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On The Stark Broadening Parameters Of The Two Nii Spectral Lines Of The 3d-4f Transition, Vladimir Milosavljevic, Stevan Djenize Jun 1997

On The Stark Broadening Parameters Of The Two Nii Spectral Lines Of The 3d-4f Transition, Vladimir Milosavljevic, Stevan Djenize

Articles

Stark parameters (width and shift) of two singly ionized nitrogen spectral lines, that belong to 3d-4f transition have been measured in a linear pulsed, low pressure, arc discharge in the nitrogen-oxygen plasma at a 54000 K electron temperature and at a 2.8×10 23 m−3 electron density. The measured values have been compared to the existing experimental and calculated data

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Anharmonic Potentials In Supercooled Liquids: The Soft-Potential Model, Ulrich Zürcher, T. Keyes Jun 1997

Anharmonic Potentials In Supercooled Liquids: The Soft-Potential Model, Ulrich Zürcher, T. Keyes

Physics Faculty Publications

Instantaneous normal modes (INM) are the harmonic approximation to liquid dynamics. This is an extension of the phonon description of lattice dynamics, in which case Bloch's theorem shows that all modes are extended. Long-range order is destroyed in liquids and glasses, and the INM spectrum has contributions from both extended and localized modes. We use the soft-potential mode to describe localized modes. This model is a high-temperature extension of the standard two-level-system model for glasses. The equilibrium position of any atom in the liquid has only temporary character, and relaxation processes in the liquid are associated with particles hopping over …

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High-Order Interior Caustics Produced In Scattering Of A Diagonally Incident Plane Wave By A Circular Cylinder, Charles L. Adler, James A. Lock, Bradley R. Stone, Claudio J. Garcia Jun 1997

High-Order Interior Caustics Produced In Scattering Of A Diagonally Incident Plane Wave By A Circular Cylinder, Charles L. Adler, James A. Lock, Bradley R. Stone, Claudio J. Garcia

Physics Faculty Publications

We examine scattering of a family of initially parallel diagonally incident rays by a dielectric circular cylinder and show that the interior and exterior caustics that occur are qualitatively identical to those produced at normal incidence. We find, however, that (1) varying the plane-wave tilt angle has the same effect on the caustics as varying the refractive index of the cylinder at normal incidence and (2) high-order interior caustics are visible because of larger internal-reflection Fresnel coefficients at diagonal incidence than at normal incidence. We also observe noncaustic ray trajectories produced by the sharp peaking of internal-reflection Fresnel coefficients at …

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Debye-Series Analysis Of The First-Order Rainbow Produced In Scattering Of A Diagonally Incident Plane Wave By A Circular Cylinder, James A. Lock, Charles L. Adler Jun 1997

Debye-Series Analysis Of The First-Order Rainbow Produced In Scattering Of A Diagonally Incident Plane Wave By A Circular Cylinder, James A. Lock, Charles L. Adler

Physics Faculty Publications

We derive the Debye-series expansion of the partial-wave scattering and interior amplitudes for the interaction of a diagonally incident beam of arbitrary profile with an infinitely long homogeneous dielectric circular cylinder. We then discuss the physical interpretation of the various terms of the series. We also consider the one-internal-reflection Debye-series terms for diagonal plane-wave incidence and examine the first-order rainbow extinction transition as a function of the tilt angle of the incident plane wave. We experimentally observe the first-order rainbow extinction transition and compare our observations with the Debye-series predictions. (C) 1997 Optical Society of America.

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Localization And Transport Effects In The Disordered Materials, Vladislav Malyshkin Jun 1997

Localization And Transport Effects In The Disordered Materials, Vladislav Malyshkin

Dissertations

No abstract provided.

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The Equation Of State For Two Flavor Qcd At N_T=6, James E. Hetrick, C. Bernard Jun 1997

The Equation Of State For Two Flavor Qcd At N_T=6, James E. Hetrick, C. Bernard

All Faculty Articles - School of Engineering and Computer Science

We improve the calculation of the equation of state for two flavor QCD by simulating on Nt = 6 lattices at appropriate values of the couplings for the deconfinement/chiral symmetry restoration crossover. For amq = 0.0125 the energy density rises rapidly to approximately 1 GeV/fm3 just after the crossover (mπ/mρ ≈ 0.4 at this point). Comparing with our previous result for Nt = 4 [1], we find large finite Nt corrections as expected from free field theory on finite lattices. We also provide formulae for extracting the speed of sound from the measured quantities.

