Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Physics Faculty Research & Creative Works

Discipline
Keyword
Publication Year

Articles 1771 - 1800 of 1959

Full-Text Articles in Physical Sciences and Mathematics

High Flux Beam Source Of Thermal Rare-Gas Metastable Atoms, D. W. Fahey, William F. Parks, Laird D. Schearer Dec 1980

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%.

Go to article

Studies Of H₂O On Ss-Agi Surfaces: An Effective Pair Potential Model, Barbara N. Hale, Jerry Kiefer Jul 1980

Studies Of H₂O On Ss-Agi Surfaces: An Effective Pair Potential Model, Barbara N. Hale, Jerry Kiefer

Physics Faculty Research & Creative Works

Effective pair potential functions are used to study the adsorption of a water molecule on surfaces of β-AgI. The water molecule is represented by a rigid point charge ST-2 model and the AgI substrate by an array of point atoms with effective charge ±0.6e, Lennard-Jones cores, and ionic polarizabilities. Maximal binding energy surfaces and optimal H2O configurations are generated for the water molecule adsorbed on the rigid and unrelaxed basal and prism AgI faces. Adsorption of the H2O above a two layer ledge, an iodine vacancy, and an H2O trapped in the …

Go to article

Angular Differential Cross Sections For Excitation Of Atomic Hydrogen To The N=2 Level By Proton Impact, John T. Park, John E. Aldag, Jerry Peacher, Jacob M. George Mar 1980

Angular Differential Cross Sections For Excitation Of Atomic Hydrogen To The N=2 Level By Proton Impact, John T. Park, John E. Aldag, Jerry Peacher, Jacob M. George

Physics Faculty Research & Creative Works

Differential cross sections for 15-145-keV proton impact excitation of atomic hydrogen to the n=2 level have been determined for center-of-mass scattering angles 0 to 1.2 mrad. The cross sections were obtained from an analysis of the angular distribution of protons which had lost an energy corresponding to the excitation of atomic hydrogen to its n=2 level. The differential cross sections obtained are in rather good agreement with available coupled-state calculations as well as the simpler Glauber-approximation calculations. However, at the larger scattering angles the cross sections obtained from the theoretical treatments appear to decrease more rapidly than the experimental data.

Go to article

Potential Use Of Chemical Spot Test Method For Submicron Aerosol Sizing, Paul C. Yue, Josef Podzimek Mar 1980

Potential Use Of Chemical Spot Test Method For Submicron Aerosol Sizing, Paul C. Yue, Josef Podzimek

Physics Faculty Research & Creative Works

A submicron particle, which is too small to be observed in an optical microscope, may form an observable spot on a chemically prepared substrate of the collector. The size of the spot or "Liesegang circle" is related to the aerodynamic diameter of the particle through a magnification factor. This paper presents the experimental results of the study of this factor using sodium chloride aerosol in the size range of 0.5 to 2 pm which has not previously been studied. We calibrated a cylindrical centrifuge with known sized latex particles. A relationship between the aerodynamic diameter and the deposition length is …

Go to article

Comment On “Cancellation Of Internal Forces”, Harry A. Brown Jan 1980

Comment On “Cancellation Of Internal Forces”, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

Go to article

More On Calculators In Beginning Physics Courses, Harry A. Brown Jan 1980

More On Calculators In Beginning Physics Courses, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

Go to article

Total Penning Ionization Cross Sections Of Cd And Zn For He(2 ³S1) Atoms, D. W. Fahey, William F. Parks, Laird D. Schearer Jan 1980

Total Penning Ionization Cross Sections Of Cd And Zn For He(2 ³S1) Atoms, D. W. Fahey, William F. Parks, Laird D. Schearer

Physics Faculty Research & Creative Works

The total Penning ionization cross sections for Cd and Zn for He(2 3S1) atoms have been measured. The method used was that of Penning ion collection from a vapor cell through which a He(2 3S1) beam was passed. The beam energy was 66 meV with a velocity spread of 45%. The measured cross sections were 106(±22) and 35(±7) Å2 for the Cd and Zn targets, respectively. © 1980 American Institute of Physics.

