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Articles 1741 - 1762 of 1762
Full-Text Articles in Physical Sciences and Mathematics
Critical Assessment Of The Polarized-Orbital Method In Atomic Scattering, Marvin H. Mittleman, Jerry Peacher
Critical Assessment Of The Polarized-Orbital Method In Atomic Scattering, Marvin H. Mittleman, Jerry Peacher
Physics Faculty Research & Creative Works
The method of polarized orbitals used in calculating electron-atom scattering amplitudes has two obvious flaws: the wave function is discontinuous, and the method is not variationally based. These are corrected in a somewhat arbitrary manner, and it is found that the results then depend upon a parameter of the theory sufficiently strongly that there are serious doubts about the predictive nature of the theory.
Modified Dispersion Relations And Π Π Scattering, David J. George, Barbara N. Hale, Arnold Tubis
Modified Dispersion Relations And Π Π Scattering, David J. George, Barbara N. Hale, Arnold Tubis
Physics Faculty Research & Creative Works
The ππ S-wave scattering-length predictions of Weinberg have been tested by using dispersion sum rules for the infinite-energy cross section. Reasonable agreement is obtained with the infinite-energy cross section (≈15 mb) estimated from the factorization theorem for the Pomeranchon Regge residues. Experimental phase-shift data of Gutay et al., Walker et al., and Baton et al. are used in estimating the dispersion integrals. The analysis seems to rule out an I = 0 S-wave scattering length ⪞0.4μ-1.
Associative Detachment: H+Hˉ→₂*+E, Joseph C.Y. Chen, Jerry Peacher
Associative Detachment: H+Hˉ→₂*+E, Joseph C.Y. Chen, Jerry Peacher
Physics Faculty Research & Creative Works
The process of associative detachment in the (H,H-) collision system is investigated at energies below 12 eV. In this energy region, the interaction potential between H and H- has recently been determined. The energy dependence of the cross section is calculated with explicit allowance for the production of "hot" hydrogen molecules. It is observed that associative detachment provides a possible mechanism for generating an inverted population of the residual molecule such as H2.
New Superconvergent Dispersion Relations For The Forward Πn Crossing-Even Amplitude, David J. George, Barbara N. Hale, Arnold Tubis
New Superconvergent Dispersion Relations For The Forward Πn Crossing-Even Amplitude, David J. George, Barbara N. Hale, Arnold Tubis
Physics Faculty Research & Creative Works
A Liu-Okubo-type dispersion relation is derived for the crossing-even pion-nucleon forward elastic scattering amplitude T(+). Two subtractions are made, one at the physical scattering threshold and the other at a previously determined zero of T(+) on the imaginary axis of the complex ω (pion lab energy) plane. The dispersion relation is well satisfied over the whole allowed range of the Liu-Okubo parameter. Moreover, it is nearly saturated by low-energy scattering for a considerable range of the parameter. It should thus serve as an extremely sensitive test of the low-energy scattering data when such data become more accurately …
Interaction Potential Between The Ground States Of H And Hˉ, Joseph C.Y. Chen, Jerry Peacher
Interaction Potential Between The Ground States Of H And Hˉ, Joseph C.Y. Chen, Jerry Peacher
Physics Faculty Research & Creative Works
An investigation of the interaction potential for H and H- in both ungerade and gerade modes is carried out by a semiempirical method in which the recently observed isotope effect in dissociative attachment of electrons to hydrogen molecules is used. The interaction obtained is complex, and the imaginary parts of the interaction account for electron emissions during the course of the interaction. A comparison of the present result with other calculations is presented. The isotope effect in dissociative attachment is also discussed. It is shown that the ratios of the survival probabilities alone do not provide an adequate approximation …
The Critical And High‐Temperature Behavior Of A Heisenberg Ferromagnet, Harry A. Brown
The Critical And High‐Temperature Behavior Of A Heisenberg Ferromagnet, Harry A. Brown
Physics Faculty Research & Creative Works
No abstract provided.
