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Full-Text Articles in Physics
On The Ising Model For Amorphous Ferromagnets, Harry A. Brown
On The Ising Model For Amorphous Ferromagnets, Harry A. Brown
Physics Faculty Research & Creative Works
A calculation is made of the effect on the critical temperature of a ferromagnet whose exchange integrals are taken to be random variables. The Bethe-Peierls-Weiss approximation is used to find the partition function, Z, for an Ising system and then a configuration average is taken to find (InZ), from which the resulting decrease in the critical temperature can be found. Other results are discussed, and comparisons made with the present result.
Isotope Effect In Electron-Capture Differential Cross Sections At Intermediate Energies, Eduard P. Rille, Ronald E. Olson, Jerry Peacher, D. M. Blankenship, Thomas J. Kvale, E. Redd, John T. Park
Isotope Effect In Electron-Capture Differential Cross Sections At Intermediate Energies, Eduard P. Rille, Ronald E. Olson, Jerry Peacher, D. M. Blankenship, Thomas J. Kvale, E. Redd, John T. Park
Physics Faculty Research & Creative Works
The isotope dependence in the angular distribution of electron-capture cross sections for protons and deuterons with equal velocity (E=40 keV/u) colliding with atomic hydrogen or deuterium targets is predicted theoretically and observed experimentally. A projectile-dependent effect is observed at small scattering angles. No target dependence was detected in the differential cross sections. A scaling relationship is determined which permits the prediction of differential cross sections for hydrogen-isotope projectiles.
Electron Capture And Ionisation In H⁺, He2++Li Collisions, Ronald E. Olson
Electron Capture And Ionisation In H⁺, He2++Li Collisions, Ronald E. Olson
Physics Faculty Research & Creative Works
Single electron capture and ionization cross sections have been calculated for H++Li and He2++Li collisions at energies ranging from 50 to 400 keV amu-1. Double electrons capture cross sections are presented for the He2++Li system. The classical-trajectory Monte Carlo method and the independent-electron model were used to calculate the cross sections. In the energy range investigated, the ionization process is dominated by electron removal of the valence Li(2s) electron, whereas the single and double electron capture processes are the result of capture from the K shell of the lithium atom.
Angular Scattering In Slow Multiple-Charged Ion, Atom Collisions, Ronald E. Olson, M. Kimura
Angular Scattering In Slow Multiple-Charged Ion, Atom Collisions, Ronald E. Olson, M. Kimura
Physics Faculty Research & Creative Works
The C6++H system is used to illustrate the importance of large-angle scattering in collisions between slow multiply charged ions and atoms. A quantum mechanical description based on a diabatic formalism of the collision system is used to obtain differential cross sections for electron capture in the relative velocity range nu =1*107 to 3*107 cm s-1 (Ecm approximately=48 to 430 eV). The threshold for angular scattering is at E theta approximately=0.2 keV deg which correlates with the curve crossing between initial and final molecular states located at Rx approximately=8a0. The centre-of-mass acceptance angles required to observe fixed fractions of the total …
Nonlinear Anelasticity Of Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Nonlinear Anelasticity Of Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
An approximate solution of the equation of motion of a nonlinear anelastic reed at or near resonance is presented. The steady state solution reproduces the well-known nonlinear resonances. The solution also predicts the existence of auto modulations, i.e., self-excited modulations of the amplitude and phase at constant power of excitation of the reed. Numerical examples of such auto modulations are presented for an antisymmetric deformation potential. Experimental studies of finite amplitude oscillations of a magnesium reed vibrating at 72 and 431 Hz at room temperature confirm the existence of auto modulations. The experimental results can be semi quantitatively described in …
Elastic Differential Cross Sections For Small-Angle Scattering Of 25-, 50-, And 100-Kev Protons By Helium Atoms, Jerry Peacher, Thomas J. Kvale, E. Redd, Paul J. Martin, D. M. Blankenship, Eduard P. Rille, V. C. Sutcliffe, John T. Park
Elastic Differential Cross Sections For Small-Angle Scattering Of 25-, 50-, And 100-Kev Protons By Helium Atoms, Jerry Peacher, Thomas J. Kvale, E. Redd, Paul J. Martin, D. M. Blankenship, Eduard P. Rille, V. C. Sutcliffe, John T. Park
Physics Faculty Research & Creative Works
