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Articles 31291 - 31320 of 36659

Full-Text Articles in Physical Sciences and Mathematics

New Upper Limit On The Decay Η→E+E-, T. E. Browder, Kenneth A. Bloom, Cleo Collaboration Nov 1997

New Upper Limit On The Decay Η→E+E-, T. E. Browder, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for the rare decay of the η meson η→e+e- using the CLEO II detector. The η’s were produced in e+e- collisions with 10 GeV center-of-mass energy at the Cornell Electron Storage Ring (CESR). We find with 90% confidence the upper limit on the branching fraction B (η→e+e-)<7.7×10-5. The application of conventional elementary particle theory to this decay predicts a branching fraction of about 10-9.

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Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xi. Intensive Monitoring Of The Ultraviolet Spectrum Of Ngc 7469, I. Wanders, Bradley M. Peterson, D. Alloin, T.R. Ayres, J. Clavel, D. Michael Crenshaw, K. Horne, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Paul T. O'Brien, G.A. Reichert, P.M. Rodriguez-Pascual, W. Wamsteker, T. Alexander, K. S.J. Anderson, E. Benitez, N.G. Bochkarev, A.N. Burenkov, F.-Z. Cheng, S.J. Collier, A. Comastri, M. Dietrich, D. Dultzin-Hacyan, B.R. Espey, A. V. Filippenko, C. Martin Gaskell, I.M. George, M.R. Goad, L.C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, Ari Laor, G.M. Macalpine, M. Mignoli, S.L. Morris, K. Nandra, S. Penton, Richard William Pogge, R.L. Ptak, J.M. Rodriguez-Espinoza, M. Santos-Lleo, A.I. Shapovalova, J.M. Shull, Stephanie A. Snedden, L.S. Sparke, G.M. Stirpe, W.-H. Sun, T.J. Turner, M.-H. Ulrich, T.-G. Wang, C. Wei, W.F. Welsh, S.-J. Xue, Z.-L. Zhou Nov 1997

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xi. Intensive Monitoring Of The Ultraviolet Spectrum Of Ngc 7469, I. Wanders, Bradley M. Peterson, D. Alloin, T.R. Ayres, J. Clavel, D. Michael Crenshaw, K. Horne, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Paul T. O'Brien, G.A. Reichert, P.M. Rodriguez-Pascual, W. Wamsteker, T. Alexander, K. S.J. Anderson, E. Benitez, N.G. Bochkarev, A.N. Burenkov, F.-Z. Cheng, S.J. Collier, A. Comastri, M. Dietrich, D. Dultzin-Hacyan, B.R. Espey, A. V. Filippenko, C. Martin Gaskell, I.M. George, M.R. Goad, L.C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, Ari Laor, G.M. Macalpine, M. Mignoli, S.L. Morris, K. Nandra, S. Penton, Richard William Pogge, R.L. Ptak, J.M. Rodriguez-Espinoza, M. Santos-Lleo, A.I. Shapovalova, J.M. Shull, Stephanie A. Snedden, L.S. Sparke, G.M. Stirpe, W.-H. Sun, T.J. Turner, M.-H. Ulrich, T.-G. Wang, C. Wei, W.F. Welsh, S.-J. Xue, Z.-L. Zhou

C. Martin Gaskell Publications

From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes. From the time delays, one can estimate the size of the region dominating the production of the UV emission lines in this source. We find the strong UV emission lines to respond to continuum variations with time delays of about 2.d3-3.d1 for Lyα, 2.d7 for C IV λ1549, 1.d9-2.d4 for N IV λ …

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Nonlinear Response Theory: Transport Coefficients For Driving Fields Of Arbitrary Magnitude, Paul Ernest Parris, Marek Kus, David H. Dunlap, Vasudev M. Kenkre Nov 1997

Nonlinear Response Theory: Transport Coefficients For Driving Fields Of Arbitrary Magnitude, Paul Ernest Parris, Marek Kus, David H. Dunlap, Vasudev M. Kenkre

Physics Faculty Research & Creative Works

A theory of nonlinear response is developed for driving fields of arbitrary magnitude. Exact and usable expressions are provided for electrical and thermal mobility, and related transport coefficients, in terms of correlation functions of the system. A generalization into the nonlinear domain is provided of the Wiedemann-Franz law connecting electrical and thermal response and of the Einstein relation relating the diffusion constant and the mobility.

