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1981

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Articles 1 - 30 of 69

Full-Text Articles in Physics

Contours Of Constant Principal Angle And Constant Principal Azimuth In The Complex Ε Plane, R. M.A. Azzam Dec 1981

Contours Of Constant Principal Angle And Constant Principal Azimuth In The Complex Ε Plane, R. M.A. Azzam

Electrical Engineering Faculty Publications

For light reflection at a planar interface between two homogeneous isotropic media with complex relative dielectric function ε, we show that the constant-principal-angle contours are a family of semicircles, whereas the constantprincipal-azimuth contours are a family of (segments of) hyperbolas in the complex ε plane. We also find the exact envelope curve of both families and hence determine the domain of the ε plane of multiple (three) principal angles that is bougded by the envelope curve and the real axis. A unique and peculiar interface with ε = (5 - j√2)/27 is shown to have three coincident principal angles of …

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Hot-Wire Anemometer Behaviour In Low Velocity Air Flow, P. J. Christman, Josef Podzimek Dec 1981

Hot-Wire Anemometer Behaviour In Low Velocity Air Flow, P. J. Christman, Josef Podzimek

Physics Faculty Research & Creative Works

The behavior characteristics of a commercially available hot-wire anemometer have been examined in the presence of low velocities, lwss than 0.1 m/s for the most part, and in both horizontal and vertical air flows. The orientation of the probe in a horizontal flow has been found to have a definite effect on velocity measurements, and a lower limit to the reliable application of hot-wire anemometry has been evaluated for a particular type of probe. Vertical flow measurements have resulted in the discovery of the magnitude of natural convective velocity, and a possible method for determining the dimensions of the temperature …

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Precision Expansion Cloud Chamber For Homogeneous Nucleation Studies, John L. Schmitt Dec 1981

Precision Expansion Cloud Chamber For Homogeneous Nucleation Studies, John L. Schmitt

Physics Faculty Research & Creative Works

The author describes an expansion cloud chamber for the study of the nucleation of a single component vapor (homogeneous nucleation). The design draws on the many years of experience in this Center in construction of chambers for homogeneous nucleation of water. Design features of the chamber are exact control of temperature (±0.03° C), pressure (±0.5 mm Hg), and automatic control of cycling. Construction features are all construction materials are stainless steel, glass, or fluorocarbon plastics; the piston seal is a very flexible welded stainless-steel bellows; the chamber can be made very clean by heating under vacuum, and it is compatible …

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Crystal Perfection Of Hgi2 Studied By Neutron And Gamma-Ray Diffraction, W. (William) B. Yelon, R. W. Alkire, M. M. Schieber, L. Van Den Berg, S. E. Rasmussen, H. Christensen, J. R. Schneider Dec 1981

Crystal Perfection Of Hgi2 Studied By Neutron And Gamma-Ray Diffraction, W. (William) B. Yelon, R. W. Alkire, M. M. Schieber, L. Van Den Berg, S. E. Rasmussen, H. Christensen, J. R. Schneider

Physics Faculty Research & Creative Works

The crystalline perfection of wire sawn pieces of vapor grown single crystals of mercuric iodide was compared with the perfection of (00l) cleaved sections of the same crystal from which nuclear radiation detectors have been fabricated. The crystalline perfection was studied using neutron and gamma-ray diffraction rocking curves. Most of the gamma-ray data were obtained using a high intensity source of 153Sm gamma rays with a wavelength of λ = 0.12 Å. Some of the data were obtained using highly penetrating 198Au gamma rays with a shorter wavelength of λ = 0.03 Å. The neutrons had a wavelength of λ …

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Bilinear Equation For The Cylinder With Overlap And The Pomeron Residue, Paul Finkler, C. Edward Jones Nov 1981

Bilinear Equation For The Cylinder With Overlap And The Pomeron Residue, Paul Finkler, C. Edward Jones

Paul Finkler Papers

A bilinear integral equation for the cylinder is derived within the meson sector of the theory of dual topological unitarization. The equation is more general than conventional linear cylinder equations since it includes regions of phase space in which produced particles overlap in rapidity. The equation also permits a simple treatment of phase space which corresponds to that of the planar bootstrap problem. Two classes of solutions are found, only one of which results in the Pomero'n-f identity. This treatment also indicates that the residue of the Pomeron may be twice as large as that suggested by earlier calculations …

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Miiiikan Award For 1981, Robert Fuller Nov 1981

Miiiikan Award For 1981, Robert Fuller

Robert G. Fuller Publications

In conclusion, for his notable and creative contributions to physics teaching, in particular how he has alerted us to the implications of our cultural assumptions, how he has found interesting physics everywhere, and how he has valued the humanity of physics, the American Association of Physics Teachers presents to Albert A. Bartlett the 1981 Robert A. Millikan Award.

