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Physics Faculty Research & Creative Works

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Articles 1591 - 1620 of 1762

Full-Text Articles in Physical Sciences and Mathematics

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 …

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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.

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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.

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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 …

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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 …

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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.

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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 …

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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.

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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 …

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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 …

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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.

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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, Judith 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, Judith 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 …

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Angular Differential Cross Sections For Excitation Of Atomic Hydrogen By 25-, 50-, And 100-Kev Protons, John T. Park, Judith 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, Judith 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.

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Electron Drift Velocities In Helium-Fluorine Gas Mixtures, Kaare J. Nygaard, John L. Fletcher, Scott R. Hunter, Stephen R. Foltyn May 1978

Electron Drift Velocities In Helium-Fluorine Gas Mixtures, Kaare J. Nygaard, John L. Fletcher, Scott R. Hunter, Stephen R. Foltyn

Physics Faculty Research & Creative Works

Using a simple time-of-flight technique, we have measured the electron drift velocity in helium with 0.1-1% fluorine additive. Our results in a 0.1% mixture are in close agreement with data in pure helium. The measured drift velocity increases with increasing fluorine concentration. © 1978, American Institute of Physics. All rights reserved.

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Note On The Constant Coupling Approximation, M. Jursich, Harry A. Brown Jan 1978

Note On The Constant Coupling Approximation, M. Jursich, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

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Two-Step Photoionization Of Potassium Atoms, Kaare J. Nygaard, Robert J. Corbin, James A. Jones Jan 1978

Two-Step Photoionization Of Potassium Atoms, Kaare J. Nygaard, Robert J. Corbin, James A. Jones

Physics Faculty Research & Creative Works

The cross section for photoionization of potassium atoms in the 4P2 states has been measured in a triple-crossed-beam experiment. © 1978 The American Physical Society.

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Production Of Cl⁻·Hcl Cluster Ions In Hcl-N2 Mixtures, R. J. Corbin, Kaare J. Nygaard, William R. Snow, Laird D. Schearer Jan 1978

Production Of Cl⁻·Hcl Cluster Ions In Hcl-N2 Mixtures, R. J. Corbin, Kaare J. Nygaard, William R. Snow, Laird D. Schearer

Physics Faculty Research & Creative Works

A drift-tube-mass-spectrometer apparatus has been used to study the production of Cl-·HCl cluster molecules in HCl-N2 mixtures. The concentration of HCl was 730 ppm and the total pressure ranged from 0.1-5 Torr. The primary ion Cl- is produced mainly by dissociative attachment of HCl and is converted to a cluster ion in a three-body collision. The rate of formation of the cluster ion is k2≃ 10-25 cm6/sec at E/N=12 Td. © 1978 American Institute of Physics.

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On The Classical‐Spin Model Of Amorphous Ferromagnets, Harry A. Brown Jan 1978

On The Classical‐Spin Model Of Amorphous Ferromagnets, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

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The Bethe‐Peierls‐Weiss Approximation For Amorphous Magnets, Harry A. Brown Jan 1978

The Bethe‐Peierls‐Weiss Approximation For Amorphous Magnets, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

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Time Resolved Fluorescence Of The A ²∑+ State Of Gef, R. (Richard) A. Anderson, L. Hanko, S. J. Davis Jan 1978

Time Resolved Fluorescence Of The A ²∑+ State Of Gef, R. (Richard) A. Anderson, L. Hanko, S. J. Davis

Physics Faculty Research & Creative Works

The radiative lifetime and quenching rates for the A 2∑ + state of GeF have been measured in the flame of GeH 4+F2 by pulsed laser induced fluorescence. In addition, the radiative lifetime of the ν′=0 level of the A 2∑ + state of SiF has been measured in the flame of SiH 4+F2. Quenching rates for He, N2, and SF 6 on GeF A 2∑ and He on SiF A 2∑ have also been determined. The average zero pressure lifetime of ν′=0, 1, and 2 levels of A 2∑ GeF is 990±100 nsec. The zero-pressure lifetime of the A …

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A Xenon Ion Pumped Blue Dye Laser, D. W. Fahey, Laird D. Schearer Jan 1978

A Xenon Ion Pumped Blue Dye Laser, D. W. Fahey, Laird D. Schearer

Physics Faculty Research & Creative Works

A pulsed xenon ion laser with an output power of 5 kW at 364.5 nm has been used as a pump source for several blue dyes. Broadband conversion efficiencies exceed 20 percent. The use of a birefringent filter provides tunable output in the blue region of the spectrum with a bandwidth of 0.08 nm and a pulse width of 120 ns. © 1978 IEEE

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Spin Correlations In Actinide Materials: A Neutron Study Of Usb, G. H. Lander, S. K. Sinha, Don M. Sparlin, O. Vogt Jan 1978

Spin Correlations In Actinide Materials: A Neutron Study Of Usb, G. H. Lander, S. K. Sinha, Don M. Sparlin, O. Vogt

Physics Faculty Research & Creative Works

Measurements have been made of the short-range spin correlations in USb, a metallic compound that orders antiferromagnetically. The system has no transverse fluctuations, and the longitudinal spin correlations are anisotropic, showing stronger interactions within the ferromagnetic sheets than between them. The results of this and other experiments can be understood with simple concepts involving the bonding of 5f electrons. © 1978 The American Physical Society.

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Intense Flowing Hollow Cathode Lamp, F. H.K. Rambow, Laird D. Schearer Dec 1977

Intense Flowing Hollow Cathode Lamp, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

An inexpensive, simple, and versatile hollow cathode lamp has been developed which produces intense ion resonance radiation of about 1 mW into 4π/25 sr. The lamp employs flowing helium gas to sustain the discharge. The construction permits a variety of cathode seed materials to be easily interchanged. The same lamp has been used as a source of ion resonance radiation for Ca, Ba, Zn, Mg, Sr, Yb, and Eu.