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Degenerate Layer At Gan/Sapphire Interface: Influence On Hall-Effect Measurements, David C. Look, Richard J. Molnar Jun 1997

Degenerate Layer At Gan/Sapphire Interface: Influence On Hall-Effect Measurements, David C. Look, Richard J. Molnar

Physics Faculty Publications

Temperature-dependent Hall-effect measurements in hydride vapor phase epitaxial GaN grown on sapphire can be well fitted over the temperature range 10–400 K by assuming a thin, degenerate n-type region at the GaN/sapphire interface. This degenerate interfacial region dominates the electrical properties below 30 K, but also significantly affects those properties even at 400 K, and can cause a second, deeper donor to falsely appear in the analysis. However, by using a two-layer Hall model, the bulk mobility and carrier concentration can be accurately ascertained.

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Breakdown Of The Independent Particle Approximation In High-Energy Photoionization, E. W. B. Dias, H. S. Chakraborty, P. C. Deshmukh, S. T. Manson, Oliver Hemmers, P. Glans, D. Hansen, H. Wang, S. B. Whitfield, Dennis W. Lindle, R. Wehlitz, Jon C. Levin, I. A. Sellin Jun 1997

Breakdown Of The Independent Particle Approximation In High-Energy Photoionization, E. W. B. Dias, H. S. Chakraborty, P. C. Deshmukh, S. T. Manson, Oliver Hemmers, P. Glans, D. Hansen, H. Wang, S. B. Whitfield, Dennis W. Lindle, R. Wehlitz, Jon C. Levin, I. A. Sellin

Environmental Studies Faculty Publications

The independent particle approximation is shown to break down for the photoionization of both inner and outer nℓ (ℓ>0) electrons of all atoms, at high enough energy, owing to interchannel interactions with the nearby ns photoionization channels. The effect is illustrated for Ne 2p in the 1 keV photon energy range through a comparison of theory and experiment. The implications for x-ray photoelectron spectroscopy of molecules and condensed matter are discussed.

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Physical Conditions Of The Coronal Line Region In Seyfert Galaxies, Jason W. Ferguson, Kirk Korista, Gary J. Ferland Jun 1997

Physical Conditions Of The Coronal Line Region In Seyfert Galaxies, Jason W. Ferguson, Kirk Korista, Gary J. Ferland

Physics and Astronomy Faculty Publications

The launch of the Infrared Space Observatory and new atomic data have opened a window for the study of high-ionization gas in active galactic nuclei (AGNs). We present the results of a large number of photoionization simulations of the "coronal line" region in AGNs, employing new atomic data from the Opacity and Iron Projects. Our grid of line emission spans 8 orders of magnitude in gas density and 14 orders of magnitude in ionizing flux in an effort to identify the optimal conditions in which these lines form. We show that coronal lines form at distances from just outside the …

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Calibration Methodology And Multiple Tip Structure By Scanning Tunneling Microscopy., Michael Stephen Gossman Jun 1997

Calibration Methodology And Multiple Tip Structure By Scanning Tunneling Microscopy., Michael Stephen Gossman

Electronic Theses and Dissertations

The scanning tunneling microscope has been in commercial use just over a decade. Due to its Quantum Mechanical nature, experiments in this area have been widely publicized to the scientific community. The apparatus is steadily growing easier to use, though fundamental problems are still present. In the first chapter, an address is given on the modem theory of tunneling to rationalize the conclusions Physicists made long ago about this phenomenon. The expanded theory generalizes the mathematical motivation for attempting such unique experiments and serves as a lead-in for the major components of the apparatus. Many texts do not quantize what …

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Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic Jun 1997

Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic

Theses and Dissertations

This dissertation had three objectives. The first objective was to develop image quality metrics that characterize Adaptive Optics System (AOS) performance. The second objective was to delineate control settings that maximize AOS performance. The third objective was to identify and characterize trade-offs between fully and partially compensated adaptive. For the first objective, three candidate image quality metrics were considered: the Strehl ratio, a novel metric that modifies the Strehl ratio by integrating the modulus of the average system optical transfer function to a 'noise-effective-cutoff' frequency at which some specified image spectrum signal-to-noise-ratio level is attained, and the noise-effective-cutoff frequency. It …