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Molecular Fluorescence At A Rough Surface: The Orientation Effects, P.T. Leung, W. L. Blacke Nov 1997

Molecular Fluorescence At A Rough Surface: The Orientation Effects, P.T. Leung, W. L. Blacke

Physics Faculty Publications and Presentations

The problem of the dynamical interaction between an emitting dipole and a metallic grating surface is considered with particular interest in the effects due to different orientations of the dipole with respect to the substrate surface. Our previous perturbative theory is extended to treat both parallel and perpendicular dipoles and the results are applied to the study of modified fluorescence characteristics for admolecules in the vicinity of a rough metal surface modeled as a grating. Numerical results show that some of the characteristics are very sensitive to the molecular orientation and the one along the grating direction is manifested with …

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A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby Nov 1997

A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby

Theses and Dissertations

The most current version of the Parameterized Real-time Ionospheric Specification Model (PRISM), version 1.7b, was validated using Digital Ionospheric Sounding System (DISS) measurements of F2 layer critical frequency (foF2) and F2 peak electron density height (hmF2) as the "ground truth." PRISM was executed, first, with no real-time input parameter and, second, with Global Positioning System (GPS) Total Electron Content (TEC) measurements as the sole real-time parameter. Hourly values of hmF2 and foF2 over 123 days in 1994-1996 (solar minimum conditions) and covering three seasons (equinox, summer solstice, and winter solstice) were compared for Wallops Island, Virginia, and Point Arguello, California, …

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Search For The Decay Τ-→4Π-3Π+(Π0)ΝΤ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration Nov 1997

Search For The Decay Τ-→4Π-3Π+(Π0)ΝΤ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for the decay of the τ lepton into seven charged particles and zero or one π0. 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 4.61 fb-. No evidence for a signal is found. Assuming all the charged particles are pions, we set an upper limit on the branching fraction B(τ-→4π-3π+(π0) ντ) < 2.4X10-6 at the 90% confidence level. This limit represents a significant improvement …

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Determination Of The Michel Parameters And The Τ Neutrino Helicity In Τ Decay, J. P. Alexander, Kenneth A. Bloom, Cleo Collaboration Nov 1997

Determination Of The Michel Parameters And The Τ Neutrino Helicity In Τ Decay, J. P. Alexander, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using the CLEO II detector at the Cornell Electron Storage Ring operated at √s =10.6 GeV, we have determined the Michel parameters ρ, ξ, and δ in τ±→l±νν̅ decay as well as the τ neutrino helicity parameter hvτ in τ±→π±π0ν decay. From a data sample of 3.02×106 produced τ pairs we analyzed events of the topologies e+e-→τ+τ-→(l±νν̅)(π±π0ν) and e+e-→τ+τ-→(π±π0ν̅)(π±π0ν). …

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Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces, R. E. Davies, John R. Dennison Nov 1997

Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces, R. E. Davies, John R. Dennison

All Physics Faculty Publications

Secondary electron emission (SEE) plays a key role in spacecraft charging [Garrett, 1981; Frooninckx and Sojka, 1992] . As a result, spacecraft charging codes require knowledge of the SEE characteristics of various materials in order to predict vehicle potentials in various orbital environments [Katz, et. al., 1986]. Because SEE is a surface phenomenon, occurring in the first few atomic layers of a material, the SEE characteristics of a given surface are extremely sensitive to changes in surface condition--e.g., the addition or removal of surface contaminants, or changes in surface morphology. That spacecraft surfaces can and generally do undergo significant evolution …

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Image Measurements Of Short Period Gravity Waves At Equatorial Latitudes, Michael J. Taylor, W. R. Pendleton Jr., S. Clark, H. Takahashi, D. Gobbi, R. A. Goldberg Nov 1997

Image Measurements Of Short Period Gravity Waves At Equatorial Latitudes, Michael J. Taylor, W. R. Pendleton Jr., S. Clark, H. Takahashi, D. Gobbi, R. A. Goldberg