The first measurements of elastic differential cross sections have been carried out for 25-, 50-, and 100-keV protons scattered through very small angles by helium atoms. The University of Missouri Rolla energy-loss spectrometer provided the required high angular resolution and also separated the elastically scattered ions from the inelastically scattered ions. The data are compared to our Born, Glauber, and classical calculations as well as a four-state calculation. All of the measured elastic differential cross sections are more sharply peaked than theory for the smallest scattering angles. At the larger scattering angles all of the measured elastic differential cross sections …
Selective Deposition Of Sio2 Thin Films In Acid Baths, M. A. Smith, L. L. Levenson
Selective Deposition Of Sio2 Thin Films In Acid Baths, M. A. Smith, L. L. Levenson
Physics Faculty Research & Creative Works
We report observation of deposition of SiO2 thin films on a variety of surfaces in nitric acid and hydrochloric acid solutions. Scanning electron microscopy shows that the films are composed of closely packed spheres 1000 Å in diameter. Chemical identification is made with Auger electron spectroscopy. The films are generally between 1000 and 2000 Å thick and are possibly hydrated. Deposition occurs in either acid for molarities in the 1-8 M range and at temperatures between 80 and 100 °C. The effects for molarities greater than 8 M and temperatures greater than 100 °C have not been investigated. Materials …
Monte Carlo Studies Of Water Monolayer Clusters On Substrates: Hexagonal Agi, Richard C. Ward, Jon M. Holdman, Barbara N. Hale
Monte Carlo Studies Of Water Monolayer Clusters On Substrates: Hexagonal Agi, Richard C. Ward, Jon M. Holdman, Barbara N. Hale
Physics Faculty Research & Creative Works
A Monte Carlo procedure is used to study the stability and structure of small water clusters adsorbed on model basal and prism faces of hexagonal AgI. Effective pair potentials for the H2O-AgI interaction [B. N. Hale and J. Kiefer, J. Chem. Phys. 73, 923 (1980)] and the revised central force potentials for the H2O-H2O interaction [F. H. Stillinger and A. Rahman, J. Chem. Phys. 68, 666 (1978)] are used to determine average internal cluster binding energy and average cluster-substrate binding energy for water clusters containing 6, 24, and 44 water molecules at temperatures 240, …
The University Of Missouri-Rolla, Absolute Aitken Nucleus Counter, John L. Schmitt, James L. Kassner, Josef Podzimek
The University Of Missouri-Rolla, Absolute Aitken Nucleus Counter, John L. Schmitt, James L. Kassner, Josef Podzimek
Physics Faculty Research & Creative Works
The authors discuss the expansion cloud chamber system known as the University of Missouri-Rolla-absolute Aitken nucleus counter. A review of the properties of an expansion chamber and how it creates a supersaturation are given and a critical examination is made of the assumptions in its operation, e.g. adiabaticity of the expansion. The design of the chamber is described in detail and an analysis of the propagation of errors is given for quantities measured and calculated. A short review of the performance of the chamber and some general comments relative to comparisons with other Aitken nucleus counting instruments are given. The …
A Study Of The Critical Cluster Size For Water Monolayer Clusters On A Model Agi Basal Substrate, Richard C. Ward, Barbara N. Hale, Sergio Terrazas
A Study Of The Critical Cluster Size For Water Monolayer Clusters On A Model Agi Basal Substrate, Richard C. Ward, Barbara N. Hale, Sergio Terrazas
Physics Faculty Research & Creative Works
We present a formalism and estimate a critical cluster size for water monolayer formation on a (rigid) model AgI basal substrate. The formalism is modified from that developed for vapor clusters [B. N. Hale and R. C. Ward, J. Stat. Phys. 28, 487 (1982)] and uses a Metropolis Monte Carlo method developed by Squire and Hoover [J. Chem. Phys. 50, 701 (1969)] to determine (Helmholtz) free energy differences for clusters containing n and n-1 molecules. Calculations for clusters of n=1, 2, 3, 4, 6, and 24 water molecules on a model AgI basal face at 265 K are …
Homogeneous Nucleation Of Ethanol, John L. Schmitt, G. W. Adams, R. A. Zalabsky
Homogeneous Nucleation Of Ethanol, John L. Schmitt, G. W. Adams, R. A. Zalabsky
Physics Faculty Research & Creative Works
The authors have used an expansion cloud chamber to measure homogeneous nucleation rate as a function of temperature and supersaturation in ethanol. Nucleation rates from 102 to 105 drops/cm3 sec were measured in the temperature range 252-272 °K. An empirical functional fit to the data is used to extrapolate for comparison with other data in the literature at a nucleation rate of 1 drop/cm3 sec and to compare with the predictions of the classical Becker-Doring homogeneous nucleation theory. A full listing of the data and thermodynamics constants used in the reduction of the data is given in an appendix. © …
On The Curie Temperatures Of Amorphous Ferromagnets, Harry A. Brown
On The Curie Temperatures Of Amorphous Ferromagnets, Harry A. Brown
Physics Faculty Research & Creative Works
No abstract provided.
