Digital Commons Network^™

Considerations Of Temperature Stability In A Cylindrical Plasma, S. Neil Rasband, Yao-Hui Xu

Faculty Publications

A variational formulation is used to consider thermal equilibrium and stability for a cylindrical plasma modeled by dissipative magnetohydrodynamics. The parameter dependence of equilibrium solutions and their stability is followed using homotopy techniques. Solution branches and their connections are studied in relation to the applied fields.

Comment On "Universality Of The Kosterlitz-Thouless Transition In 4he Films As A Function Of Thickness", Rolfe G. Petschek

Faculty Scholarship

[No abstract available]

Surface-Reconstruction-Induced Changes In Free-Carrier Scattering From The W(100) Surface: Aninfrared Surface-Electromagnetic-Wave Study, D. Mark Riffe, L. M. Hanssen, A. J. Sievers

All Physics Faculty Publications

Using the infrared-absorption technique of surface-electromagnetic-wave spectroscopy (SEWS) we have studied the effects of H₂ and D₂ chemisorption on the SEW attenuation coefficient α in the 10-μm region between 165 and 350 K. The change in α at room temperature has also been measured for N₂, O₂, and CO adsorption. The coverage (CTHETA) dependence of α for N₂, O₂, and CO is fairly simple [either a monotonic increase (N₂) or a peak at some intermediate coverage (O₂, CO)] and points to changes in free-carrier (FC) surface …

Observation Of Resonant Tunneling In Silicon Inversion Layers, A. B. Fowler, G. L. Timp, J. J. Wainer, Richard A. Webb

Faculty Publications

Measurements of the temperature and carrier-density dependence of the strongly localized conductance of short silicon inversion layers are reported. At the lowest temperatures we observe well-isolated, large conductance peaks whose width and temperature dependence are only consistent with resonant tunneling and are inconsistent with Mott hopping. Several new features are observed which we believe may be the result of Coulomb interactions.

The Average Magnetic Field Draping And Consistent Plasma Properties Of The Venus Magnetotail, David J. Mccomas, Harlan E. Spence, C. T. Russell, M. A. Saunders

Physics & Astronomy

A new technique has been developed to determine the average structure of the Venus magnetotail (in the range from −8 R_v to −12 R_v) from the Pioneer Venus magnetometer observations. The spacecraft position with respect to the cross-tail current sheet is determined from an observed relationship between the field-draping angle and the magnitude of the field referenced to its value in the nearby magnetosheath. This allows us statistically to remove the effects of tail flapping and variability of draping for the first time and thus to map the average field configuration in the Venus tail. From this …

Comment On ‘‘Valence-Bond Theory And The Evaluation Of Electronic Energy Matrix Elements Between Nonorthogonal Slater Determinants’’, Gordon A. Gallup

Gordon Gallup Publications

In a recent article [Phys. Rev. A 31, 2107 (1985)] Leasure and Balint-Kurti claim to give a more efficient algorithm than any previously available for determining matrix elements of the Hamiltonian in valence-bond calculations. Actually, an algorithm of no significant difference and the same efficiency has been available since 1972 and has been applied to valence-bond calculations.

Relationship Between The P And S Fresnel Reflection Coefficients Of An Interface Independent Of Angle Of Incidence, R. M.A. Azzam

Electrical Engineering Faculty Publications

The Fresnel reflection coefficients r_p and r_s of p- and s-polarized light at the planar interface between two linear isotropic media are found to be interrelated by (r_s - r_p)/(1 - r_sr_p) = cos 2β, independent of the angle of incidence ø, where tan²β = ∊ and ∊ is the (generally complex) ratio of dielectric constants of the media of refraction and incidence. This complements another relation (found earlier), (r²_s - r_p)/(r_s - r_sr_p) = …

The Cal Poly House Doctor Lab, David W. Hafemeister

Physics

No abstract provided.

Saturation Of Beat-Excited Plasma Waves By Electrostatic Mode Coupling, C. Darrow, Donald P. Umstadter, T. Katsouleas, W.B. Mori, C.E. Clayton, C. Joshi

Donald Umstadter Publications

The nature of plasma waves which are resonantly excited when two laser beams beat in a rippled-density plasma is explored both theoretically and experimentally. A theoretical model is presented which, for commonly encountered experimental parameters, predicts rapid saturation of the high—phase-velocity beat wave at an amplitude below that expected for relativistic detuning. Results of experimental studies of this process are presented.

Structure-Induced Electronic States For Hg Overlayers On Ag(100), M. Onellion, J.L. Erskine, Y.J. Kime, Shikha Varma, Peter A. Dowben

Peter Dowben Publications

Angle-resolved photoemission was used to observe the electronic band structure of one and two monolayers of Hg on Ag(100). Evidence for new Hg electronic states and band structure arising from the hybridization of the atomic 5d_5/2 orbitals is presented. Low-energy electron diffraction results indicate that the Hg overlayers assume the face-centered-cubic (fcc) structure of the Ag(100) substrate, which is not the natural (rhombohedral) structure of bulk Hg. The new electronic states are induced as a result of the bonding of Hg atoms with adjacent metal atoms.

