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Physics Faculty Research & Creative Works

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Articles 1171 - 1200 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Ultralow-Energy Electrons From Fast Heavy-Ion Helium Collisions: The “Target Cusp“, W. Schmitt, R. Moshammer, F. S.C. O'Rourke, H. Kollmus, L. Sarkadi, R. Mann, S. Hagmann, Ronald E. Olson, J. Ullrich Nov 1998

Ultralow-Energy Electrons From Fast Heavy-Ion Helium Collisions: The “Target Cusp“, W. Schmitt, R. Moshammer, F. S.C. O'Rourke, H. Kollmus, L. Sarkadi, R. Mann, S. Hagmann, Ronald E. Olson, J. Ullrich

Physics Faculty Research & Creative Works

Doubly differential cross sections d2σ / dν ‖ dν⊥ have been obtained by mapping the 3-dimensional velocity space of ultralow- and low-energy electrons \ (1.5 meV < = Ee < = 100 eV \) emitted in singly ionizing 3.6 MeV / u Au53+ on helium collisions. A sharp \ ( ΔEFWHMe⊥< = 22 meV \) asymmetric peak centered at = 0 is observed to emerge at ultralow energies from the strongly forward shifted low-energy electron velocity distribution. The shape of this "target cusp," which is very sensitive on the details of the two-center potential, is in excellent accord with theoretical predictions. © 1998 The American Physical Society.

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Do Interactions Increase Or Reduce The Conductance Of Disordered Electrons? It Depends!, Thomas Vojta, Frank Epperlein, Michael Schreiber Nov 1998

Do Interactions Increase Or Reduce The Conductance Of Disordered Electrons? It Depends!, Thomas Vojta, Frank Epperlein, Michael Schreiber

Physics Faculty Research & Creative Works

We investigate the influence of electron-electron interactions on the conductance of two-dimensional disordered spinless electrons. We present an efficient numerical method based on diagonalization in a truncated basis of Hartree-Fock states to determine with high accuracy the low-energy properties in the entire parameter space. We find that weak interactions increase the dc conductance in the strongly localized regime while they decrease the dc conductance for weak disorder. Strong interactions always decrease the conductance. We also study the localization of single-particle excitations at the Fermi energy which turns out to be only weakly influenced by the interactions.

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Comparison Of Electron-Atom Collision Parameters For S To P Transitions Under Reversal Of Energy Transfer, Max Shurgalin, Andrew James Murray, William R. Macgillivray, M. C. Standage, Don H. Madison, Kathrin D. Winkler, Igor Bray Nov 1998

Comparison Of Electron-Atom Collision Parameters For S To P Transitions Under Reversal Of Energy Transfer, Max Shurgalin, Andrew James Murray, William R. Macgillivray, M. C. Standage, Don H. Madison, Kathrin D. Winkler, Igor Bray

Physics Faculty Research & Creative Works

Inelastic and superelastic electron scattering from the optically prepared 32P3/2 state of sodium has enabled atomic collision parameters to be deduced for the 4S-3P deexcitation and the 3S-3P excitation processes. These data are compared with convergent close coupling and second order distorted wave Born calculations. For excitation, both theories agree with experiment, whereas for deexcitation the close coupling theory is in better agreement. A long-standing proposal relating to the sign of the transferred angular momentum is not supported.

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Essential Role Of Correlations In Governing Charge Transport In Disordered Organic Materials, Sergei V. Novikov, David H. Dunlap, Vasudev M. Kenkre, Paul Ernest Parris, Anatoly V. Vannikov Nov 1998

Essential Role Of Correlations In Governing Charge Transport In Disordered Organic Materials, Sergei V. Novikov, David H. Dunlap, Vasudev M. Kenkre, Paul Ernest Parris, Anatoly V. Vannikov

Physics Faculty Research & Creative Works

The transport of photoinjected charges in disordered organic films is often interpreted using a formula based on a Gaussian disorder model (GDM) that neglects spatial correlations due to charge-dipole interactions, even though such correlations have recently been shown to explain the universal electric field dependence observed in these systems. Based on extensive computer simulations of a 3D disorder model that includes such correlations, we present a new formula for analyzing experiments that accurately describes transport in these materials.