Molecular Treatment Of Electron Capture By Protons From The Ground And Excited States Of Alkali-Metal Atoms, M. Kimura, Ronald E. Olson, J. Pascale
Molecular Treatment Of Electron Capture By Protons From The Ground And Excited States Of Alkali-Metal Atoms, M. Kimura, Ronald E. Olson, J. Pascale
Physics Faculty Research & Creative Works
Electron-capture cross sections for H+ plus alkali-metal atom (Na, K, Rb, and Cs) systems have been computed for projectile energies from 10 eV to 10 keV. An impact parameter perturbed-stationary-state theory using molecular states that incorporate electron translation factors was used to calculate the cross sections. The wave functions were generated by employing the pseudopotential method. These yield equilibrium parameters Re and De for the A +2 molecular state that are in good agreement with ab initio results. Interaction energies are also presented for the LiH+ system. Basis sets of up to eight molecular states were used to calculate the …
Electron Density Measurements In A Laser Induced Na Plasma, D. J. Krebs, Laird D. Schearer
Electron Density Measurements In A Laser Induced Na Plasma, D. J. Krebs, Laird D. Schearer
Physics Faculty Research & Creative Works
The optical emission spectrum of a recombining Na plasma is observed. The shift and broadening of the spectral line emission due to electron collisions is observed. Electron densities on the order of 5x1014 cm -3 are calculated from the shift measurements. The results agree well with electron densities obtained in the same system from Saha plots of excited state densities. © 1982 American Institute of Physics.
A Note On The Use Of A Photoelectric Counter For Total Particle Counting, Josef Podzimek, Paul C. Yue
A Note On The Use Of A Photoelectric Counter For Total Particle Counting, Josef Podzimek, Paul C. Yue
Physics Faculty Research & Creative Works
The ability of the Nolan-Pollak counter to function as a "total" particle counter was investigated. Comparison with the UMR Absolute Aitken Nuclei Counter operated at an expansion pressure ratio of 1.33 revealed that in mean, the N-P counter measurements (at an expansion pressure ratio of 1.21) were 30% less. This correction, however, depends on particle nature, concentration and size distribution and assumes that particle losses in the central part of the UMRAAN counter are negligible. © 1982.
Measurement Of The Wear Properties Of Metallic Solids With A Falex Lubricant Testing Machine, Edward Boyd Hale, Chun-Ping John Meng, Ronald A. Kohser
Measurement Of The Wear Properties Of Metallic Solids With A Falex Lubricant Testing Machine, Edward Boyd Hale, Chun-Ping John Meng, Ronald A. Kohser
Physics Faculty Research & Creative Works
A modified Falex Lubricant Testing Machine has been used to determine wear properties of metallic solids. In particular, wear mass loss, wear volume loss, wear rates, and other parameters have been determined for a basic steel, as heat treated and after ion implantation. Wear rate improvements of more than an order of magnitude were found in a nickel-chrome steel (SAE 3135) implanted with 2.5x1017 N+2/cm2. Wear tests were conducted with a cylinder-in-groove geometry in a mild lubricating oil with loads greater than 540 N, which corresponded to pressures which exceeded 108N/m2 …
Electron-Capture Collisions Of H+ With Ground- And Excited-State Na, M. Kimura, Ronald E. Olson, J. Pascale
Electron-Capture Collisions Of H+ With Ground- And Excited-State Na, M. Kimura, Ronald E. Olson, J. Pascale
Physics Faculty Research & Creative Works
Pseudopotential molecular-structure calculations have been used to obtain the low-lying interaction energies for NaH+. The wave functions were used to calculate accurate radial and rotational coupling matrix elements. Scattering calculations which include electron translational factors were performed using up to eight coupled channels for laboratory energies 0.1 to 10 keV. Electron capture from ground-state Na 3s yields cross sections in the 10-15-cm2 range of which the dominant products are H 2s and H 2p. Electron capture from excited Na 3p does not show an enhanced cross section relative to capture from the ground state even though the energy gap E(R=) …
Production Of Highly Charged Rare-Gas Recoil Ions By 1.4-Mev/Amu U44+, A. S. Schlachter, W. Groh, A. Müller, H. F. Beyer, R. Mann, Ronald E. Olson
Production Of Highly Charged Rare-Gas Recoil Ions By 1.4-Mev/Amu U44+, A. S. Schlachter, W. Groh, A. Müller, H. F. Beyer, R. Mann, Ronald E. Olson
Physics Faculty Research & Creative Works
