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Fourier Transform Of The Multicenter Product Of 1s Hydrogenic Orbitals And Coulomb Or Yukawa Potentials And The Analytically Reduced Form For Subsequent Integrals That Include Plane Waves, Jack C. Straton May 1989

Fourier Transform Of The Multicenter Product Of 1s Hydrogenic Orbitals And Coulomb Or Yukawa Potentials And The Analytically Reduced Form For Subsequent Integrals That Include Plane Waves, Jack C. Straton

Physics Faculty Publications and Presentations

The Fourier transform of the multicenter product of N 1s hydrogenic orbitals and M Coulomb or Yukawa potentials is given as an (M+N-1)-dimensional Feynman integral with external momenta and shifted coordinates. This is accomplished through the introduction of an integral transformation, in addition to the standard Feynman transformation for the denominators of the momentum representation of the terms in the product, which moves the resulting denominator into an exponential. This allows the angular dependence of the denominator to be combined with the angular dependence in the plane waves.

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Equilibrium Polymerization On The Equivalent-Neighbor Lattice, Miron Kaufman Apr 1989

Equilibrium Polymerization On The Equivalent-Neighbor Lattice, Miron Kaufman

Physics Faculty Publications

The equilibrium polymerization problem is solved exactly on the equivalent-neighbor lattice. The Flory-Huggins entropy of mixing is exact for this lattice. We verify the discrete version of the n-vector model when n→0 is equivalent to the equal reactivity polymerization process in the whole parameter space, including the polymerized phase. The polymerization processes for polymers satisfying the Schulz distribution exhibit nonuniversal critical behavior. A close analogy is found between the polymerization problem of index r and the Bose-Einstein ideal gas in d=-2r dimensions, with the critical polymerization corresponding to the Bose-Einstein condensation.

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Differential Cross Sections For Ejection Of Electrons From Rare Gases By 7.5- 150-Kev Protons, Wen-Qin Cheng, M. Eugene Rudd, Ying-Yuan Hsu Mar 1989

Differential Cross Sections For Ejection Of Electrons From Rare Gases By 7.5- 150-Kev Protons, Wen-Qin Cheng, M. Eugene Rudd, Ying-Yuan Hsu

M. Eugene Rudd Publications

Absolute cross sections for the ejection of electrons by ;proton impact that are differential in the angle and energy of the electrons have been measured for :helium, neon, and krypton. The primary energy ranged from 7.5 to 150 keV, the angles from 10° to 160°, and the measured energies from 1 to 550 eV. These data along with earlier data on argon are used to study the systematics of proton impact ionization of the rare gases. An analytical model is employed to correlate and systematize the cross-section differential in ejected-electron energy. For low-energy collisions the angular distribution of electrons ejected …

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Nature Of Carbon-Carbon Bonding In Evaporated And Ion-Sputtered (Diamondlike) Amorphous Carbon From (E, 2e) Spectroscopy, Chao Gao, Yun Yu Wang, A. L. Ritter, John R. Dennison Feb 1989

Nature Of Carbon-Carbon Bonding In Evaporated And Ion-Sputtered (Diamondlike) Amorphous Carbon From (E, 2e) Spectroscopy, Chao Gao, Yun Yu Wang, A. L. Ritter, John R. Dennison

All Physics Faculty Publications

The local carbon-carbon bonding in evaporated (e-C) and ion-sputtered (i-C) amorphous carbon has been investigated by transmission electron-energy-loss spectroscopy (EELS) and by (e, 2e) spectroscopy. The EELS data indicate that the e-C is graphiclike and the i-C is diamondlike. The (e, 2e) data demonstrate that the concentration of sp2 bonding is ∼100% in both materials (0.85≤csp2≤1.0) for e-C and 0.75≤csp2≤1.0 for i-C). There is significant rehybridization of the π orbital in i-C.

