Physics Commons^™

Near-Field Measurements On Contrail Properties From Fuels With Different Sulfur Content, Andreas Petzold, Reinhold Busen, Franz Peter Schroder, Robert Baumann, Markus Kuhn, Johan Strom, Donald E. Hagen, Philip D. Whitefield, Darrel G. Baumgardner, Frank Arnold, Stephan Borrmann, Ulrich Schumann

Physics Faculty Research & Creative Works

Microphysical properties of jet exhaust aerosol and contrails were studied in the near field of the emitting aircraft for different fuel sulfur contents. Measurements were performed behind two different aircraft (ATTAS test aircraft of type VFW 614 and Airbus A310-300) using fuels with sulfur contents of 6 ppm and 2700 ppm, respectively. At closest approach (plume age < 1 s), the total number concentrations exceeded the measuring range of the condensation particle counter, i.e., N > 10⁵ cm^-3. The concentration of the dry accumulation mode aerosol, i.e., predominantly soot particles, was not affected by the fuel sulfur content. At a plume age of 10 s, an increase in total number concentration (Dp > 0.01 μm) by a …

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, …

Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang

Alexander H. King

Bismuth segregation in copper has been studied using energy-dispersive X-ray spectrometry (EDX) in a JEOL 2010F transmission electron microscope. In addition to the expected solute enrichment at grain boundaries, we have observed extremely high concentrations of bismuth at certain triple junctions, with significantly greater enrichment factors than in the adjacent grain boundaries. It is shown here that the triple junction segregation is a function of the parameters of the grain boundaries at the triple line, and existence of this type of segregation implies that the affected triple junctions embody excess free energy. At least one of the observed triple junctions …

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.

Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff

Chemistry and Biochemistry Faculty Research

Experimental and theoretical studies are reported on the inelastic (Raman) scattering of wavelength-selected polarized x rays from the K edge of gas-phase chlorine molecules. The polarized emission spectra exhibit prominent nondipole features consequent of phase variations of the incident and emitted radiation over molecular dimensions, as predicted by the Kramers-Heisenberg scattering formalism. Issues pursuant to the detection of core-hole localization by resonant Raman scattering from homonuclear diatomic molecules are critically examined. [S0031-9007(97)03486-8]

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.

Computer Modeling Of Molecular Vibration Frequencies And Its Application To The Modeling Of Silane Compounds, Ryan T. Merrell

Honors Capstone Projects and Theses

No abstract provided.

In Situ Observations Of Air Traffic Emission Signatures In The North Atlantic Flight Corridor, Hans Schlager, Paul Konopka, P. Schulte, U. Schumann, H. Ziereis, F. Arnold, M. Klemm, Donald E. Hagen, Philip D. Whitefield, J. Ovarlez

Physics Faculty Research & Creative Works

Focussed aircraft measurements have been carried out over the eastern North Atlantic to search for signals of air traffic emissions in the flight corridor region. Observations include NO, NO₂, HNO₃, SO₂, O₃, H₂O, total condensation nuclei (CN), and meteorological parameters. A flight pattern with constant-altitude north-south legs across the major North Atlantic air traffic tracks was flown. Signatures of air traffic emissions were clearly detected for NO_x, SO₂, and CN with peak concentrations of 2 ppbv, 0.25 ppbv, and 500 cm^-3, respectively, exceeding background …

Studies Of V, Nb, Cr, And Zr Substituted 2:17 Compounds And Their Carbides Using Neutron Diffraction, H. Luo, Z. Hu, Muguo Chen, William B. Yelon, G. K. Marasinghe, Peter C. Ezekwenna, William Joseph James, W. C. Chang, S. H. Tsai

Physics Faculty Research & Creative Works

Samples of Nd₂Fe_17-xT_xC_y with T=V, Nb, Cr, and Zr were prepared by melting of the constituent elements including C and studied by neutron diffraction. Comparing with their uncarbided counterparts, we found that the substituents transfer, more or less, from the 6c site to the 18f and 18h sites with the introduction of C atoms. This behavior appears to relate to the electronegativities between the C atoms and the early transition series elements because the 18f and 18h sites are near neighbors of the interstitial C site. However, the C effects in the V. …