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Kinetics And Spectroscopy Of Brno, Patrick E. Godfrey Jun 1997

Kinetics And Spectroscopy Of Brno, Patrick E. Godfrey

Theses and Dissertations

The infrared spectra and photochemistry of nitrosyl bromide, BrNO, are important to characterizing the performance of a recently demonstrated Br(2P1/2)-NO(v=2 → v=1) transfer laser pumped by photolysis of iodine molecules. This wavelength agile, mid-infrared laser may be a desirable source for remote sensing and infrared countermeasures missions. Nitrosyl bromide also plays a role in the destruction of stratospheric ozone. The kinetics of BrNO formation and destruction were examined using time-resolved photolysis techniques. The equilibrium constant for the dark reaction Br2 + 2NO (reversible reaction) 2BrNO was determined as Keq 168 ± 23 /atm and …

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Differential Cross Sections Of D*± Photoproduction In Ep Collisions At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, R. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, R. Giusti, G. Iacobucci, G. Laurenti, G. Levi May 1997

Differential Cross Sections Of D*± Photoproduction In Ep Collisions At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, R. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, R. Giusti, G. Iacobucci, G. Laurenti, G. Levi

Faculty Publications

Inclusive photoproduction of D*± in ep collisions at HERA has been measured with the ZEUS detector for photon-proton centre of mass energies in the range 115 < W < 280 GeV and photon virtuality Q2 < 4 GeV2. The cross section σ → D*X integrated over the kinematic region pDz.ast;⊥ > 3 GeV and -1.5 < ηD* < 1.0 is (10.6 ± 1.7(stat.) ± 1.61.3 (syst.)) nb. Differential cross sections as functions of pD*⊥, ηD* and W are given. The data are compared with two next-to-leading order perturbative QCD predictions. For a calculation using a massive charm scheme the predicted cross sections are smaller than the measured ones. A recent calculation using a massless charm scheme is in agreement with the data. © 1997 Published by Elsevier Science B.V.

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Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Ix. Ultraviolet Observations Of Fairall, P.M. Rodriguez-Pascual, D. Allion, J. Clavel, D. Michael Crenshaw, K. Horne, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Paul T. O'Brien, Bradley M. Peterson, G.A. Reichert, W. Wamsteker, T. Alexander, P. Barr, R.D. Blandford, J.N. Bergman, T.E. Carone, S. Clements, T.-J. Courvoisier, M.M. De Robertis, M. Dietrich, H. Dottori, R.A. Edelson, A. V. Filippenko, C. Martin Gaskell, J. P. Huchra, J.B. Hutchings, W. Kollatschny, A.P. Koratkar, Kirk T. Korista, Ari Laor, G.M. Macalpine, P. G. Martin, D. Maoz, B. Mccollum, S.L. Morris, G.C. Perola, Richard William Pogge, R.L. Ptak, M.C. Recondo-Gonzalez, J.M. Rodriguez-Espinoza, E.L. Rokaki, M. Santos-Lleo, K. Sekiguchi, J.M. Schull, M.A.J. Snuders, L.S. Sparke, G.M. Stirpe, R.E. Stoner, W.-H. Sun, S.J. Wagner, I. Wanders, Belinda J. Wilkes, C. Winge, W. Zheng May 1997

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Ix. Ultraviolet Observations Of Fairall, P.M. Rodriguez-Pascual, D. Allion, J. Clavel, D. Michael Crenshaw, K. Horne, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Paul T. O'Brien, Bradley M. Peterson, G.A. Reichert, W. Wamsteker, T. Alexander, P. Barr, R.D. Blandford, J.N. Bergman, T.E. Carone, S. Clements, T.-J. Courvoisier, M.M. De Robertis, M. Dietrich, H. Dottori, R.A. Edelson, A. V. Filippenko, C. Martin Gaskell, J. P. Huchra, J.B. Hutchings, W. Kollatschny, A.P. Koratkar, Kirk T. Korista, Ari Laor, G.M. Macalpine, P. G. Martin, D. Maoz, B. Mccollum, S.L. Morris, G.C. Perola, Richard William Pogge, R.L. Ptak, M.C. Recondo-Gonzalez, J.M. Rodriguez-Espinoza, E.L. Rokaki, M. Santos-Lleo, K. Sekiguchi, J.M. Schull, M.A.J. Snuders, L.S. Sparke, G.M. Stirpe, R.E. Stoner, W.-H. Sun, S.J. Wagner, I. Wanders, Belinda J. Wilkes, C. Winge, W. Zheng

C. Martin Gaskell Publications

No abstract provided.

