Digital Commons Network^™

Radar Measurements Of High-Latitude Ion Composition Between 140 And 300 Km Altitude, J. D. Kelly, Vincent B. Wickwar

All Physics Faculty Publications

The Chatanika radar has been used to measure the ratio of atomic (O⁺) ions to molecular (O₂ ⁺, NO⁺) ions in the high-latitude ionosphere. The radar results agreed well with simultaneous in situ rocket data, giving confidence in the radar method of deducing ion composition. Measurements made over long periods of time show seasonal variations, diurnal variations, and variations due to auroral processes. The transition altitude, where the number densities of atomic and molecular ions are equal, is a convenient parameter for describing the composition variation with altitude or ‘composition altitude profile.’ The transition …

An Intense Wave/Particle Event In The Auroral Ionosphere, A. D. Johnstone, Jan Josef Sojka, W. Gibbons, B. K. Madahar, L.J. C. Woolliscroft

All Physics Faculty Publications

An intense burst of VLF waves, at frequencies just above the local proton gyrofrequency, was observed shortly after each of two intense bursts of field‐aligned suprathermal electrons (E < 250eV) by instruments carried on a sounding rocket flown in diffuse aurora. If the two phenomena are associated with each other, the implication is that the electron acceleration occurred nearby, in a relatively small volume.

Auroral Plasma Lines: A First Comparison Of Theory And Experiment, E. S. Oran, Vincent B. Wickwar, W. Kofman, A. Newman

All Physics Faculty Publications

In this preliminary report on low-energy (0.3 to 3 eV) secondary electrons in the auroral E layer (90 to 150 km), we compare intensities of plasma lines observed with the Chatanika radar to theoretical predictions obtained from a detailed numerical model. The model calculations are initiated with a flux of energetic auroral primary electrons which enter the atmosphere and lose energy to electrons, ions, and neutrals through a combination of elastic and inelastic collisions. This flux is chosen in order that the total calculated ionization rate matches one that is deduced from the radar measurements. From these same calculations the …

Plasma Density Features Associated With Strong Convection In The Winter High-Latitude F Region, Jan Josef Sojka, W. John Raitt, Robert W. Schunk

All Physics Faculty Publications

We combined a simple plasma convection model with an ionospheric-atmospheric composition model in order to study the plasma density features associated with strong convection in the winter high-latitude F region. Our numerical study produced time-dependent, three-dimensional, ion density distributions for the ions NO+, O2 +, N2 +, O+, N+, and He+. We covered the high-latitude ionosphere above 42° N magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day. From our study, we found the following: (1) For strong convection, the electron density exhibits a significant variation with altitude, latitude, longitude, and …

Excitation Transfer Collisions And Electron Seeding Processes In A Resonantly Excited Sodium Vapor, D. J. Krebs, Laird D. Schearer

Physics Faculty Research & Creative Works

A dense sodium vapor in a high-pressure buffer of argon has been simultaneously excited by short (4 ns) laser pulses from two lasers: the first tuned to one of the D line transitions at 589 nm and the second tuned to the photoionization threshold of the 3p states near 406 nm. The temporal evolution of the system was studied with and without the photoionizing laser pulses. At early times (∼100 ns) excited state populations are determined by energy transfer collisions between two laser-excited 3p atoms while the ion/electron density is controlled by super elastic heating of "seed" electrons followed by …

O++ In The Venusian Ionosphere, Jane L. Fox, G. A. Victor

Physics Faculty Publications

It is shown that the revised photochemical theory for O⁺⁺ in the earth's ionopshere, where double photoionization of O is the dominant source, is consistent with recent O⁺⁺ measurements on Venus. A rate coefficient of 1.5 × 10⁻¹⁰ cm³ s⁻¹ for O⁺⁺ + O is obtained, and the possible importance of O⁺⁺ chemistry on minor atomic ions and airglow emissions is explored.

Autooscillations In Zinc, Manfred Wuttig, Alex Aning, Tetsuro Suzuki

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

N,L Distributions In Aq++H Electron-Capture Collisions, R. (Ronald) E. Olson

Physics Faculty Research & Creative Works

The classical-trajectory Monte Carlo method has been used to determine product-state distributions in Aq++HA(q-1)+(nl)+H+ electron-capture collisions at energies 50 and 100 keV/amu for fully stripped ions in charge states q=1to 20. In the energy region studied, the electron-capture products are found to populate predominately principal quantum numbers around nmq34. Such behavior implies the captured electron tries to preserve both its original orbital energy and dimensions after the electron-capture collision. The orbital-angular-momentum quantum numbers l are more highly peaked than statistical to large l values for nnm. © 1981 The American Physical Society.