Cell Model Of A Fluid. Ii. Thermodynamic Properties Of The System, Ralph G. Tross, Louis H. Lund
Cell Model Of A Fluid. Ii. Thermodynamic Properties Of The System, Ralph G. Tross, Louis H. Lund
Physics Faculty Research & Creative Works
In Paper I of this series (preceding paper) the model was formulated mathematically, and the solution derived in the form of an infinite series. The convergence and analyticity of the solution were investigated. It was then applied to one-, two-, and three-dimensional systems with nearest-neighbor interactions, and low-temperature series for these systems were obtained. In the present article the thermodynamics of the model are investigated. The series solution of the partition function derived in Paper I is applied to systems with interaction potentials of increasing complexity. The validity of the model is established by showing that in the appropriate limits …
Cell Model Of A Fluid. I. Evaluation Of The Partition Function And Series Expansions, Ralph G. Tross, Louis H. Lund
Cell Model Of A Fluid. I. Evaluation Of The Partition Function And Series Expansions, Ralph G. Tross, Louis H. Lund
Physics Faculty Research & Creative Works
The partition function of a one-dimensional system of particles with all interactions active is formulated in terms of Ising ferromagnetic spin states. It is shown how the partition function for two- and three-dimensional systems can be obtained from the one-dimensional one by restricting the number of bonds per particle. After writing the partition function in matrix form, the operator of interest is diagonalized and its trace expressed in the form of a convenient infinite series. The series is shown to be absolutely convergent and its analytic properties are briefly investigated. It is then applied to one-, two-, and three-dimensional systems …
Dielectric Properties Of Solid Solutions Of Bifeo₃ With Pb(Ti, Zr)O₃ At High Temperature And High Frequency, Robert Travis Smith, Gary D. Achenbach, Robert Gerson, William Joseph James
Dielectric Properties Of Solid Solutions Of Bifeo₃ With Pb(Ti, Zr)O₃ At High Temperature And High Frequency, Robert Travis Smith, Gary D. Achenbach, Robert Gerson, William Joseph James
Physics Faculty Research & Creative Works
Solid solutions of BiFeO3 with PbTiO3, PbTi0.5Zr0.5O3, and PbZrO3 were prepared. The crystallographic data on these solutions, which are basically perovskitic, are given. The dielectric constants of the materials were determined at a frequency of 0.53 GHz and at temperatures up to 800°C. Dielectric Curie points were found in solutions containing up to 90 mole % BiFeO3. These results leave little doubt that BiFeO3 is ferroelectric or antiferroelectric. The extrapolated Curie point for BiFeO3 is above 850°C. BiFeO3 appears more likely to be ferroelectric than …
The Magnetic Dilution Problem, Harry A. Brown, William F. Parks
The Magnetic Dilution Problem, Harry A. Brown, William F. Parks
Physics Faculty Research & Creative Works
No abstract provided.
The Bethe-Weizsäcker Mass Formula And Lennard-Jones N-N Potentials, James Paul Wesley, Alex E.S. Green
The Bethe-Weizsäcker Mass Formula And Lennard-Jones N-N Potentials, James Paul Wesley, Alex E.S. Green
Physics Faculty Research & Creative Works
An elementary derivation of the Bethe-Weizscker semiempirical nuclear mass formula which is in the spirit of current views of nuclear structure, is given. Lennard-Jones potentials are assumed to act between nuclear. Thus, the major interaction between nn, pp, and np pairs is taken of the form —g/r3+h/r4, where r is the separation distance between nuclear, and g and h are constants. An additional "symmetry" interaction of the form s/r3 is assumed for np pairs. Summing the potential energy over all nucleon pairs and using the Fermi statistical estimate of the kinetic energy, the Bethe-Weizscker semiempirical mass formula is obtained directly. …
Strong-Coupled Piezoelectric Polaron, Wayne E. Tefft
Strong-Coupled Piezoelectric Polaron, Wayne E. Tefft
Physics Faculty Research & Creative Works
A semiclassical, variational calculation for the strong-coupled piezoelectric polaron gives the following results for the ground-state energy and polaron radius, respectively: U0=-0.47(m*/m) (κ2/ε)2eV, and R=3.5(ε/κ2) (m/m*)â ã where m* is the band effective mass, κ is the electromechanical coupling constant, and ε is the strain-free dielectric constant. The theory is expected to be valid when |U0| is larger than thermal energies and R is considerably larger than unit-cell dimensions. A calculation of the polaron effective mass, having a more limited region of validity, gives mp~m*[1+2|U0|/m*vs2], where vs is the velocity of sound. …
Survival Probability In Dissociative Attachment, Joseph C.Y. Chen, Jerry Peacher