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Ionization Of Aligned Rydberg Atoms By Ion Impact, K. R. Cornelius, J. Wang, Ronald E. Olson Oct 1998

Ionization Of Aligned Rydberg Atoms By Ion Impact, K. R. Cornelius, J. Wang, Ronald E. Olson

Physics Faculty Research & Creative Works

The classical trajectory Monte Carlo method has been used to calculate capture and ionization cross sections and final-state electron momentum distributions in H+ + H(n = 25) collisions to show how the collision mechanisms evolve over the range of intermediate projectile speeds v* = vp/ve = 1.0-5.0. A circular Rydberg target was aligned in two orientations defined by the orbital angular momentum vector of the electron being either antiparallel or perpendicular to the incident momentum vector of the projectile. Aligning the target atom in this manner helps us to single out specific collision processes otherwise obscured in a randomly oriented …

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Evidence Of Initial-State Two-Center Effects For (E, 2e) Reactions, Sindu P. Jones, Don H. Madison Oct 1998

Evidence Of Initial-State Two-Center Effects For (E, 2e) Reactions, Sindu P. Jones, Don H. Madison

Physics Faculty Research & Creative Works

Coincidence, or (e, 2e), measurements of electron-impact ionization of atoms have established that the largest values of triply differential cross sections are obtained in collisions involving small momentum transfer to the target. Absolute measurements for these reactions are now available for hydrogen at 54.4-eV impact energy, and relative data have recently been reported at 27.2 eV. Previous theoretical works have concentrated on employing asymptotically correct two-center wave functions for the final state, leaving the initial state described by the Born approximation. Here we report results for which asymptotically correct two-center wave functions are used for both the initial and final …

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Protein Fragmentation Due To Slow Highly Charged Ion Impact, Christiane Ruehlicke, Dieter Schneider, Markus Schneider, Robert D. Dubois, Rod Balhorn Sep 1998

Protein Fragmentation Due To Slow Highly Charged Ion Impact, Christiane Ruehlicke, Dieter Schneider, Markus Schneider, Robert D. Dubois, Rod Balhorn

Physics Faculty Research & Creative Works

We present first results of experiments on the fragmentation of biomolecules using highly charged heavy ions. Fragmentation and modification of oligopeptides, such as dimerization and attachment of ionic salt components, have been observed by means of mass spectrometry. Plasmid DNA molecules were imaged with an atomic force microscope after ion irradiation and profound molecular damage was found.

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Shakeoff Measurement Of The L = 3 States Of Barium, Heider N. Ereifej, J. Greg Story Sep 1998

Shakeoff Measurement Of The L = 3 States Of Barium, Heider N. Ereifej, J. Greg Story

Physics Faculty Research & Creative Works

Isolated core excitation was used to produce low-energy continuum electrons in the l = 3 angular momentum state of barium. Data were taken over a region of energy that coincided with the energy of the 6p3/2nf doubly excited states. Analysis of the data using multichannel quantum defect theory allowed the measurement of the widths of the 6p3/2nf states and the energy-dependent phase of the continuum electronic wave functions due to interaction with the doubly excited states. The phase of the continuum electrons is shown to vary continuously with energy, due to the anomalously broad widths of …

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Low-Field Hopping Among Randomly-Distributed Sites With Uncorrelated Energetic Disorder, Paul Ernest Parris Sep 1998

Low-Field Hopping Among Randomly-Distributed Sites With Uncorrelated Energetic Disorder, Paul Ernest Parris

Physics Faculty Research & Creative Works

The low-field mobility μ of a small concentration of charge carriers hopping among a random distribution of transport sites is studied, as a function of the mean interparticle spacing ρ and the temperature T, for model systems having different site-energy distribution functions. For a uniform density of states our calculations show that the mobility obeys empirical scaling laws similar to those found in the theory of variable-range hopping. For a binary distribution of site energies we observe a crossover as a function of site density between trap-limited conduction and trap-mediated conduction. For a Gaussian density of states our results confirm …