Effective Swarm Parameters And Transport Coefficients In Co2 Laser Mixtures, R. A. Sierra, H. L. Brooks, A. J. Sommerer, S. R. Foltyn, Kaare J. Nygaard

Physics Faculty Research & Creative Works

A pulsed electron swarm technique has been used to obtain effective attachment and ionization cross-sections as well as electron drift velocities in mixtures of CO₂ laser interest. In binary CO₂:N 2 mixtures, below a reduced electric field of E/N=60*10 -17 V cm2, attachment was the principal ion production process. (N is the total gas number density.) The reduced attachment coefficients measured were small and in excellent agreement with numerical predictions. In ternary mixtures of He:CO₂:N2, positive ion formation described by Townsend's first ionisation coefficient played a more important role over the same range of E/N. …

Excitation Transfer In Ion Rydberg-Atom Collisions, R. (Ronald) E. Olson

Physics Faculty Research & Creative Works

Recently, electron-loss cross sections were presented by Kim and Meyer [Phys. Rev. Lett. 44, 1047 (1980)] for 40 keV/amu N3+ + H**(n) collisions which scaled as n3.12, where n is the principal quantum number of the excited H0. Such results are in contrast to an n2 scaling predicted by classical and first-Born theoretical methods. Our calculations indicate that a major component of the experimentally observed ion signal was due to Stark ionization by deflector grids of highly excited H0 produced in excitation-transfer collisions. Inclusion of the excitation process in a theoretical interpretation reveals qualitative agreement between theory and experiment and …

Modern Spectroscopy With A Spectrometer By The Optogalvanic Effect, Kenneth Arnett, Richard A. Anderson, Ralph William Alexander

Physics Faculty Research & Creative Works

An Experiment Involving the Optogalvanic Effect Suitable for the Advanced Physics Laboratory is Described. This Experiment Complements the Usual Basic Experiment in Atomic Spectroscopy Where Spectra Are Recorded on Photographic Film with a Spectrograph or with a Monochromator and Photomultiplier. the Optogalvanic Effect Used the Atoms Being Studied as the Detector and a Tunable Dye Laser as the Source. Linewidths Observed Are Those of the Dye Laser that Are Considerably Smaller Than Those Obtained with the Usual Laboratory Monochromator. the student is Introduced to the Techniques of Spectroscopy with Pulsed Dye Lasers and to a Spectrum for Which LS Coupling …

A Study Of Leslie Model Under Stochastic Environments, Kamran Shaukat

Dissertations and Theses

The prediction and analysis of changes in the numbers of biological populations rest on mathematical formulations of demographic events (births and deaths) classified by the age of individuals. The development of demographic theory when birth and death rates vary statistically over time is the central theme of this work. A study of the standard Leslie model for the demographic dynamics of populations in variable environments is made. At each time interval a Leslie matrix of survival rates and fertilities of a population is chosen according to a Markov process and the population numbers in different age classes are computed. Analytical …

Mossbauer Spectroscopy Of Iron-Containing Dermal Granules From Molpadia Intermedia, S. Ofer, G. C. Papaefthymiou, R. B. Frankel, H. A. Lowenstam

Physics

Dermal granules containing hydrous ferric oxide cores from Molpadia intermedia were studied by Mössbauer spectroscopy from 1.5 t0 300 K and in magnetic fields up to 80 kOersted at 4.2 K. A magnetic phase transition to an antiferromagnetically ordered state is observed at 10 K. The results are compared with the magnetic behavior of micellar cores of ferritin from eukaryotes and iron-storage materials from prokaryotes.

Simultaneous X-Ray And Optical Observations Of An Ursae Majoris During A Low State, Paula Szkody, Edward G. Schmidt, Lidia Crosa, Robert Schommer

Edward Schmidt Publications

X-ray observations throughout the orbital cycle of AN UMa during its low state were conducted with the Einstein Observatory simultaneously with ground-based optical UBV photometry and spectroscopy. The observed low X-ray flux of 7 × 10^–13 ergs cm^–2 s^–1 is a factor of 40 below the high-state X-ray flux, and F_x/F_opt is about a factor of 50 lower than for AM Her and 2A 0311–227. There is marginal evidence for an X-ray eclipse coincident with an optical minimum and for increased X-ray flux at magnetic phase 0.4 which does not correlate with any optical …

Synchronized Slide-Tapes In The Physics Laboratory, Loren Quan

University of the Pacific Theses and Dissertations

Media play a large part in most of our daily lives. We watch television; we go to the movies; we listen to the radio. For years educators have been adapting media-related technological advancements for the purpose of teaching in the classroom. Here at the Physics Department of the University of the Pacific, we have adapted the medium of synchronized slide-tapes for use in the laboratory component of our calculus-based introductory physics course.