Survival Probability In Dissociative Attachment, Joseph C.Y. Chen, Jerry Peacher
Physics Faculty Research & Creative Works
The survival probability in dissociative attachment is investigated with special attention to the (e, H2 ) system. It is shown that the simple expression for the dissociative-attachment cross section, as given by the product of a capture cross section and a survival probability, is equivalent to the s -wave approximation for the g → g dissociative attachment. This expression, however, does not constitute an approximation for the g → u dissociative attachment, since the parity of the initial rotational states of H2 is always opposite to that of the relative angular momentum states of H and H- …
Rapid Calculation Of Electron Scattering Factors, Jerry Peacher, John G. Wills
Rapid Calculation Of Electron Scattering Factors, Jerry Peacher, John G. Wills
Physics Faculty Research & Creative Works
The phase amplitude method is used to reduce the radial Schrödinger equation to two separate differential equations, one for the phase and one for the amplitude. These functions are both smooth as opposed to the rapidly oscillating solution of the radial Schrödinger equation for electron energies in the kilovolt range. The partial-wave phase shifts were obtained rapidly by integrating the differential equations for the phase and amplitude numerically. Hartree-Fock and Thomas-Fermi-Dirac fields were used in the calculation. Results for argon and uranium are given in order to compare with previous results. It was found that the WKBJ approximation to the …
Effect Of Environmental Hydrogen Pressure On The Hydrogen Yield From X‐Irradiated Polyethylenes, Otto H. Hill, R. Pat Lightfoot
Effect Of Environmental Hydrogen Pressure On The Hydrogen Yield From X‐Irradiated Polyethylenes, Otto H. Hill, R. Pat Lightfoot
Physics Faculty Research & Creative Works
An experimental assembly incorporating a capacitance‐type, differential pressure transducer, which provides resolutions of 3 x 10−4 torr at pressures extending to 30 torr, has been employed to monitor the effect of hydrogen environmental pressure on the hydrogen yield from x‐irradiated polyethylene's. Contrary to the observations of previous investigators, the hydrogen yield is found to be independent of hydrogen environmental pressures extending over the critical range up to at least 30 torr. It is demonstrated that neglecting the temperature and density gradients inherent in closed‐volume irradiation assemblies employing cryogenic traps to separate liberated gases into condensable and non condensable fractions may …
Ferroelectric Properties Of Pbzro₃-Bifeo₃ Solid Solutions, Robert Gerson, Pen-Chu Chou, William Joseph James
Ferroelectric Properties Of Pbzro₃-Bifeo₃ Solid Solutions, Robert Gerson, Pen-Chu Chou, William Joseph James
Physics Faculty Research & Creative Works
Solid solutions of BiFeO and PbZrO3 were investigated for crystallographic and dielectric properties. A new pseudocubic perovskite phase was found, which has been tentatively indexed as orthorhombic with the same unit cell as PbZrO3 but with dielectric properties characteristic of a ferroelectric substance. The Curie point in this series of solid solutions has a minimum of about 155°C at a composition of about (PbZrO3)0.80 (BiFeO3)0.20, which at room temperature lies on the boundary between the orthorhombic antiferroelectric and the pseudocubic ferroelectric phases. This composition has a relative dielectric constant of 800 …
Spectrographic Study Of The Afterglow Of Mercury, Edward E. Stepp, Richard A. Anderson
Spectrographic Study Of The Afterglow Of Mercury, Edward E. Stepp, Richard A. Anderson
Physics Faculty Research & Creative Works
The short duration afterglow of 14 Hg lines was examined, at temperatures of 150°, 200°, 250°, and 300°F, in a cell that had been excited by an rf source. All of the lines exhibited a smooth exponential decay at the lowest temperature. At some temperature above 150°F, however, all of the lines, except the 2537- and 4079- Å lines, exhibited an enhancement of intensity in the time region between 50 and 100 µsec. At the highest temperature all of the lines originating from levels at an energy of 8.84 eV or above, except those originating from the 61D …
A Ti-Hg Collision Cross Section, Edward E. Stepp, Richard A. Anderson
A Ti-Hg Collision Cross Section, Edward E. Stepp, Richard A. Anderson
Physics Faculty Research & Creative Works
The lifetime of the 63P1 state of Hg was observed as a function of Tl density at two different Hg pressures. From these data it appears that at high Tl densities the lifetime of the 63P1 state of Hg is controlled by collisions with Tl atoms. Using this assumption and simple gas kinetic theory, a cross section for these collisions was calculated.