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Elastic Angular Differential Cross Sections For Quasi-Oneelectron Collision Systems At Intermediate Energies: (Na+, Li+)+H And (Mg+, Be+)+He, J. L. Peacher, E. Redd, D. G. Seely, Timothy J. Gay, D. M. Blakenship, J. T. Park Feb 1989

Elastic Angular Differential Cross Sections For Quasi-Oneelectron Collision Systems At Intermediate Energies: (Na+, Li+)+H And (Mg+, Be+)+He, J. L. Peacher, E. Redd, D. G. Seely, Timothy J. Gay, D. M. Blakenship, J. T. Park

Timothy J. Gay Publications

Measurements of elastic angular differential cross sections have been carried out for four quasi-one-electron collision systems at intermediate energies. Data are presented for Na++H collisions at laboratory energies of 35.94, 51.75, 63.89, and 143.75 keV, for Li++H collisions at energies of 19.44 and 43.75 keV, for Mg++He collisions at energies of 30, 66.7, and 150 keV, and for Be++He collisions at an energy of 56.25 keV. The highest energy in each case corresponds to a projectile velocity of (1/2 a.u. Born and Eikonal calculations, in which we model the projectile ion as …

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Elastic Angular Differential Cross Sections For Quasi-One-Electron Collision Systems At Intermediate Energies: (Na⁺, Li⁺)+H And (Mg⁺, Be⁺)+He, Jerry Peacher, E. Redd, Denver G. Seely, Timothy Gay, D. M. Blankenship, John T. Park Feb 1989

Elastic Angular Differential Cross Sections For Quasi-One-Electron Collision Systems At Intermediate Energies: (Na⁺, Li⁺)+H And (Mg⁺, Be⁺)+He, Jerry Peacher, E. Redd, Denver G. Seely, Timothy Gay, D. M. Blankenship, John T. Park

Physics Faculty Research & Creative Works

Measurements of elastic angular differential cross sections have been carried out for four quasi-one-electron collision systems at intermediate energies. Data are presented for Na++H collisions at laboratory energies of 35.94, 51.75, 63.89, and 143.75 keV, for Li++H collisions at energies of 19.44 and 43.75 keV, for Mg++He collisions at energies of 30, 66.7, and 150 keV, and for Be++He collisions at an energy of 56.25 keV. The highest energy in each case corresponds to a projectile velocity of (1/2 a.u. Born and Eikonal calculations, in which we model the projectile ion as …

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The 157 Nm Photodissociation Of Ocs, C. E. Strauss, George C. Mcbane, P. L. Houston, I. Burak, J. W. Hepburn Jan 1989

The 157 Nm Photodissociation Of Ocs, C. E. Strauss, George C. Mcbane, P. L. Houston, I. Burak, J. W. Hepburn

Peer Reviewed Articles

The photodissociation of OCS at 157 nm has been investigated by using tunable vacuum ultraviolet radiation to probe the CO and S photoproducts. Sulfur is produced almost entirely in the 1S state, while CO is produced in its ground electronic state and in vibrational levels from v=0-3 in the appropriate ratio (v=0):(v=1):(v=2):(v=3) = (1.0):(1.0):(0.5):(0.3). The rotational distribution for each vibrational level is found to be near Boltzmann, with temperatures that decrease from 1350 K for v=0 to 780 K for v=3. Measurements of the CO Doppler profiles demonstrate that the dissociation takes place from …

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Magnetospheric Plasma Pressures In The Midnight Meridian: Observations From 2.5 To 35 Re, Harlan E. Spence, M. G. Kivelson, R. J. Walker, D. J. Mccomas Jan 1989

Magnetospheric Plasma Pressures In The Midnight Meridian: Observations From 2.5 To 35 Re, Harlan E. Spence, M. G. Kivelson, R. J. Walker, D. J. Mccomas