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Nature Of Resonant Photoemission In Gd, Shubhra R. Mishra, Thomas K. Cummins, George Daniel Waddill, W. J. Gammon, Gerrit V. Van Der Laan, Kyle W. Goodman, James G. Tobin Aug 1998

Nature Of Resonant Photoemission In Gd, Shubhra R. Mishra, Thomas K. Cummins, George Daniel Waddill, W. J. Gammon, Gerrit V. Van Der Laan, Kyle W. Goodman, James G. Tobin

Physics Faculty Research & Creative Works

The phenomenon of resonant photoemission happens when, in addition to a direct photoemission channel, a second indirect channel opens up as the absorption threshold of a core level is crossed. A massive increase in emission cross section can occur, but the nature of the process remains clouded. Using novel magnetic linear dichroism in photoelectron spectroscopy experiments and theoretical calculations, we can now clearly demonstrate that temporal matching of the processes as well as energy matching is a requirement for true "resonant photoemission.".

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Next-To-Leading Order Qcd Corrections For The B⁰B⁰ Mixing With An Extended Higgs Sector, Jorg Org Urban, Frank Krauss, Ulrich D. Jentschura, Gerhard Soff Jul 1998

Next-To-Leading Order Qcd Corrections For The B⁰B⁰ Mixing With An Extended Higgs Sector, Jorg Org Urban, Frank Krauss, Ulrich D. Jentschura, Gerhard Soff

Physics Faculty Research & Creative Works

We present a calculation of the B0B0 mixing including next-to-leading order (NLO) QCD corrections within the Two-Higgs Doublet Model (2HDM). The QCD corrections at NLO are contained in the factor denoted by η2 which modifies the result obtained at the lowest order of perturbation theory. In the Standard Model case, we confirm the results for η2 obtained by Buras, Jamin and Weisz [Nucl. Phys, B 347 (1990) 491]. The factor η2 is gauge and renormalization prescription invariant and it does not depend on the infrared behaviour of the theory, which constitutes an important test …

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Nonlinear Field Dependence Of The Mobility Of A Charge Subjected To A Superposition Of Dichotomous Stochastic Potentials, A. M. Kenkre, Marek Kus, David H. Dunlap, Paul Ernest Parris Jul 1998

Nonlinear Field Dependence Of The Mobility Of A Charge Subjected To A Superposition Of Dichotomous Stochastic Potentials, A. M. Kenkre, Marek Kus, David H. Dunlap, Paul Ernest Parris

Physics Faculty Research & Creative Works

A general prescription is presented to address a large variety of forms of the nonlinear dependence of the static charge mobility on the applied electric field. The system consists of a classical charge subjected to an arbitrarily strong steady state electric field and to a stochastic potential consisting of a linear superposition of an unlimited number of dichotomous potentials in one-dimensional space. It is shown that the nonlinear mobility can be calculated for arbitrary forms of the density function of the individual dichotomous components of the stochastic potential. Specific cases of physical interest are analyzed. One of them provides a …

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Particulate Sizing And Emission Indices For A Jet Engine Exhaust Sampled At Cruise, Donald E. Hagen, Philip D. Whitefield, J. Paladino, Max B. Trueblood, H. Lilenfeld May 1998

Particulate Sizing And Emission Indices For A Jet Engine Exhaust Sampled At Cruise, Donald E. Hagen, Philip D. Whitefield, J. Paladino, Max B. Trueblood, H. Lilenfeld

Physics Faculty Research & Creative Works

Particle size and emission indices measurements for jet engines, primarily the Rolls Royce RB211 engines on a NASA 757 aircraft are reported. These data were used to estimate the fraction of fuel sulfur that was converted to particulates. These measurements were made in-situ with the sampling aircraft several kilometers behind the source. Some complimentary ground measurements on the same source aircraft and engines are also reported. Significant differences are seen between the ground observations and the in-situ observations, indicating that plume processes are changing the aerosol' s characteristics.