All Physics Faculty Publications

A high-performance, all-sky imaging system has been used to obtain novel data on the morphology and dynamics of short-period (<1 hour) gravity waves at equatorial latitudes. Gravity waves imaged in the upper mesosphere and lower thermosphere were recorded in three nightglow emissions, the near-infrared OH emission, and the visible wavelength OI (557.7 nm) and Na (589.2 nm) emissions spanning the altitude range ∼80–100 km. The measurements were made from Alcantara, Brazil (2.3°S, 44.5°W), during the period August-October 1994 as part of the NASA/Instituto Nacional de Pesquisas Espaciais “Guara campaign”. Over 50 wave events were imaged from which a statistical study of the characteristics of equatorial gravity waves has been performed. The data were found to divide naturally into two groups. The first group corresponded to extensive, freely propagating (or ducted) gravity waves with observed periods ranging from 3.7 to 36.6 min, while the second group consisted of waves of a much smaller scale and transient nature. The later group exhibited a bimodal distribution for the observed periods at 5.18 ± 0.26 min and 4.32 ± 0.15 min, close to the local Brunt-Vaisala period and the acoustic cutoff period, respectively. In comparison, the larger-scale waves exhibited a clear tendency for their horizontal wavelengths to increase almost linearly with observed period. This trend was particularly well defined around the equinox and can be represented by a power-law relationship of the form λ h = ( 3.1 ± 0.5 ) τ ob 1.06 ± 0.10 , where λ h is measured in kilometers and τob in minutes. This result is in very good agreement with previous radar and passive optical measurements but differs significantly from the relationship λ h ∝ τ105 ob inferred from recent lidar studies. The larger-scale waves were also found to exhibit strong anisotropy in their propagation headings with the dominant direction of motion toward the-NE-ENE suggesting a preponderance for wave generation over the South American continent.

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Observational Evidence Of Wave Ducting And Evanescence In The Mesosphere, J. R. Isler, Michael J. Taylor, D. C. Fritts Nov 1997

Observational Evidence Of Wave Ducting And Evanescence In The Mesosphere, J. R. Isler, Michael J. Taylor, D. C. Fritts

All Physics Faculty Publications

A collaborative radar and imaging study of gravity waves over the Hawaiian Islands was performed during October 1993 as part of the Airborne Lidar and Observations of Hawaiian Airglow 1993/Coupling and Dynamics of Regions Equatorial (ALOHA-93/CADRE) campaign to investigate the propagation characteristics of short-period (<1 hour) waves at nightglow altitudes. The horizontal wavelengths and apparent phase speeds of quasi-monochromatic wave events were measured in four separate nightglow emissions using data obtained by a high-resolution CCD imager. This information was correlated with simultaneous MF radar wind measurements over the same height interval (∼80–100 km) to infer intrinsic wave parameters in each case. Correlating the two data sets allowed the determination of the local vertical wavenumber for each event, in particular whether it be real (indicative of freely propagating waves) or imaginary (indicative of ducted or evanescent waves). The results of this study indicate a preponderance of ducted or evanescent waves at 80–100 km during the time of the observations, with up to ∼75% of the events recorded exhibiting ducted or evanescent behavior. Also noted was a tendency for ducted behavior to be more prevalent among waves with shorter horizontal wavelengths, in agreement with Doppler ducting theory. These results suggest that ducted waves are relatively common in the upper mesosphere and lower thermosphere region, at least over the mid-Pacific Ocean. As small-scale waves which are ducted have the potential to travel much longer horizontal distances than freely propagating waves, the frequency of their occurrence should be taken into account in efforts to quantify gravity wave effects at these altitudes.

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Hands-On Phasors And Multiple-Slit Interference, Rand S. Worland, Matthew J. Moelter Nov 1997

Hands-On Phasors And Multiple-Slit Interference, Rand S. Worland, Matthew J. Moelter

Physics

No abstract provided.

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Dispersion Coefficients For Highly Excited Molecular States Of K2, Mircea Marinescu, Anthony F. Starace Nov 1997

Dispersion Coefficients For Highly Excited Molecular States Of K2, Mircea Marinescu, Anthony F. Starace

Anthony F. Starace Publications

We report results of theoretical calculations for the dispersion coefficients associated with the long-range interaction of two 39K atoms in the states 39K(4s)- 39K(5d,6d,7s). These results have been found by Wang et al. [Phys. Rev. Lett. 78, 4173 (1997)] to be in a good agreement with their measurements.