On The Calculation Of Multicenter Two-Electron Repulsion Integrals Involving Slater Functions, Russell A. Bonham, Jerry Peacher, Henry L. Cox
On The Calculation Of Multicenter Two-Electron Repulsion Integrals Involving Slater Functions, Russell A. Bonham, Jerry Peacher, Henry L. Cox
Physics Faculty Research & Creative Works
Integral transforms are used to evaluate many-center two-electron repulsion integrals involving Slater s-type functions. The reduction of a general four-center integral of this type to a form convenient for computational purposes is presented. The technique described has the important advantage that all lesser many-center and one-center integrals can be obtained from the four-center case by proper choice of constants. The form of the result is such that simple single-precision numerical techniques yield rapid and accurate evaluations of many-center integrals. Several numerical examples are presented.
Decay Of Intensity Of Certain Hg Lines In An Hg-Ar Discharge, Edward E. Stepp, Richard A. Anderson
Decay Of Intensity Of Certain Hg Lines In An Hg-Ar Discharge, Edward E. Stepp, Richard A. Anderson
Physics Faculty Research & Creative Works
The afterglow of four mercury spectral lines was examined in a mercury-argon electric discharge. The 2537- Å line decays in a complex fashion with three definite modes of decay. The 4077-, 4358-, and 5461- Å lines exhibited an even more complicated decay. These lines exhibited an initial rapid decay followed by an increase in intensity. Finally the intensity of these lines went through two maxima before they decayed in intensity at a slow constant rate. The actual intensity behavior of the 2537- Å line was masked by the imprisonment of resonance radiation. It is postulated that the main processes governing …
Theory Of The Effect Of Temperature On The Electron Diffraction Patterns Of Diatomic Molecules, Russell A. Bonham, Jerry Peacher
Theory Of The Effect Of Temperature On The Electron Diffraction Patterns Of Diatomic Molecules, Russell A. Bonham, Jerry Peacher
Physics Faculty Research & Creative Works
The effect of temperature on the electron diffraction pattern of a diatomic molecule is considered from the standpoint of the simple kinematic scattering theory utilizing a quartic vibrational potential. The potential is obtained by an expansion of ħ2J( J+1)/2μr2+D exp[-2a(r-re)]-2D exp[-a(r-re)] about its minimum value r0. The second-order wavefunction for the nth vibrational and 7th rotational state of the system has been obtained, and expressions for the electron diffraction quantities rg, le 2, and M (s) have been computed. General results for the quantity M (s) …
Glass-To-Sapphire End Window Seals, Edward E. Stepp, Richard A. Anderson
Glass-To-Sapphire End Window Seals, Edward E. Stepp, Richard A. Anderson
Physics Faculty Research & Creative Works
SAPPHIRE windows have been used in laboratory devices where radiation from the ultraviolet through the infrared must be transmitted. Sapphire windows have been valuable in chambers which contain the alkali metals, for the alkali metals are known to react with Pyrex 7740 glass and quartz leaving them pitted and darkened. This paper is a report on an improved glass-to-sapphire end window seal.