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Magnetic And Electrical Properties Of Iron-Nickel-Chromium-Metalloid Glasses, H. Sadate-Akhavi, George C. Hadjipanayis, David J. Sellmyer Nov 1981

Magnetic And Electrical Properties Of Iron-Nickel-Chromium-Metalloid Glasses, H. Sadate-Akhavi, George C. Hadjipanayis, David J. Sellmyer

David Sellmyer Publications

The magnetic and electrical properties of amorphous (Fe1-xNix)78-yCrySi10B12 alloys have been measured between 4.2 and 300 K. Alloys with x≤0.9 and y=5 order ferromagnetically. High-field magnetization measurements show saturation in moderate fields suggesting a relatively high value of magnetic anisotropy which was estimated to be K≃106 erg/cm3. The magnetization at low temperatures follows a T3/2 law leading to a spin-wave stiffness coefficient D≃90 meV Å2. The x=1, y=5 alloy behaves like a "cluster glass" with a cluster ordering temperature around 20 …

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Statistics Of Multicharge Centers In Semiconductors - Applications, David C. Look Nov 1981

Statistics Of Multicharge Centers In Semiconductors - Applications, David C. Look

Physics Faculty Publications

A general formula is derived for the electron occupation numbers appropriate for multicharge centers in semiconductors, including excited states. The results are used to rederive and generalize several formulas of interest in the literature, in order to show exactly how the degeneracies of individual states enter in. Particular attention is paid to certain subjects which are sometimes confusing, such as how the statistics of band states differ from those those of localized states. Another subject of much recent interest, negative-U centers, is dealt with in some detail. We show how the dependence of the average occupation number on Fermi …

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Massive Neutrinos And The Stellar Stopping Power Via The Neutrino Magnetic Moment, P.T. Leung, M. L. Rustgi, J. E. Turner, Werner Brandt Nov 1981

Massive Neutrinos And The Stellar Stopping Power Via The Neutrino Magnetic Moment, P.T. Leung, M. L. Rustgi, J. E. Turner, Werner Brandt

Physics Faculty Publications and Presentations

An exact expression is derived within the high-Q approximation for the spectrum of energy losses of neutrinos interacting via their magnetic moment with electrons. A formula for the stopping power of matter for neutrinos is derived and applied to the study of the solar neutrino anomaly. The total inelastic cross section is given. An upper limit is deduced for the neutrino magnetic moment from the antineutrino spectrum as recently parameterized by Lee (1979). It confirms the bound reported by Cowan and Reines. The distance for stellar neutrinos to thermalize by the interactions studied here, through encounters with stars is found …

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Explicit Determination Of Thickness Of A Transparent Film On A Transparent Substrate From Angles Of Incidence Of Equal P And S Reflectivities, R. M.A. Azzam Oct 1981

Explicit Determination Of Thickness Of A Transparent Film On A Transparent Substrate From Angles Of Incidence Of Equal P And S Reflectivities, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

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Orientation Of Atoms Excited By Charged Particles At High Impact Energies, Don H. Madison, Kieth H. Winters Oct 1981

Orientation Of Atoms Excited By Charged Particles At High Impact Energies, Don H. Madison, Kieth H. Winters

Physics Faculty Research & Creative Works

A perturbation-expansion approach is used to examine the sign of the orientation vector as a function of scattering angle and projectile charge. It is shown that for small angles, the sign of the orientation vector is different for oppositely charged projectiles consistent with the prediction of the classical grazing model. At large angles, on the other hand, the orientation vector for oppositely charged projectiles is shown to have the same sign.

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Existence Of The Dielectric Constant In Dipolar Fluid Mixtures, John D. Ramshaw, Norman D. Hamer Oct 1981

Existence Of The Dielectric Constant In Dipolar Fluid Mixtures, John D. Ramshaw, Norman D. Hamer

Physics Faculty Publications and Presentations

The existence of the dielectric constant epsilon is investigated for fluid mixtures of rigid polar molecules. The investigation is performed using the functional-derivative formalism for mixtures, and is closely analogous to that previously carried out for pure dipolar fluids (J. Chem. Phys. 68, 5199 (1978)). Sufficient conditions for the existence of epsilon are obtained in terms of the direct correlation function matrix c/sub alphabeta/(12). It is found that epsilon exists if c/sub alphabeta/(12) depends only on relative positions and orientations, and becomes asymptotic to -theta/sub alphabeta/(12)/kT at long range, where theta/sub alphabeta/(12) is the dipole--dipole potential between a molecule of …

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Glory In Optical Backscattering From Air Bubbles, Dean S. Langley, Philip L. Marston Sep 1981

Glory In Optical Backscattering From Air Bubbles, Dean S. Langley, Philip L. Marston

Physics Faculty Publications

Observations of light backscattered from air bubbles in a viscous liquid demonstrate an enhancement due to axial focusing. A physical-optics approximation for the cross-polarized scattering correctly describes the spacing of regular features observed. The non-cross polarized scattering is not adequately described by a single class of rays.