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Particulate Sizing And Emission Indices For A Jet Engine Exhaust Sampled At Cruise, Donald E. Hagen, Philip D. Whitefield, Jonathan D. Paladino, Max B. Trueblood May 1998

Particulate Sizing And Emission Indices For A Jet Engine Exhaust Sampled At Cruise, Donald E. Hagen, Philip D. Whitefield, Jonathan D. Paladino, Max B. Trueblood

Physics Faculty Research & Creative Works

Particle size and emission indices measurements for jet engines, primarily the Rolls Royce RB211 engines on a NASA 757 aircraft are reported. These data were used to estimate the fraction of fuel sulfur that was converted to particulates. These measurements were made in-situ with the sampling aircraft several kilometers behind the source. Some complimentary ground measurements on the same source aircraft and engines are also reported. Significant differences are seen between the ground observations and the in-situ observations, indicating that plume processes are changing the aerosol's characteristics.

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Sources And Chemistry Of Noₓ In The Upper Troposphere Over The United States, Lyatt Jaegle, Daniel J. Jacob, Yuhua Wang, Andrew J. Weinheimer, Brian A. Ridley, Teresa L. Campos, Glen W. Sachse, Donald E. Hagen May 1998

Sources And Chemistry Of Noₓ In The Upper Troposphere Over The United States, Lyatt Jaegle, Daniel J. Jacob, Yuhua Wang, Andrew J. Weinheimer, Brian A. Ridley, Teresa L. Campos, Glen W. Sachse, Donald E. Hagen

Physics Faculty Research & Creative Works

The origin of NOx in the upper troposphere over the central United States is examined using aircraft observations obtained during the SUCCESS campaign in April–May of 1996. Correlations between NOy (sum of NOx and its oxidation products) and CO at 8–12 km altitude indicate that NOx originates primarily from convective transport of polluted boundary layer air. Lightning and aircraft emissions appear to be only minor sources of NOx. Chemical steady state model calculations constrained by local observations of NO underestimate the measured NOx/NOy concentration ratio at 8–12 km altitude by a …

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Solvable Model Of Two-Dimensional Dilaton Gravity Coupled To A Massless Scalar Field, Marco Cavaglia Apr 1998

Solvable Model Of Two-Dimensional Dilaton Gravity Coupled To A Massless Scalar Field, Marco Cavaglia

Physics Faculty Research & Creative Works

We present a solvable model of two-dimensional dilaton-gravity coupled to a massless scalar field. We locally integrate the field equations and briefly discuss the properties of the solutions. For a particular choice of the coupling between the dilaton and the scalar field the model can be interpreted as the two-dimensional effective theory of 2+1 cylindrical gravity minimally coupled to a massless scalar field.

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A Neutron Diffraction Structural Study Of R₂Fe₁₇₋ₓalx(C) (R=Tb,Ho) Alloys, William B. Yelon, H. Luo, Mingxing Chen, W. C. Chang, S. H. Tsai Jan 1998

A Neutron Diffraction Structural Study Of R₂Fe₁₇₋ₓalx(C) (R=Tb,Ho) Alloys, William B. Yelon, H. Luo, Mingxing Chen, W. C. Chang, S. H. Tsai

Physics Faculty Research & Creative Works

No abstract provided.

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Neutron Diffraction And Frequency Dependence Of The A.C. Susceptibility Of The System Zncr₂Xal₂-₂Xs₄, M. Hamedoun, A. Hourmatallah, N. Benzakour, K. Mediouri, J. Ilali, William B. Yelon, H. Luo Jan 1998

Neutron Diffraction And Frequency Dependence Of The A.C. Susceptibility Of The System Zncr₂Xal₂-₂Xs₄, M. Hamedoun, A. Hourmatallah, N. Benzakour, K. Mediouri, J. Ilali, William B. Yelon, H. Luo

Physics Faculty Research & Creative Works

No abstract provided.

