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Full-Text Articles in Physics
Magnetic Transitions And Scaling Behavior In Gd-Rich Glasses , M.J. O'Shea, David J. Sellmyer
Magnetic Transitions And Scaling Behavior In Gd-Rich Glasses , M.J. O'Shea, David J. Sellmyer
David Sellmyer Publications
The magnetic properties of amorphous alloys with composition GdxLa72-xGa18B10 have been investigated using ac-susceptibilty and dc-magnetization techniques in the temperature range 4.2–300 K. This system shows double-transition behavior for x≳67 and paramagnetic–spin-glass transition behavior for x<67. Time-dependent magnetization effects are present in the spin-glass phase and these effects vanish in finite fields, in qualitative agreement with mean-field theory. The magnetic isotherms around both the paramagnetic-ferromagnetic and ferromagnetic–spin-glass transitions scale according to the scaling hypothesis, and these results are discussed in some detail. A magnetic phase diagram for this system is obtained from the transition temperatures determined from scaling.
Use Of The Fock Expansion For 1State Wave Functions Of Two-Electron Atoms And Ions, James M. Feagin, Joseph Macek, Anthony F. Starace
Use Of The Fock Expansion For 1State Wave Functions Of Two-Electron Atoms And Ions, James M. Feagin, Joseph Macek, Anthony F. Starace
Anthony F. Starace Publications
The exact representation of a two-electron wave function near the origin is the Fock expansion, i.e., a double summation over powers of R and of lnR [where R≡(r12+r22)1/2] with coefficients dependent on the five remaining angular variables. Using a representation of hyperspherical harmonics, we present here the first numerical solution of the equations for the Fock coefficients. We present also a general procedure for matching a linear combination of Fock-series solutions onto a basis of adiabatic hyperspherical functions at a matching radius R0. This matching procedure ensures …
Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Donald Umstadter Publications
Clayton et al. Respond: The authors of the Comment are quite correct when they point out that the ruby-laser scattering system used in our study can only respond to beat-excited density fluctuations with ky = k2, where the CO2 (ruby) beam propagates in the z (y) direction.
Ionization Cross Sections For 10-300-Kev/U And Electron-Capture Cross Sections For 5- 150-Kev/U 3He2+ Ions In Gases, M. Eugene Rudd, T. V. Goffe, A. Itoh
Ionization Cross Sections For 10-300-Kev/U And Electron-Capture Cross Sections For 5- 150-Kev/U 3He2+ Ions In Gases, M. Eugene Rudd, T. V. Goffe, A. Itoh
M. Eugene Rudd Publications
Cross sections for production of positive and negative charge for 10-300-keV/u He2+ ions on He, Ne, Ar, Kr, H2, N2, CO, O2, CH4, N2O, and C02 were measured by the transverse-field method. Single- and double-electron-capture cross sections at 5-150 keV/u for the same targets were measured by the method of deflection of different charge-state components of the beam after passing through a known length of target gas. A secondary-emission detector was used to detect the neutral component of the beam. A small least-squares adjustment of the cross sections …
Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Y-K. Kim, D. H. Madison, J. W. Gallagher
Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Y-K. Kim, D. H. Madison, J. W. Gallagher
M. Eugene Rudd Publications
Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given.