Physics & Astronomy

Plasma pressure data from the ISEE 2 fast plasma experiment (FPE) were statistically analyzed to determine the plasma sheet pressure versus distance in the midnight local time sector of the near-earth (12–35 RE) magnetotail plasma sheet. The observed plasma pressure, assumed isotropic, was mapped along model magnetic field flux tubes (obtained from the Tsyganenko and Usmanov [1982] model) to the magnetic equator, sorted according to magnetic activity, and binned according to the mapped equatorial location. In regions (L ≳ 12 RE) where the bulk of the plasma pressure was contributed by particles in the energy range of the FPE (70 …

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Inverse Ac Josephson Effect At Terahertz Frequencies, W C. Danchi, William Golightly, E C. Sutton Jan 1989

Inverse Ac Josephson Effect At Terahertz Frequencies, W C. Danchi, William Golightly, E C. Sutton

Physics and Astronomy

The inverse ac Josephson effect occurs when a Josephson junction driven by a microwave source of frequency  f  produces constant‐voltage steps at integer multiples of h f/2e. For low‐leakage current hysteretic junctions driven at microwave frequencies below about 100 GHz, some of these steps can cross the zero dc bias current axis. These zero‐crossing steps allow modern series array voltage standards to operate without individually biasing the junctions in the array. We reexamine the theory behind these steps and show that they can exist at frequencies much higher than thought previously. The Riedel singularity in the supercurrent …

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Modeled F Region Response To Auroral Dynamics Based Upon Dynamics Explorer Auroral Observations, Jan Josef Sojka, Robert W. Schunk, J. D. Cravens, L. A. Frank, J. Sharber, J. D. Winningham Jan 1989

Modeled F Region Response To Auroral Dynamics Based Upon Dynamics Explorer Auroral Observations, Jan Josef Sojka, Robert W. Schunk, J. D. Cravens, L. A. Frank, J. Sharber, J. D. Winningham

All Physics Faculty Publications

Auroral images from the Dynamics Explorer 1 (DE 1) scanning auroral imager have been combined with in situ auroral precipitation data from the DE 2 low altitude plasma instrument to form a time-dependent global auroral energy flux model. This model has both good time (12 min) and spatial (100 km) resolution compared to that currently available for global scale ionospheric and thermospheric modeling. The development and comparison of this model with others are discussed. Data from an aurorally active period, November 25, 1981, are presented and used as a case study for this model. Using a global ionospheric model, the …

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Continuum Model Of Thin-Film Deposition And Growth, Andrew J. Bernoff, Seth Lichter Jan 1989

Continuum Model Of Thin-Film Deposition And Growth, Andrew J. Bernoff, Seth Lichter

All HMC Faculty Publications and Research

A continuum theory for the deposition and growth of solid films is presented. The theory is developed in a coordinate-independent manner and so incorporates the fully nonlinear physics. The evolution of the film is modeled in three steps. First, the adsorption of atoms in the incident beam is modeled as a ballistic process. Second, the random motion of the adatoms is treated as a diffusive process. Finally, sticking of adatoms to the film occurs as a Poisson process. The resulting system of differential equations is examined in several parameter limits. The diffusively dominated limit appears similar to zone 1 of …

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Global Scale, Physical Models Of The F Region Ionosphere, Jan Josef Sojka Jan 1989

Global Scale, Physical Models Of The F Region Ionosphere, Jan Josef Sojka

All Physics Faculty Publications

During the last decade, ionospheric F region modeling has reached an accurate climatological level. We now have global computer models of the F region which simulate the interactions between physical processes in the ionosphere. Because of their complexity, these climatological models are confined to modern day supercomputers. This review focuses on the development and verification of these physical ionospheric models. Such models are distinct from local models, steady state models, and empirical models of the ionosphere, which are, by their conception, unable to represent physically the range of F region variability or storm dynamics. This review examines the limitations of …

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A Three-Dimensional Time-Dependent Model Of The Polar Wind, Robert W. Schunk, Jan Josef Sojka Jan 1989