Magnetic And Structural Properties Of Nd₂Fe₁₇₋ₓmnₓ Solid Solutions, Peter C. Ezekwenna, G. K. Marasinghe, William Joseph James, Oran Allan Pringle, Gary J. Long, H. Luo, Z. Hu, William B. Yelon, Ph. I'Héritier

Chemistry Faculty Research & Creative Works

A series of Nd₂Fe_17-xMn_x solid solutions with x values between 0 and and 6 were prepared and analyzed using magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. All of the Nd₂Fe_17-xMn_x samples crystallized in the Th₂Zn_17-x-type rhombohedral structure. The lattice parameters and unit cell volumes decrease with increasing manganese content up to ∼ x equal to 2, and then increase for higher manganese content. The magnetizations of Nd₂Fe_17-xMn_x decrease with increasing manganese content and Nd₂Fe_17-xMn_x is paramagnetic …

Microwave Plasma Chemical Vapor Deposited Diamond Tips For Scanning Tunneling Microscopy, Sacharia Albin, Jianli Zheng, John B. Cooper, Weihai Fu, Arnel C. Lavarias

Electrical & Computer Engineering Faculty Publications

Diamond microparticles were grown on etched tungsten wires using a microwave plasma-assisted chemical vapor deposition process. The apexes on cubo-octahedral particles bound by {100} and {111} facets were effectively used as tunneling tips for scanning tunneling microscopy. The atomically resolved surface image of highly oriented pyrolytic graphite was acquired. Tunneling characteristics revealed a higher electron emission from the diamond tips than that from the platinum–iridium tips. The same diamond tips were used to produce surface indentation and its image. © 1997 American Institute of Physics.

Microstructural Characterization Of An Ultra-High-Performance Polyimide, April Heather Baugher

Dissertations, Theses, and Masters Projects

The motivation for this study was to further characterize a relatively new high-temperature polymer for application as a matrix resin for carbon fiber composites. The two primary questions addressed in this study dealt with the structural and chemical changes occurring in these polymers on exposure to high temperature.;To investigate the structural changes in the heat-treated samples, a positron annihilation lifetime spectrometer was designed, built and optimized. Because the lifetime of a positron in a material reflects the electronic structure of the material in which it annihilates, measurements by positron annihilation lifetime spectroscopy can be used to investigate changes in a …

Observation Of Upper Tropospheric Sulfur Dioxide- And Acetone-Pollution: Potential Implications For Hydroxyl Radical And Aerosol Formation, F. Arnold, J. Schneider, K. Gollinger, H. Schlager, P. Schulte, Donald E. Hagen, Philip D. Whitefield, Peter F. J. Van Velthoven

Physics Faculty Research & Creative Works

Aircraft-based measurements of sulfur dioxide, acetone, carbon dioxide, and condensation nuclei (CN) were made over the north-eastern Atlantic at upper tropospheric altitudes, around 9000 m. On October 14, 1993, strong SO ₂- and acetone-pollution (both up to 3 ppbv) were observed, which were accompanied by a CO ₂-enhancement of up to 6 ppmv, and large CN-concentrations of up to about 1500 cm ^-3 (for radii ≥ 6 nm). CN, excess CO ₂, and to a lesser degree also acetone, were positively correlated with SO ₂. Air mass trajectory analyses indicate, that most of the air masses …

Characterization Of Iron Oxides And Atmospheric Corrosion Of Steel, Sei Jin Oh

Physics Theses & Dissertations

The study of corrosion behavior was performed using three different analytical techniques, which provided information on the formation, development and layering of iron oxides on the corrosion products as a function of atmospheric conditions, exposure time and type of steel. In particular, the protective layer formed on weathering steel was investigated as a function of different amounts of alloying elements in the steel, atmospheric conditions and exposure times. Combined together, the results provided a better understanding of the atmospheric corrosion behavior of steel, and formed a part of database of the atmospheric corrosion characteristics.

