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Differential Cross Sections For Electron Capture From Helium By 25- To 100-Kev Incident Protons, Paul J. Martin, Kenneth E. Arnett, D. M. Blankenship, Thomas J. Kvale, Jerry Peacher, E. Redd, V. C. Sutcliffe, John T. Park, Chiidong Lin, Jim H. Mcguire

Physics Faculty Research & Creative Works

Experimentally and theoretically determined differential cross sections are reported for electron capture in collisions of protons with helium atoms for incident proton energies of 25, 30, 50, and 100 keV and for center-of-mass scattering angles of 0.0 to 2.0 mrad. The magnitudes of the experimentally determined differential cross sections decrease from 10^-10 to 10^-12 cm²/sr within the 0.0-0.8-mrad range of the center-of-mass scattering angle. At approximately 0.8 mrad a distinct change in the slope of the differential cross section is observed. The experimental results which are for capture into all bound states of hydrogen are compared …

Brownian Motion In A Flowing Fluid Revisited, John D. Ramshaw

Physics Faculty Publications and Presentations

It is shown how the phenomenon of osmosis may be treated using the phenomenological theory of Brownian motion in a flowing fluid. The theory is also generalized to include viscous stresses in the particle and mixture momentum equations.

A Critical Study Of Nonlinear Echo Phenomena, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

The present thesis attempts to give a concise and critical account of the evolution of the echo phenomena over the last thirty years. Starting with spin and photon echoes, which were among the earliest to be observed and studied, the thesis explores the experimental findings and the models proposed in connection with the more contemporary echo experiments, viz. those involving electroacoustic or polarization echoes in single and polycrystalline piezoelectric materials and in powders. Although the investigations regarding the various mechanisms of short and long term echo formation are by no means complete, a coherent picture is beginning to emerge as …

Energy Dependence Of Alignment In Foil Collision-Excited N=3 States Of He I, Timothy J. Gay, H. G. Berry, R. Deserio, H. P. Garnir, R. M. Schectman, N. Schaffel, R. D. Hight, D.J. Burns

Timothy J. Gay Publications

We have measured the beam-foil collision-induced alignment of the 3p ¹P, 3p ³P, 3d ¹D, and 3d ³D states of He I for He+ beam energies between 30 and 1300 keV. The alignment of all four states is found to vary with beam-current density as well as energy. The number of secondary electrons emitted per incident ion, γ, has also been measured as a function of foil temperature and beam energy between 400 and 1400 keV. The rate of change of both alignment and γ with foil temperature exhibits …

Molecular Effects In Beam-Foil Collision-Induced Alignment Of He I, Timothy J. Gay, H. G. Berry, R. Deserio

Timothy J. Gay Publications

We have measured the alignment of beam-foil collision-excited states of He I produced by bombarding carbon foils of various (1.3-110 μg/cm²) areal densities with beams of He⁺ and HeH⁺. In addition, we have measured the total light yield of several transitions in He I, He II, and H as a function of foil thickness using beams of HeH⁺ ions. Experiments were done with He-foil exit energies of 125, 500, 550, and 650 keV. He I alignment decreases in all cases for the thinnest foils when molecular projectiles are used. Total light intensities generally increase …

Angular Differential And Total Cross Sections For The Excitation Of Atomic Hydrogen To Its N=2 State By Helium Ions, John E. Aldag, Jerry Peacher, Paul J. Martin, V. C. Sutcliffe, Jacob M. George, E. Redd, Thomas J. Kvale, D. M. Blankenship, John T. Park

Physics Faculty Research & Creative Works

Differential cross sections for 15-100 keV He⁺ excitation of atomic hydrogen to its n=2 level have been determined for c.m. angles from 0 to 8 mrad. The differential cross sections are obtained from an analysis of the angular distribution of the scattered ions which have lost an energy corresponding to the excitation of the target to its n=2 level. The shape of the differential cross section changes rapidly with increasing incident energy. At 15 keV, the differential cross section falls off by a factor of 5 in 6 mrad. At 100 keV, the differential cross section decreases by nearly …

Four-Color And Hβ Photometry Of The Galactic Cluster Ngc 7790, Edward G. Schmidt

Edward Schmidt Publications

Observations have been obtained on the four-color and Hβ system of 16 stars in the field of NGC 7790. These represent virtually all of the stars which are in the B-star region of the cluster color-magnitude diagram. I discuss the membership of these stars and find three which are possibly field stars. The remaining stars indicate a true distance modulus of 11.98 ± 0.13 for the cluster and a color excess of E(b – y) = 0.403.

Effect Of Polarization And Absorption On Differential Cross Sections And Angular Correlation Parameters For Electron Excitation Of Helium, M. E. Stewart, Don H. Madison

Physics Faculty Research & Creative Works

The effects of local polarization and absorption potentials on differential cross sections and angular correlation parameters are studied within the distorted-wave approximation for electron excitation of the 2 ¹P state of helium. For examining the effect of local polarization, we have compared a recent numerical self-consistent adiabatic polarization potential for helium with the commonly used hydrogenic adiabatic polarization potential. Different radial regions for the polarization potential were studied to determine their contribution to the overall effect of polarization. Calculations are also presented which show the effects of different strengths for a local absorption potential.