Go to article

Water And Ice Nucleation Sites From Ion Implantation Of Silicon, William H. Stlnebaugh, Don M. Sparlin, James L. Kassner Jan 1980

Water And Ice Nucleation Sites From Ion Implantation Of Silicon, William H. Stlnebaugh, Don M. Sparlin, James L. Kassner

Physics Faculty Research & Creative Works

Ion implantation has a substantial effect on the heterogeneous nucleation of water and ice. An enhancement of water nucleation and a suppression of ice nucleation occurred for samples of silicon implanted with ions of various species and dosage. These effects were noticeable only for samples implanted with ion doses approaching or exceeding the critical dose necessary to produce amorphous silicon. The behavior of the water droplet and ice crystal growth can be related to the amount of ion produced damage to the substrate surface. The nature of the damage can be controlled by variation of the incident ion species, dose, …

Go to article

Injection-Locked Dye Laser Pumped By A Xenon-Lon Laser, E. R. Carney, D. W. Fahey, Laird D. Schearer Jan 1980

Injection-Locked Dye Laser Pumped By A Xenon-Lon Laser, E. R. Carney, D. W. Fahey, Laird D. Schearer

Physics Faculty Research & Creative Works

Injection locking of a dye laser is reported for a 4-minor ring-cavity dye User pumped by a xenon-ion laser. Both a He-Ne laser and tunable CW dye laser were used as the injection sources. Copyright © 1980 by The Institute of Electrical and Electronics Engineers, Inc.

Go to article

Large-Angle Electron-Photon Coincidence Experiment In Atomic Hydrogen, E. Weigold, L. Frost, K. (Kaare) J. Nygaard Jan 1980

Large-Angle Electron-Photon Coincidence Experiment In Atomic Hydrogen, E. Weigold, L. Frost, K. (Kaare) J. Nygaard

Physics Faculty Research & Creative Works

1s-2p excitation in hydrogen has been studied by observing the angular correlation of Lyman photons detected in coincidence with inelastically scattered electrons at 54.4 eV incident energy. The electron scattering angles ranged from 10°to 133°; the results at scattering angles larger than 20°cannot be explained by currently available theories. © 1980 The American Physical Society.

Go to article

Nonequilibrium Thermodynamics Of Fuel Cells: Heat Release Mechanisms And Voltage, Gerald Wilemski Jan 1980

Nonequilibrium Thermodynamics Of Fuel Cells: Heat Release Mechanisms And Voltage, Gerald Wilemski

Physics Faculty Research & Creative Works

Nonequilibrium thermodynamics is used to analyze the spatial distribution of heat release mechanisms occurring in fuel cells operating under load in nonisothermal steady states. Novel contributions to heat release in the bulk electrolyte are found which are analogous to Peltier and Thomson effects in metallic conductors. Expresions for the heat release at individual electrodes are presented. An equation for the voltage of these cells is also derived. © 1980 American Institute of Physics.

Go to article

Nickel Carbide: Its Formation And Characterization By Transmission Electron Diffraction, Auger Electron Spectroscopy And Electron Spectroscopy For Chemical Analysis, J. Kleefeld, L. L. Levenson Dec 1979

Nickel Carbide: Its Formation And Characterization By Transmission Electron Diffraction, Auger Electron Spectroscopy And Electron Spectroscopy For Chemical Analysis, J. Kleefeld, L. L. Levenson

Physics Faculty Research & Creative Works

Nickel carbide (NiC3) films are formed by the carburization of nickel films in CO at 350°C. The presence of Ni3C is demonstrated by transmission electron diffraction. The carbon Auger electron signal of Ni3C is identical with the carbon Auger spectra attributed to Ni3C by previous authors. The position of the C 1s electron spectroscopy for chemical analysis peak is within 1 eV of the C 1s peak produced by graphite. The grain size of polycrystalline Ni3C is significantly larger than the grain size of the nickel film from which it is grown. © 1979.

Go to article

Electron Drift Velocities In N2, Co2, And (N 2+Co2) Laser Mixtures, Rafael A. Sierra, Howard L. Brooks, Kaare J. Nygaard Dec 1979

Electron Drift Velocities In N2, Co2, And (N 2+Co2) Laser Mixtures, Rafael A. Sierra, Howard L. Brooks, Kaare J. Nygaard

Physics Faculty Research & Creative Works

A time-of-flight technique has been used to obtain electron drift velocities in N2, CO2, and N2-CO2 mixtures covering the E/N range 3-93 Td. In the case of the pure gases, excellent agreement with previous work is obtained over the entire E/N range. The mixtures, which are of laser importance, have not been studied previously.