A Three-Dimensional Time-Dependent Model Of The Polar Wind, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

A time-dependent global model of the polar wind was used to study transient polar wind perturbations during changing magnetospheric conditions. The model calculates three-dimensional distributions for the NO+, O2+, N2+, N+ and O+ densities and the ion and electron temperatures from diffusion and heat conduction equations at altitudes between 120 and 800 km. At altitudes above 500 km, the time-dependent nonlinear hydrodynamic equations for O+ and H+ are solved self-consistently with the ionospheric equations. The model takes account of supersonic ion outflow, shock formation, and ion energization during …

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Thermospheric Dynamics During September 18-19, 1984, 2, Validation Of The Ncar Thermospheric General Circulation Model, G Crowley, B A. Emery, R G. Roble, H C. Carlson Jr., J E. Salah, Vincent B. Wickwar, K L. Miller, W L. Oliver, R G. Burnside, F A. Marcos Jan 1989

Thermospheric Dynamics During September 18-19, 1984, 2, Validation Of The Ncar Thermospheric General Circulation Model, G Crowley, B A. Emery, R G. Roble, H C. Carlson Jr., J E. Salah, Vincent B. Wickwar, K L. Miller, W L. Oliver, R G. Burnside, F A. Marcos

All Physics Faculty Publications

The validation of complex nonlinear numerical models such as the National Center for Atmospheric Research thermospheric general circulation model (NCAR TGCM) requires a detailed comparison of model predictions with data. The Equinox Transition Study (ETS) of September 17-24, 1984, provided a unique opportunity to address the verification of the NCAR TGCM, since unusually large quantities of high-quality thermospheric and ionospheric data were obtained during an intensive observation interval. In a companion paper (paper 1) by Crowley et al. (this issue) a simulation of the September 18-19 ETS interval was described. Using a novel approach to modeling, the TGCM inputs were …

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Ion Beam Mixing In Ag-Pd Alloys, J L. Klatt, R S. Averback, David Peak Jan 1989

Ion Beam Mixing In Ag-Pd Alloys, J L. Klatt, R S. Averback, David Peak

All Physics Faculty Publications

Ion beam mixing during 750 keV Kr+ irradiation at 80 K was measured on a series of Ag‐Pd alloys using Au marker atoms. The mixing in pure Ag was the greatest and it decreased monotonically with increasing Pd content, being a factor of 10 higher in pure Ag than in pure Pd. This large difference in mixing cannot be explained by the difference in cohesion energy between Ag and Pd in the thermodynamic model of ion beam mixing proposed by Johnson et al. [W. L. Johnson, Y. T. Cheng, M. Van Rossum, and M‐A. Nicolet, Nucl. …

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World Sheet Diffeomorphisms And The Canonical String, Charles G. Torre Jan 1989

World Sheet Diffeomorphisms And The Canonical String, Charles G. Torre

All Physics Faculty Publications

The degree to which the phase space of a closed bosonic string carries a representation of the two‐dimensional diffeomorphism group Diff(M) is investigated. In particular, homomorphic mappings from the associated Lie algebra diff(M) into the Poisson algebra of functions on three natural phase spaces associated with the string are constructed. Two of these spaces are extended phase spaces based on the conformal and harmonic gauges, respectively. The third space is essentially the original phase space; the homomorphism in this case relies on the validity of the light‐cone gauge. Homomorphisms from diff(M) into the extended phase spaces of the Batalin–Fradkin–Vilkovisky formalism …

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Infrared Monitoring Of Nuclear Power In Space, David W. Hafemeister Jan 1989

Infrared Monitoring Of Nuclear Power In Space, David W. Hafemeister

Physics

This paper assesses the level of confidence for monitoring a ban on nuclear power in earth orbit using unclassified information from astronomical observatories based on Maui, Hawaii, and from the Kuiper Airborne Observatory. It is concluded that existing military and astronomical observatories can detect and identify operating nuclear reactor sources, such as the Soviet RORSAT and US SP-100, on satellites with a very high level of confidence out to distances beyond geosynchronous orbit. The smaller radioisotope thermal sources, RTG and DIPS, could be detected with a medium level of confidence under certain conditions.