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Empirical Studies Of Ionospheric Electric Fields, Ludger Scherliess May 1997

Empirical Studies Of Ionospheric Electric Fields, Ludger Scherliess

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The first comprehensive study of equatorial- to mid-latitude ionospheric electric fields (plasma drifts) is presented, using extensive incoherent scatter radar measurements from Jicamarca, Arecibo, and Millstone Hill, and F-region ion drift meter data from the polar orbiting DE-2 satellite. Seasonal and solar cycle dependent empirical quiet-time electric field models from equatorial to mid latitudes are developed, which improve and extend existing climatological models. The signatures of electric field perturbations during geomagnetically disturbed periods, associated with changes in the high-latitude currents and the characteristics of storm-time dynamo electric fields driven by enhanced energy deposition into the high-latitude ionosphere, are studied. Analytical …

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A Measurement Of Rb Using A Lifetime-Mass Tag, R. Barate, Manoj Thulasidas May 1997

A Measurement Of Rb Using A Lifetime-Mass Tag, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

ALEPH's published measurement of Rb = Γ(Ζ → bb̄)/Γ(Ζ → hadrons) using a lifetime tag is updated using the full LEP 1 data sample. Considerable effort has been devoted to understanding systematic effects. Charm background is better controlled by combining the lifetime tag with a tag based on the b/c hadron mass difference. Furthermore, the algorithm used to reconstruct the event primary vertex is designed so as to reduce correlations between the two hemispheres of an event. The value of Rb is measured to be 0.2167 ± 0.0011 (stat) ± 0.0013 (syst).

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Analyses Of D+→KS0K+ And D+ → KS0Π+, M. Bishai, Kenneth A. Bloom, Cleo Collaboration Apr 1997

Analyses Of D+→KS0K+ And D+ → KS0Π+, M. Bishai, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using data collected with the CLEO II detector at the Cornell Electron Storage Ring, we present new measurements of the branching fractions for D+→KSK+and D+ → KSπ+ . These results are combined with other CLEO measurements to extract the ratios of isospin amplitudes and phase shifts for D → KK and D → K π.

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Intrinsic Decoherence In Mesoscopic Systems, P. Mohanty, E. M.Q. Jariwala, Richard A. Webb Apr 1997

Intrinsic Decoherence In Mesoscopic Systems, P. Mohanty, E. M.Q. Jariwala, Richard A. Webb

Faculty Publications

We present measurements of the phase coherence time τφ in six quasi-1D Au wires and clearly show that τφ is temperature independent at low temperatures. We suggest that zero-point fluctuations of the phase coherent electrons are responsible for the observed saturation of τφ. We introduce a new functional form for the temperature dependence and present the results of a calculation for the saturation value of τφ. This explains the observed temperature dependence of our samples as well as many 1D and 2D systems reported to date.

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Efficiency Of Molecular Hydrogen Formation On Silicates, Gianfranco Vidali, Valerio Pirronello, Ofer Biham, Chi Liu, Lyiong Shen Apr 1997

Efficiency Of Molecular Hydrogen Formation On Silicates, Gianfranco Vidali, Valerio Pirronello, Ofer Biham, Chi Liu, Lyiong Shen

Physics - All Scholarship

We report on laboratory measurements of molecular hydrogen formation and recombination on an olivine slab as a function of surface temperature under conditions relevant to those encountered in the interstellar medium. On the basis of our experimental evidence, we recognize that there are two main regimes of H coverage that are of astrophysical importance; for each of them we provide an expression giving the production rate of molecular hydrogen in interstellar clouds.