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Analysis Of Uranium Oxide Weathering By Molecular Spectroscopy, Matthew S. Zickafoose Nov 1997

Analysis Of Uranium Oxide Weathering By Molecular Spectroscopy, Matthew S. Zickafoose

Theses and Dissertations

A preliminary study of the weathering of uranium oxide particles diluted in diamond dust at ambient environmental conditions is presented. The primary weathering reaction is oxidation of the uranium from the 4 to 6 oxidation state, although formation of compounds such as carbonates and hydroxides is possible. Identification of the state of uranium oxide has been attempted using luminescence spectroscopy and diffuse reflectance Fourier transform infrared spectroscopy DRIFTS. Luminescence spectra of nominal samples of three common oxides, UO3, U3O8, and UO2, have been measured showing significant spectral differences in peaks at 494 nm, 507 nm, 529 nm, and 553 nm. …

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Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker Oct 1997

Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker

Theses and Dissertations

Fabrication of silicon carbide SiC semiconductor devices are of interest for aerospace applications because of their high-temperature tolerance. Growth of an insulating SiO2 layer on SiC is a poorly understood process, and sometimes produces interface defects that degrade device performance. Accurate theoretical models of surface chemistry, using quantum mechanics QM, do not exist because of the huge computational cost of solving Schroedingers equation for a molecular cluster large enough to represent a surface. Molecular mechanics MM, which describes a molecule as a collection of atoms interacting through classical potentials, is a fast computational method, good at predicting molecular structure, …

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Role Of Multiple Scattering In Cross-Correlated Light Scattering With A Single Laser Beam, James A. Lock Oct 1997

Role Of Multiple Scattering In Cross-Correlated Light Scattering With A Single Laser Beam, James A. Lock

Physics Faculty Publications

Previous systems for measuring cross-correlated light scattering by small particles suspended in a liquid with multiple-scattering suppression have illuminated the particles with two laser beams. It is shown that multiple-scattering suppression should also occur in cross correlation for a system that employs a single laser beam and two closely spaced detectors with wide fields of view. The single-scattering, double-scattering, and single-double-scattering cross-term contributions to the intensity cross-correlation function are calculated. It is found that the two cross terms, when added together, are unimportant for both autocorrelation and cross correlation. The amplitude of the double-scattering term can be greatly diminished by …

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Multiple-Scattering Suppression By Cross Correlation, William V. Meyer, David S. Cannell, Anthony E. Smart, Thomas W. Taylor, Padetha Tin Oct 1997

Multiple-Scattering Suppression By Cross Correlation, William V. Meyer, David S. Cannell, Anthony E. Smart, Thomas W. Taylor, Padetha Tin

Physics Faculty Publications

We describe a new method for characterizing particles in turbid media by cross correlating the scattered intensity fluctuations at two nearby points in the far field. The cross-correlation function selectively emphasizes single scattering over multiple scattering. The usual dynamic light-scattering capability of inferring particle size from decay rate is thus extended to samples that are so turbid as to be visually opaque. The method relies on single-scattering speckle being physically larger than multiple-scattering speckle. With a suitable optical geometry to select nearby points in the far field or equivalently slightly different scattering wave vectors (of the same magnitude), the multiple-scattering …

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Hybrid Reflection-Transmission Surface Light-Scattering Instrument With Reduced Sensitivity To Surface Sloshing, William V. Meyer, James A. Lock, H. Michael Cheung, Thomas W. Taylor, Padetha Tin, J. Adin Mann Oct 1997

Hybrid Reflection-Transmission Surface Light-Scattering Instrument With Reduced Sensitivity To Surface Sloshing, William V. Meyer, James A. Lock, H. Michael Cheung, Thomas W. Taylor, Padetha Tin, J. Adin Mann

Physics Faculty Publications

A hybrid reflection-transmission surface light-scattering instrumental design is presented, examined theoretically, and tested experimentally. The purpose of the design is to reduce the sensitivity of the instrument to vibration in general and surface sloshing in particular while sacrificing Little performance. Traditional optical arrangements and two new optical configurations with varying trade-offs between slosh resistance and instrumental simplicity and accuracy are examined by use of Fourier optics methods. The most promising design was constructed and tested with acetone, ethanol, and water as subject fluids. The test involved backcalculation of the wave number of the capillary wave examined with the known physical …