Accurate characterization of the iron oxides …

Kinetic-Energy- And Angular-Resolved Fragmentation Of Co In Vibrational-Resolved C 1s Excitation, N. Saito, Franz Heiser, Oliver Hemmers, K. Wieliczek, J. Viefhaus, U. Becker

Environmental Studies Faculty Publications

Angular distributions of C⁺+O⁺ from CO were measured, following vibrationally resolved C 1s excitations into the 2pπ, 3sσ, and 3pπ orbitals as well as into higher unresolved orbitals. A time-of-flight mass spectrometer, with a multihit-type position-sensitive anode, was used for the measurements. The anisotropy parameters (β) of C⁺+O⁺ approach their theoretically expected values as the released kinetic energy in the fragmentation increases. The value of the β parameters remains constant for all vibrational states within each orbital.

First Results From The High-Brightness X-Ray Spectroscopy Beamline 9.3.1 At Als, W. Ng, G. Jones, Rupert C. Perera, D. Hansen, J. Daniels, Oliver Hemmers, P. Glans, S. B. Whitfield, H. Wang, Dennis W. Lindle

Environmental Studies Faculty Publications

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1–6 keV photon energy range. This beamline is designed to achieve the goal of high brightness at the sample for use in the x‐ray atomic and molecular spectroscopy (XAMS) science, surface and interface science, biology and x‐ray optical development programs at ALS. X‐ray absorption and time‐of‐flight photoemission measurements in 2–5 keV photon energy range along with the flux, resolution, spot size and stability of the beamline will be discussed. Prospects for future XAMS measurements will also be presented.

Cross Sections For The Production Of He+ (Np) 2p0 States By 50 To 150 Kev Proton Impact On Helium, Wayne C. Stolte, R. Bruch

Chemistry and Biochemistry Faculty Research

Cross sections have been measured for the production of He⁺ (np) ²P^o states, n=2,3,4, by proton impact on helium over a projectile velocity range of 1.42–2.45 a.u. (50 ≤E≤150 keV). Cross sections were determined by measuring the extreme ultraviolet photons emitted from excited He1 ions. The data indicate a lower energy than expected for the maximum cross section. A comparison of the present results in terms of projectile energy dependance with the cross sections for excitation to He (1snp) ¹P^o, ionization, and total electron capture suggests the primary mechanism …

Neutron Diffraction Structural Study Of Ce₂Fe₁₇₋ₓgaₓ, H. Luo, Z. Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow

Physics Faculty Research & Creative Works

Six samples of Ce₂Fe_17-xGa_x with nominal Ga content x equal to 0, 0.3, 0.5, 0.7, 1.0, 2.0 have been studied by powder neutron diffraction at room temperature. Both crystalline and magnetic refinements have been carried out. All six samples adopt the Th₂Zn₁₇-type rhombohedral structure. The only additional phase found is α-iron. Gallium atoms are found to have high affinity for the iron 18h site, and are absent from the 9d and 18f sites. The Ga substitution for Fe leads to an expansion of both the a and c axes. The Curie …

38th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 38th 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, July 21-26, 1996.

Structure, Dynamics, And Phase Transitions In The Fullerene Derivatives C_{60}O And C_{61}H_{2}, C. Meingast, G. Roth, L. Pintschovius, R. H. Michel, C. Stoermer, M. M. Kappes, Paul A. Heiney, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

The effect of perturbing the icosohedral symmetry of C₆₀ by the addition of the side groups -O and -CH₂ upon orientational order-disorder and glass transitions in solid C₆₀ has been studied by a combination of high-resolution capacitance dilatometry and single-crystal x-ray and powder inelastic neutron scattering. Both fullerene derivatives C₆₀O (epoxide) and C₆₁H₂ (6,5-annulene) are shown to undergo a sequence of transitions similar to that found in pure C₆₀, i.e., a first-order orientational ordering transition just below room temperature followed by an orientational glass transition at lower temperatures. Although the …

Reconnecting The Sciences, John Eggebrecht, Raymond Dagenais, Don Dosch, Norman J. Merczak, Margaret N. Park, Susan C. Styer, David Workman

Faculty Publications & Research

During the last three years at the Illinois Mathematics and Science Academy, we have been working on a partial reconstruction of Whitehead's "one subject matter," a course reconnecting biology, chemistry, earth and space sciences, and physics into an Integrated Science program.