Interaction Effects Among Two-Dimensional Electrons And Holes, S. Washburn, Richard A. Webb, E. E. Mendez, L. L. Chang, L. Esaki

Faculty Publications

We report large logarithmic corrections to the conductivity of two-dimensional electrons and holes in GaSb-InAs-GaSb double heterostructures. From ∼ 40 mK to 1 K, the conductivity increased with the logarithm of the temperature but with a slope as much as 30 times larger than estimated from the theories of weak localization and carrier interaction. The discrepancy apparently results from electron-hole interactions not included in the theory.

Origin Of Nonuniversality In Micellar Solutions: Comment, R. G. Caflisch, Miron Kaufman, J. R. Banavar

Physics Faculty Publications

No abstract provided.

Radiation Pressure And Emission Clouds Around Active Galactic Nuclei, Moshe Elitzur, Gary J. Ferland

Physics and Astronomy Faculty Publications

Detailed calculations of the contribution of the trapped line photons to the overall pressure in line-emitting regions around active galactic nuclei are presented. They lead to the conclusion that radiation pressure is a significant factor in determining the stability of these clouds.

Experimental Measurements Of Phase Space, Roger Mcwilliams, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

Direct measurements of integrated phase-space densities, e.g., f(x,vy,t), have been made in an experiment. Using spectroscopically active ions, measurements in a plasma show the ion response, fi(x,v,t), to linear and nonlinear waves and phase-space particle bunching. Time-resolved measurements show coherent and incoherent phase-space density changes in the presence of waves, indicating that transitions to turbulence and chaos may be studied. The time, space, and velocity-space resolution may allow experimental tests of predictions from the Boltzmann equation.

Application Of A Scaled Homogeneous Nucleation-Rate Formalism To Experimental Data At T≪TC, Barbara N. Hale

Physics Faculty Research & Creative Works

It is pointed out that for temperatures T<0.5T_c, where T_c is the critical temperature, the classical steady-state nucleation-rate formalism of Becker and Doring predicts an approximate critical supersaturation ratio S_cr (for the onset of nucleation) given by lnS_cr/Ω^3/2~0.53(T_c/T-1)^3/2. Ω is a material-dependent quantity approximately equal to the excess surface entropy per molecule. For most substances Ω ~ 2.0 and for associated liquids Ω ~ 1.5.The experimental data (for nucleation from vapor to liquid) from diffusion chamber and nozzle beam studies are found to be consistent with the above …

Symmetric Solutions To The Gauss-Bonnet Extended Einstein Equations, James Thomas Wheeler

All Physics Faculty Publications

Low-energy limits of string theories suggest that gravity lagrangians should include quadratic and higheorder curvature terms, in the form of dimensionally continued Gauss-Bonnet densities. In an arbitrary number of dimensions, we consider the static, spherically symmetric solutions to the lowest order Gauss-Bonnet extended Einstein equations. We also find isotropic, homogeneous cosmological solutions with an ideal fluid source.

Solar- Terrestrial Physics: A Space Age Birth, R. W. Schunk

Faculty Honor Lectures

Solar- Terrestrial Physics, in its broadest sense, is concerned with the transport of energy, particles, and fields from the sun to the earth and their consequent effect on the terrestrial environment. Most of the solar energy eventually deposited in our atmosphere, at a rate of approximately a trillion megawatts, arrives in the form of visible light. The study of how this energy affects our environment falls within the purview of meteorology, a discipline that has experienced an independent development and that has sufficiently different problems from solar-terrestrial physics that it can be regarded as a separate but neighboring discipline. In …

Surface Segregation In Binary Alloys, Uresh Vahalia, Peter A. Dowben, Allen Miller

Peter Dowben Publications

A semiempirical calculation is outlined that allows analysis of experimental results for the apparent surface concentration of binary alloys, obtained by x-ray photoelectron spectroscopy, (XPS). A segregation profile giving the enrichment of the segregating element at and near the surface is obtained from the analysis. Using previously published data for Cu ₁₇ Ni ₈₃ ( 100) and Cu ₁₇ Ni ₈₃ ( 111 ), it is shown that copper segregation is not restricted to the first few layers, but instead extends significantly into the selvedge (near-surface) region. This occurrence is not explainable by the use of present ideal solution models. …

Maine Yankee Shutdown Assessment: A Report To Governor Joseph E. Brennan, Maine State Planning Office

Maine Collection

Maine Yankee Shutdown Assessment: A Report to Governor Joseph E. Brennan

Maine State Planning Office, Maine Office of Energy Resources, Maine Public Advocate

Executive Department - May 1986

Contents: Legal Process / Decommissioning Constraints and Costs / Public and Economic Costs and Benefits / Apprendices

Mössbauer Spectroscopic Studies Of Hemoglobin And Its Isolated Subunits, G. R. Hoy, D. C. Cook, R. L. Berger, F. K. Friedman

