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Physics Faculty Research & Creative Works

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Articles 1381 - 1410 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Experimental And Theoretical Study Of The Electron Spectra In 66.7350-Kev/U C++He Collisions, L. H. Toburen, R. (Robert) D. Dubois, C. O. Reinhold, D. R. Schultz, Ronald E. Olson Jan 1990

Experimental And Theoretical Study Of The Electron Spectra In 66.7350-Kev/U C++He Collisions, L. H. Toburen, R. (Robert) D. Dubois, C. O. Reinhold, D. R. Schultz, Ronald E. Olson

Physics Faculty Research & Creative Works

Measurements of the differential and total cross sections for production of free electrons are reported for collisions of 66.7350-keV/u C+ ions with He. The experimental data are compared with theoretical calculations that include electron emission from both target and projectile using the classical-trajectory Monte Carlo method and the independent-electron approximation. Good agreement is observed between theory and experiment, and structures appearing in the electron spectra can be explained in terms of either, or both, target and projectile ionization. © 1990 The American Physical Society.

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Binary Nucleation Of Ethanol And Water, John L. Schmitt, J. Whitten, G. W. Adams, R. A. Zalabsky Jan 1990

Binary Nucleation Of Ethanol And Water, John L. Schmitt, J. Whitten, G. W. Adams, R. A. Zalabsky

Physics Faculty Research & Creative Works

The authors have used a fast expansion cloud chamber to measure binary homogeneous nucleation rates in several ethanol-water mixtures as a function of temperature, ethanol and water activities and nucleation rate. Data (ethanol and water activities) are presented for a range in nucleation rate from 10 3 to 105 drops/cm3 s from 263 to 293 K for mixtures having mole ratios (ethanol/water) of 10, 4, 0.1, 0.01, and 0.001. A comparison of the extensive data set to other data in the literature shows good agreement. We find current theory, as expected, is unable to accurately predict the data at low …

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Rotational Effects In The Continuous Vacuum-Ultraviolet Fluorescence Spectrum Of H2 Associated With Spontaneous Dissociation, H. Schmoranzer, T. Noll, E. Roueff, H. Abgrall, Ronald James Bieniek Jan 1990

Rotational Effects In The Continuous Vacuum-Ultraviolet Fluorescence Spectrum Of H2 Associated With Spontaneous Dissociation, H. Schmoranzer, T. Noll, E. Roueff, H. Abgrall, Ronald James Bieniek

Physics Faculty Research & Creative Works

The effects of rotational-vibrational interaction, and of rotational coupling between the B 2p u+1 and C 2p u1 electronic states, on the B X fluorescence continuum of H2 associated with spontaneous dissociation were investigated spectroscopically using monochromatized synchrotron radiation for selective excitation of rovibronic states. The rotational shifts and perturbations in the modulated continua intensities observed agree well with close-coupling and Jeffreys-Wentzel-Kromers-Brillouin (JWKB) calculations also performed and are explained in terms of nonadiabatic coupling effects and rainbow-interference structures. A straightforward experimental technique is described to detect mixed electronic states. © 1990 The American Physical Society.

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Enhanced Polarization Of Electron Spins In He4 By Simultaneous Optical Pumping With Circularly And Linearly Polarized Resonance Radiation, Laird D. Schearer, Padetha Tin Jan 1990

Enhanced Polarization Of Electron Spins In He4 By Simultaneous Optical Pumping With Circularly And Linearly Polarized Resonance Radiation, Laird D. Schearer, Padetha Tin

Physics Faculty Research & Creative Works

The polarization of helium (23S1) metastable atoms saturates at 50% when the ensemble is optically pumped with the D0 (23S1-23P0) transition. We have obtained polarizations approaching 100% with a simple, straightforward modification to the conventional experimental arrangement. The addition of a small amount of -polarized D0 light incident on the cell perpendicular to the defining field direction doubles the polarization produced by circularly polarized + light along the field direction. A simple rate-equation model illustrates the enhancement. © 1990 The American Physical Society.

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State-Selective Capture In Collisions Between Ions And Ground- And Excited-State Alkali-Metal Atoms, J. Pascale, Ronald E. Olson, C. O. Reinhold Jan 1990

State-Selective Capture In Collisions Between Ions And Ground- And Excited-State Alkali-Metal Atoms, J. Pascale, Ronald E. Olson, C. O. Reinhold

Physics Faculty Research & Creative Works

Total cross sections for state-selective electron capture in collisions between ions and alkali-metal atoms have been calculated by means of a three-body classical-trajectory Monte Carlo (CTMC) method using model potentials to describe the electron ionic-core interactions. Calculations have been performed for Na+-Na(28d) collisions and for N5+ and Ar8+-Cs(6s) collisions. The collision velocity range corresponds to 0.5vp/ve2, where vp is the projectile velocity in the laboratory frame and ve is the initial orbital velocity of the electron bound to the alkali-metal core. In the case of Na++Na(28d) collisions, calculations of the final n,l,m distributions …