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Fiber-Optics Surface-Light-Scattering Spectrometer, Padetha Tin, J. Adin Mann, William V. Meyer, Thomas W. Taylor Oct 1997

Fiber-Optics Surface-Light-Scattering Spectrometer, Padetha Tin, J. Adin Mann, William V. Meyer, Thomas W. Taylor

Physics Faculty Publications

We have developed a fiber-optics surface-light-scattering spectrometer completely designed with optical fiber components. To the best of our knowledge, this is the first demonstration of a noninvasive measurement of the surface tension and the viscosity of simple liquid-vapor interfaces with a fiber-optics-based sensor system. With this approach we obtain a compact size, a significant increase in the signal-to-noise ratio, and the ability to select from a continuum of wave vectors. (C) 1997 Optical Society of America.

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Controlled Formation Of Weakly Bound Atomic Negative Ions By Electron Transfer From State-Selected Rydberg Atoms, M. Reicherts, T. Roth, A. Gopalan, M.-W. Ruf, Harmut Hotop, C. Desfrançuois, Ilya I. Fabrikant Oct 1997

Controlled Formation Of Weakly Bound Atomic Negative Ions By Electron Transfer From State-Selected Rydberg Atoms, M. Reicherts, T. Roth, A. Gopalan, M.-W. Ruf, Harmut Hotop, C. Desfrançuois, Ilya I. Fabrikant

Department of Physics and Astronomy: Faculty Publications

Using crossed atomic beams and mass spectrometric ion detection we have studied the formation of negative Ca ions in slow collisions between laser-excited state-selected Ne**(ns; J = 2) and Ne** (nd; J = 4) Rydberg atoms and ground state Ca atoms. The rate coefficients exhibit resonant behavior with maxima at an effective principal quantum number n* of about 11.5 and an estimated peak value of about 10-8 cm3 s-1. Two different theoretical calculations, based on a curve-crossing model and on a modified adiabatic theory, respectively, yield n* …

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Reaction Of Dioxygen With A Cross-Conjugated Carbon-Carbon Double Bond In A Bis-Macrocycle Diiron Compound, D. Brent Macqueen, Christopher Lange, Melvin Calvin, John W. Otvos, Larry O. Spreer, Christian B. Allan, Anna Ganse, Richard B. Frankel Oct 1997

Reaction Of Dioxygen With A Cross-Conjugated Carbon-Carbon Double Bond In A Bis-Macrocycle Diiron Compound, D. Brent Macqueen, Christopher Lange, Melvin Calvin, John W. Otvos, Larry O. Spreer, Christian B. Allan, Anna Ganse, Richard B. Frankel

Physics

Dioxygen at atmospheric pressure attacks a cross-conjugated carbon-carbon double bond in a diiron complex to form two, like, keto macrocyclic iron(II) complexes. This reaction occurs with high yield in both solution and in the solid state. A dioxetane intermediate is, therefore, invoked. The rate of the reaction is very dependent on the nature of the axial ligands on the low-spin iron(II) ions in the bimetallic complex. The rate is at least a factor of 104 faster with DMF ligands than with CH3CN axial ligands. This rate dependence is explained by stabilization of a peroxo biradical transition state …

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Nonuniversal Scaling And Conformational Crossover Of Polymer Chains In An Electrophoretic Deposition, Grace M. Foo, Ras B. Pandey Oct 1997

Nonuniversal Scaling And Conformational Crossover Of Polymer Chains In An Electrophoretic Deposition, Grace M. Foo, Ras B. Pandey

Faculty Publications

A computer simulation model of electrodeposition of polymer chains on an impenetrable wall is used to evaluate the power-law scaling exponents (νx(y)) for the longitudinal and transverse spread, Rgx(y)∼Lcνx(y); we find that the exponents νx(y) depend on the field strength, i.e., they are nonuniversal. A conformational crossover is observed for the transverse spread from the bulk with νy≃1/3-2/3 to the wall with νy≃2/3-1. A similar crossover also occurs for the longitudinal component of Rg but with an opposite trend, i.e., magnitude of νx is larger …