A Variation-Perturbation Method For Atomic And Molecular Interactions. I. Theory, Gordon A. Gallup, J. Gerratt
A Variation-Perturbation Method For Atomic And Molecular Interactions. I. Theory, Gordon A. Gallup, J. Gerratt
Gordon Gallup Publications
We have developed a variation-perturbation procedure for calculating intermolecular forces. It is based on the valence bond method of constructing wave functions and involves a number of interlocking techniques and approximations that are justified by the small size of the interaction potential relative to the total energy. In this article we give an outline of the theory of our technique. We have used this procedure to determine the potential between a Ne atom and a rigid HF molecule. The results of this calculation are given in the next article. The Journal of Chemical Physics is copyrighted by The American Institute …
A Variation-Perturbation Method For Atomic And Molecular Interactions. Ii. The Interaction Potential And Van Der Waals Molecule For Ne–Hf, Gordon A. Gallup, J. Gerratt
A Variation-Perturbation Method For Atomic And Molecular Interactions. Ii. The Interaction Potential And Van Der Waals Molecule For Ne–Hf, Gordon A. Gallup, J. Gerratt
Gordon Gallup Publications
A recently developed variation-perturbation theory for calculating intermolecular forces has been applied to the Ne–HF system for fixed H–F distances. The maximum well depth is 0.49 kJ/mol (41 cm-1) for a linear configuration with the H between the Ne and F and the Ne–H distance approximately 5.5 bohr. A secondary minimum of depth 0.24 kJ/mol (20 cm-1) was found for the other linear configuration at a Ne–F distance of about 7.0 bohr. A saddle point, about 0.20 kJ/mol (17 cm-1) deep, for the T-shaped configuration is present also at about 7.0 bohr. The potential …
Angular Differential Cross Sections For The Excitation Of 11S Helium To The 21S And 21P States By 25- To 100-Kev-Proton Impact, T. J. Kvale, D. G. Seely, D. M. Blakenship, E. Redd, Timothy J. Gay, M. Kimura, E. Rille, J. L. Peacher, J. T. Park
Angular Differential Cross Sections For The Excitation Of 11S Helium To The 21S And 21P States By 25- To 100-Kev-Proton Impact, T. J. Kvale, D. G. Seely, D. M. Blakenship, E. Redd, Timothy J. Gay, M. Kimura, E. Rille, J. L. Peacher, J. T. Park
Timothy J. Gay Publications
Angular differential cross sections for the proton-impact excitation of ground-state helium (11S) to the 21S and 21P states have been measured for the first time in the energy range 25 to 100 keV with use of the energy-loss technique. The data indicate that, for very small scattering angles, at 25 keV the 21S differential cross section is greater than the 21P differential cross section. For impact energies greater than 50 keV, the 21P differential cross section clearly dominates over the 21S cross section in the very small scattering …
Birefringence Measurements Of The Uniaxial-Stress Dependence Of The Incommensurate Phase Transition In K2Seo4, D. P. Billesbach, F. G. Ullman, John R. Hardy
Birefringence Measurements Of The Uniaxial-Stress Dependence Of The Incommensurate Phase Transition In K2Seo4, D. P. Billesbach, F. G. Ullman, John R. Hardy
John R. Hardy Papers
The uniaxial-stress dependence of the incommensurate-phase-transition temperature (at 130 K) in K2SeO4 was measured along all three crystal axes by observation of the anomalies in the birefringence caused by the structure change. The results for the c-axis-stress dependence (- 17.0±0.2 K/kbar) agree with previous studies of other workers. This experiment has also provided the first direct measurements of the a-axis- and b-axis-stress dependences (+ 3.1 ±0.2 K/kbar and +7.7± 0.2 K/kbar, respectively). Also, a value of -6.2±0.3 K/kbar was calculated from these data for the dependence of the transition temperature on hydrostatic pressure. This …
Cross Sections For Ionization Of Gases By 10-2000-Kev He+ Ions And For Electron Capture And Loss By 5-350-Kev He+ Ions, M. Eugene Rudd, T. V. Goff, A. Itoh, R. D. Dubois
Cross Sections For Ionization Of Gases By 10-2000-Kev He+ Ions And For Electron Capture And Loss By 5-350-Kev He+ Ions, M. Eugene Rudd, T. V. Goff, A. Itoh, R. D. Dubois
M. Eugene Rudd Publications
Cross sections for production of positive and negative charge for 10-2000-keV He+ ions on He, Ne, Ar, Kr, H2, N2, CO, O2, CH4, and CO2 were measured by the transverse-field method. Electron-capture and -loss cross sections for 5-350-keV He+ ions on the same targets were measured by the method of beam deflection of various charge states after passing through a known length of target gas. Secondary-emission detectors were used to detect neutral, singly charged, and doubly charged beam components. The equation σ+- σ- = σ10 …
Thindown In Radiobiology, Robert Katz, D. E. Dunn, G. L. Sinclair
Thindown In Radiobiology, Robert Katz, D. E. Dunn, G. L. Sinclair
Robert Katz Publications
A new expression for the radial dose distribution, tested against available data, and yielding good agreement with enzyme and virus cross sections, is used to calculate cellular inactivation cross sections from track theory models and parameters. We use a cellular model and radiosensitivity parameters, fitted to HILAC data 15 years ago, to represent mammalian cells irradiated at the UNILAC. The observed branching with Z and the decline in cellular action cross sections with an increase in ion LET are attributed to thindown; that is, to the limits imposed by the maximum radial penetration of delta rays. Target size and structure …
Angle-Resolved Photoemission From Bromine Chemisorbed On Ni(100), Peter A. Dowben, Y. Sakisaka, T.N. Rhodin
Angle-Resolved Photoemission From Bromine Chemisorbed On Ni(100), Peter A. Dowben, Y. Sakisaka, T.N. Rhodin
Peter Dowben Publications
Molecular bromine dissociatively adsorbs to form a chemisorbed overlayer on Ni(100). The bromine induced 4px,y and 4pz orbitals have been identified at Γ̅ with binding energies of 6.6 ± 0.2 eV and 5.3 ± 0.2 eV below the Fermi energy, respectively. The relative ionization cross-section variations of the two bromine levels 4px and 4pz are observed to differ with changing photon energy.