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Enhanced Radiative Auger Emission From Lithiumlike S13+16, E. M. Bernstein, M. W. Clark, C. S. Oglesby, J. A. Tanis, W. G. Graham, Robert H. Mcfarland, T. J. Morgan, B. M. Johnson, K. W. Jones Jan 1990

Enhanced Radiative Auger Emission From Lithiumlike S13+16, E. M. Bernstein, M. W. Clark, C. S. Oglesby, J. A. Tanis, W. G. Graham, Robert H. Mcfarland, T. J. Morgan, B. M. Johnson, K. W. Jones

Physics Faculty Research & Creative Works

The radiative Auger emission (RAE) from 0.946.25-MeV/u 16S13+ (lithiumlike) projectiles excited in collisions with He target atoms has been measured. For these highly stripped ions the intensity of RAE photons relative to K x-ray emission is enhanced by about a factor of five compared with theoretical calculations and an earlier experimental measurement for S ions with few electron vacancies. The enhancement of RAE for S13+ is qualitatively similar to results reported previously for lithiumlike 23V20+; however, some differences between S and V are evident. © 1990 The American Physical Society.

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Physical Properties Of Coarse Aerosol Particles And Haze Elements In Polluted Urban-Marine Environment, Josef Podzimek Jan 1990

Physical Properties Of Coarse Aerosol Particles And Haze Elements In Polluted Urban-Marine Environment, Josef Podzimek

Physics Faculty Research & Creative Works

Measurements of coarse particles (with r ≥ 1.0 μm) with the aid of a cascade impactor and of particle (droplet) identification in sensitized gelatine layers reveal their mean concentration of about 1.5 cm-3 during the months of May and June 20 km west from Napoli in Italy. Haze particles (droplets) are usually featured by insoluble core and many small particles deposited on their surface. Sea salt aerosol does not play a dominant role in the haze element formation at this site of measurement. © 1990.

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The Role Of Small-Impact-Parameter Electron-Loss Processes On Ion Temperatures Measured By Active-Beam Plasma Diagnostics, A. J.H. Donné, F. J. De Heer, Ronald E. Olson Dec 1989

The Role Of Small-Impact-Parameter Electron-Loss Processes On Ion Temperatures Measured By Active-Beam Plasma Diagnostics, A. J.H. Donné, F. J. De Heer, Ronald E. Olson

Physics Faculty Research & Creative Works

The shape of the energy distribution of scattered particles in an active beam scattering experiment can be influenced considerably by the presence of highly charged impurity ions in the plasma. In this work it is shown theoretically that multiply charged impurities have only a small effect on the scattering distribution at low energies (/amu) and at high energies (>75 keV/amu). The effect of the impurities is the most pronounced for energies close to 50 keV/amu. The results of the calculations are in good agreement with experimental results at various energies. Extrapolation to higher beam energies leads to the conclusion …

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Study Of The Dependence Of The Electron Emission Spectra On The Projectile Charge In H⁺, He2++He Collisions, C. O. Reinhold, Ronald E. Olson Dec 1989

Study Of The Dependence Of The Electron Emission Spectra On The Projectile Charge In H⁺, He2++He Collisions, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

The classical trajectory Monte Carlo method (CTMC) has been used to calculate doubly differential ionized-electron cross sections for the impact of He2+ and H+ on He at collision energies of 50 and 100 keV amu-1. The results exhibit the capture to the continuum peak and agree in both shape and magnitude with experimental data. The dependence of the cross sections on the projectile charge ZP is analyzed and it is found to be very asymmetric with regard to the capture to the continuum peak. This behavior is in agreement with very recent experimental data. Large deviations from the Z2P scaling …

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Quantum Transport In The Presence Of Random Traps, John Wm Edwards, Paul Ernest Parris Oct 1989

Quantum Transport In The Presence Of Random Traps, John Wm Edwards, Paul Ernest Parris

Physics Faculty Research & Creative Works

We calculate the asymptotic decay of a quantum particle moving in a d-dimensional medium doped with randomly placed trapping impurities, focusing on contributions from slowly decaying long-wavelength modes centered in large compact regions devoid of traps. By averaging the decay over the statistical distribution associated with these regions we find that the survival probability, P(t) ~exp(-Atd/(d+3)), decays more slowly in any dimension than for diffusive transport.