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Optical Pulse Compression In A Cholesteric Liquid Crystal, D. N. Ghosh Roy, D.V.G.L.N. Rao, H. Bronk Sep 1981

Optical Pulse Compression In A Cholesteric Liquid Crystal, D. N. Ghosh Roy, D.V.G.L.N. Rao, H. Bronk

Physics Faculty Publications

A 20‐ns laser pulse is compressed to nearly 2.5 ns in a 10‐cm‐long sample of liquid‐crystal cholesteryl oleate in the isotropic phase. Pulse compression in a length as short as only 5 cm has been observed. A semiquantitative explanation is given in terms of stimulated Brillouin scattering.

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Theoretical Study Of The Structural Phase Transition In Rbcaf3, L. L. Boyer, John R. Hardy Sep 1981

Theoretical Study Of The Structural Phase Transition In Rbcaf3, L. L. Boyer, John R. Hardy

John R. Hardy Papers

We have made a first-principles study of the structural phase transition at Tc = 193 K in RbCaF3, using interionic potentials derived by the Gordon-Kim approach, and a new extension of the quasiharmonic approximation for the free energy. The transition is caused by instability of a triply degenerate R-point vibration which leads to a coordinated rotation of the CaF6 octahedra. We find that, as the lattice contracts, the quasiharmonic frequency of the R-point vibrations becomes imaginary at approximately 1280 K: Below this temperature the static lattice energy, as a function of CaF6 rotation, has a …

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Time-Dependent Direct Correlation Function, John D. Ramshaw Sep 1981

Time-Dependent Direct Correlation Function, John D. Ramshaw

Physics Faculty Publications and Presentations

A time-dependent direct correlation function (TDDCF) is defined and discussed. The definition (which differs from that proposed by Percus and Yevick) is motivated by linear response theory. The TDDCF consequently has a functional-derivative or stimulus-response interpretation closely analogous to that of the static direct correlation function. Mean-field considerations suggest that the TDDCF separates into a term which is simply related to the pair potential and a spatially shorter-ranged remainder. This behavior is confirmed in the Vlasov-Zwanzig approximation.

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The Water Monomer On The Prism Face Of Ice And Above A Four Layer Ice Basal Face Ledge: An Effective Pair Potential Model, Barbara N. Hale, Jerry Kiefer, Carolyn A. Ward Aug 1981

The Water Monomer On The Prism Face Of Ice And Above A Four Layer Ice Basal Face Ledge: An Effective Pair Potential Model, Barbara N. Hale, Jerry Kiefer, Carolyn A. Ward

Physics Faculty Research & Creative Works

A previous study of the water monomer on the basal faces of ice is extended to consider the interaction of the water molecule with a rigid prism face of ice and with an ice basal face ledge. The effective central force H2O-H2O potentials of Stillinger and Rahman are used to generate maximal binding energy surfaces for the H2O adsorbed on the sample substrates. The results indicate that the prism face of ice binds the water molecule more strongly than the basal faces, and the step on the basal face serves to expose high binding …

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Macroscopic Quantum Tunneling In 1-Μm Nb Josephson Junctions, Richard F. Voss, Richard A. Webb Jul 1981

Macroscopic Quantum Tunneling In 1-Μm Nb Josephson Junctions, Richard F. Voss, Richard A. Webb

Faculty Publications

The probability distributions for switching out of the superconducting state of low-cur-rent-density 1-μm Nb Josephson junctions with capacitance ≈ 0.1 pF have been measured as a function of temperature T down to 3 mK. Below 100 mK the distribution widths become independent of T. The results are in excellent agreement with predictions for the quantum tunneling of the (macroscopic) junction phase that include the reduction of tunneling rates due to dissipation.

