Physical Sciences and Mathematics Commons^™

Electron Self-Energy For The K And L Shells At Low Nuclear Charge, Ulrich D. Jentschura, Peter J. Mohr, Gerhard Soff

Physics Faculty Research & Creative Works

A nonperturbative numerical evaluation of the one-photon electron self-energy for the K- and L-shell states of hydrogenlike ions with nuclear charge numbers Z =1 to 5 is described. Our calculation for the 1S_1/2 state has a numerical uncertainty of 0.8 Hz in atomic hydrogen, and for the L-shell states (2S_1/2 , 2P_1/2 , and 2P_3/2) the numerical uncertainty is 1.0 Hz. The method of evaluation for the ground state and for the excited states is described in detail. The numerical results are compared to results based on known terms in the expansion of the self-energy …

Cross Sections Spring 2001, Department Of Physics And Astronomy

Cross Sections

No abstract provided.

Tests Of Enhanced Leading Order Qcd In W Boson Plus Jets Events From 1.8 Tev P̅P Collisions, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a study of events with W bosons and hadronic jets produced in p̅p collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W→eν decay candidates from 108 pb^-1 of integrated luminosity collected using the CDF detector at the Fermilab Tevatron collider. Cross sections and jet production properties have been measured for W+≥1 to ≥4 jet events. The data compare well to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.

Interchannel Coupling In The Photoionization Of The M-Shell Of Kr Well Above Threshold: Experiment And Theory, H. S. Chakraborty, D. L. Hansen, Oliver Hemmers, P. C. Deshmukh, P. Focke, I. A. Sellin, Clemens Heske, Dennis W. Lindle, S. T. Manson

Environmental Studies Faculty Publications

Photoionization cross sections and asymmetry (β) parameters for Kr 3s, 3p, and 3d subshells have been measured and calculated in the 300–1300-eV photon energy range. Good agreement between experiment and theory is found for both cross-section branching ratios and β parameters. Interchannel coupling among the channels arising from 3s, 3p, and 3d subshells is found to be necessary for quantitative accuracy of the theory. This shows that the interchannel coupling phenomenology far above threshold, found previously for outer shells of Ne and Ar, is also operative for inner atomic shells.

Organization And Bifurcation Of Planar Closed Orbits Of An Atomic Electron In Crossed Fields, D. M. Wang, John B. Delos

Arts & Sciences Articles

We describe the patterns of creation and splitting of planar closed orbits of electrons in hydrogen atoms in crossed electric and magnetic fields. These orbits lie in the plane perpendicular to the magnetic field, and they start and end at the nucleus. Using a Poincaré map to study the regular motions, we observe that the bifurcations of planar closed orbits fall into an ordered sequence as energy changes: a “tangent bifurcation” creates one closed orbit that splits into two; subsequently, one of them becomes periodic, and splits by a “pitchfork bifurcation” into two periodic orbits and one closed orbit. Based …

Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch

Electrical & Computer Engineering Theses & Dissertations

A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 μm. This wavelength …

Mitigation Of Water Vapor Interference For Infrared Polarization-Modulated Gas Filter Correlation Radiometry, David K. Lockwood

Electrical & Computer Engineering Theses & Dissertations

Gas filter correlation radiometry (GFCR) is a high-resolution, high-specificity technique for sensing gaseous species. A variation of absorption spectroscopy, GFCR has a long-proven record on orbital platforms for quantitative measurements of atmospheric constituents, as well as common usage in ground-based sensing applications. PMGFCR (Polarization-modulated GFCR) is a recent refinement of the technique with several advantages over the traditional method, including reducing the number of photodetectors required, increased sensitivity, and elimination of moving parts.

To date, no infrared remote sensors have successfully measured nitric oxide (NO) in vehicle exhaust due to spectral overlap by strong water vapor (H₂O_{v …}

Turbulent Conductivity Measurements In A Spherical Liquid Sodium Flow, Amy Reighard , '01, Michael R. Brown

Physics & Astronomy Faculty Works

We report the first measurement of a reduction in the conductivity of liquid sodium due to turbulence in a spherical flow (the beta effect). The sodium is contained in a 0.15 m diameter sphere, typical flow speeds are about 1 m/s, and magnetic Reynold's numbers range from 1 to 8. We find a reduction from the molecular value of the conductivity of about 4%. Results are in rough agreement with simple predictions from mean-field electrodynamics.