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Magnetic And Thermal Properties Of Pr In La₁₋ₓprxbacacu₃O₇ System With 0.0, Rajvir Singh, S. Uma, E. Gmelin, William B. Yelon, V. P. S. Awana, S. X. Dou, A. V. Narlikar, Satish K. Malik Jan 1998

Magnetic And Thermal Properties Of Pr In La₁₋ₓprxbacacu₃O₇ System With 0.0, Rajvir Singh, S. Uma, E. Gmelin, William B. Yelon, V. P. S. Awana, S. X. Dou, A. V. Narlikar, Satish K. Malik

Physics Faculty Research & Creative Works

No abstract provided.

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Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd₂Fe₁₇N₃, R. Luo, William B. Yelon, Yusheng S.. Zhao, M. Ellouze, Ph. I'Héritier, G. K. Marasinghe, Peter C. Ezekwenna, R. B. Von Dreele, William Joseph James Jan 1998

Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd₂Fe₁₇N₃, R. Luo, William B. Yelon, Yusheng S.. Zhao, M. Ellouze, Ph. I'Héritier, G. K. Marasinghe, Peter C. Ezekwenna, R. B. Von Dreele, William Joseph James

Physics Faculty Research & Creative Works

No abstract provided.

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Complete Single-Ionization Momentum Spectra For Strong Perturbation Collisions, Ronald E. Olson, C. J. Wood, H. Schmidt-Böcking, R. Moshammer, J. Ullrich Jan 1998

Complete Single-Ionization Momentum Spectra For Strong Perturbation Collisions, Ronald E. Olson, C. J. Wood, H. Schmidt-Böcking, R. Moshammer, J. Ullrich

Physics Faculty Research & Creative Works

The combination of recoil ion and ionized electron momentum spectroscopy provides an unparalleled method to investigate the details of ion-atom collision dynamics in kinematically complete experiments. To predict single ionization scattering behavior at the level now realized by experiment, the classical trajectory three-body Monte Carlo method has been used to obtain complete momenta information for the ionized electron, recoil ion, and projectile in the collision plane defined by the incident projectile and outgoing recoil ion. Strongly coupled systems were considered where the charge state of the projectile divided by the speed of the collision [Formula Presented] is greater than unity. …

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Effect Of Exchange Interactions At Antiferromagnetic/Ferromagnetic Interfaces On Exchange Bias And Coercivity, D. Dimitrov, Shufeng Zhang Jan 1998

Effect Of Exchange Interactions At Antiferromagnetic/Ferromagnetic Interfaces On Exchange Bias And Coercivity, D. Dimitrov, Shufeng Zhang

Physics Faculty Research & Creative Works

We report on the correlation between unidirectional and uniaxial anisotropy in exchange-biased ferromagnetic Permalloy layers. The dependence of exchange bias and coercivity on temperature and the antiferromagnetic and ferromagnetic layer thickness was studied and compared with the predictions of different theoretical models. A thorough explanation of the experimental data is provided by theoretical extension of Malozemoff's model. © 1998 The American Physical Society.

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Ionization Dynamics In Fast Ion-Atom Collisions. Ii. Final-State Momentum Distributions Of The Ionization Products In Collisions Of He With Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, Ronald E. Olson, L. Gulyas Jan 1998

Ionization Dynamics In Fast Ion-Atom Collisions. Ii. Final-State Momentum Distributions Of The Ionization Products In Collisions Of He With Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, Ronald E. Olson, L. Gulyas

Physics Faculty Research & Creative Works

We have used the energy and angular distributions of the low-energy electron emission cross sections from the preceding paper [Lokesh C. Tribedi et al., Phys. Rev. A 58, 3619 (1998)] to derive the doubly differential final-state longitudinal momentum distributions of the electrons, recoil ions, and projectiles in ion-atom ionization for [Formula Presented] The complementary nature of the electron spectroscopy and the recoil-ion momentum spectroscopy have been investigated using a formulation based on three-body kinematics to explore the ionization dynamics in detail. The influence of the three-body ionization as well as the binary-encounter processes on the recoil-ion (and projectile) longitudinal momentum …

