chain Conformations In The Rna-Recognition Motif Of Heterogeneous Nuclear Ribonucleoprotein A1, Jacqueline Vitali, Jianzhong Ding, Jianzhong Jiang, Ying Zhang, Adrian R. Krainer, Rui-Ming Xu

Physics Faculty Publications

The RNA-recognition motif (RRM) is a common and evolutionarily conserved RNA-binding module. Crystallographic and solution structural studies have shown that RRMs adopt a compact α/β structure, in which four antiparallel β-strands form the major RNA—binding surface. Conserved aromatic residues in the RRM are located on the surface of the β-sheet and are important for RNA binding. To further our understanding of the structural basis of RRM—nucleic acid interaction, we carried out a high resolution analysis of UP1, the N-terminal, two-RRM domain of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), whose structure was previously solved at 1.75–1.9 Å …

Improvements In Wavelength Modulation Spectroscopy Using Ratios Of Higher Harmonics, James Michael Barrington

Electrical & Computer Engineering Theses & Dissertations

Experiments in Wavelength Modulation Spectroscopy have been conducted at Old Dominion University since 1996. The method provides a highly sensitive, nonintrusive method of probing gases. Research has concentrated on effectively modeling the higher harmonic shapes that are measured experimentally. Accurately modeling these signals will result in the ability to reliably extract the information contained in transition line shapes.

In order to accurately depict the signals, the theory must be thoroughly understood. This thesis develops the theory of Wavelength Modulation Spectroscopy from two aspects: a direct Fourier series expansion of a time varying intensity profile and through communication theory. In addition, …

Temperature Dependence Of Dark Current In A Ccd, Ralf Widenhorn, Morley M. Blouke, Alexander Weber, Armin Rest, Erik Bodegom

Physics Faculty Publications and Presentations

We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, …

Doubly Differential Electron-Emission Spectra In Single And Multiple Ionization Of Noble-Gas Atoms By Fast Highly-Charged-Ion Impact, Tom Kirchner, Laszlo Gulyas, Robert Moshammer, Michael Schulz, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Low-energy electron emission spectra are studied in collisions of 3.6 MeV/amu Au⁵³⁺ ions with neon and argon atoms for well-defined degrees of target ionization. We calculate doubly differential cross sections as functions of the recoil-ion charge state in the continuum-distorted-wave with eikonal initial-state approximation using a binomial analysis of the total and differential ionization probabilities, and compare them with the present and with previously published experimental data. Very good agreement is found for the single-ionization spectra and for double ionization of neon, while some discrepancies are observed in the spectra for double and triple ionization of argon.

Spin Structure Functions Of The Deuteron, Junho Yun

Physics Theses & Dissertations

Inclusive double spin asymmetries have been measured in [special characters omitted] using the CLAS detector and a polarized [special characters omitted] target at. Jefferson Lab in 1998. The goal of these measurements is to study the spin structure of the deuteron and the neutron in the low Q² transition region between the real photon point, where the Gerasimov-Drell-Hearn (GDH) sum rule is expected to be satisfied, and the deep inelastic scattering limit. The analysis and the results for virtual photon asymmetries, the spin structure function [special characters omitted] and its first moment within a Q² range of 0.2 …

A Short History Of Valence Bond Theory, Gordon A. Gallup

Gordon Gallup Publications

Shortly after quantum mechanics evolved Heitler and London [1] applied the then new ideas to the problem of molecule formation and chemical valence. Their treatment of the H₂ molecule was qualitatively very successful, and this led to numerous studies by various workers applying the same ideas to other substances. Many of these involved refinements of the original Heitler-London procedure, and within three or four years, a group of ideas and procedures had become reasonably well codified in what was called the valence bond (VB)* method for molecular structure.

A few calculations were carried out earlier, but by 1929 Dirac …

Decomposition Of Carbon Dioxide In A Capacitively Coupled Radio Frequency Discharge, Thao Hoang Dinh

Physics Theses & Dissertations

Decomposition of CO₂ was studied in a capacitively coupled radio frequency discharge using Martian Simulant Gas mixture that contains 95% CO₂. The discharge was operated at a gas pressure of 3 to 6 Torr and a discharge power density of less than 2.0 W/cm³. The main mechanism of the CO₂ decomposition process is the electron impact dissociation and the rate of the process depends on the electron density, Ne, the concentration of CO₂, and the reduced electric field, E/N. A self-consistent model was established to describe the CO …