Experimental Observation Of Rainbow Scattering By A Coated Cylinder: Twin Primary Rainbows And Thin-Film Interference, Charles L. Adler, James A. Lock, Justin K. Nash, Kirk W. Saunders

Physics Faculty Publications

We experimentally examine the primary rainbow created by the illumination of a coated cylinder. We present a simple technique for varying the coating thickness over a wide range of values, and we see evidence for two different scattering regimes. In one, where the coating thickness is large, twin rainbows are produced. In the second, where the coating is thin enough to act as a thin film, a single rainbow is produced whose intensity varies periodically as the coating thickness varies. We find good agreement with previous theoretical predictions. (C) 2001 Optical Society of America.

Ratio Of Jet Cross Sections At √S = 630 Gev And 1800 Gev, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

The D0 Collaboration has measured the inclusive jet cross section in p̅p collisions at √s = 630 GeV. The results for pseudorapidities ∣η∣ < 0.5 are combined with our previous results at √s =1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.

First-Principles Elastic Constants And Electronic Structure Of Α-Pt2si And Ptsi, Gus L. W. Hart, O. Beckstein, J. E. Klepeis, O. Pankratov

Faculty Publications

We have carried out a first-principles study of the elastic properties and electronic structure for two room-temperature stable Pt silicide phases, tetragonal α-Pt2Si, and orthorhomic PtSi. We have calculated all of the equilibrium structural parameters for both phases; the a and c lattice constants for α-Pt2Si and the a, b, and c lattice constants and four internal structural parameters for PtSi. These results agree closely with experimental data. We have also calculated the zero-pressure elastic constants, confirming prior results for pure Pt and Si and predicting values for the six (nine) independent, nonzero elastic constants of α-Pt2Si (PtSi). These calculations …

The Geometrical Structure Of 2d Bond-Orientational Order, Mark Bowick, Alex Travesset

Physics - All Scholarship

We study the formulation of bond-orientational order in an arbitrary two dimensional geometry. We find that bond-orientational order is properly formulated within the framework of differential geometry with torsion. The torsion reflects the intrinsic frustration for two-dimensional crystals with arbitrary geometry. Within a Debye-Huckel approximation, torsion may be identified as the density of dislocations. Changes in the geometry of the system cause a reorganization of the torsion density that preserves bond-orientational order. As a byproduct, we are able to derive several identities involving the topology, defect density and geometric invariants such as Gaussian curvature. The formalism is used to derive …

Magnetic Phase Diagram Of The Diluted Metamagnet Fe0.95Mg0.05Br2, H. Aruga Katori, K. Katsumata, O. Petracic, Wolfgang Kleemann, T. Kato, Christian Binek

Christian Binek Publications

The axial magnetic phase diagram of the antiferromagnet Fe_0.95Mg_0.05Br₂ is studied by specific heat, superconducting quantum interference device, and Faraday rotation techniques. The diamagnetic impurities give rise to random-field criticality along the second-order phase line H_c(T) between T_N=13.1 K and a multicritical point at T_m≈5 K, and to a spin-flop line between T_m and the critical end-point temperature T_e≈3.5 K. The phase line H₁(T)c(T) ending at T_m is probably due to symmetric nondiagonal exchange.

Universality Classes Of Self-Avoiding Fixed-Connectivity Membranes, Mark Bowick, Angelo Cacciuto, Gudmar Thorleifsson, Alex Travesset

Physics - All Scholarship

We present an analysis of extensive large-scale Monte Carlo simulations of self-avoiding fixed-connectivity membranes for sizes (number of faces) ranging from 512 to 17672 (triangular) plaquettes. Self-avoidance is implemented via impenetrable plaquettes. We simulate the impenetrable plaquette model in both three and four bulk dimensions. In both cases we find the membrane to be flat for all temperatures: the size exponent in three dimensions is nu=0.95(5) (Hausdorff dimension d_H=2.1(1)). The single flat phase appears, furthermore, to be equivalent to the large bending rigidity phase of non-self-avoiding fixed-connectivity membranes - the roughness exponent in three dimensions is xi=0.63(4). This suggests that …

Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal

Theses and Dissertations

More than 100,000 spectral features from a Bi₂(X¹ Σ⁺_g → A(0⁺_u)) absorption spectrum, encompassing 0 ≤ v' ≤ 91, 0 ≤ v" ≤ 7 and J2(A). Ground state constants, reported by Barrow et al. [1], remain unchanged. The new constants are used to redefine the A-state potential using traditional RKR methods and to set the dissociation energy at De = 29,913 cm"1, which correlates A-state dissociation products to ⁴S + ²D atoms. A pulsed dye laser apparatus was used to obtain lifetime data for Bi₂A(0⁺_u) …

Interacting Ferromagnetic Nanoparticles In Discontinuous Co80Fe20/Al2O3 Multilayers: From Superspin Glass To Reentrant Superferromagnetism, W. Kleeman, O. Petracic, Christian Binek, G.N. Kakazei, Yu. G. Pogorelov, J.B. Sousa, Susana Cardoso De Freitas, P.P. Freitas

Christian Binek Publications

Dipolar superferromagnetism with reentrant low-temperature superspin glass behavior is observed on a randomly distributed ferromagnetic nanoparticle systems in discontinuous metal-insulator multilayers [Co₈₀Fe₂₀/Al₂O₃ (3 nm)] ₁₀ with nominal thickness 1.1<~t<~1.3 nm by use of ac susceptometry and dc magnetometry. At t=1.0 nm, superspin glass-like freezing is evidenced by the criticality of dynamic and nonlinear susceptibilities.