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Electron Removal From Molecular Hydrogen By Fully Stripped Ions At Intermediate Energies, L. Meng, C. O. Reinhold, Ronald E. Olson Jan 1989

Electron Removal From Molecular Hydrogen By Fully Stripped Ions At Intermediate Energies, L. Meng, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

A classical phase-space model of the hydrogen molecule is presented and applied to the study of the electron-capture and -ionization processes in collisions of fully stripped ions with H2 at intermediate impact energies and charge states from 1 to 10. The model is based on the independent-electron and the impact-parameter approximations. The electron impinging-ion and electron target-nuclei interactions are exactly taken into account. The interaction between the electrons is approximated by model potentials. The calculated total cross sections for production of free electrons and capture of one electron are in good agreement with different experimental data. The ratio between the …

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Single- And Double-Ionization Cross Sections For Angular Scattering Of Fast Protons By Helium, R. (Ronald) E. Olson, J. Ullrich, R. Dörner, H. Schmidt-Böcking Jan 1989

Single- And Double-Ionization Cross Sections For Angular Scattering Of Fast Protons By Helium, R. (Ronald) E. Olson, J. Ullrich, R. Dörner, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

The angular scattering of H+ by He has been investigated for single ionization at energies of 0.5, 1.0, and 3.0 MeV; and for double ionization at 1.0 MeV. The classical-trajectory Monte Carlo method has been used within one- and two-electron models to illustrate the collision dynamics. The angular differential single-ionization cross sections are in good agreement with experiment and display the combined effects of proton scattering from the He nucleus and its electrons. The relative fraction of double ionization, as a function of scattering angle, shows a maximum at 0.9 mrad that is in agreement with the experiments of …

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Static And Dynamic Scaling Relationships In The Light Scattering Properties Of Polystyrenes In Good Solvents, Mamta Bhatt, Alexander M. Jamieson, Rolfe G. Petschek Jan 1989

Static And Dynamic Scaling Relationships In The Light Scattering Properties Of Polystyrenes In Good Solvents, Mamta Bhatt, Alexander M. Jamieson, Rolfe G. Petschek

Faculty Scholarship

Static light scattering measurements are reported on narrow molecular weight distribution polystyrenes (Mw = 3.84 × 106) in the four good solvents, ethylbenzene, benzene, toluene, and tetrahydrofuran at 25°C. These data are plotted in a "scaling" form to directly compare the equilibrium structure factor of identical polystyrene samples in the different solvent systems. The results in tetrahydrofuran are clearly distinct from those in the aromatic solvents and apparently suggest that THF is a thermodynamically better solvent. These distinctions between our results for identical, high molecular weight polymer samples in different good solvents demonstrate that these molecular weights are not high …

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N, L Distributions For Electron-Capture From H(1s) By C⁶⁺And O8+, Ronald E. Olson, D. R. Schultz Jan 1989

N, L Distributions For Electron-Capture From H(1s) By C⁶⁺And O8+, Ronald E. Olson, D. R. Schultz

Physics Faculty Research & Creative Works

Total cross sections for electron-capture from the ground state of hydrogen by C6+(40, 50, 60, 80, 100 and 120 keV/u) and O8+(40, 50, 60, 80, 100, 120 and 140keV/u) have been calculated using the classical-trajectory Monte Carlo (CTMC) technique. We tabulate these cross sections as a function of projectile energy for (i) capture to all product states, (ii) capture to product n-levels, and (iii) capture to product n, l-levels. The results of these calculations agree with and extend previous CTMC n, ldistribution results. © 1989 IOP Publishing Ltd.