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Determination Of The Preexponential Frequency Factor For Superparamagnetic Maghemite Particles In Magnetoferritin, Bruce M. Moskowitz, Richard B. Frankel, Sarah A. Walton, Dominic P. E. Dickson, K. K. W. Wong, T. Douglas, Stephen Mann Oct 1997

Determination Of The Preexponential Frequency Factor For Superparamagnetic Maghemite Particles In Magnetoferritin, Bruce M. Moskowitz, Richard B. Frankel, Sarah A. Walton, Dominic P. E. Dickson, K. K. W. Wong, T. Douglas, Stephen Mann

Physics

Magnetization and Mössbauer measurements on maghemite particles with an average particle diameter of 10 nm have been made in the temperature range from 5 K to 353 K spanning the superparamagnetic (SPM) and stable single domain (SD) regimes. The maghemite particles were produced within the iron-storage protein ferritin, resulting in a narrowly-sized, weakly interacting nanocomposite material called magnetoferritin. Experiments combining hysteresis measurements, low temperature remanence, and Mössbauer spectroscopy were used to characterize magnetoferritin and to provide experimental estimates of (1) the pre-exponential frequency factor ƒ0 in the Néel-Arhennius relaxation equation; (2) the SPM threshold size at room temperature for …

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Observation Of Laser Satellites In A Plasma Produced By A Femtosecond Laser Pulse, S.A. Pikuz, Anatoly Maksimchuk, Donald Umstadter, M. Nantel, I. Yu. Skobelev, A. Ya. Faenov, A. Osterheld Oct 1997

Observation Of Laser Satellites In A Plasma Produced By A Femtosecond Laser Pulse, S.A. Pikuz, Anatoly Maksimchuk, Donald Umstadter, M. Nantel, I. Yu. Skobelev, A. Ya. Faenov, A. Osterheld

Donald Umstadter Publications

Laser satellites are detected in the emission spectra of magnesium and aluminum plasmas produced by femtosecond laser pulses. This is made possible by the realization of picosecond time resolution in a highluminosity x-ray spectrograph with a spherically curved mica crystal. The temporal characteristics of these newly recorded spectral lines show unequivocally that they are formed as a result of nonlinear processes.

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Nitrogen 1s Electron Binding Energy Assignment In Carbon Nitride Thin Films With Different Structures, Niklas Hellgren, Wei Tao Zheng, Ke Zhao Xing, Michael Lögdlund, Åsa A. Johansson, U Gelivs, William R. Salaneck, Jan Eric Sundgren Oct 1997

Nitrogen 1s Electron Binding Energy Assignment In Carbon Nitride Thin Films With Different Structures, Niklas Hellgren, Wei Tao Zheng, Ke Zhao Xing, Michael Lögdlund, Åsa A. Johansson, U Gelivs, William R. Salaneck, Jan Eric Sundgren

Educator Scholarship & Departmental Newsletters

Carbon nitride thin films deposited by dc unbalanced magnetron sputtering have been analyzed by high-resolution X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XPS data show that N 1s binding states depend on substrate temperature (Ts). By comparison with the Raman spectra, N 1s binding states are assigned in which nitrogen atoms are mainly bound to sp2 and sp3 carbon atoms at Ts = 100°C, whereas at Ts = 500°C nitrogen atoms are mainly bonded to sp2, sp3 and sp1 carbon atoms.

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Structure Factors And Their Distributions In Driven Two-Species Models, G. Korniss, Beate Schmittmann Oct 1997

Structure Factors And Their Distributions In Driven Two-Species Models, G. Korniss, Beate Schmittmann

Beate Schmittmann

We study spatial correlations and structure factors in a three-state stochastic lattice gas, consisting of holes and two oppositely “charged” species of particles, subject to an “electric” field at zero total charge. The dynamics consists of two nearest-neighbor exchange processes, occurring on different times scales, namely, particle-hole and particle-particle exchanges. Using both Langevin equations and Monte Carlo simulations, we study the steady-state structure factors and correlation functions in the disordered phase, where density profiles are homogeneous. In contrast to equilibrium systems, the average structure factors here show a discontinuity singularity at the origin. The associated spatial correlation functions exhibit intricate …

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Deuteron Threshold Electrodisintegration At High Momentum Transfer, W M. Schmitt, K S. Lee, H Baghaei, S Churchwell, R S. Hicks, R Miskimen, Gerald Alvin Peterson, K Wang Oct 1997

