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Physics Faculty Research & Creative Works

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Articles 1801 - 1830 of 1959

Full-Text Articles in Physical Sciences and Mathematics

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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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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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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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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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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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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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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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, John 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, John 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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Final-State Effects In Carbon Auger Spectra Of Transition-Metal Carbides, M. A. Smith, L. L. Levenson Jan 1977

Final-State Effects In Carbon Auger Spectra Of Transition-Metal Carbides, M. A. Smith, L. L. Levenson

Physics Faculty Research & Creative Works

The carbon Auger spectra of TiC, VC, and Cr3C2 are measured with a resolution of 1.2 eV. Background subtraction is performed, and a deconvolution technique is used to remove energy-dependent broadening from the spectra. An analysis of the data in terms of density-of-states calculations, x-ray emission work, and x-ray photoelectron data shows that final-state effects dominate the Auger spectra. For all of the carbides three peaks are identified as spectral terms resulting directly from final-state hole interactions. Other peaks appearing in the Auger spectra can be identified without final-state considerations. © 1977 The American Physical Society.

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Note On The Van Der Waals Equation, Louis H. Lund Jan 1977

Note On The Van Der Waals Equation, Louis H. Lund

Physics Faculty Research & Creative Works

No abstract provided.

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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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Heisenberg Theory Of Ferromagnetism: Constant Coupling Revisited, Harry A. Brown Jan 1977

Heisenberg Theory Of Ferromagnetism: Constant Coupling Revisited, Harry A. Brown

Physics Faculty Research & Creative Works

The Heinsenberg theory of ferromagnetism has been treated by many types of approximations; one of the more successful is known as constant coupling. The literature constants several different ways of arriving at results like those of the constant-coupling approximation, but proofs that they are indeed equivalent are lacking in some cases. It is shown that two of these methods are equivalent for spin 1/2 and explicitly demonstrated that both yield exactly the constant-coupling results, though simpler in use and concept than the latter. Finally, it is shown that one of the two methods yields the same Curie temperatures as constant …

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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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Valence-Band Information From The Auger Kvv Spectrum Of Graphite, M. A. Smith, L. L. Levenson Jan 1977

Valence-Band Information From The Auger Kvv Spectrum Of Graphite, M. A. Smith, L. L. Levenson

Physics Faculty Research & Creative Works

The Auger KVV and x-ray photoelectron valence-band spectra of atomically clean, well-ordered graphite are measured. After background subtraction is performed and a deconvolution technique is used to remove energy-dependent features from the Auger data, the transition density function is calculated for the graphite valence band. A comparison is made with other experimental work and with a density-of-states calculation. It is found that the transition density closely resembles the density of states if localized hole effects are considered. © 1977 The American Physical Society.

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Surface Electromagnetic Waves With Damping. Ii. Anisotropic Media, G. S. Kovener, Ralph William Alexander, I. L. Tyler, Robert John Bell Jan 1977

Surface Electromagnetic Waves With Damping. Ii. Anisotropic Media, G. S. Kovener, Ralph William Alexander, I. L. Tyler, Robert John Bell

Physics Faculty Research & Creative Works

The Technique of Plotting the Attenuated-Total-Reflection (ATR) Reflectance as a Function of Both Frequency and Incident Angle using a Three-Dimensional Plot is Applied to Surface Electromagnetic Waves (SEW) in a Uniaxial Material, MnF2. It is Shown that Dispersion Curves Calculated Without Absorption Do Not Completely Describe the ATR Reflectivity. Experimental Data Confirming the Reflectance Surface Features Are Presented. Also, Additional Minima in the Reflectance Surface Not Associated with SEW Are Discussed. © 1977 the American Physical Society.

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Energy Dependence Of Amorphizing Implant Dose In Silicon, John R. Dennis, Edward Boyd Hale Dec 1976

Energy Dependence Of Amorphizing Implant Dose In Silicon, John R. Dennis, Edward Boyd Hale

Physics Faculty Research & Creative Works

The radiation-induced transformation from crystalline to amorphous silicon was studied using ion implantation. The ion energy was varied from 20 to 180 keV for Li+, N+, Ne+, Ar+, and Kr +. The energy dependence of the critical amorphizing dose was determined by electron spin resonance. Comparison of the data with theoretical calculations of the energy density deposited into atomic processes showed good agreement. This energy-dependent agreement gave evidence that energy density is important to the transformation at both low and high implantation temperatures.

