Physical Sciences and Mathematics Commons^™

Lamb Shift Of 3p And 4p States And The Determination Of Α, Ulrich D. Jentschura, Gerhard Soff, Peter J. Mohr

Physics Faculty Research & Creative Works

The fine-structure interval of P states in hydrogenlike systems can be determined theoretically with high precision, because the energy levels of P states are only slightly influenced by the structure of the nucleus. Therefore a measurement of the fine structure may serve as an excellent test of QED in bound systems, or alternatively as a means of determining the fine-structure constant a with very high precision. In this paper an improved analytic calculation of higher-order binding corrections to the one-loop self-energy of 3P and 4P states in hydrogenlike systems with a low nuclear charge number Z is presented. The method …

Nonlinear Front Evolution Of Hydrodynamic Chemical Waves In Vertical Cylinders, J. W. Wilder, D. A. Vasquez, Boyd F. Edwards

All Physics Faculty Publications

The nonlinear stability of three-dimensional reaction-diffusion fronts in vertical cylinders is considered using the viscous hydrodynamic fluid equations in the limit of infinite thermal diffusivity. A nonlinear front evolution equation is presented and used to examine the transition from nonaxisymmetric to axisymmetric convection observed in experiments performed in cylinders. Comparisons with experiments show excellent agreement in both the shape and speed of the front.

Gravity And Bf Theory Defined In Bounded Regions, V. Husain, Seth Major

Articles

We study Einstein gravity in a finite spatial region. By requiring a well-defined variational principle, we identify all local boundary conditions, derive surface observables, and compute their algebra. The observables arise as induced surface terms, which contribute to a non-vanishing Hamiltonian. Unlike the asymptotically flat case, we find that there are an infinite number of surface observables. We give a similar analysis for SU(2) BF theory.

Study Of The Effects Of Initial-Bred Nuclei On Zeolite Naa Crystallization By Quasi-Elastic Light Scattering Spectroscopy And Electron Microscopy, Leszek Gora, Kiril A. Streletzky, Robert W. Thompson, George D.J. Phillies

Physics Faculty Publications

Synthesis studies have been conducted at 25, 60, and 80 °C with a clear solution batch composition that produces zeolite NaA. Aluminosilicate precursor material was added to promote the synthesis and to evaluate the effects of adding initial-bred nuclei that were created by a precursor “seed” reaction. It is shown that the initial-bred nuclei promoted the crystallization rate, that the crystalline mass produced was increased when using the initial-bred nuclei, and that the nucleation of a second population was not inhibited by the addition of initial-bred nuclei as seeds.

Ion Acceleration And Anomalous Transport In The Near Wake Of A Plasma Limiter, D. P. Sheehan, J. Bowles, R. Mcwilliams

Physics and Biophysics: Faculty Scholarship

Ion acceleration and anomalous transport were studied experimentally in the near wake region of an electrically floating disk limiter immersed in two different types of collisionless, supersonically flowing, magnetized plasmas: the first initially quiescent, the second initially turbulent. Ion densities and velocity distributions were obtained using a nonperturbing laser induced fluorescence diagnostic. Large-amplitude, low-frequency turbulence was observed at the obstacle edge and in the wake. Rapid ion and electron configuration space transport and ion velocity space transport were observed. Configuration space and velocity space transport were similar for both quiescent and turbulent plasma-obstacle systems, suggesting that plasma-obstacle effects outweigh the …

Absolute Triply Differential (E,2E) Cross Section Measurements For H With Comparison To Theory, J. Roder, H. Erhardt, Cheng Pan, Anthony F. Starace, Igor Bray, Dmitry V. Fursa

Anthony F. Starace Publications

Absolute triply differential (e,2e) cross section measurements are presented for H (for incident energies, E₀, of 15.6 and 17.6 eV) for equal energy sharing and the θ₁₂ = π configuration. Results of distorted partial wave calculations agree with the measurements; those of convergent close coupling calculations agree with the relative angular distributions, but are lower than experiment by factors of from 2 to 7. Relative experimental results for H for E₀ = 14.6 eV show a qualitative change in shape, which agrees with theory. Implications of the absolute experimental results for the …

Recurrence Spectroscopy Of A Time-Dependent System: A Rydberg Atom In An Oscillating Field, Neal Spellmeyer, Daniel Kleppner, M. R. Haggerty, V. Kondratovich, John B. Delos, J. Gao

Arts & Sciences Articles

We report the results of an experimental and theoretical investigation of the recurrence spectra of Rydberg atoms in a static plus weak oscillating electric field. Experiments reveal the systematic weakening of orbits in a recurrence spectrum as the oscillating field strength and frequency are changed. We describe a generalization of closed orbit theory to time-dependent systems and show that it provides a qualitative and quantitative description of the phenomena.