Study Of Iron In Magnetotactic Bacteria, Richard B. Frankel, Richard P. Blakemore

Physics

Bacteria have recently been discovered directing their movements by sensing the earth's magnetic field. They contain arrays of crystals of lodestone or magnetite which they synthesize from iron in the ocean. The discovery of the same type of crystals in the abdomens of honey bees and the brains of homing pigeons suggests that nature is not oblivious to the earth's magnetic field. The biological mechanism for sensing magnetic fields has never been determined. These bacteria are capable of biologically synthesizing highly purified single domain magnets that would be very expensive to produce chemically.

The tiny perfect magnetite crystals made by …

Electron Transport Coefficients And Excitation Processes In Gaseous Mixtures Containing Mercuric Bromide, Howard Lundgren Brooks

Doctoral Dissertations

"A comprehensive set of measurements of the electron drift velocities and apparent ion formation cross sections has been completed for gaseous mixtures containing mercuric bromide using electron swarm techniques. Results are presented for binary mixtures of HgBr₂ and the rare gases neon, argon and xenon, with the concentration of HgBr₂ varied from 0.01% to 0.2% of the total. None of the measured quantities show a temperature dependence from 100 ° C to 150 ° Cover the range studied from 1 to 100 Townsend (1 Townsend = 1 Td = 10^-17 volt•cm²) in all of the …

Kinetic Processes In A High Pressure Laser Generated Plasma, Danny Joe Krebs

Doctoral Dissertations

"A dense sodium vapor in a high-pressure noble buffer has been simultaneously excited by short (4 ns) laser pulses from two lasers: ii the first tuned to one of the 'D' line transitions and the second tuned to either the photoionization threshold of the 3p states near 406 nm or to a higher level 3p-nd resonance. The population densities of the excited levels of atomic sodium were measured with temporal resolution by absolute intensity measurements of excited state fluorescence. At early times (~100 ns), excited state populations are determined by energy transfer collisions between two laser-excited 3p atoms while the …

Boron Implanted Strontium Titanate, Connie Macdonald Cooper

Doctoral Dissertations

"Single crystals of strontium titanate implanted with boron were found to have highly conductive surface layers. The effects of varying dose from 10¹⁶ to 10¹⁷ ions/cm², implantation voltage from 50 to 75 keV, and annealing conditions on the room temperature surface resistance and Hall mobility are presented in this study. A major result is that, for the most part, variation of the implantation voltage did not have a major effect on the sheet resistances obtained by boron implantation of strontium titanate, while dose and annealing conditions have major effects.

Doses of 5 X 10¹⁶ ions/cm …

An Experiment In Discovery, Daniel J. Steck

Physics Faculty Publications

No abstract provided.

Thermal Decomposition Kinetics Of Asf5-Doped Polyacetylene In Vacuum, T. Inoue, J. E. Osterholm, H. Yasuda, L. L. Levenson

Physics Faculty Research & Creative Works

Electrical conductivity measurements, mass spectra of desorbing species, and ESCA surface analysis are reported for AsF5-doped polyacetylene heated between 50 and 130°C in vacuum. All measurements indicate first-order decomposition kinetics with activation energies between 13 and 20 kcal mole-1. Decomposition leads to the desorption of AsF3 and F2. Metallic arsenic remains in the polyacetylene as a decomposition by-product.

High Flux Beam Source Of Thermal Rare-Gas Metastable Atoms, D. W. Fahey, William F. Parks, Laird D. Schearer

Physics Faculty Research & Creative Works

A high-flux beam source has been constructed for the production of helium, neon and argon metastable atoms. The source is a DC electric discharge maintained in an expanding gas. A metastable flux of 3.5*1014, and 7.2*1013 atoms s-1 sr-1 has been achieved with most probable energies of 66, 72 and 74 meV for the helium, neon and argon sources, respectively. Time-of-flight measurements showed the widths of the respective velocity distributions to be 45%, 27% and 27%.