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Aerosol Particle Scavenging By Fog And Haze Droplets, Josef Podzimek Jan 1998

Aerosol Particle Scavenging By Fog And Haze Droplets, Josef Podzimek

Physics Faculty Research & Creative Works

Droplet imprints in thin gelatin layers have been used for the investigation of coarse particles embedded in fog (haze) droplets in comparison to interstitial particles. Droplet samples were taken in less polluted regions of Missouri and Illinois and also in more polluted marine-urban environment in Italy. Considerable differences in particle size distribution and particle location inside the droplets have been found in samples collected on four sampling sites. The deduced relationships can be applied for the description of the aerosol scavenging process in fogs. The pollution of fog (haze) droplets may be related to the droplet mean volume radius and …

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Bound Μ⁺Μˉ System, Ulrich D. Jentschura, Gerhard Soff, Vladimir G. Ivanov, Savely Karshenboim Dec 1997

Bound Μ⁺Μˉ System, Ulrich D. Jentschura, Gerhard Soff, Vladimir G. Ivanov, Savely Karshenboim

Physics Faculty Research & Creative Works

We consider the hyperfine structure, the atomic spectrum, and the decay channels of the bound μ+μ- system (dimuonium). The annihilation lifetimes of low-lying atomic states of the system lie in the 10-12 s range. The decay rates could be measured by detection of the decay products (high-energy photons or electron-positron pairs). The hyperfine-structure splitting of the dimuonic system and its decay rate are influenced by electronic vacuum polarization effects in the far timelike asymptotic region. This constitutes a previously unexplored kinematic regime. We evaluate next-to-leading-order radiative corrections to the decay rate of low-lying atomic states. We …

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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 Dec 1997

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 …

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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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Quantum Coulomb Glass Within A Hartree-Fock Approximation, Frank Epperlein, Michael Schreiber, Thomas Vojta Sep 1997

Quantum Coulomb Glass Within A Hartree-Fock Approximation, Frank Epperlein, Michael Schreiber, Thomas Vojta

Physics Faculty Research & Creative Works

We study the influence of electron-electron interactions on the electronic properties of disordered materials. In particular, we consider the insulating side of a metal-insulator transition where screening breaks down and the electron-electron interaction remains long ranged. The investigations are based on the quantum Coulomb glass, a generalization of the classical Coulomb glass model of disordered insulators. The quantum Coulomb glass is studied by decoupling the Coulomb interaction by means of a Hartree-Fock approximation and exactly diagonalizing the remaining localization problem. We investigate the behavior of the Coulomb gap in the density of states when approaching the metal-insulator transition and study …

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Lamb Shift Of 3p And 4p States And The Determination Of Α, Ulrich D. Jentschura, Gerhard Soff, Peter J. Mohr Sep 1997

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

Physics Faculty Research & Creative Works

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

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Small Angle Neutron Scattering From Nanodroplet Aerosols, Barbara Ellen Wyslouzil, Janice L. Cheung, Gerald Wilemski, Reinhard Strey Jul 1997

Small Angle Neutron Scattering From Nanodroplet Aerosols, Barbara Ellen Wyslouzil, Janice L. Cheung, Gerald Wilemski, Reinhard Strey

Physics Faculty Research & Creative Works

We report the first measurements of small angle neutron scattering from an aerosol. The aerosol was produced by expanding a D2O-N2 vapor mixture in a supersonic Laval nozzle. The neutron wavelength (0.5 nm) is less than the typical particle size, and we can therefore derive the average particle size (5-8 nm), number density (~1012 cm-3), and polydispersity of the size distribution directly from the experimental data rather than by inferring them from complex models of particle formation and growth. We also predict and observe a Doppler shift-induced anisotropy in the scattering pattern due to …

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