Symmetry, Symmetry Breaking, And The Current View Of The Dirac Monopole, Erik Kristian Leder

Dissertations and Theses

The ideas of symmetry and symmetry breaking are considered in the context of classical gauge theory. Local U(l) symmetry is developed for a complex scalar field and electromagnetism is identified as the associated gauge field. Local S0(3) theory for a triplet of real scalar fields is derived and the incorporation of additional gauge fields is demonstrated. Symmetry breaking for the S0(3) gauge theory is performed and the gauge fields are shown to acquire mass by the Higgs mechanism. The equations of the t'Hooft-Polyakov monopole are derived and compared to those of the magnetic monopole of Dirac.

High Temperature Superconducting Josephson Junctions In A Stacked Bicrystal Geometry, H.Q. Li, R.H. Ono, L.R. Vale, D.A. Rudman, Sy_Hwang Liou

Sy-Hwang Liou Publications

Bicrystal grain boundary Josephson junctions were fabricated in a stack of two layers of YBa₂Cu₃O_χ separated by epitaxial SrTiO₃. Weak link behavior was observed in the bridges formed in both layers that had similar shunted-junction characteristics but significantly different critical currents. Characteristic voltages up to 1.9 mV were measured at 4.5 K. The resonant structure was seen in the current–voltage characteristics of the upper-layer junctions, and interactions between junctions in the two layers were evident.

Observation Of The Decay DS+ → Ωπ+, R. Balest, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using e⁺e^- annihilation data collected by the CLEO II detector at CESR, we have observed the decay D_s⁺ → ωπ⁺. This final state may be produced through the annihilation decay of the i>D_s⁺, or through final state interactions. We find a branching ratio of γ(D_s⁺ → ωπ⁺)/γ(D_s⁺ →ηπ⁺) = 0.16±0.04±0.03, where the first error is statistical and the second is systematic.

Toy Model For Breaking Super Gauge Theories At The Effective Lagrangian Level, Joseph Schechter, Francesco Sannino

Physics - All Scholarship

We propose a toy model to illustrate how the effective Lagrangian for super QCD might go over to the one for ordinary QCD by a mechanism whereby the gluinos and squarks in the fundamental theory decouple below a given supersymmetry breaking scale m. The implementation of this approach involves a suitable choice of possible supersymmetry breaking terms. An amusing feature of the model is the emergence of the ordinary QCD degrees of freedom which were hidden in the auxiliary fields of the supersymmetric effective Lagrangian.

Forming B1-XCX Semiconductor Layers By Chemical Vapor Deposition, Peter A. Dowben

Peter Dowben Publications

Active semiconductor devices including heterojunction diodes and thin film transistors are formed by PECVD deposition of a boron carbide thin film on an N-type substrate. The boron to carbon ratio of the deposited material is controlled so that the film has a suitable band gap energy. Boron carbides such as B_4.7C, B_7.2C and B₁₉C have suitable band gap energies between 0.8 and 1.7 eV. The stoichiometry of the film can be selected by varying the partial pressure of precursor gases, such as nido pentaborane and methane. The precursor gas or gases are energized. e.g., …

Search For Neutrinoless Τ Decays Involving Π0 Or Η Mesons, G. Bonvicini, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for lepton flavor violating decays of the τ lepton using final states with an electron or a muon and one or two π⁰ or η mesons but no neutrinos. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.68 fb^-1. No evidence for signals was found, resulting in much improved limits on the branching fractions for the one-meson modes and the first upper limits for the two-meson modes.

Numerical Observation Of A Tubular Phase In Anisotropic Membranes, Mark Bowick, Marco Falcioni, Gudmar Thorleifsson

Physics - All Scholarship

We provide the first numerical evidence for the existence of a tubular phase, predicted by Radzihovsky and Toner (RT), for anisotropic tethered membranes without self-avoidance. Incorporating anisotropy into the bending rigidity of a simple model of a tethered membrane with free boundary conditions, we show that the model indeed has two phase transitions corresponding to the flat-to-tubular and tubular-to-crumpled transitions. For the tubular phase we measure the Flory exponent \nu_F and the roughness exponent \zet. We find \nu_F=0.305(14) and \zeta=0.895(60), which are in reasonable agreement with the theoretical predictions of RT --- \nu_F=1/4 and \zeta=1.

Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = ³/₂ Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with g_eff values of 2.20, 3.92, and …

Search For The Decays B0 → D (*)+D (*)-, D. M. Asner, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using the CLEO-II data set we have searched for the decays B⁰ → D^(*)+D^(*)-. We observe one candidate signal event for the decay B⁰ → D^*+D^*- with an expected background of 0.022 ± 0.011 events. This yield corresponds to a branching fraction of B(B⁰ → D^*+D^*-) = [5.317_-3.7^+7.1(stat) ± 1.0(syst)] x 10^-4 and an upper limit of B(B⁰ → D^*+D^*-) < 2.2 X 10^-3 at the 90% C.L. We see no significant excess of signal above …

39th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Preliminary program and registration information for the 39th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 3-7, 1997.

Magneto-Aerotaxis In Marine Coccoid Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Mark S. Johnson, Barry L. Taylor

Physics

Magnetotactic cocci swim persistently along local magnetic field lines in a preferred direction that corresponds to downward migration along geomagnetic field lines. Recently, high cell concentrations of magnetotactic cocci have been found in the water columns of chemically stratified, marine and brackish habitats, and not always in the sediments, as would be expected for persistent, downward-migrating bacteria. Here we report that cells of a pure culture of a marine magnetotactic coccus, designated strain MC-1, formed microaerophilic bands in capillary tubes and used aerotaxis to migrate to a preferred oxygen concentration in an oxygen gradient. Cells were able to swim in …

Spurious Electrons In Electron Spectrometers And Their Effect On Differential Electron Impact Ionization Cross-Section Measurements, M. Eugene Rudd

M. Eugene Rudd Publications

The effect of the nonideal response characteristics of electrostatic analyzers is described and equations are derived, which allow a calculation of the distortion that this causes in measurements of angular and energy distributions of electrons from atomic collisions, especially in electron impact. Examples are given that show how a contamination as small as 10^-5 from spurious electrons generated inside an analyzer can explain the peak seen at zero angle in some angular distribution measurements and the filling in of the minimum in the energy distributions in others.

Magnetism In One Dimension: Fe On Cu(111), J. Shen, Ralph Skomski, M. Klaua, H. Jenniches, S. Sundar Manoharan, J. Kirschner

Ralph Skomski Publications

The magnetism and the morphology of one-dimensional Fe stripes on a Cu(111) vicinal surface with perpendicular magnetization are investigated. Scanning tunneling microscopy shows that the Fe stripes have nanometer width and are aligned in parallel along the [011] direction. From the magnetization curves it is inferred that the stripes exhibit a ferromagnetic behavior well below the nominal thickness of one monolayer. In contrast to two-dimensional films, the magnetization of the stripes is not only temperature but also time dependent. The dynamics of the stripes have been described by a micromagnetic Ising model with Glauber dynamics, yielding an effective anisotropy constant …

Simulation Of A Microdosimetry Problem: Behavior Of A Pseudorandom Series At A Low Probability, P. Meyer, J. E. Groetz, Robert Katz, M. Fromm, A. Chambaudet

Robert Katz Publications

The carcinogenic effects for low dose irradiations are not very well known. Estimations usually are made based on the effects observed at high doses that are then extrapolated to low doses. To estimate low dose effects, the ICRP (International Commission on Radiological Protection) uses a linear extrapolation matched with a dose-rate reduction factor equal to two. This proportionality of the effect and dose, even for the lowest doses and dose-rates, leads to two assumptions which must be questioned :
1. the efficiency of DNA repair in cells does not vary with the dose and the dose-rate,
2. when one single …

Experimental Investigation Of Nonlinear Dynamics In Single Mode Semiconductor Laser Diodes With Phase Conjugate Feedback, Gordon T. Hengst

Theses and Dissertations

The semiconductor laser diode offers a unique system to investigate nonlinear dynamics when optical feedback is applied. Although there is extensive research of laser diodes with optical feedback from normal dielectric mirrors, very little has been done experimentally to analyze the effects of degenerate phase conjugate feedback from a BaTiO₃ crystal. This research experimentally investigated the dynamics of a single-mode laser diode with weak phase conjugate feedback using both the self-pumped and double phase conjugate geometries. The experimental results validated a mathematical model which numerically evaluates the Lang-Kobayahsi coupled differential equations. The model simulated the nonlinear behavior of a …

Vacuum Structure Of Two-Dimensional Gauge Theories On The Light Front, Gary Mccartor, David G. Robertson, Stephen S. Pinksy