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Multiflavor Massive Schwinger Model With Non-Abelian Bosonization, Joseph Schechter, David Delphenich Apr 1997

Multiflavor Massive Schwinger Model With Non-Abelian Bosonization, Joseph Schechter, David Delphenich

Physics - All Scholarship

We revisit the treatment of the multiflavor massive Schwinger model by non-Abelian Bosonization. We compare three different approximations to the low-lying spectrum: i) reading it off from the bosonized Lagrangian (neglecting interactions), ii) semi-classical quantization of the static soliton, iii) approximate semi-classical quantization of the ``breather'' solitons. A number of new points are made in this process. We also suggest a different ``effective low-energy Lagrangian'' for the theory which permits easy calculation of the low-energy scattering amplitudes. It correlates an exact mass formula of the system with the requirement of the Mermin-Wagner theorem.

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Generalization Of The Bound State Model, Joseph Schechter, Masayasu Harada, Francesco Sannino, Herbert Weigel Apr 1997

Generalization Of The Bound State Model, Joseph Schechter, Masayasu Harada, Francesco Sannino, Herbert Weigel

Physics - All Scholarship

In the bound state approach the heavy baryons are constructed by binding, with any orbital angular momentum, the heavy meson multiplet to the nucleon considered as a soliton in an effective meson theory. We point out that this picture misses an entire family of states, labeled by a different angular momentum quantum number, which are expected to exist according to the geometry of the three-body constituent quark model (for N_C=3). To solve this problem we propose that the bound state model be generalized to include orbitally excited heavy mesons bound to the nucleon. In this approach the missing angular momentum …

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Accurate Hydrogen Spectral Simulations With A Compact Model Atom, Jason W. Ferguson, Gary J. Ferland Apr 1997

Accurate Hydrogen Spectral Simulations With A Compact Model Atom, Jason W. Ferguson, Gary J. Ferland

Physics and Astronomy Faculty Publications

Many large-scale numerical simulations of astrophysical plasmas must also reproduce the hydrogen ionization and the resulting emission spectrum, in some cases quite accurately. We describe a compact model hydrogen atom that can be readily incorporated into such simulations. It reproduces the recombination efficiency and line spectrum predicted by much larger calculations for a very broad range of densities and temperatures. Uncertainties in hydrogen collision data are the largest source of differences between our compact atom and predictions of more extensive calculations and underscore the need for accurate atomic data.

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Angle-Resolved Study Of Ar 2p₁/₂,₃/₂⁻1Ns,D Resonant Auger Decay, Marc Andrew Humphrey Apr 1997

Angle-Resolved Study Of Ar 2p₁/₂,₃/₂⁻1Ns,D Resonant Auger Decay, Marc Andrew Humphrey

Honors Theses

Angle-resolved measurements of the Ar 2p1/2,3/2-14s,3d,4d and 2p3/2-14s,3d,4d resonant Auger transitions have been carried out using photons from an undulator beamline at the Advanced Light Source of Lawrence Berkeley National Laboratory. The intensity distributions and angular distribution anisotropy (β) parameters have been reported for nearly all of the possible 3p4nl final ionic states. These results further verify the predictions of the spectator model for the 2p1/2,3/2-14s resonances and the subsequent breakdown of this model for the 2p1/2,3/2-13d and 2p1/2,3/2-14d relative intensities. This work …

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Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, Michael James Murphy , '98, Catharine Glasheen , '97, Frank Moscatelli, T. D. Donnelly Apr 1997

Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, Michael James Murphy , '98, Catharine Glasheen , '97, Frank Moscatelli, T. D. Donnelly

Physics & Astronomy Faculty Works

We report on experiments investigating the optimization of laser-ablated plasmas which are used to produce recombination-pumped, short-wavelength lasers. We evaluate the density of electrons and neutral atoms in laser ablated lithium and carbon plasmas as a function of time and distance away from the ablated target surface. We use an interferometric technique which can reveal information about the temperature of the plasma electrons. We find that the cold electrons which result in gain in recombination-pumped lithium lasers on the Lyman-cr transition are produced by the high-intensity pump pulse rather than the lower intensity ablating pulse.