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Multiple-Ionization Collision Dynamics, R. (Ronald) E. Olson, J. Ullrich, H. Schmidt-Böcking Jan 1989

Multiple-Ionization Collision Dynamics, R. (Ronald) E. Olson, J. Ullrich, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

The 1.4-MeV/u U32++Ne collision system is studied in detail in order to elucidate the dynamics of multiple ionization in energetic, heavy-ion atom collisions. Differential cross sections versus recoil-ion charge state, calculated by the n-body classical-trajectory Monte Carlo method, are presented for the and cphi angle dependences of the projectile, recoil ion, and ejected electrons. The calculations show a high degree of ejected-electron asymmetry towards the projectile side of the target nucleus which strongly effects the transverse-momentum balance between the heavy particles. Experimental and calculated cross sections differential in the recoil-ion charge state and transverse momentum are found to …

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Classical Two-Center Effects In Ejected-Electron Spectra From P+, P-, And He2++He Collisions At Intermediate Energies, C. O. Reinhold, Ronald E. Olson Jan 1989

Classical Two-Center Effects In Ejected-Electron Spectra From P+, P-, And He2++He Collisions At Intermediate Energies, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

Doubly and singly differential cross sections for electron emission have been calculated by means of the classical trajectory Monte Carlo method for the p+, p-, and He2++He systems at impact energies of 50 and 100 keV/amu. The calculations for the p+ and He2++He systems exhibit the capture to the continuum peak and agree in both shape and magnitude with experimental data. Analysis of the classical trajectories has helped to understand the dynamical formation of this peak. The dependence of the cross sections on the projectile charge (-1, +1, and +2) is analyzed and …

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Three-Body Interactions In Proton-Helium Angular Scattering, R. Dörner, J. Ullrich, H. Schmidt-Böcking, Ronald E. Olson Jan 1989

Three-Body Interactions In Proton-Helium Angular Scattering, R. Dörner, J. Ullrich, H. Schmidt-Böcking, Ronald E. Olson

Physics Faculty Research & Creative Works

H++He scattering at 0.5 MeV has been investigated using a coincidence technique that completely determines the three-body transverse momentum exchange in single ionization collisions. Three scattering regions could be distinctly recognized that are dominated by proton"helium-nucleus, proton-electron, or electron"helium-nucleus interactions. Calculations and the experimental data show that the coupling between the electronic and nuclear degrees of freedom is required to understand the dynamics for more than 97% of the ionizing collisions. © 1989 The American Physical Society.

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Specific Heat Of Pure And Thoriated Ube13 At Low Temperatures In High Magnetic Fields, M. J. Graf, Nathanael A. Fortune, J. S. Brooks, J. L. Smith, Z. Fisk Jan 1989

Specific Heat Of Pure And Thoriated Ube13 At Low Temperatures In High Magnetic Fields, M. J. Graf, Nathanael A. Fortune, J. S. Brooks, J. L. Smith, Z. Fisk

Physics: Faculty Publications

We have measured the specific heat of pure and thoriated (3.3% thorium) UBe13 in the temperature interval 0.3 1.8 K in applied magnetic fields up to 20 T, and find striking qualitative differences between the two systems. For pure UBe13 the electronic coefficient of specific heat el(=Cel(T)/T) is noticeably suppressed by a field of 20 T at 1.8 K; below 1 K, however, this reduction from the low-field, normal-state value tends to zero. For the 3.3% thoriated sample, the high-temperature value of el is relatively insensitive to strong magnetic fields, but at lower temperatures the suppression of el becomes much …

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User-Friendly Model For The Energy Distribution Of Electrons From Proton Or Electron Collisions, M. Eugene Rudd Jan 1989

User-Friendly Model For The Energy Distribution Of Electrons From Proton Or Electron Collisions, M. Eugene Rudd