Broken Supersymmetric Shape Invariant Systems And Their Potential Algebras, Asim Gangopadhyaya, Jeffrey Mallow, Uday P. Sukhatne

Physics: Faculty Publications and Other Works

Although eigenspectra of one dimensional shape invariant potentials with unbroken supersymmetry are easily obtained, this procedure is not applicable when the parameters in these potentials correspond to broken supersymmetry, since there is no zero energy eigenstate. We describe a novel two-step shape invariance approach as well as a group theoretic potential algebra approach for solving such broken supersymmetry problems.

Crossover From Phase Fluctuation To Amplitude-Dominated Superconductivity: A Model System, Richard P. Barber Jr., L. Merchant, J. Ostrick, Robert C. Dynes

Physics

We have experimentally studied a model system that demonstrates the crossover from a superconductor that is dominated by phase fluctuations, to one in which the amplitude of the order parameter is the controlling influence on Tc. This model system is comprised of two-dimensional granular Pb with an overlayer of Ag. The system displays many aspects of the phase diagram of the concentration dependence of Tc in the high-Tc superconductors, and this crossover has been applied to explain the phase diagram in that case. We point out the similarities and differences between the model system presented in this paper and the …

Ratios Of Multijet Cross Sections In Pp̅ Collisions At √S = 1.8 Tev, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We report on a study of the ratio of inclusive three-jet to inclusive two-jet production cross sections as a function of total transverse energy in pp̅ collisions at a center-of-mass energy√s = 1.8 TeV, using data collected with the D0 detector during the 1992–1993 run of the Fermilab Tevatron Collider. The measurements are used to deduce preferred renormalization scales in perturbative O(α_s³) QCD calculations in modeling soft-jet emission.

High Mobility In N-Type Gan Substrates, A. Saxler, David C. Look, S. Elhamri, J. R. Sizelove, William C. Mitchel, C. M. Sung, S. S. Park, K. Y. Lee

Physics Faculty Publications

No abstract provided.

Review Of Integrated Physics And Calculus By Andrew F. Rex And Martin Jackson, Robert Fuller

Robert G. Fuller Publications

Are you ready to try something that seems obvious and yet is innovative? If so, then maybe you are ready to teach a combined physics and calculus course. In fact, many of us who have been teaching calculus-based physics have always felt that we had to teach both physics and calculus, because our students seemed to be unable to do anything we thought they had learned to do in the prerequisite calculus course(s).

Now, at last, a courageous physicist and mathematician have worked together to create a combined physics and calculus textbook. Professors Rex and Jackson have written a textbook …

Open Strings, 2d Gravity, And Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We present a detailed discussion of the duality between dilaton gravity on AdS₂ and open strings. The correspondence between the two theories is established using their symmetries and field theoretical, thermodynamic, and statistical arguments. We use the dual conformai field theory to describe two-dimensional black holes. In particular, all the semiclassical features of the black holes, including the entropy, have a natural interpretation in terms of the dual microscopic conformai dynamics. The previous results are discussed in the general framework of the anti-de Sitter/conformal field theory dualities.

Effects Of Concentration And Temperature On The Coupled Heat And Mass Transport In Liquid Mixtures, Yaşar Demirel, Stanley I. Sandler

Papers in Thermal Mechanics

Using published experimental data on the thermal conductivity, mutual diffusivity, and heats of transport, the degree of coupling between heat and mass flows has been calculated for binary and ternary nonideal liquid mixtures. The binary mixtures consist of two types: the first is six systems of six-to-eight-carbon straight and branched chain alkanes in chloroform and in carbon tetrachloride; and the second is mixtures of carbon tetrachloride with benzene, toluene, 2-propanone, n-hexane, and 11-octane. The ternary mixture considered is toluene-chlorobenzene-bromobenzene. The published data are available at 35°C, 30°C, and 35°C and ambient pressure. Using the linear nonequilibi-ium thermodynainics (LNET) and the …