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The Water Monomer On The Basal Plane Of Ice Iₕ: An Effective Pair, Central Force Potential Model Of The Static Interaction, Jerry Kiefer, Barbara N. Hale Oct 1977

The Water Monomer On The Basal Plane Of Ice Iₕ: An Effective Pair, Central Force Potential Model Of The Static Interaction, Jerry Kiefer, Barbara N. Hale

Physics Faculty Research & Creative Works

The H2O-H2O intermolecular central force potential of Lemberg and Stillinger is used to obtain optimal binding energy surfaces, vibrational frequencies, and bonding configurations of an adsorbed water monomer on a model basal plane of ice Ih. The monomer interacts (pairwise) with 50 molecules arranged in two layers of the unrelaxed bulk ice lattice. The results of calculations for three model surface sites of differing proton arrangement indicate the existence of diffusion barriers of the order of 2.5 kcal/mole and optimal monomer bonding sites at about 9 kcal/mole with nonepitaxial characteristics. Perspective computer-drawn plots of …

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Erratum: Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation (Physical Review A (1977) 16, 2), Ralph V. Calhoun, Don H. Madison, W. Neil Shelton Aug 1977

Erratum: Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation (Physical Review A (1977) 16, 2), Ralph V. Calhoun, Don H. Madison, W. Neil Shelton

Physics Faculty Research & Creative Works

No abstract provided.

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X-Ray Investigation Of The Critical Exponent Η In Argon, Harold D. Bale, J. S. Lin, Duane A. Dolejsi, James L. Casteel, Oran Allan Pringle, Paul W. Schmidt Jul 1977

X-Ray Investigation Of The Critical Exponent Η In Argon, Harold D. Bale, J. S. Lin, Duane A. Dolejsi, James L. Casteel, Oran Allan Pringle, Paul W. Schmidt

Physics Faculty Research & Creative Works

Measurements were made of the small-angle x-ray scattering intensity from argon near the critical point. After the scattering curves are corrected for all known effects except those resulting from irrelevant variables, a value of the critical exponent η=0.09±0.02 is obtained, while if a correction for the estimated effect of irrelevant variables is also made, η=0.03±0.03. The scattering data for argon therefore show that if irrelevant variables can be neglected, the critical exponent η for argon is in good agreement with the value obtained by Warkulwiz, Mozer, and Green from small-angle neutron scattering data for neon. These values of η, however, …

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Differential Energy-Loss Cross Sections For Ionization Of Atomic Hydrogen By 25-200-Kev Protons, John T. Park, Judith E. Aldag, Jacob M. George, Jerry Peacher, Jim H. Mcguire Feb 1977

Differential Energy-Loss Cross Sections For Ionization Of Atomic Hydrogen By 25-200-Kev Protons, John T. Park, Judith E. Aldag, Jacob M. George, Jerry Peacher, Jim H. Mcguire

Physics Faculty Research & Creative Works

Ionization continuum cross sections, differential in energy loss, have been determined from the energy-loss spectra of 25-, 50-, 75-, 145-, and 200-keV protons scattered from atomic hydrogen. The theoretical differential cross sections in the Glauber and Born approximations that are presented show that the theory and the experimental results for 200-keV proton impact agree very well, but below 200 keV there are differences. These differences, which are more pronounced at the lower projectile energies, may be explained in terms of charge transfer to the continuum, which is not treated in our Born and Glauber calculations of direct Coulomb ionization. The …

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Results Of A Remedial Laboratory Program Based On A Piaget Model For Engineering And Science Freshmen, Robert Gerson Jan 1977

Results Of A Remedial Laboratory Program Based On A Piaget Model For Engineering And Science Freshmen, Robert Gerson

Physics Faculty Research & Creative Works

Engineering and science freshmen who enter our institution with algebra deficiencies have a very low probability of performing satisfactorily in the required college-level calculus course. Two years ago, a remedial one-semester program was conducted for 36 freshmen who were identified by an entrance examination as being weak in algebra. The course was based on the assumption that the students were "concrete" in the Piagetian sense. The main part of the course required a general physics laboratory that provided selected experiences to bridge the concrete-formal gap. After three semesters, 31% of the participants in the course were receiving grades of C …

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Interaction Of Electric And Magnetic Charges, I. Adawi Jan 1977

Interaction Of Electric And Magnetic Charges, I. Adawi

Physics Faculty Research & Creative Works

It is shown classically that in a head-on collision between an electric and a magnetic charge a repulsive polarization force of the form r-5 results (where r is the distance between the charges), if one (both) charge(s) is (are) assigned a finite spherical size. This force leads to a minimum distance of approach and prevents one particle from going through the other, and thus guards against the violation of the conservation of angular momentum. This polarization force is a manifestation of the diamagnetism (diaelectricity) of extended electric (magnetic) charges. © 1977 The American Physical Society.

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Light Emission From Atom Beam - Plasma Interactions, Kaare J. Nygaard Jan 1977

Light Emission From Atom Beam - Plasma Interactions, Kaare J. Nygaard

Physics Faculty Research & Creative Works

A beam of atoms penetrating a plasma can be considered a line source of contaminants. Atoms excited by the plasma electrons yield information about the spatially resolved electron density and temperature. The light intensity as a function of time and position along the beam can be conveniently observed with an optical multichannel analyzer Since the beam atoms are different from the plasma constituents, the method does not suffer from self-absorption. Copyright © 1977 by The Institute of Electrical and Electronics Engineers, Inc.

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