Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Chemistry (62)
- Computer Sciences (44)
- Numerical Analysis and Scientific Computing (44)
- Engineering (19)
- Materials Science and Engineering (10)
-
- Metallurgy (5)
- Aerospace Engineering (4)
- Mechanical Engineering (4)
- Social and Behavioral Sciences (3)
- Earth Sciences (2)
- Geology (2)
- Psychology (2)
- Biochemical and Biomolecular Engineering (1)
- Chemical Engineering (1)
- Civil and Environmental Engineering (1)
- Electrical and Computer Engineering (1)
- Library and Information Science (1)
- Nuclear Engineering (1)
- Keyword
-
- Ionization (58)
- Electrons (42)
- Quantum Theory (42)
- Helium (36)
- Atoms (34)
-
- Hydrogen (34)
- Electrodynamics (32)
- Gravitational waves (30)
- Gravity waves (29)
- Molecules (29)
- Gravitational effects (28)
- Photons (28)
- Impact ionization (25)
- Atomic physics (22)
- Gravitation (21)
- Impact Ionization (19)
- Quantum theory (19)
- Electron Energy Levels (18)
- Atomic Physics (17)
- Photoionization (17)
- Stars (17)
- Ions (16)
- Mathematical models (16)
- Projectiles (16)
- Electron impact-ionization (15)
- Hamiltonians (15)
- Polarization (15)
- Quantum Electrodynamics (15)
- Electron energy levels (14)
- Gravitational-wave signals (14)
- Publication Year
Articles 1471 - 1500 of 1562
Full-Text Articles in Physics
On The Lambda Transition In Solid Orthohydrogen, Harry A. Brown
On The Lambda Transition In Solid Orthohydrogen, Harry A. Brown
Physics Faculty Research & Creative Works
No abstract provided.
Optical Pumping In A Flowing Helium Afterglow With Additive Metal Impurity Atoms, Laird D. Schearer
Optical Pumping In A Flowing Helium Afterglow With Additive Metal Impurity Atoms, Laird D. Schearer
Physics Faculty Research & Creative Works
It is demonstrated that in a Penning collision of optically oriented metastable helium atoms with an impurity metal atom such as barium, both the longitudinal and transverse components of spin angular momentum are conserved. This results in a polarization of the ion which may be detected by optical emission in the case of excited ion levels or absorption for the ground states. A series of experiments is described which demonstrates the spin dependence of the Penning-collision process. The magnetic resonance of excited-state ions may be observed directly; from the resonance-linewidth radiative lifetimes may be measured. © 1974 The American Physical …
Fresnel Drag In Uniformly Moving Media, William F. Parks, J. T. Dowell
Fresnel Drag In Uniformly Moving Media, William F. Parks, J. T. Dowell
Physics Faculty Research & Creative Works
A general first-order formula is derived for the Fresnel-drag effect in a uniformly moving medium with a plane surface. The two classical equations due to Lorentz and Laub are shown to be special cases corresponding to different experimental arrangements. The recent experiment of Bilger and Zavodny on Fresnel drag in a ring laser is discussed. © 1974 The American Physical Society.
Evaluation Of Model For The Contributin Of Phonon-Induced Tunneling To Donor Esr Spectral Narrowing In Germanium, David L. Meier, William F. Parks, Edward Boyd Hale
Evaluation Of Model For The Contributin Of Phonon-Induced Tunneling To Donor Esr Spectral Narrowing In Germanium, David L. Meier, William F. Parks, Edward Boyd Hale
Physics Faculty Research & Creative Works
The model commonly assumed to explain the narrowing of the ESR spectra of donor impurities in germanium is examined in detail. This model combines the Anderson line-narrowing theory with the Miller and Abrahams theory for the phonon-induced tunneling (hopping) of an electron between impurities. The predictions of this model are found to be in drastic disagreement with experimental results now available. It is shown that the narrowed linewidth should depend strongly on donor concentration, acceptor concentration, and temperature. Future spin-resonance experiments in highly compensated samples may show the effects of hopping, but no evidence now exists which indicates that hopping …
Erratum: Radiative And Predissociative Lifetimes Of The A ²Σ+ State Of Oh, Richard A. Anderson, R. A. Sutherland
Erratum: Radiative And Predissociative Lifetimes Of The A ²Σ+ State Of Oh, Richard A. Anderson, R. A. Sutherland
Physics Faculty Research & Creative Works
No abstract provided.