Neutron Diffraction And Magnetic Studies Of Rfe₁₂₋ₓtₓcY (R=Y,Er; T=V,Ti,Mo) Alloys, Z. Hu, William B. Yelon, X. D. Zhang, William Joseph James

Physics Faculty Research & Creative Works

RFe_12-xT_xC_y, (R=Y,Er; T=V,Ti,Mo) alloys were prepared by rf induction melting and analyzed using neutron powder diffraction and superconducting quantum interference device (SQUID) measurements. Rietveld analysis of the neutron diffraction data indicates that V, Ti, and Mo atoms all prefer the 8i sites. The refined amount of carbon atoms found in the interstitial sites from neutron diffraction data is significantly less than the nominal carbon content. All samples have the easy direction along the c axis. The Er sublattice couples to the Fe sublattice antiferromagnetically. The average Fe site moments range from 1.3 to 2.8 …

Neutron Diffraction Studies Of Ndₙfeₘ₋ₓ₋YVₓalY [(N,M)=(1,12), (2,17), (3,29)], Z. Hu, William B. Yelon, William Joseph James

Physics Faculty Research & Creative Works

Several Nd_nFe_m-x-yV_xAl_y [(n,m)=(1,12), (2,17), (3,29)] samples were prepared and analyzed using neutron powder diffraction. Rietveld analysis of the neutron diffraction data indicates that the V and Al substituents take those sites with similar environments in all three phases, as observed in our previous study of Ti-substituted compounds. It was confirmed that the diffraction data of the 3:29 compound can be better refined using the A2/m space group than using the P2₁/c space group. The SQUID measurements show that all samples have Curie temperatures well above room temperature. The neutron diffraction results …

Site Affinity Of Substituents In Nd₂Fe₁₇₋ₓtₓ (T=Cu,Zr,Nb,Ti,V) Alloys, William B. Yelon, Z. Hu, William Joseph James, G. K. Marasinghe

Physics Faculty Research & Creative Works

In order to understand the magnetic properties of the substituted rare-earth-iron alloys, it is especially important to know the location of the substitutional atoms within the iron lattice. The site distributions of some nontransition-metal substituents in the substituted Nd₂Fe_17-xT_x alloys have previously been reported. Here we report the site distributions of some transition-metal substituents (Cu,Zr,Nb,Ti,V) in the Nd₂Fe_17-xT_x alloys and compare them with those of the nontransition-metal substituted compounds. Rietveld analysis of neutron powder diffraction data indicates that the nontransition-metal substituents show very similar site affinity at low substituent content. …

Auger Resonant Raman Spectroscopy Used To Study The Angular Distributions Of The Xe 4d5/2 → 6p Decay Spectrum, B. Langer, N. Berrah, A. Farhat, Oliver Hemmers, J. Bozek

Environmental Studies Faculty Publications

The Auger resonant Raman effect can be used as a method to eliminate natural lifetime broadening in resonant Auger spectra. We have coupled this method with high-resolution photons from the Advanced Light Source to study angular distributions and decay rates of the Xe4d_5/2→6p resonant Auger lines. The angular distribution parameters β of almost all possible final ionic 5p⁴(³P, ¹D, ¹S)6p states have been determined. Our data, which remove the discrepancy between previous lower-resolution experimental results, are compared to different theoretical results.

Neutron Diffraction And Mössbauer Spectral Study Of The Nd₂Fe₁₆Ticₓ Solid Solutions, Gaya Kanishka Marasinghe, Peter C. Ezekwenna, William Joseph James, Gary J. Long, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, Fernande Grandjean

Chemistry Faculty Research & Creative Works

Three samples of , with x equal to 0.0, 0.3, and 2.8, with the Th₂Zn₁₇-type rhombohedral structure, have been studied by powder x-ray and neutron diffraction, magnetic measurements, and Mössbauer spectroscopy. Nd₂Fe₁₆Ti and Nd₂Fe₁₆TiC_0.3 were synthesized by induction melting stoichiometric amounts of the constituent elements, whereas Nd₂Fe₁₆TiC_2.8 was synthesized by methane-derived gas phase insertion of carbon into finely ground Nd₂Fe₁₆Ti at 600 K. The neutron diffraction determined titanium site occupancies are similar in both Nd₂Fe_{16 …}