Fractal Quasar Clouds, Mark Bottorff, Gary J. Ferland

Physics and Astronomy Faculty Publications

This paper examines whether a fractal cloud geometry can reproduce the emission-line spectra of active galactic nuclei (AGNs). The nature of the emitting clouds is unknown, but many current models invoke various types of magnetohydrodynamic confinement. Recent studies have argued that a fractal distribution of clouds, in which subsets of clouds occur in self-similar hierarchies, is a consequence of such confinement. Whatever the confinement mechanism, fractal cloud geometries are found in nature and may be present in AGNs too. We first outline how a fractal geometry can apply at the center of a luminous quasar. Scaling laws are derived that …

Phase Modulation At 125 Khz In A Michelson Interferometer Using An Inexpensive Piezoelectric Stack Driven At Resonance, Barbara M. Hoeling, Andrew D. Fernandez, Richard C. Haskell, Daniel C. Petersen

All HMC Faculty Publications and Research

Fast phase modulation has been achieved in a Michelson interferometer by attaching a lightweight reference mirror to a piezoelectric stack and driving the stack at a resonance frequency of about 125 kHz. The electrical behavior of the piezo stack and the mechanical properties of the piezo-mirror arrangement are described. A displacement amplitude at resonance of about 350 nm was achieved using a standard function generator. Phase drift in the interferometer and piezo wobble were readily circumvented. This approach to phase modulation is less expensive by a factor of roughly 50 than one based on an electro-optic effect.

Measurement Of The Angular Distribution Of Electrons From W→Eν Decays Observed In Pp̅ Collisions At √S =1.8 Tev, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We present the first measurement of the electron angular distribution parameter α₂ in W→eν events produced in proton-antiproton collisions as a function of the W boson transverse momentum. Our analysis is based on data collected using the DØ detector during the 1994–1995 Fermilab Tevatron run. We compare our results with next-to-leading order perturbative QCD, which predicts an angular distribution of (1 ± α₁cos θ*+ α₂ cos² θ*), where θ* is the polar angle of the electron in the Collins-Soper frame. In the presence of QCD corrections, the parameters a1 and a2 become functions of …

X-Ray Velocimetry Of Solar Wind Ion Impact On Comets, P. Beiersdorfer, C. M. Lisse, Ronald E. Olson, G. V. Brown, H. Chen

Physics Faculty Research & Creative Works

Laboratory measurements of the interaction of low-energy, bare, and hydrogen-like ions with neutral gases are presented. The measurements demonstrate that charge-exchange-induced cometary K-shell X-ray spectra represent rich spectral diagnostics for determining the speed of the solar wind and the collision dynamics within the coma. We show that the K-shell spectrum observed from low-energy ion-neutral collisions (≤ 50 km s-1) has a distinct high-energy component that is suppressed in high-energy collisions (≥800 km s-1). As a result, the hardness ratio of the K-shell spectrum increases by as much as a factor of 4 as the ions decelerate in the coma. The …

Effects Of Relativity On The Time-Resolved Tunneling Of Electron Wave Packets, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

We solve numerically the time-dependent Dirac equation for a quantum wave packet tunneling through a potential barrier. We analyze the spatial probability distribution of the transmitted wave packet in the context of the possibility of effectively superluminal peak and front velocities of the electron during tunneling. Both the Dirac and Schrodinger theories predict superluminal tunneling speeds. However, in contrast to the Dirac theory the Schrodinger equation allows a possible violation of causality. Based on an analysis of the tunneling process in full temporal and spatial resolution, we introduce an instantaneous tunneling speed that can be computed inside the potential barrier.

Critical Wavelength For River Meandering, Boyd F. Edwards, D. H. Smith

All Physics Faculty Publications

A fully nonlinear modal analysis identifies a critical centerline wave number q_c for river meandering that separates long-wavelength bends, which grow to cutoff, from short-wavelength bends, which decay. Exact, numerical, and approximate analytical results for q_c rely on the Ikeda, Parker, and Sawai [J. Fluid Mech. 112, 363 (1981)] model, supplemented by dynamical equations that govern the river migration and length. Predictions also include upvalley bend migration at long times and a peak in lateral migration rates at intermediate times. Experimental tests are suggested.

New Solvable Singular Potentials , R. Dutt, Asim Gangopadhyaya, C. Rasinariu, Uday P. Sukhatne

Physics: Faculty Publications and Other Works

We obtain three new solvable, real, shape invariant potentials starting from the harmonic oscillator, Pöschl-Teller I and Pöschl-Teller II potentials on the half-axis and extending their domain to the full line, while taking special care to regularize the inverse square singularity at the origin. The regularization procedure gives rise to a delta-function behavior at the origin. Our new systems possess underlying non-linear potential algebras, which can also be used to determine their spectra analytically.