Recoil-ion-production cross sections in rare gases are measured for 1.4-MeV/amu U44+ ions and are calculated for 1-5-MeV/amu projectiles in charge state 44 + with the use of the classical-trajectory Monte Carlo method and the independent-electron model. The calculations reasonably predict the net-charge-production cross sections, which exceed 10-13 cm2 for the heavy rare gases; the calculations are found to underestimate the cross sections for low-charge-state recoil ions and to overestimate the cross sections for high-charge-state recoil ions. The experimental cross sections for production of highly charged recoil ions are found to be large, e.g., greater than 1x10-16 cm2 for production of …
D- Production By Charge Transfer Of (0.3 - 3)-Kev D+ In Thick Alkaline-Earth Vapor Targets: Interaction Energies For Cah+, Cah, And Cah-, R. (Robert) H. Mcfarland, A. S. Schlachter, J. W. Stearns, B. Liu, R. (Ronald) E. Olson
D- Production By Charge Transfer Of (0.3 - 3)-Kev D+ In Thick Alkaline-Earth Vapor Targets: Interaction Energies For Cah+, Cah, And Cah-, R. (Robert) H. Mcfarland, A. S. Schlachter, J. W. Stearns, B. Liu, R. (Ronald) E. Olson
Physics Faculty Research & Creative Works
Equilibrium charge-state fractions of energetic deuterium ions and atoms emerging from alkaline-earth (magnesium, calcium, strontium, and barium) vapor targets are reported in the range of 0.3- to 3-keV incident D+ energy. Deuterium negative-ion production in thick barium and calcium vapor targets equals similar production in cesium vapor (34%). Moreover, the maximum D- production in strontium vapor exceeds that for all other known gas or vapor targets and reaches 50% at 500 eV. Theory does not quantitatively describe these results, although ab initio molecular-interaction-energy calculations on the neutral and negative-ion CaH systems lead to the prediction of large D- yields at …
Determination Of The Absolute Structure Factor For The Forbidden (222) Reflection In Silicon Using 0.12-Γ Rays, R. W. Alkire, W. (William) B. Yelon, J. R. Schneider
Determination Of The Absolute Structure Factor For The Forbidden (222) Reflection In Silicon Using 0.12-Γ Rays, R. W. Alkire, W. (William) B. Yelon, J. R. Schneider
Physics Faculty Research & Creative Works
A room-temperature determination of the absolute structure factor for the forbidden (222) reflection in silicon has been conducted at the University of Missouri Research Reactor with 103-keV gamma rays. The measured structure factor of F(222)=1.456 is in excellent agreement with five of the earlier intensity measurements and is significantly different from any value determined using Pendellösung techniques. An increase in accuracy over previous intensity measurements by a factor of between 2 and 10 has been achieved and is made possible through the use of monoenergetic, short-wavelength gamma rays, which allow absolute measurements to be made in Laue geometry on relatively …
A Study Of Poly(P‐Xylylene)‐Coated Asf5‐Doped Polyacetylene, J. E. Osterholm, H. Yasuda, L. L. Levenson
A Study Of Poly(P‐Xylylene)‐Coated Asf5‐Doped Polyacetylene, J. E. Osterholm, H. Yasuda, L. L. Levenson
Physics Faculty Research & Creative Works
Electrical conductivity measurements and scanning electron microscopy have been used to study uncoated and poly(p‐xylylene)‐coated samples of polyacetylene doped with AsF5. These initial results indicate a considerable reduction in the decay rate of conductivity in the presence of oxygen as well as a decreased rate of thermal decomposition of the dopant when heated between 50°C and 115°C in vacuum by the coating. Copyright © 1982 John Wiley & Sons, Inc.
Phaseautomodulation In Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Phaseautomodulation In Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
No abstract provided.
Comparison Of Several Aitken Nuclei Counters, Josef Podzimek, John C. Carstens, P. C. Yue
Comparison Of Several Aitken Nuclei Counters, Josef Podzimek, John C. Carstens, P. C. Yue
Physics Faculty Research & Creative Works
The basic thermodynamical processes leading to the formation of droplets in the central part of the Nolan-Pollak counter are analyzed in some detail. The comparison of the UMR-Absolute Aitken Nuclei counter with Nolan-Pollak, General Electric and Gardner counters showed consistently higher counts of the UMR-AAN counter. The mean deviations varied between 20% and 50% depending on the type of the counter, nuclei concentration and nature. Several observations are made on ultrafine particle counting. © 1981.
Rare-Gas, Collision-Induced Shifts Of The Nd States Of Sodium, D. J. Krebs, Laird D. Schearer
Rare-Gas, Collision-Induced Shifts Of The Nd States Of Sodium, D. J. Krebs, Laird D. Schearer
Physics Faculty Research & Creative Works
We have measured line shifts of the 3P-nD transitions in sodium induced by collisions with helium, argon, and krypton for n=5 to 18. The shifts of the diffuse series transitions increase rapidly with principal quantum number and asymptotically approach the limit predicted by the Fermi model at high quantum numbers. © 1982 The American Physical Society.