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Photoionization Of The 4D10 Subshell Of Cadmium: Photoelectron Angular Distributions And Polarization Of Fluorescence Radiation, Constantine E. Theodosiou, Anthony F. Starace, B.R. Tambe, Steven T. Manson Jul 1981

Photoionization Of The 4D10 Subshell Of Cadmium: Photoelectron Angular Distributions And Polarization Of Fluorescence Radiation, Constantine E. Theodosiou, Anthony F. Starace, B.R. Tambe, Steven T. Manson

Anthony F. Starace Publications

Relativistic Dirac-Fock calculations are presented for the photoelectron angular distribution asymmetry parameter β corresponding to 4d-subshell photoionization in Cd and for the linear polarization PL of the subsequent fluorescence radiation, for photon energies less than 185 eV. Near threshold, our results for β lie lower than previous relativistic Dirac-Slater and nonrelativistic many-body-perturbation-theory (MBPT) calculations. The agreement with very recent measurements by Heinzmann and Schönhense is very good. Our calculations show that PL (2D5/2→2P3/2)=-0.059 and -0.058 at incident photon energies hν=40.2 and 45.6 eV, respectively. These results lie …

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Negative Acceleration Components For A Relativistic Particle, James A. Lock Jul 1981

Negative Acceleration Components For A Relativistic Particle, James A. Lock

Physics Faculty Publications

Newtonian acceleration is considered in the light of special relativity theory with the result that the component of acceleration in the direction of an arbitrary applied force is always positive.(AIP)

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Magnetotactic Bacteria At The Geomagnetic Equator, Richard B. Frankel, R. P. Blakemore, F. F. Torres De Araujo, D. M. S. Esquivel, J. Danon Jun 1981

Magnetotactic Bacteria At The Geomagnetic Equator, Richard B. Frankel, R. P. Blakemore, F. F. Torres De Araujo, D. M. S. Esquivel, J. Danon

Physics

Magnetotactic bacteria are present in fresh water and marine sediments of Fortaleza, Brazil, situated close to the geomagnetic equator. Both South-seeking and North-seeking bacteria are present in roughly equal numbers in the same samples. This observation is consistent with the hypothesis that the vertical component of the geomagnetic field selects the predominant polarity type among magnetotactic bacteria in natural environments.

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A Unidirectional, Pulsed Far-Infrared Ring Laser, W.A. Peebles, Donald P. Umstadter, D.L. Brower, N.C. Luhmann Jr. Jun 1981

A Unidirectional, Pulsed Far-Infrared Ring Laser, W.A. Peebles, Donald P. Umstadter, D.L. Brower, N.C. Luhmann Jr.

Donald Umstadter Publications

The first study of a pulsed, far-infrared, ring laser is described. Unidirectional, traveling-wave operation is observed, thereby eliminating the spatial hole burning effects present in linear cavities. Single-mode output powers of 100 kW have been obtained.

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Brownian Motion In A Flowing Fluid Revisited, John D. Ramshaw Jun 1981

Brownian Motion In A Flowing Fluid Revisited, John D. Ramshaw

Physics Faculty Publications and Presentations

It is shown how the phenomenon of osmosis may be treated using the phenomenological theory of Brownian motion in a flowing fluid. The theory is also generalized to include viscous stresses in the particle and mixture momentum equations.

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Electron Capture At Very Small Scattering Angles From Atomic Hydrogen By 25-125-Kev Protons, Paul J. Martin, D. M. Blankenship, Thomas J. Kvale, E. Redd, Jerry Peacher, John T. Park Jun 1981

Electron Capture At Very Small Scattering Angles From Atomic Hydrogen By 25-125-Kev Protons, Paul J. Martin, D. M. Blankenship, Thomas J. Kvale, E. Redd, Jerry Peacher, John T. Park

Physics Faculty Research & Creative Works

Differential cross sections for electron capture in collisions between protons and hydrogen atoms have been experimentally determined for incident proton energies of 25, 60, and 125 keV in the center-of-mass scattering-angle range of 0-3 mrad. The experimental results compare more favorably with the results of both a multistate and a two-state calculation than with the results of a continuum distorted-wave-approximation calculation. There is no evidence of a Jackson-Schiff-type minimum.