A Magnetic Neutron Diffraction, And Mössbauer Spectral Study Of The Ce₂Fe₁₇₋ₓalₓ Solid Solutions, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, Zhongbo Hu, William B. Yelon, Fernande Grandjean, K. H. J. Buschow

Chemistry Faculty Research & Creative Works

The magnetic properties of a series of Ce₂Fe_17-xAl_x solid solutions with x equal to 0.00, 0.88, 2.06, 2.81, 3.98, 5.15, 6.08, 7.21, 8.20, 9.08, 9.84, and 10.62 have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. The compounds crystallize in the rhombohedral Th₂Zn₁₇-type structure. Magnetization studies indicate that the Curie temperature increases uniformly from 238 K for Ce₂Fe₁₇ to 384 K for Ce₂Fe₁₄Al₃ and then decreases at higher aluminum content. Powder neutron diffraction results, obtained at 295 K, indicate that aluminum …

Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis

Edward Yu

The synthesis and structural characterization of a new class of “basic” trinuclear acetate clusters with solely divalent metal ions and a central μ3-OH ligand are reported. These molecules with the [(py)5MII3(OAc)3(μ3-OH)(cat)] stoichiometry (M = Mn, Fe, Co, Ni) are X-ray isomorphous and isostructural and contain octahedrally coordinated metal ions. The core consists of an antiferromagnetically coupled M3 unit with the metals arranged in the corners of an isosceles triangle. Two of the M−M distances vary between 2.98 and 3.16 Å, and the longer M−M distance is observed between 3.65 and 3.76 Å. As expected from the relative ionic radius lengths, …

Synthesis And Characterization Of Boron-Containing Polymeric Materials For Neutron Shielding Applications, Michael B. Glasgow

Dissertations, Theses, and Masters Projects

The development of boron-containing polymeric materials for neutron shielding applications was undertaken. Three types of materials were characterized for physical and thermal properties: boron powder-filled epoxy composites, carborane polyamides having boron chemically bonded into the polymer, and boron-loaded polyimide thin films. Addition of amorphous submicron boron powder did not affect significantly the thermal performance of the epoxy. The 17% boron loading produced a 26% increase in compressive failure strength and a 68% increase in the compressive modulus. 0.125 inch thick specimens containing 17% boron absorbed 92% of incident neutrons from a 5-Curie Pu/Be source compared with {dollar}<{dollar}1% for the neat epoxy. Dispersion of the boron in the epoxy was improved with the addition of larger size crystalline boron powders. Carborane polyamides containing up to 35% boron were thermally stable up to 400{dollar}\sp\circ{dollar}C in air. The polymers had hydrogen/boron ratios from 2.0 to 3.8 and were soluble in several organic solvents. Polymer solutions were processed into clear, colored thin films. Boron-filled polyamic acid solutions of a PMDA-ODA polyimide containing up to 10% boron were processed into thin films. Neutron absorption of the opaque films measured in a 5-Curie Pu/Be neutron source was linear with boron concentration and film thickness. The fraction of neutrons absorbed varied linearly with boron concentration and film thickness. The applicability of boron-containing materials to the aerospace, nuclear power and accelerator industries was investigated.

Study Of The Long-Term Desorption Of Trichloroethylene From Clay Soils Using Infrared Spectroscopy, Mary P. Stager

Theses and Dissertations

Slow desorption of contaminants from soil presents one of the greatest challenges to modeling contaminant fate and transport and implementing effective remediation technologies. The kinetics of long-term desorption of trichloroethylene (TCE) from powdered clay soils were studied to determine the desorption rates and mechanism. Infrared absorption spectroscopy was used to monitor the concentration of TCE desorbed from contaminated flint clay for 71 hours. Observed gas phase TCE concentrations as a function of time were compared to that predicted by a one-site Langmuir desorption mechanism. The Langmuir model, with a single type of bonding site, did not account for the release …