Physics Faculty Scholarship

We discuss the problem of vacuum structure in light-front field theory in the context of (1+1)-dimensional gauge theories. We begin by reviewing the known light-front solution of the Schwinger model, highlighting the issues that are relevant for reproducing the θ structure of the vacuum. The most important of these are the need to introduce degrees of freedom initialized on two different null planes, the proper incorporation of gauge field zero modes when periodicity conditions are used to regulate the infrared, and the importance of carefully regulating singular operator products in a gauge-invariant way. We then consider SU(2) Yang-Mills theory in …

Precision Determination Of The Neutron Spin Structure Function G1n, K Abe, C M. Berisso, S Churchwell, R S. Hicks, Yu G. Kolomensky, Gerald Alvin Peterson

Gerald Alvin Peterson

We report on a precision measurement of the neutron spin structure function g1n using deep inelastic scattering of polarized electrons by polarized 3He. For the kinematic range 0.014

Bern Porter International: Volume 1 Number 1 (Summer, 1997), Bern Porter, Sheila Holtz, Natasha Bernstein

Newsletters

A Literary Newspaper

Featuring the Bern Porter International mission statement with an introduction to the Institute of Advanced Thinking and Porter's literary philosophy.

Calculation Of Heavy Ion Inactivation And Mutation Rates In Radial Dose Model Of Track Structure, Francis A. Cucinotta, John W. Wilson, Mark R. Shavers, Robert Katz

Robert Katz Publications

In the track structure model, the inactivation cross section is found by summing an inactivation probability over all impact parameters from the ion to the sensitive sites within the cell nucleus. The inactivation probability is evaluated by using the dose response of the system to gamma rays and the radial dose of the ions and may be equal to unity at small impact parameters. We apply the track structure model to recent data with heavy ion beams irradiating biological samples of E. Coli, Bacillus Subtilis spores, and Chinese hamster (V79) cells. Heavy ions have observed cross sections for inactivation that …

Neutron Resonance Spectroscopy Of 107ag, And 109ag, L Y. Lowie, J D. Bowman, Bret E. Crawford, P P J. Delheij, T Haseyama, J N. Knudsen, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Parity violation has been observed in a number of previously unreported neutron resonances in silver. Analysis of these parity violation data requires improved neutron resonance spectroscopy. The neutron total cross section for natural silver was measured for E_n=10–800 eV with the time-of-flight method at the Los Alamos Neutron Scattering Center. The neutron capture reaction was studied with both a natural silver target and a highly enriched sample (98.29%) of ¹⁰⁷Ag. A total of 38 previously unreported resonances were observed. The combination of the two measurements allowed assignment of the newly observed resonances to ¹⁰⁷Ag or to …

Core Scattering Of Stark Wave Packets, M. L. Naudeau, C. I. Sukenik, P. H. Bucksbaum

Physics Faculty Publications

We investigate the wave packet dynamics of electrons bound in the nonseparable potential of cesium in a static electric field using time-domain Ramsey interferometry. Specially shaped wave packets with low radial dispersion enable us to view the interaction between the wave packet and the atomic core. Experiments in cesium, together with quantum defect calculations of cesium and hydrogen, demonstrate changes in the motion and shape of these wave packets due to core scattering.

Monte Carlo Study Of The Square-Lattice Annealed Ising Model On Percolating Clusters, P. D. Scholten, Miron Kaufman

Physics Faculty Publications

Simulations of an Ising q-state Pods model which is equivalent to the Ising model on annealed percolation clusters are used to determine the phase diagram of the model in two dimensions. Three topologically different phase diagrams are obtained: (i) for q=2, there are two critical Ising lines meeting at T=0 at the four-state Potts critical point; (ii) for 24, the Ising:critical line intersects a Line of first-order transitions at a critical end point.

Quantum Manifestations Of Bifurcations Of Closed Orbits In The Photodetachment Cross Section Of H- In Parallel Fields, Aaron D. Peters, Charles Jaffé, J. Gao, John B. Delos

Arts & Sciences Articles

In the preceding paper, we showed that the semiclassical approximation diverges at a bifurcation, and that this divergence coincides with the passage of a focused cusp through the origin. Here we obtain a wave function in the vicinity of this cusp, and we use that wave function to eliminate the divergences in the photodetachment cross section. To describe the focused cusp, we first discuss the wave function of an ordinary two-dimensional (nonfocused) cusp. This wave function is known as a Pearcey function, and it has been studied extensively. Then we show how the formulas that lead to the Pearcey function …