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Analysis Of Experimental Nucleation Data For Silver And Sio Using Scaled Nucleation Theory, Barbara N. Hale, Paul R. Kemper, Joseph A. Nuth Oct 1989

Analysis Of Experimental Nucleation Data For Silver And Sio Using Scaled Nucleation Theory, Barbara N. Hale, Paul R. Kemper, Joseph A. Nuth

Physics Faculty Research & Creative Works

The experimental vapor phase nucleation data of Nuth et al., for silver [J. A. Nuth, K. A. Donnelly, B. Donn, and L. U. Lilleleht, J. Chem. Phys. 77, 2639 (1982)] and SiO [J. A. Nuth and B. Donn, J. Chem. Phys. 85, 1116 (1986)] are reanalyzed using a scaled model for homogeneous nucleation [B. N. Hale, Phys. Rev. A 33, 4156 (1986)]. The approximation is made that the vapor pressure at the nucleation site is not diminished significantly from that at the source (crucible). It is found that the data for ln S have a temperature dependence consistent with the …

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Full Optical Potential For The Electron-Hydrogen Entrance Channel, Igor Bray, Don H. Madison, Ian E. Mccarthy Sep 1989

Full Optical Potential For The Electron-Hydrogen Entrance Channel, Igor Bray, Don H. Madison, Ian E. Mccarthy

Physics Faculty Research & Creative Works

Differential and total elastic and total reaction cross sections are calculated for electron-hydrogen scattering at 30, 100, and 400 eV using an ab initio optical potential that treats bound and continuum nonelastic channels in the distorted-wave Born approximation. Multichannel and partial wave expansions are carried out to numerical convergence. Convergence criteria and quadratures for the continuum-energy integration are chosen for 1% overall accuracy. Results are compared with experiment and less detailed calculations.

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One-Dimensional Quantum Transport In The Presence Of Traps, Paul Ernest Parris Sep 1989

One-Dimensional Quantum Transport In The Presence Of Traps, Paul Ernest Parris

Physics Faculty Research & Creative Works

A study is made of the survival probability P(t) for a quantum particle moving coherently on an ordered one-dimensional chain containing randomly placed irreversible traps in concentration q. We consider two separate models of the trapping process, focusing on the long-time limit of each. In the first model, intended to describe substitutional traps, the trapping impurities act as disruptive absorbing barriers which prevent further motion along the chain. For this model it is shown that -ln[P(t)]1/4t1/4. The second model is intended to describe interstitial trapping impurities which do not disrupt the transport. It is argued for this case …

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Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel Aug 1989

Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel

Physics Faculty Research & Creative Works

We have observed dielectronic and direct excitation of H-like S15+ and Ca19+ and He-like Ti20+ ions in silicon channels caused by collision with weakly bound target electrons which behave as a free-electron gas. As in vacuo, relaxation of the doubly excited states can occur radiatively leading to ions of decreased charge, but in a crystal channel collisional effects can cause double ionization. The effects are seen in both the x-ray yields and charge-state fractions, and, in the case of Ti20+, in charge-state x-ray coincidences.

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Single And Double-Electron Removal From H− In Energetic Collisions With Multiply-Charged Argon Ions, F. Melchert, W. Debus, M. Liehr, Ronald E. Olson, E. Salzborn Jul 1989

Single And Double-Electron Removal From H− In Energetic Collisions With Multiply-Charged Argon Ions, F. Melchert, W. Debus, M. Liehr, Ronald E. Olson, E. Salzborn

Physics Faculty Research & Creative Works

Absolute cross-sections have been measured and compared to CTMC-calculations for single and double-electron removal from H− in collisions with Arq+ ions (q ≤ 8) at Ec.m. = 50 keV. The single-electron removal cross-sections are found to scale with q1.3, and for the H− + Ar4+ system, this cross-section is found to have a weak energy dependence from 3 keV to 100 keV. A major implication of our measurements is that plasma neutralizers based on multiply charged ions for high-efficiency conversion of intense H− beams into H0 gain little in expected reduced …

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Shake-Off Measurements Of Electron-Ion-Scattering Phase Shifts, J. Greg Story, William E. Cooke May 1989

Shake-Off Measurements Of Electron-Ion-Scattering Phase Shifts, J. Greg Story, William E. Cooke

Physics Faculty Research & Creative Works

Continuum electrons are produced in a specific l state with high-energy resolution using shake-off photoionization. This process is well characterized, so that the photoionization signal is an accurate measurement of the difference between the continuum electrons wave-function phase and that produced by a hydrogenic interaction. Measurements are reported showing the phase of a Ba++e- in a d wave, in cases where it is well behaved, and in cases where doubly excited resonances produce rapid phase variations.

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Long-Range Hopping In Substitutionally Disordered Solids, Paul Ernest Parris May 1989

Long-Range Hopping In Substitutionally Disordered Solids, Paul Ernest Parris

Physics Faculty Research & Creative Works

A theoretical approach for studying charge-carrier and energy diffusion due to long-range hopping in substitutionally disordered solids is presented. Unlike some earlier theories, which invoke a pair approximation to treat back-transfer processes, the current theory makes use of the exact solution to an appropriate single-defect problemone in which long-range jumps into, out of, and between both the defect site and all other active sites in the lattice are explicitly included. From this exact solution a new long-range effective-medium theory is constructed to describe the configurationally averaged transport properties of the disordered system.