Crystalline And Amorphous Feti And Fe2Ti, C.L. Chien, Sy_Hwang Liou
Crystalline And Amorphous Feti And Fe2Ti, C.L. Chien, Sy_Hwang Liou
Sy-Hwang Liou Publications
Amorphous FeTi, Fe2Ti, and their crystalline counterparts are compared by measurements of x-ray diffraction, conductivity, and 57Fe Mössbauer spectroscopy. In FeTi one has the unique opportunity to compare a cubic crystal with its amorphous analog. X-ray diffraction and hyperfine interactions indicate no clear correlation between the crystalline and the amorphous states. The electrical conductivity exhibits distinctive behavior for the two states.
First-Principles Study Of Structural Instabilities In Halide-Based Perovskites: Competition Between Ferroelectricity And Ferroelasticity, J. W. Flocken, R. A. Guenther, John R. Hardy, L. L. Boyer
First-Principles Study Of Structural Instabilities In Halide-Based Perovskites: Competition Between Ferroelectricity And Ferroelasticity, J. W. Flocken, R. A. Guenther, John R. Hardy, L. L. Boyer
John R. Hardy Papers
We have made a systematic theoretical survey of the competition between ferroelastic and ferroelectric instabilities in the family of halide-based perovskites of formula ABX3, where A is an alkali-metal ion, B is a Be, Mg, or Ca ion, and X is a halide ion. Initially we surveyed the whole series of such compounds, making a theoretical lattice-dynamical study using first-principles interionic potentials composed of a long-range pure Coulomb interaction between the spherically symmetric free ions, and a short-range component calculated by the Gordon-Kim approach from the overlapping free-ion charge densities. We then proceeded to examine in more detail …
Relativistic Plasma-Wave Excitation By Collinear Optical Mixing, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Relativistic Plasma-Wave Excitation By Collinear Optical Mixing, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Donald Umstadter Publications
The relativistic plasma wave excited when the frequency difference between two copropagating CO2 laser beams equals the plasma frequency is detected for the first time. The plasma-wave frequency, wave number, spatial extent, and saturation time are directly measured by use of 7-mrad, collective, ruby Thomson scattering and the forward-scattered ir spectrum. The wave amplitude ñ/n0 is inferred to be (1-3)% which gives a longitudinal electric field of 0.3 to 1 GV/m at a laser intensity of 1.7×1013 W/cm2, in reasonable agreement with theory.
Experimental Study Of Spin-Exchange Effects In Elastic And Ionizing Collisions Of Polarized Electrons With Polarized Hydrogen Atoms, G. D. Fletcher, M. J. Alguard, Timothy J. Gay, V. W. Hughes, P.F. Wainwright, M. S. Lubell, W. Raith
Experimental Study Of Spin-Exchange Effects In Elastic And Ionizing Collisions Of Polarized Electrons With Polarized Hydrogen Atoms, G. D. Fletcher, M. J. Alguard, Timothy J. Gay, V. W. Hughes, P.F. Wainwright, M. S. Lubell, W. Raith
Timothy J. Gay Publications
Using crossed beams of polarized electrons and polarized hydrogen atoms we have investigated the effect of spin exchange on 90° elastic scattering from 4.4 to 30.3 eV and impact ionization from 14.1 to 197.0 eV. Our results suggest that the range of validity of various theoretical approximation methods is more restricted than had been assumed previously.
Beyond The Rigid-Ion Approximation With Spherically Symmetric Ions, L. L. Boyer, M. J. Mehl, J. L. Feldman, John R. Hardy, J. W. Flocken, C. Y. Fong
Beyond The Rigid-Ion Approximation With Spherically Symmetric Ions, L. L. Boyer, M. J. Mehl, J. L. Feldman, John R. Hardy, J. W. Flocken, C. Y. Fong
John R. Hardy Papers
Ab initio calculations show that a spherically symmetric charge relaxation of ions in a crystal, in response to the long-range electrostatic potential, is important for understanding the splitting between longitudinal- and transverse-optic-mode frequencies, and the violation of the Cauchy relations among elastic constants.