Deuteron Threshold Electrodisintegration At High Momentum Transfer, W M. Schmitt, K S. Lee, H Baghaei, S Churchwell, R S. Hicks, R Miskimen, Gerald Alvin Peterson, K Wang

Gerald Alvin Peterson

Absolute differential cross sections for the threshold electrodisintegration of the deuteron with good resolution were measured at a laboratory scattering angle of 160° for five values of Q2 ranging from 8.66 to 42.4fm-2. Comparisons of the data averaged over Enp from 0 to 3 MeV and from 0 to10 MeV are made with nonrelativistic meson exchange calculations. These calculations are sensitive to the nucleon electromagnetic form factors, nucleon-nucleon potential, and relativistic effects. The data are also compared with a hybrid quark-hadron model calculation that describes the deuteron as a six-quark cluster for the short range part of the interaction. Some …

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Do The Broad Emission Line Clouds See The Same Continuum That We See?, Kirk Korista, Gary J. Ferland, Jack Baldwin Oct 1997

Do The Broad Emission Line Clouds See The Same Continuum That We See?, Kirk Korista, Gary J. Ferland, Jack Baldwin

Physics and Astronomy Faculty Publications

Recent observations of quasars, Mrk 335 and the HST quasar composite spectrum, have indicated that many quasars have remarkably soft ionizing continua (f ∝ ~ ν-2, 13.6-100 eV). We point out that the number of photons with hν > 54.4 eV is insufficient to create the observed strengths of the He II emission lines. While the numbers of photons which energize C IV λ1549 and O VI λ1034 are sufficient, even the most efficiently emitting clouds for these two lines must each cover at least 20%-40% of the source. If the typical quasar ionizing continuum is indeed this …

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A Novel Laboratory Course On Advanced Chemical Engineering Experiments, Jochen A. Lauterbach, S. White, X. Lui, G. M. Bodner, W. N. Delgass Oct 1997

A Novel Laboratory Course On Advanced Chemical Engineering Experiments, Jochen A. Lauterbach, S. White, X. Lui, G. M. Bodner, W. N. Delgass

Faculty Publications

The chemical engineering curriculum in the United States has trained generations of technical experts who have successfully optimized chemical processes and products once they entered the chemical industry. The U.S. chemical industry, however, has entered a critical stage in which it must be able to create new and differentiated value through technical innovations that arc essential for long-term survival. This innovation process will require new skills that go far beyond the traditional expertise for the optimization of tasks possessed by young chemical engineers. The innovators must be able to identify new opportunities, explore the boundaries of technology, evaluate critical issues, …

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Inclusive Decays B→Dx And B→D*X, L. Gibbons, Kenneth A. Bloom, Cleo Collaboration Oct 1997

Inclusive Decays B→Dx And B→D*X, L. Gibbons, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We report new measurements of the differential and total branching ratios for inclusive B decay to D0, D+, and D*+ and the first measurement of the same quantities for inclusive B decay to D*0. Here B is the mixture of Bd and Bu from Υ(4S) decay. Furthermore, since more than one charm particle (or antiparticle) of the same kind can be produced in B decay, here ‘‘inclusive B branching ratio’’ is used to mean the average number of charm particles and their antiparticles of a certain species …

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Two-Dimensional Spectral Analysis Of Mesospheric Airglow Image Data, F. J. Garcia, Michael J. Taylor, M. C. Kelley Oct 1997

Two-Dimensional Spectral Analysis Of Mesospheric Airglow Image Data, F. J. Garcia, Michael J. Taylor, M. C. Kelley

All Physics Faculty Publications

A technique to analyze short-period (<1 hour) gravity wave structure in all-sky images of the airglow emissions is described. The technique involves spatial calibration, star removal, geographic projection, regridding, and flat fielding of the data prior to the determination of the horizontal wave parameters (wavelength, velocity, and period), by use of standard two-dimensional Fourier analysis techniques. The method was developed to exploit the information that is now available with wide-field solid state imaging systems. This technique permits interactive and quantitative investigations of large, complex data sets. Such studies are important for investigating gravity wave characteristics, their interaction with the airglow emissions, and their geographic and seasonal variability. We study one event of this type here and present possible evidence of a nonlinear wave–wave interaction in the upper atmosphere.

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