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Spectroscopy Of The 6p3/2Np States Of Barium, J. Greg Story, E. G. Yap, William E. Cooke May 1989

Spectroscopy Of The 6p3/2Np States Of Barium, J. Greg Story, E. G. Yap, William E. Cooke

Physics Faculty Research & Creative Works

The 6p3/2np states of barium have been observed for n values between 14 and 21. The energies, linewidths, and transition strengths have been measured and characterized in terms of one- and two-electron interactions, using a single-configuration approximation.

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Electron-Electron Interactions In Transfer And Excitation In F⁸⁺ →₂ Collisions, Michael Schulz, J. P. Giese, J. K. Swenson, Sheldon Datz, Peter F. Dittner, Herbert F. Krause, Harald Schone, Charles Randy Vane, Malika Benhenni, Stephen M. Shafroth Apr 1989

Electron-Electron Interactions In Transfer And Excitation In F⁸⁺ →₂ Collisions, Michael Schulz, J. P. Giese, J. K. Swenson, Sheldon Datz, Peter F. Dittner, Herbert F. Krause, Harald Schone, Charles Randy Vane, Malika Benhenni, Stephen M. Shafroth

Physics Faculty Research & Creative Works

We have measured projectile Auger electrons emitted after collisions of H-like F with H2. The cross sections for emission of KLL, KLM, KLN, and KLO Auger electrons show maxima as a function of the projectile energy. One maximum in the KLL emission cross section is due to resonant transfer and excitation. A second maximum in the cross section for KLL emission as well as the maxima in the emission cross section for the higher-n Auger electrons are attributed to a new transfer and excitation process. This involves excitation of a projectile electron by one target electron accompanied by …

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Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs Mar 1989

Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs

Physics Faculty Research & Creative Works

A systematic series of condensation coefficient measurements of water have been made using the University of Missouri-Rolla cooled-wall expansion chamber which simulates the thermodynamics of cloud. This coefficient is seen to decrease from a value near unity, at the outset of simulation, to a value in the neighborhood of 0.01 toward the end of a simulation. Final values of this coefficient are sufficiently low as to contribute significantly to the broadening of the drop-size distribution in cloud.

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One-Dimensional Trapping Kinetics At Zero Temperature, Paul Ernest Parris Mar 1989

One-Dimensional Trapping Kinetics At Zero Temperature, Paul Ernest Parris

Physics Faculty Research & Creative Works

The asymptotic decay of the survival probability is calculated for a quantum particle moving at zero temperature on a one-dimensional tight-binding chain possessing randomly placed irreversible traps of strength γ. The survival probability exhibits a decay, P(t) ~ exp(-At1/4), which is slower than that associated with a diffusing particle.

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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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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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Mössbauer Effect Studies Of Nd₂Fe₁₄₋ₓsiₓb And Y₃Fe₁₄₋ₓsiₓb, Oran Allan Pringle, Gary J. Long, G. K. Marasinghe, William Joseph James, Antoni T. Pedziwiatr, W. E. Wallace, Fernande Grandjean Jan 1989

Mössbauer Effect Studies Of Nd₂Fe₁₄₋ₓsiₓb And Y₃Fe₁₄₋ₓsiₓb, Oran Allan Pringle, Gary J. Long, G. K. Marasinghe, William Joseph James, Antoni T. Pedziwiatr, W. E. Wallace, Fernande Grandjean

Physics Faculty Research & Creative Works

No abstract provided.

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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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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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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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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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Exciton Diffusion At Finite Frequency: Luminescence Observables For Anisotropic Percolating Solids, Paul Ernest Parris Jan 1989

Exciton Diffusion At Finite Frequency: Luminescence Observables For Anisotropic Percolating Solids, Paul Ernest Parris

Physics Faculty Research & Creative Works

A study is made of the luminescence intensities associated with exciton diffusion and trapping on a three-dimensional anisotropic percolating lattice. The calculation is based upon a relationship that exists between the frequency dependent diffusion tensor at frequencies comparable to the inverse excitation lifetime, and luminescence observables such as the host and trap luminescence intensities for conditions of constant illumination. The present approach allows the study of crossover behavior in percolative systems that are of intermediate transport dimensionality 2 < dt < 3. Our results suggest that curvature seen in luminescence observables near the transition need not always be a direct reflection of the critical indices associated with classical isotropic percolation. We have identified three possible sources of deviation from the classical behavior: (1) the radiative time scale of the luminescence measurements, (2) the functional dependence of the luminescence yields on the diffusion tensor, and (3) the demands of dimensional crossover in the critical region arising from the anisotropy of the medium.

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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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