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Differential Cross Sections For Electron Capture From Helium By 25- To 100-Kev Incident Protons, Paul J. Martin, Kenneth E. Arnett, D. M. Blankenship, Thomas J. Kvale, Jerry Peacher, E. Redd, V. C. Sutcliffe, John T. Park, Chiidong Lin, Jim H. Mcguire Jun 1981

Differential Cross Sections For Electron Capture From Helium By 25- To 100-Kev Incident Protons, Paul J. Martin, Kenneth E. Arnett, D. M. Blankenship, Thomas J. Kvale, Jerry Peacher, E. Redd, V. C. Sutcliffe, John T. Park, Chiidong Lin, Jim H. Mcguire

Physics Faculty Research & Creative Works

Experimentally and theoretically determined differential cross sections are reported for electron capture in collisions of protons with helium atoms for incident proton energies of 25, 30, 50, and 100 keV and for center-of-mass scattering angles of 0.0 to 2.0 mrad. The magnitudes of the experimentally determined differential cross sections decrease from 10-10 to 10-12 cm2/sr within the 0.0-0.8-mrad range of the center-of-mass scattering angle. At approximately 0.8 mrad a distinct change in the slope of the differential cross section is observed. The experimental results which are for capture into all bound states of hydrogen are compared …

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Detection Of Vibrationally Excited Nitrogen By Trapped Electron And Electron Transmission Methods, J.A. Michejda, L.J. Dube, Paul Burrow May 1981

Detection Of Vibrationally Excited Nitrogen By Trapped Electron And Electron Transmission Methods, J.A. Michejda, L.J. Dube, Paul Burrow

Paul Burrow Publications

Two techniques for detection of vibrationally excited nitrogen using low-energy electron scattering are described. The first technique uses the trapped electron method to observe excitation from N2ν into the B3Пg state near threshold. From the known Franck-Condon factors, the contribution from excited vibrational levels may be unfolded. The second technique employs the electron transmission method to detect sharp structure in the total scattering cross section resulting from the formation of temporary negative ions. Because of uncertainties in the total scattering cross sections from each of the vibrational levels, the transmission method is less accurate than …

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A Critical Study Of Nonlinear Echo Phenomena, Monish Ranjan Chatterjee May 1981

A Critical Study Of Nonlinear Echo Phenomena, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

The present thesis attempts to give a concise and critical account of the evolution of the echo phenomena over the last thirty years. Starting with spin and photon echoes, which were among the earliest to be observed and studied, the thesis explores the experimental findings and the models proposed in connection with the more contemporary echo experiments, viz. those involving electroacoustic or polarization echoes in single and polycrystalline piezoelectric materials and in powders. Although the investigations regarding the various mechanisms of short and long term echo formation are by no means complete, a coherent picture is beginning to emerge as …

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Theory Of Near-Adiabatic Collisions. Iii. Coupled Equations Arising From Expansions Involving Single-Center States, John B. Delos May 1981

Theory Of Near-Adiabatic Collisions. Iii. Coupled Equations Arising From Expansions Involving Single-Center States, John B. Delos

Arts & Sciences Articles

The conventional quantum-mechanical formulation of near-adiabatic collision theory is known to have a number of defects. These defects arise because the usual description does not account for the displacement of electronic states with moving nuclei, or for the change of momentum of the electron as it jumps from one moving nucleus to the other. The purpose of this series of papers is to develop an improved theory, in which such effects are taken into account. In this paper, we show that displacement and momentum-transfer effects can be incorporated into the theory in a very simple way, provided that the wave …

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Rare-Earth-Rich Metallic Glasses. I. Magnetic Hysteresis, George C. Hadjipanayis, David J. Sellmyer, B. Brandt Apr 1981

Rare-Earth-Rich Metallic Glasses. I. Magnetic Hysteresis, George C. Hadjipanayis, David J. Sellmyer, B. Brandt

David Sellmyer Publications

An anomalous magnetic behavior has been observed in rare-earch-rich metallic glasses of the composition (R75Au25)100-xBx where R denotes Pr, Gd, Tb, Er and x=0,10. The observed hysteresis in all samples except Gd at liquid-helium temperatures is due to the large anisotropy which develops below the ordering temperature. High-field-magnetization measurements up to 220 kOe were used to determine the spontaneous magnetization and the magnetic anisotropy constant which was found to be of order 108 erg/cm3 for the Tb and Er glasses. These parameters were used together with the observed remanence ratio to …

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Ionization By Low And Intermediate Energy Ion And Neutral Beams, M. Eugene Rudd Apr 1981

Ionization By Low And Intermediate Energy Ion And Neutral Beams, M. Eugene Rudd

M. Eugene Rudd Publications

One of the most important basic processes that take place in collisions of atomic systems is ionization resulting in the emission of electrons. A complete understanding of this process is complicated by the fact that electron emission can take place via a number of mechanisms, some of which are related. Simple measurements of the cross section for electron ejection as a function of projectile velocity does not usually provide enough information to unravel the various mechanisms. But cross sections which are differential in the angle and energy of the ejected electrons, which are now available for protons on a variety …

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