M. Eugene Rudd Publications

A model is presented which gives cross sections (differential in the ejected secondary electron energy) for the ionization of atoms and molecules in proton or electron collisions. The model is in the form of an analytical equation which holds for all primary and secondary energies and for any target gas for which certain parameters are known. The accuracy is estimated to be 15-20%. The model is based on the classical binary encounter model modified to agree with the Bethe theory at high energies and, for proton impact, with the molecular promotion model at low energies. For multi-shell targets, the partial …

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Perspectives On The Development Of Track Physics, Robert Katz Jan 1989

Perspectives On The Development Of Track Physics, Robert Katz

Robert Katz Publications

Let me thank all of you for being here, Tony Starace, for having conceived this meeting, and Bob Wood and Matesh Varma, for over 20 years of support without which there would have been no track physics. There are many others to thank: the students, postdoctorates, and senior visitors who actually did all the work, and the many investigators around the world who made measurements that proved to be essential to developing and testing the notions of particle tracks.

This enterprise began when I undertook to rewrite an introductory physics text by Henry Semat to adapt it to a calculus-based …

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Pressure Dependence Of Ozone Interference In The Laser Fluorescence Measurement Of Oh In The Atmosphere [Comment], Thomas M. Hard, C. Y. Chan, A. A. Mehrabzadeh, Robert J. O'Brien Jan 1989

Pressure Dependence Of Ozone Interference In The Laser Fluorescence Measurement Of Oh In The Atmosphere [Comment], Thomas M. Hard, C. Y. Chan, A. A. Mehrabzadeh, Robert J. O'Brien

Chemistry Faculty Publications and Presentations

The authors comment on the paper by Shirinzadeh et al. (Applied Optics, vol. 26, p. 2102, 1987). They point out three errors which caused the overprediction of spurious HO data.

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Large-Angle Scattering In Positron-Helium And Positron-Krypton Collisions, D. R. Schultz, C. O. Reinhold, Ronald E. Olson Jan 1989

Large-Angle Scattering In Positron-Helium And Positron-Krypton Collisions, D. R. Schultz, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

We have calculated differential cross sections as a function of the projectile scattering angle for positron-helium and positron-krypton collisions using the classical-trajectory Monte Carlo technique. These intermediate- velocity collisions have been simulated by various independent-electron and n-electron models, using both screened Coulomb and quantum model potentials to approximate the effects of electron-electron interactions. These several models all indicate that scattering of positrons to large angles in ionizing collisions persists to high impact velocities. In a previous work [Phys. Rev. A 38, 1866 (1988)] we proposed that the recent experiments that have measured the total cross section for positronium formation could …

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Strong Continuum-Continuum Couplings In The Direct Ionization Of Ar And He Atoms By 6-Mev/U U38+ And Th38+ Projectiles, D. Schneider, D. Dewitt, A. S. Schlachter, Ronald E. Olson, W. G. Graham, J. R. Mowat, R. (Robert) D. Dubois, D. H. Loyd, V. Montemayor, G. Schiwietz Jan 1989

Strong Continuum-Continuum Couplings In The Direct Ionization Of Ar And He Atoms By 6-Mev/U U38+ And Th38+ Projectiles, D. Schneider, D. Dewitt, A. S. Schlachter, Ronald E. Olson, W. G. Graham, J. R. Mowat, R. (Robert) D. Dubois, D. H. Loyd, V. Montemayor, G. Schiwietz

Physics Faculty Research & Creative Works

Doubly differential cross sections have been measured as a function of the electron energy and observation angle for electron emission following collisions of 6-MeV/u U38+ and Th38+ on He and Ar. The electron-emission data show an enhancement at forward angles and a decrease at backward angles with respect to scaled-cross-section results based on the Born approximation. Comparison with classical-trajectory Monte Carlo calculations suggests that the deviation from the Born approximation can be explained by continuum-continuum couplings. By comparing with previously published data, we found that the forward enhancement as well as the backward decrease follow a q/vp (q,vp …

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