Observation Of The Transition From Semiconductor To High-Tc Superconductor In (Snxeu1-X)Ymo6s8 Under High Pressure, D. W. Harrison, K. C. Lim, J. D. Thompson, C. Y. Huang, Paul D. Hambourger, H. L. Luo

Physics Faculty Publications

Pressure-induced high-temperature superconductivity is observed in semiconducting (Sn_xEu_1-x)_yMo₆S₈, where 0<~x<~0.1 and y=1.0 and 1.2, having a carrier concentration ≃10¹⁹/cm³ at 4.2 K as determined from Hall-effect measurements. Above a threshold pressure ≃7 kbar, superconductivity appears with dT_c/dP≃2 K/kbar. The maximum superconducting temperature (T_c∼10 K), reached at ∼ 12 kbar, represents the highest pressure-induced T_c in any semiconductor. For P>~13 kbar, the temperature-dependent resistance appears metallic.

Elevated Electron Temperatures In The Auroral E Layer Measured With The Chatanika Radar, Vincent B. Wickwar, C. Lathuillere, W. Kofman, G. Lejeune

All Physics Faculty Publications

An extensive series of spectral measurements has been made in the auroral E region with the Chatanika incoherent scatter radar. Becasue of the small scale length for variations of electron density, temperatures, and ion-neutral collisions we used the operating mode with the best possible range resolution—9 km. About 5% of the time the data exhibited an unusual spectral shape that was most pronounced at 105 and 110 km. Instead of being almost Gaussian with only a small hint of two peaks, the spectra are much wider, with two well-developed peaks. After carefully considering the validity of the measurements and their …

A Numerical Investigation Of A Certain One-Dimensional Ising Model, Jimmy Green

Masters Theses & Specialist Projects

The model is a linear chain in which each spin interacts with its 2r nearest neighbors, the interaction energy being proportional to 1/r. Using a method similar to that of Montroll, the partition function of the model in the thermodynamic limit is shown to be related to the largest eigenvalue of a certain matrix. The largest eigenvalue of the matrix is determined numerically for 3 < r < 12.

Also, a correct method is demonstrated for evaluating an improper limit of the model, in which the interaction range is set to the chain length before the limit of an infinite number of spins is …

A Theoretical Study Of The High-Latitude Winter F Region At Solar Minimum For Low Magnetic Activity, Jan Josef Sojka, W. J. 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 high-latitude winter F region at solar minimum for low magnetic activity. 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 54°N magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day. The main result we obtained was that high-latitude ionospheric features, such as the ‘main trough,’ the ‘ionization hole,’ the ‘tongue of ionization,’ the ‘aurorally produced …

Small Angle Neutron Scattering From High Impact Polystyrene, Oran Allan Pringle

Faculty Research & Creative Works

"It is difficult to imagine a world without plastics. Although the development of most modern plastic materials took place after 1930, such mat􀃞ria1s are so common today that the word "plastic" is often used as an adjective to connote cheapness or lack of substance. Nevertheless, it 1s important to remember that for many uses plastics offer technical and cost advantages over other materials. "Wood warps and rots, iron rusts and much glass is brittle, yet no one disputes the enormous value of the s e mate r i a 1 s. " although plastic (Bryd son, 1970, p. 7.) Similarly, …

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 …

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 …

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 …

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.

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.

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.

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 …

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 …

Orientation And Alignment Of The 3P 1P And 4D 1D Levels Of Neutral Helium, R. M. Schectman, R. D. Hight, S. T. Chen, L. J. Curtis, H. G. Berry, Timothy J. Gay, R. Deserio

Timothy J. Gay Publications

The alignment and orientation produced by the tilted-foil excitation of He was studied for a wide range of foil tilt angles and outgoing-atom velocities. In particular, two quantum states of different orbital angular momentum (3p ¹P and 4d ¹D) were investigated and the results were compared with a number of previously proposed models.

Heavy Ion Beam Model For Radiobiology, Rose Ann Roth, Robert Katz

Robert Katz Publications

An ad hoc model of energetic heavy ion beams, including secondary and tertiary particles, has been constructed for predicting radiobiological experiments. While the beam model is relatively primitive, it yields depth-dose and depth-radiobiological calculations in good agreement with experiment upstream of the Bragg peak. Beyond the peak, the model is somewhat coarse grained and seems to underestimate low-LET fragment production. These defects can be repaired at some cost in computer time. Presently a complete set of depth-dose and radiobiological results (RBE, OER, aerobic and hypoxic survival) is obtained in 4–8 min, for a single beam, at a cost of $10. …

A Study Of The Target Thickness Effect For Chlorine On Germanium From 25 To 49.5 Mev, James Robert Slusser

Masters Theses

No abstract provided.

Development Of A System For Water Quality Analysis Using Particle Induced X-Ray Emission, James Albert Andrus

Masters Theses

Particle induced x-ray emission (PIXE) has been in use for several years at Western's accelerator laboratory. Its primary purpose has been to provide trace element analysis of various types of solid samples. The analysis of water samples has not been done because of problems involving target preparation for the accelerator. A process called vapor filtration, developed at Purdue University, allows adequate sample preparation for the accelerator. This process is being adapted for use here at WMU. When completely operational, this system will give the WMU accelerator program the additional capability of performing water quality analyses to concentrations of parts per …

Automation Of A Popular Monochromator, David C. Look, J. W. Farmer, R. N. Ely

Physics Faculty Publications

A wavelength‐scan and intensity‐control system for a widely‐used, high‐intensity monochromator is described. The wavelength scan is bidirectional and variable speed, and may be controlled manually or by TTL logic from a computer. The intensity control is effected by use of a programmable dc power supply and D–A converter. Various filters are described which allow an intensity of up to 2×10¹⁴ photons/cm² s to be achieved in a 1 cm×3 cm area over a wavelength range 0.76–2.50 μm, at 0.07 μm bandwidth, with a single grating. (A lesser intensity is available to 3.4 μm.) This wide range is made …