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Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation, Ralph V. Calhoun, Don H. Madison, W. Neil Shelton Oct 1976

Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation, Ralph V. Calhoun, Don H. Madison, W. Neil Shelton

Physics Faculty Research & Creative Works

The differential cross sections for excitation of the n=2 state of atomic hydrogen by the impact of electrons with energies of 54, 100, 136, and 200 eV are calculated in the distorted-wave approximation with exchange included. Cross sections for excitation of the 2s1/2, 2p1/2, and 2p3/2 states are calculated and summed to give the n=2 differential cross sections. The results of this calculation are compared with previous theoretical calculations and with recent absolute experimental data.

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Cross Sections For Excitation Of Atomic Hydrogen To The N=2, 3, And 4 States By 15-200-Kev Protons, John T. Park, John E. Aldag, Jacob M. George, Jerry Peacher Aug 1976

Cross Sections For Excitation Of Atomic Hydrogen To The N=2, 3, And 4 States By 15-200-Kev Protons, John T. Park, John E. Aldag, Jacob M. George, Jerry Peacher

Physics Faculty Research & Creative Works

Cross sections for the processes H++H(1 s)H++H*(n = 2, 3, 4) have been extracted from the energy-loss spectra of 15- to 200-keV protons by using a spectrum-fitting technique. Absolute cross sections have been obtained by normalization of the spectra to the theoretical cross section through the use of the Born approximation at 200 keV. The cross-section curves are very similar in shape with maxima at 60 keV. The results have been compared with available theoretical calculations. The n = 2 and n = 3 cross-section measurements are in very good agreement in curve shape with Glauber-approximation …

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Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, Don H. Madison Jul 1976

Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, Don H. Madison

Physics Faculty Research & Creative Works

Absolute values of doubly differential cross sections are obtained for electron production in helium by 5- to 100-keV proton impact. The measured values along with earlier data at higher energies are compared with theoretical plane-wave Born-approximation functions obtained from a Hartree-Fock potential. Not only is good agreement obtained at high impact energies (above 300 keV), but fairly good agreement is found at low energies (below about 20 keV). For electrons ejected in the backward hemisphere, unexpectedly poor agreement is noted at intermediate energies where the measured cross sections dip to 50% of the calculated values in some cases. Singly differential …

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Thomson's Monopoles, I. Adawi Jan 1976

Thomson's Monopoles, I. Adawi

Physics Faculty Research & Creative Works

The angular momentum L of the electromagnetic field due to an electric point charge e, and a magnetic point charge (pole) g, is calculated by several methods to obtain J. J. Thomson's result that L = eg/c, and L is directed along the line joining the electric monopole to the magnetic monopole. The relation to Dirac's monopoles is discussed, and particle size is considered. © 1991, American Association of Physics Teachers. All rights reserved.

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The Magnification Factor For Sodium Chloride Liesegang Circles Established With An Aerosol Centrifuge, O. Preining, Josef Podzimek, P. Yue Jan 1976

The Magnification Factor For Sodium Chloride Liesegang Circles Established With An Aerosol Centrifuge, O. Preining, Josef Podzimek, P. Yue

Physics Faculty Research & Creative Works

Sodium chloride particles deposited on a gelatin film containing silver nitrate form in a humid environment clearly visible dark brown reaction spots (Liesegang circles) after development in u.v.-light. The size of these reaction spots depends on the mass of NaCl in the particles. To establish the spot size vs particle size relation, particles produced by nebulising NaCl-solutions and sea water were sampled in an aerosol centrifuge. The location of deposition yields the aerodynamic diameter of the particle, and the spot size is measured microscopically. In this way the spot size vs aerodynamic diameter relation is established experimentally in the so …

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Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen Jan 1976

Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen

Physics Faculty Research & Creative Works

No abstract provided.

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Radiative Lifetimes Of Some Group Ii Ions By The Hanle Effect In A Fast-Flowing Helium Afterglow, F. H.K. Rambow, Laird D. Schearer Jan 1976

Radiative Lifetimes Of Some Group Ii Ions By The Hanle Effect In A Fast-Flowing Helium Afterglow, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

Radiative lifetimes of the first P322 state of Mgu, Cau, Znu, Sru, Cdu, and Bau are reported as measured by the Hanle effect in a fast-flowing helium afterglow. They are, respectively, 3.65(0.12), 6.61(0.30), 2.4(0.3), 6.64(0.10), 2.86(0.25), 6.78(0.40) in units of 10-9 sec. The ions in the afterglow are created by Penning ionization of the neutral metal atoms, thus providing a steady-state, field-free region for observation. Comparisons are made with measurements by other methods, and discrepancies are discussed. © 1976 The American Physical Society.

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