Physics Faculty Publications

Samples of 90% enriched ⁵⁷Fe hemoglobin and its isolated subunits have been prepared. Mössbauer spectroscopic measurements have been made on three such samples. Sample one contained contributions of oxyhemoglobin, deoxyhemoglobin, and carbonmonoxyhemoglobin. This sample was studied from a temperature of 90 K down to 230 mK. Measurements were also made at 4.2 K using a small applied magnetic field of 1.0 T. In general, the measured quadrupole splittings and isomer shifts for each component agreed with previous measurements on single component samples in the literature, and thus demonstrated that chemically enriched hemoglobin has not been altered. The second and …

Ionic And Neutral Decompssition Of Gaseous Bromochloromethanes, D.C. Driscoll, J.A. Bishop, B.J. Sturm, Peter A. Dowben, C.G. Olsen

Peter Dowben Publications

The ionization potentials for CCl ₄, CCl ₃Br, CBr ₂Cl ₂, CBr ₄, CCl ₃, and CBr ₃ have been measured using electron impact techniques. These numbers have been combined with previously published thermodynamic values in order to construct thermodynamic cycles for ionic and neutral decomposition of the bromochloromethanes. The n to σ*, n to s, and n to p electronic transition energies have also been determined on the basis of photoabsorption spectra.

Epitaxial Growth Of Iron Iodide Films On Fe(L10), D.R. Mueller, T.N. Rhodin, Peter A. Dowben

Peter Dowben Publications

The interaction of iodine vapor on an Fe(110) single crystal surface at room temperature has been investigated primarily through the use of LEED and UPS. Both a series of chemisorbed overlayers and an epitaxial iodide layer are observed. Iodide formation proceeds through an island growth mechanism with the iodide basal plane parallel to the Fe(110) surface. Evidence is presented that the defects introduced on the surface during argon ion sputtering may be important as nucleation sites for iodide growth. The results are compared with the results of previous studies.

A Priori Predictions Of Phase Transitions In Kcaf3 And Rbcaf3: Existence Of A New Ground State, John W. Flocken, R. A. Guenther, John R. Hardy, L. L. Boyer

Physics Faculty Publications

We have made an a prior; theoretical study of the potential-energy surfaces for KCaF₃ and RbCaF₃, and have examined the relative stability of the various lower-symmetry structures generated from the cubic perovskite phase by "rotations" of the CaF₆ octahedra. A completely new ground state was discovered which, when included in the sequence of energy levels, allows us to give a full account both qualitatively and, in the case of RbCaF₃, quantitatively of the phase transition sequences in both systems.

A Priori Predictions Of Phase Transitions In Kcaf3 And Rbcaf3: Existence Of A New Ground State, J. W. Flocken, R. A. Guenther, John R. Hardy, L. L. Boyer

John R. Hardy Papers

We have made an a prior; theoretical study of the potential-energy surfaces for KCaF₃ and RbCaF₃, and have examined the relative stability of the various lower-symmetry structures generated from the cubic perovskite phase by "rotations" of the CaF₆ octahedra. A completely new ground state was discovered which, when included in the sequence of energy levels, allows us to give a full account both qualitatively and, in the case of RbCaF₃, quantitatively of the phase transition sequences in both systems.

Calculations For The Excitation Of High Spin Natural Parity States In Hypernuclei Via (Π+, K+), Yizhang Ho

Masters Theses

No abstract provided.

Microscopic Optical Potentials, Michael R. Sloothaak

Masters Theses

No abstract provided.

Magnetic Skeletons In Davy Jones' Locker, Richard B. Frankel

Physics

No Abstract.

Relativistic Corrections To The Bethe Sum Rule, P.T. Leung, M. L. Rustgi, S. A. Long

Physics Faculty Publications and Presentations

Relativistic corrections to order alpha² to the Bethe sum rule have been obtained for a one-electron system employing the Foldy-Wouthuysen transformation. The results have wide applications in high-Z systems at large momentum transfers.

Shell Correction For The Stopping Power Of K Electrons, P.T. Leung, M. L. Rustgi, S. A. Long

Physics Faculty Publications and Presentations

In view of the inapplicability of the asymptotic expressions for the stopping number available in the literature at high energies, an alternative approach is taken to compute the shell correction to the stopping number of K electrons. Anholt's formula (1979) for the K-shell ionization has been used to calculate the excitation function for longitudinal interaction and numerical integration over energy has been carried out to evaluate the shell correction. Comparison with other theoretical calculations is made. It is proposed that, with the inclusion of relativistic effects, an asymptotic expansion of the stopping number with a leading-term logarithmic in the energy …

Medium Modified Proton Densities Deduced From Electron Scattering Experiments, Steven Paul Deryke

Masters Theses

Recently two fundamental problems in nuclear physics have been resolved by applying the concept of nucleon size increases over that of free nucleons. These successes have encouraged the use of medium-modified proton densities to explain the differences between Hartree-Fock calculations and experimental charge densities. These differences constituted a long standing problem in nuclear physics.

The covariant soliton model of density dependent nucleon form factors was employed to explain these differences. This model predicts a non-linear relationship between point proton densities and charge densities. This work was able to provide a self-consistent proton density for ²⁰⁸Pb by inverting this relationship. …