Go to article

The Hanle Effect In Penning-Excited Ions, D. W. Fahey, William F. Parks, Laird D. Schearer Dec 1979

The Hanle Effect In Penning-Excited Ions, D. W. Fahey, William F. Parks, Laird D. Schearer

Physics Faculty Research & Creative Works

A thermal beam of helium (23S1) metastable atoms was used to excite coherently the 2P3/2 levels of Ca, Sr and Ba in a Penning ionizing collision. The coherent excitation of the ions appears as a linear polarization of the optical emission from the excited ions. The degree of linear polarization is 5.5, 3.5 and 0.5% for Ca, Sr and Ba, respectively, with the polarization parallel to the beam direction. Hanle effect signals from the 2P3/2 level of Sr were observed and the radioactive decay rate measured.

Go to article

Conductive Strontium Titanate Layers Produced By Boron-Ion Implantation, Connie M. Cooper, P. S. Nayar, Edward Boyd Hale, Robert Gerson Dec 1979

Conductive Strontium Titanate Layers Produced By Boron-Ion Implantation, Connie M. Cooper, P. S. Nayar, Edward Boyd Hale, Robert Gerson

Physics Faculty Research & Creative Works

The ion implantation of boron has been found to be an effective method for increasing the conductivity of strontium titanate. A highly conductive layer was formed by implantations at doses of 3.6x1016 to 1.0x1017 ions/cm2, using an accelerating voltage of 100 kV, corresponding to a boron range of about 300 nm. The conductivity of the implanted layer was found to be further enhanced by about four orders of magnitude after annealing at 225 °C. The surface resistivity attained was typically 1000 Ω/square at room temperature. The resistance increased with rising temperature between 77 and 500 K. All samples were found …

Go to article

Doubly Differential Cross Sections For Proton-Impact Ionization Of Argon, Don H. Madison, Steven Trent Manson Sep 1979

Doubly Differential Cross Sections For Proton-Impact Ionization Of Argon, Don H. Madison, Steven Trent Manson

Physics Faculty Research & Creative Works

Proton-impact-ionization cross sections for argon which are differential in the energy and angle of the ejected electron have been calculated within the framework of the Born approximation using both Hartree-Slater and Hartree-Fock wave functions for the ejected electron. Results of the two types of calculations are compared with each other and with experiment. Differential cross sections for all five sub shells of argon are examined and particular attention is given to some interesting features of the K-shell cross sections. The range of applicability of the theoretical models is discussed.

Go to article

Excitation Of Cd, Zn, And Sr By A Beam Of Active Nitrogen, D. W. Fahey, William F. Parks, Laird D. Schearer Jan 1979

Excitation Of Cd, Zn, And Sr By A Beam Of Active Nitrogen, D. W. Fahey, William F. Parks, Laird D. Schearer

Physics Faculty Research & Creative Works

Excitation of the electronic levels of Cd, Zn, and Sr is observed when these metal vapors collide with a thermal-energy, active nitrogen beam. The beam is extracted from a glow discharge in pure N2. The active beam component is inferred to be vibrationally excited N2 in the A 3Σu+ electronic state. The absolute relative intensity of the emission lines in each element was measured. The excitation rates of the Cd and Zn target levels were found to depend exponentially on their energies indicating an effective temperature of approximately 4000°K. We believe that this temperature is related to the vibrational temperature …

Go to article

The Oguchi-Kaneyoshi Method For Spin-Glasses, M. Jursich, Harry A. Brown Jan 1979

The Oguchi-Kaneyoshi Method For Spin-Glasses, M. Jursich, Harry A. Brown

Physics Faculty Research & Creative Works

The results of an effective field calculation of the phase diagram and order parameters for a random exchange Ising model are presented. This calculation was based on an exchange coupled pair instead of the single-spin molecular-field theory. This approach should be an improvement over the infinite-ranged models because it includes localized effects. The results indicate that the local disorder effects are especially important at low temperatures. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

Go to article

Dissociative Excitation Of Hgbr2 In Collisions With A Beam Of Metastable Nitrogen, D. W. Fahey, Laird D. Schearer Jan 1979

Dissociative Excitation Of Hgbr2 In Collisions With A Beam Of Metastable Nitrogen, D. W. Fahey, Laird D. Schearer

Physics Faculty Research & Creative Works

No abstract provided.