Spin-Glass And Double-Transition Behavior In Gd-La Glasses, Michael J. O'Shea, David J. Sellmyer
Spin-Glass And Double-Transition Behavior In Gd-La Glasses, Michael J. O'Shea, David J. Sellmyer
David Sellmyer Publications
We report studies of high-field magnetization, field-cooled magnetization, thermoremanent magnetization, and isothermal remanent magnetization as a function of temperature in the metallic glass sytem GdxLa72-xG28 where G28=Ga18B10 for the compositions x=72, 68, 64. The first two compositions show double-transition behavior and the last one shows only a paramagnetic to spin-glass transition. The approach to saturation at intermediate fields (up to 40 kOe) is of the form 1/H1/2 as predicted by a mean field model which incorporates a small random anisotropy. The field-cooled magnetization in these samples is …
Random Magnetism In Amorphous Rare-Earth Alloys (Invited), David J. Sellmyer, S. Nafis
Random Magnetism In Amorphous Rare-Earth Alloys (Invited), David J. Sellmyer, S. Nafis
David Sellmyer Publications
Several aspects of the magnetic transitions seen in rare-earth metallic glasses are discussed, particularly with reference to recent theoretical work. These include: (a) apparent double transitions observed in Gd glasses where exchange fluctuations are important, (b) evidence for a correlated speromagnetic state recently predicted by Chudnovsky and Serota, and (c) the analysis of a Tb glass with strong random anisotropy in terms of an Ising-type spin-glass transition. Journal of Applied Physics is copyrighted by The American Institute of Physics.
Anomalous Magnetic Hysteresis In An Amorphous Nd54Co36B10 Alloy, George C. Hadjipanayis, S.H. Aly, David J. Sellmyer
Anomalous Magnetic Hysteresis In An Amorphous Nd54Co36B10 Alloy, George C. Hadjipanayis, S.H. Aly, David J. Sellmyer
David Sellmyer Publications
The hysteresis and crystallization behavior of an amorphous Nd54Co36B10 alloy have been examined over a range of temperatures. Crystallization studies show a glass transition temperature around 210 °C, two crystallization peaks at around 220 and 360 °C, and two endothermic peaks at around 530 and 600 °C, respectively. ac susceptibility measurements show an ordering temperature of 38 K for the amorphous phase. Four additional magnetic phases have been observed in the crystallized samples with ordering temperatures 17, 45, 90, and 190 K, respectively. Magnetic measurements on melt-spun ribbons reveal a coercivity of 6 kOe at …
Rapidly Quenched FeXTa100-X Alloys, C.L. Chien, Sy_Hwang Liou, B.K. Ha, K.M. Unruh
Rapidly Quenched FeXTa100-X Alloys, C.L. Chien, Sy_Hwang Liou, B.K. Ha, K.M. Unruh
Sy-Hwang Liou Publications
Binary alloys of FexTa100-x were made by high-rate sputtering. A sharply defined boundary separates the composition ranges in which crystalline alloys (93 ≤ x ≤100) and amorphous alloys (15 ≤ x ≤ 90) are formed. The amorphous alloys with Fe concentrations up to the threshold of xc ≈ 65 are nonmagnetic. For the samples with x > xc, the magnetic ordering temperature (Tc) varies monotonically with Fe content to 200 K for a-Fe90Ta10. However, the crystalline alloys, with slightly higher Fe content, are strongly ferromagnetic. Their T …
Magnetic Properties And Hyperfine Interactions Of Amorphous Fe-Hf Alloys, Sy_Hwang Liou, G. Xiao, J.N. Taylor, C.L. Chien
Magnetic Properties And Hyperfine Interactions Of Amorphous Fe-Hf Alloys, Sy_Hwang Liou, G. Xiao, J.N. Taylor, C.L. Chien
Sy-Hwang Liou Publications
Alloys of FexHf100-x (20 ≤ x ≤ 100) were fabricated by a vapor-quench method. The amorphous state, as verified by x-ray diffraction, is realized over a wide composition range of 20 ≤ x ≤ 94. The magnetic phase diagram was determined. The variation with Fe content of the magnetic ordering temperature (Tc) in Fe-Hf amorphous alloys shows a maximum at xp≈87. In contrast, the effective magnetic hyperfine field and therefore the Fe moment increases monotonically with x. Amorphous pure Fe is likely to be magnetic (Tc ~200 K) with …
Lung Cancer Incidence In A Chinese High Background Area — Epidemiological Results And Theoretical Interpretation, Werner Hofmann, Robert Katz, Chunxiang Zhang
Lung Cancer Incidence In A Chinese High Background Area — Epidemiological Results And Theoretical Interpretation, Werner Hofmann, Robert Katz, Chunxiang Zhang
Robert Katz Publications
A survey of inhabitant exposures arising from the inhalation of radon and thoron daughters, and lung cancer mortality has been carried out in two adjacent areas in Guangdong province, China, designated as the "high background" and the "control" area. Annual exposure rates are 0.38 WLM/yr in the high background, and 0.16 WLM/yr in the control area, while age-adjusted mortality rates are 2.7 per 105 living people of all ages in the high background, and 2.9 per 105 in the control area. From this data we conclude that we are unable to determine the excess lung cancer rate over normal fluctuations …