Sound Absorption In N2-H2O Gas Mixtures At Elevated Temperatures, Roger W. Meredith

Physics Theses & Dissertations

Sound absorption measurements were conducted in N₂ -H₂O gas mixtures at 297, 343, and 387 Kelvin to determine the location of the vibrational relaxation peak of nitrogen on the frequency/pressure, (f/P), axis as a function of humidity and temperature. At low humidities the best fit of the data is to a linear relationship between (f/P)_max and humidity (h) yields a slope of 1 .84 X 10⁴ Hz/ atm mole fraction at all three temperatures. The slope is the same as that reported by Zuckerwar and Griffin (2.00 X 10⁴ Hz/atm mole fraction) but is …

High Resolution Laser Absorption Spectroscopy Of Ozone Near 1129.4 Cm-1, Lawrence N. Majorana

Physics Theses & Dissertations

A Beer's Law experiment was performed with a tunable laser to determine self broadened line shape parameters of one infrared absorption ozone line in the v1 band for ten pressures from 0.26 to 6.29 Torr at 285K. SO₂ line positions were used for wavelength calibration. Line shapes were iteratively fitted to the Voigt function at a Doppler width of 29.54 MHz (HWHM) resulting in values for the integrated line• strength, ( S), of (0.144 +/- 0.007 ) x ·10^-20 cm-1/molecule cm-2, line center frequency, (υ_ο) of 1129.426 cm-1 and the Lorentzian contributions to half width, (α …

Stopping Power Of Matter For Alpha Particles At Extreme Relativistic Energies, P.T. Leung, M. L. Rustgi, J. E. Turner

Physics Faculty Publications and Presentations

The stopping power of matter for alpha particles at extreme relativistic energies has been calculated by incorporating the charge form factor. A table is presented for aluminum, copper, and lead. It is found that at the highest energies considered, inclusion of form factor reduces the mass stopping power by about 6-8% in comparison with that predicted by Bethe's relativistic formula.

Improving Physics Teaching, Robert Fuller

Robert G. Fuller Publications

I began this editorial with a desire to take up battle against the recent ills of physics teaching. I paused to peruse the AAPT reprint book, 50 Years on Teaching Physics, edited by Melba Phillips.

Trends In The Theory Of Atomic Photoionization, Anthony F. Starace

Anthony F. Starace Publications

For VUV photon energies, detailed theoretical understanding of the photoionization process has been achieved for the case of a single electron ionized from one of the outer subshells of a closed-shell atom. This understanding is based qualitatively upon a few properties of realistic atomic central potentials and quantitatively upon a few distinct types of electronic interactions known generically as particle-hole interactions. Current theoretical research is mainly directed at understanding a broader class of atomic photoionization phenomena involving, e.g., open-shell atoms, electronic interactions not of the particle-hole class, real two-electron processes, and external electric and magnetic fields.

Dielectric Saturation In Dipolar Fluids. I. The Single-Molecule Distribution Function, John D. Ramshaw

Physics Faculty Publications and Presentations

The functional-derivative formalism is used to investigate the form of the equilibrium single-molecule distribution function n(1) in a finite fluid system of rigid polar molecules subjected to a strong external electric field that varies slowly with position. The investigation is based on the assumption that the long-range asymptotic behavior of the direct correlation function is independent of the external field, and is hence the same as in the unperturbed fluid. This assumption implies that n(1) has the form of a single-molecule Boltzmann factor in which the interaction energy is that of a deformable quasidipole with the local Lorentz electric field …

Electrostatic Tem Studies Of Magnetic Domains In Thin Iron Films, Hideaki Karamon

Dissertations and Theses

An electron microscope with electrostatic lenses was used for high resolution studies of magnetic domains in thin iron films.

Observation methods used to determine the directions of local magnetization in iron thin films were the Lorentz method and the Foucault method.

We studied how Bloch line-crosstie pairs and crosstie main walls behave in applied, in-plane magnetic fields. We found that crosstie main walls remain unchanged until crosstie density goes nearly to zero when the field is applied perpendicular to the main wall. A twisted type of domain appears where crossties disappear.

10 Kw Per Capita, Harry A. Brown

UMR-MEC Conference on Energy / UMR-DNR Conference on Energy

The rate of energy use in the U.S. is discussed. Possible savings in the principal areas of use are considered. The conclusion is that significant reductions could be made in five to ten years without new technology, but are not likely under present conditions.