Go to article

Alignment Of Ions In Penning Collisions, D. W. Fahey, Laird D. Schearer, William F. Parks Jan 1979

Alignment Of Ions In Penning Collisions, D. W. Fahey, Laird D. Schearer, William F. Parks

Physics Faculty Research & Creative Works

The authors have observed the alignment of the 5p P322 state of strontium ions produced in Penning collisions between an unpolarized beam of helium metastable atoms and a strontium vapor target. The alignment is shown by a linear polarization of the optical emission from the excited ion. For a 66-meV beam of helium metastable atoms a 3.5% linear polarization of the emission relative to the beam axis was measured. It is shown how the alignment may be used to determine the probabilities for populating the various final Quasi molecular states of the ion-atom pair. The alignment of the Penning ions …

Go to article

Negative Ion Production Rates In Rare Gas-Halide Lasers, Kaare J. Nygaard, Howard L. Brooks, Scott R. Hunter Jan 1979

Negative Ion Production Rates In Rare Gas-Halide Lasers, Kaare J. Nygaard, Howard L. Brooks, Scott R. Hunter

Physics Faculty Research & Creative Works

This paper reports on dissociative electron attachment in F2, NF3, Cl2, and I2. The principle of the method is to produce a short burst of photoelectrons from a photocathode by means of light from an argon-fluoride laser. Subsequently, by studying the motion of electrons and negative ions in a constant electric field (E) region, information is obtained about drift velocities and effective attachment cross sections. Helium, argon, and nitrogen were used as buffer gases. Of particular interest is a very strong temperature dependence of the attachment coefficient in I2. Measurements were taken from 35 to 110°C, covering an E/N range …

Go to article

Precision Doubly Differential Cross Section Measurements, John T. Park Jan 1979

Precision Doubly Differential Cross Section Measurements, John T. Park

Physics Faculty Research & Creative Works

Ion Energy Loss Spectrometry has been applied to the measurement of cross sections differential in both scattering angle and ion energy loss. Differential cross sections obtained for excitation of the n=2 level of atomic hydrogen by various ions provides unexpectedly good agreement with the available theories. Copyright © 1978 by The Institute of Electrical and Electronics Engineers, Inc.

Go to article

Temperature Dependence Of The Electron Attachment Coefficient In Iodine, Howard L. Brooks, Scott R. Hunter, Kaare J. Nygaard Jan 1979

Temperature Dependence Of The Electron Attachment Coefficient In Iodine, Howard L. Brooks, Scott R. Hunter, Kaare J. Nygaard

Physics Faculty Research & Creative Works

The attachment coefficient for iodine in a (1% I2+99% N 2) mixture, 50 Torr total pressure, has been measured in an electron swarm experiment from 1 to 50 Townsends (1 Townsend=1Td=10-17 V cm2). As the temperature was increased from 35 to 110°C, the attachment coefficient increased for any E/N (electric field intensity/gas number density) values greater than 7 Td. These results are compared to other experimental data and an explanation for the temperature dependence, based on the population of upper vibrational states, is presented. © 1979 American Institute of Physics.

Go to article

Diffusion Of Nickel In Silicon Below 475 °C, G. L.P. Berning, L. L. Levenson Dec 1978

Diffusion Of Nickel In Silicon Below 475 °C, G. L.P. Berning, L. L. Levenson

Physics Faculty Research & Creative Works

Nickel films were deposited on (100) and (111) surfaces of single-crystal silicon and were then annealed. The conditions under which the nickel is deposited determine whether or not an NiSi compound forms on annealing. It is postulated that defects are necessary for the formation of an NiSi compound at annealing temperatures below at least 475 °C, although the presence of defects may not necessarily cause the formation of a silicide. For substrate temperatures below 70 °C, defects are created during the vapor deposition of nickel on silicon. These defects always result in the formation of nickel silicide when the sample …

Go to article

Electron Attachment In Dilute Fluorine-Helium Mixtures, Kaare J. Nygaard, Scott R. Hunter, John L. Fletcher, Stephen R. Foltyn Dec 1978

Electron Attachment In Dilute Fluorine-Helium Mixtures, Kaare J. Nygaard, Scott R. Hunter, John L. Fletcher, Stephen R. Foltyn

Physics Faculty Research & Creative Works

We have made an absolute determination of the electron attachment coefficient η (cm-1) in helium containing 0.1-1% fluorine covering an E/N range from 3Td-17Td. At an estimated average energy of 5 eV we find a rate coefficient equal to (7.5±1.5) x10-10 cm3/sec.