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Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, M. Murphy, C. Glasheen, F. A. Moscatelli, Thomas D. Donnelly Apr 1997

Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, M. Murphy, C. Glasheen, F. A. Moscatelli, Thomas D. Donnelly

All HMC Faculty Publications and Research

We report on experiments investigating the optimization of laser-ablated plasmas which are used to produce recombination-pumped, short-wavelength lasers. We evaluate the density of electrons and neutral atoms in laser ablated lithium and carbon plasmas as a function of time and distance away from the ablated target surface. We use an interferometric technique which can reveal information about the temperature of the plasma electrons. We find that the cold electrons which result in gain in recombination-pumped lithium lasers on the Lyman-α transition are produced by the high-intensity pump pulse rather than the lower intensity ablating pulse.

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Wind Climatology At 87 Km Above The Rocky Mountains At Bear Lake Observatory--Fabry-Perot Observations Of Oh, V. B. Wickwar, I K. Monson, C M. Vadnais, D Rees Apr 1997

Wind Climatology At 87 Km Above The Rocky Mountains At Bear Lake Observatory--Fabry-Perot Observations Of Oh, V. B. Wickwar, I K. Monson, C M. Vadnais, D Rees

Reports

This paper presents the neutral -wind climatology at approximately 87-km 53 altitude from Utah State University's Bear Lake Observatory (BLO). a mid-latitude site 54 situated in the middle of the Rocky Mountains. The winds were determined using a very 55 sensitive Fabry-Perot interferometer (FPI) observing the OH Me inel (6-2) PI (3) line al 56 843 nm. The climatology. determined from monthly averages of the nightly evolution of 57 the geographic meridional and zonal wind components over forty· five months, has three 58 distinct seasonal patterns: winter (November- February), summer (May-Jul y), and late 59 Slimmer (August and September). The …

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Chemistry Of The Jovian Auroral Ionosphere, J. J. Perry, Y. H. Kim, Jane L. Fox, H. S. Porter Apr 1997

Chemistry Of The Jovian Auroral Ionosphere, J. J. Perry, Y. H. Kim, Jane L. Fox, H. S. Porter

Physics Faculty Publications

No abstract provided.

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Search For Neutrinoless Τ Decays: Τ→Eγ And Τ→Μγ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration Apr 1997

Search For Neutrinoless Τ Decays: Τ→Eγ And Τ→Μγ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

A search for the lepton-family-number-violating decays τ→eγ and τ→μγ has been performed using CLEO II data. No evidence of a signal has been found and the corresponding upper limits are B(τ→eγ) < 2.7X10-6 and B (τ→μγ),3.0 X 10-6 at 90% C.L.

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Nonanalytic Behavior Of The Spin Susceptibility In Clean Fermi Systems, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta Apr 1997

Nonanalytic Behavior Of The Spin Susceptibility In Clean Fermi Systems, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

The wave vector and temperature-dependent static spin susceptibility, Xs(Q, T), of clean interacting Fermi systems is considered in dimensions 1 ≤ d ≤ 3. We show that at zero temperature Xs is a nonanalytic function of |Q|, with the leading nonanalyticity being |Q|d-1 for 1 < d < 3, and Q2ln|Q| for d = 3. For the homogeneous spin susceptibility we find a nonanalytic temperature dependence Td-1 for 1 < d < 3. We give qualitative mode-mode coupling arguments to that effect, and corroborate these arguments by a perturbative calculation to second order in the electron-electron interaction amplitude. The implications of this, in particular for itinerant ferromagnetism, are discussed. We also point out the relation between our findings and established perturbative results for one-dimensional systems, as well as for the temperature dependence of Xs(Q = 0) in d = 3.

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Sea Brightness Temperature And Effects Of Spray And Whitecaps, Richard P. Barber Jr., Jin Wu Mar 1997

Sea Brightness Temperature And Effects Of Spray And Whitecaps, Richard P. Barber Jr., Jin Wu

Physics

Following the approach of Tang [1974], the microwave brightness of the sea surface is recalculated with recent parameterizations in terms of wind velocity for the slope distribution and whitecap coverage of the sea surface and the contribution of sea spray. The difference between this revised calculation with no free parameters and the earlier one becomes more significant as the wind velocity increases; it reaches 10 K or more at a wind velocity of 20 m s-1. Present predictions compare favorably with experimental results, suggesting that this model does include the essential physical mechanisms.

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