Self-Consistent Phases In Topological Particle Theory, Paul Finkler, C. Edward Jones
Self-Consistent Phases In Topological Particle Theory, Paul Finkler, C. Edward Jones
Paul Finkler Papers
To be a self-contained theory, topological particle theory should explain from the basis of its own stated framework of assumptions (nonlinear self-consistency equations, pole factorization, crossing symmetry, and Hermitian analyticity} all the mathematical properties and numerical values of scattering amplitudes. This paper attempts to move the theory in this direction by showing that the phases of the zero-entropy amplitudes in the theory are, in fact, determined by the above framework of assumptions except for trivial ambiguities that appear to have no physical consequences. This extends previous work on this subject and removes the need for certain extra assumptions. Once the …
Derivation Of Discrete Invariances (T, C, And P) And The Connection Between Spin And Statistics In Topological Particle Theory, C. E. Jones, Paul Finkler
Derivation Of Discrete Invariances (T, C, And P) And The Connection Between Spin And Statistics In Topological Particle Theory, C. E. Jones, Paul Finkler
Paul Finkler Papers
For purely hadronic processes, the standard connection between spin and statistics as well as separate invariances under charge conjugation, parity, and time reversal are shown to be consequences of self-consistency in topological particle theory.
Photoemission, Electronic Structure, And Magnetism In Vpd3, D.K. Misemer, S. Auluck, David J. Sellmyer, Sitaram Jaswal, A.J. Arko
Photoemission, Electronic Structure, And Magnetism In Vpd3, D.K. Misemer, S. Auluck, David J. Sellmyer, Sitaram Jaswal, A.J. Arko
David Sellmyer Publications
Electronic and magnetic states in the ordered compound VPd3 have been investigated with photoemission measurements and self-consistent band-structure calculations. The linear combination of muffin-tin orbitals method was used to study VPd3 in a hypothetical cubic crystal structure and the actual tetragonal crystal structure, and the calculations were performed for both paramagnetic and spin-polarized configurations. The results for the cubic structure are in agreement with earlier calculations, while the results from the tetragonal structure are in much better agreement with the photoemission and other measurements.
Electron Doubly Differential Cross Section For 0.5-Mev H--He Detachment Collisions, Chang-Hwan Park, Anthony F. Starace, Joseph Macek
Electron Doubly Differential Cross Section For 0.5-Mev H--He Detachment Collisions, Chang-Hwan Park, Anthony F. Starace, Joseph Macek
Anthony F. Starace Publications
A comprehensive theoretical treatment is presented for the electron detachment cross section, differential in both electron momentum and direction, for collisions of 0.5-MeV H- projectiles on He targets. Our calculation, which assumes that the residual H atom is left in the 1s state, employs the usual first Born approximation as well as the closure approximation (in order to sum over all He target final states). Electron correlations within the H- system are treated in detail within the framework of the adiabatic hyperspherical coordinate approximation. In particular, for the first time for this collision process, angular correlations are included. The …
Radial Distribution Of Dose And Cross-Sections For The Inactivation Of Dry Enzymes And Viruses, Zhang Chunxiang, D. E. Dunn, Robert Katz
Radial Distribution Of Dose And Cross-Sections For The Inactivation Of Dry Enzymes And Viruses, Zhang Chunxiang, D. E. Dunn, Robert Katz
Robert Katz Publications
A new semi-empirical algorithm for the radial distribution of dose is compared with available data. The algorithm is used to calculate the inactivation cross section for dry enzymes and viruses using an extended target model of a 1-hit detector. Agreement with data is at about the 15% level, approximating the precision of the data itself.
Cross Sections For Ionization Of Water Vapor By 7-4000-Kev Protons, M. Eugene Rudd, T. V. Goffe, R. D. Dubois, L. H. Toburen
Cross Sections For Ionization Of Water Vapor By 7-4000-Kev Protons, M. Eugene Rudd, T. V. Goffe, R. D. Dubois, L. H. Toburen
M. Eugene Rudd Publications
Cross sections for production of electrons and positive ions by proton impact on water vapor have been measured from 7-4000 keV by the transverse-field method.