Go to article

High-Flux Beam Source Of Fast Neutral Helium, D. W. Fahey, Laird D. Schearer, William F. Parks Dec 1978

High-Flux Beam Source Of Fast Neutral Helium, D. W. Fahey, Laird D. Schearer, William F. Parks

Physics Faculty Research & Creative Works

A high-flux beam source of fast neutral helium has been constructed by extending the designs of previous authors. The source is a dc or pulsed electric discharge in an expanding gas nozzle. The beam produced has a flux on the order of 1015 atoms/ssr and a mean velocity on the order of 107 cm/s. The composition of the beam has been determined by the use of particle detectors and by the observation of the excitation of certain target gases. An upper bound of 3.7*10-5 has been estimated for the He(2 3S1)/He(1S0) beam density ratio and a value of 0.2 found …

Go to article

Crystalline To Amorphous Transformation In Ion-Implanted Silicon: A Composite Model, John R. Dennis, Edward Boyd Hale Dec 1978

Crystalline To Amorphous Transformation In Ion-Implanted Silicon: A Composite Model, John R. Dennis, Edward Boyd Hale

Physics Faculty Research & Creative Works

The transformation of silicon to the amorphous state by implanted ions was studied both experimentally and theoretically. Experimentally, the amount of transformed silicon and the critical ion dose necessary to amorphized the entire implanted layer were determined by ESR. How the critical dose varies with ion mass (Li, N, Ne, Ar, and Kr), ion energy (20-180 keV), and implant temperature (77-475 K) was determined. Theoretically, several phenomenological models were used to analyze these data. The overlap-damage model was used to determine the critical dose from the data, the size of the amorphous region around the ion track, and the degree …

Go to article

The Formation And Decomposition Of Nickel Carbide In Evaporated Nickel Films On Graphite, S. Sinharoy, L. L. Levenson Aug 1978

The Formation And Decomposition Of Nickel Carbide In Evaporated Nickel Films On Graphite, S. Sinharoy, L. L. Levenson

Physics Faculty Research & Creative Works

Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to study nickel carbide (Ni3C) formed during the evaporation of nickel onto the surface of single-crystal graphite. It is shown that Ni3C formed in this manner extends from the surface to close to the interface. A model is proposed to explain the mechanism of Ni3C formation. The 1s photoelectron peak from Ni3C is observed to have a binding energy 0.6 eV lower than that of pure graphite. This is attributed to the lack of any significant ionic bonding in Ni3C. © 1978.

Go to article

Angular Differential Cross Sections For 25-, 50-, And 100-Kev-Proton Excitation Of Helium To The N=2 Level, John T. Park, Jacob M. George, Jerry Peacher, John E. Aldag Jul 1978

Angular Differential Cross Sections For 25-, 50-, And 100-Kev-Proton Excitation Of Helium To The N=2 Level, John T. Park, Jacob M. George, Jerry Peacher, John E. Aldag

Physics Faculty Research & Creative Works

Differential cross sections for 25-, 50-, and 100-keV-proton excitation of helium to the n=2 level have been determined for center-of-mass scattering angles from 0 to 1.2 mrad. The cross sections were obtained from an analysis of the angular distribution of the scattered protons which had lost an energy corresponding to the excitation of the helium target to its n=2 level. The differential cross section is very sharply peaked in the forward direction and decreases by a factor of 45 in 1.0 mrad at 25 keV and by a factor of 650 in 1.0 mrad at 100 keV. The data are …

Go to article

Angular Differential Cross Sections For Excitation Of Atomic Hydrogen By 25-, 50-, And 100-Kev Protons, John T. Park, John E. Aldag, Jerry Peacher, Jacob M. George Jun 1978

Angular Differential Cross Sections For Excitation Of Atomic Hydrogen By 25-, 50-, And 100-Kev Protons, John T. Park, John E. Aldag, Jerry Peacher, Jacob M. George

Physics Faculty Research & Creative Works

Angular differential cross sections for the process H+ + H(1s ) → H+ (θ ) + H ( n = 2 ) are presented for 25-, 50-, and 100-keV protons incident on atomic hydrogen. The experimental results are in fair agreement with Glauber-approximation calculations.

Go to article

First Prev Next Last