Electron Spin Resonance In Argon-Ion-Implanted Silicon, Keh Chang Chu, Weiler R. Hurren, Edward Boyd Hale, John Reigle
Electron Spin Resonance In Argon-Ion-Implanted Silicon, Keh Chang Chu, Weiler R. Hurren, Edward Boyd Hale, John Reigle
Physics Faculty Research & Creative Works
A new paramagnetic center with g = 2.0029 is observed, in both n- and p-type silicon after they are heavily implanted (higher than 1017 ions/cm2) with 150-keV argon ions. © 1973 American Institute of Physics.
Properties Of Microwave Cavities Containing Magnetic Resonant Samples, Kathy A. Rages, Robert E. Sawyer, Edward Boyd Hale
Properties Of Microwave Cavities Containing Magnetic Resonant Samples, Kathy A. Rages, Robert E. Sawyer, Edward Boyd Hale
Physics Faculty Research & Creative Works
Properties of TE011 cylindrical, microwave cavities containing cylindrical samples of various radii and dielectric constants are calculated. The properties considered are the resonant frequency, quality factor (Q), relevant magnetic filling factor for spin transitions (ε), and a signal sensitivity factor (Qε) for a lossless sample. Sample sizes range from zero radius to full cavity radius with some experimental data on less than full length samples. The choice of dielectric constants ranges from one to sixteen. The data are presented in dimensionless form since they will be of use to other ESR experimentalists. It is shown that use of large samples …
Distorted-Wave Approximation And Its Application To The Differential And Integrated Cross Sections For Electron-Impact Excitation Of The 2¹P State Of Helium, Don H. Madison, W. Neil Shelton
Distorted-Wave Approximation And Its Application To The Differential And Integrated Cross Sections For Electron-Impact Excitation Of The 2¹P State Of Helium, Don H. Madison, W. Neil Shelton
Physics Faculty Research & Creative Works
Theoretical results are given for the application of the distorted-wave approximation to electron-atom impact excitation for transitions from an L-S coupled initial state to an arbitrarily coupled final state. Expressions for the differential cross section and spin polarization of the emitted electrons are given for unpolarized electron beams incident upon unpolarized atoms. These results are applied to excitation of helium from its ground state to the 1s2p1P1 excited state for incident-electron energies between 26.5 and 300 eV. The results are compared with previous theoretical and experimental works. It is found that the distorted-wave calculation is superior to …
Spin Polarization And Differential Cross Section For Electron-Impact Excitation Of The 6s6p ¹P₁ State Of Mercury: Distorted-Wave Treatment, Don H. Madison, W. Neil Shelton
Spin Polarization And Differential Cross Section For Electron-Impact Excitation Of The 6s6p ¹P₁ State Of Mercury: Distorted-Wave Treatment, Don H. Madison, W. Neil Shelton
Physics Faculty Research & Creative Works
The results of the distorted-wave theory for electron-impact excitation of atoms are applied to the excitation of the 6s6p 1P1 state of mercury. The spin polarization and the differential cross section are given for unpolarized incident electron beams with energies between 25 and 180 eV. The distorted-wave results are compared with experimental data, and good agreement is found for both the spin polarization and differential cross section.
Molecular Beam Measurements Of Total Collision Cross Sections Of H 22o, William R. Snow, J. T. Dowell, J. G. Chevrenak, H. E. Berek
Molecular Beam Measurements Of Total Collision Cross Sections Of H 22o, William R. Snow, J. T. Dowell, J. G. Chevrenak, H. E. Berek
Physics Faculty Research & Creative Works
The total cross section for H22O-H22O scattering is measured with a supersonic nozzle beam system. The primary beam has a narrow velocity distribution, and the velocity is varied by control of the nozzle temperature. Velocities are determined by time-of-flight techniques. Cross sections obtained are averages over a Maxwellian distribution of the target molecules. Data at three velocities are presented. The cross sections for H2O are surprisingly small, for example, 3.07 x10-14 cm2 at 1x105 cm/sec, indicating little contribution from the dipole-dipole interaction.
Possible Applications Of Surface Electromagnetic Waves To Measure Absorption Coefficients, Ralph William Alexander, Robert John Bell, C. A. Ward, James Roger Weaver, I. L. Tyler, B. Fischer
Possible Applications Of Surface Electromagnetic Waves To Measure Absorption Coefficients, Ralph William Alexander, Robert John Bell, C. A. Ward, James Roger Weaver, I. L. Tyler, B. Fischer
Physics Faculty Research & Creative Works
We Show that Surface Electromagnetic Waves Can Probably Be Used to Measure the Absorption Coefficients of Materials overlaying Metals. the Proposed Experimental Method is Illustrated in the Infrared Frequency Range using Water, Teflon, and Polyethylene as Sample Materials.
Total Electron Impact Ionization Cross Section In Rubidium From Threshold To 250 Ev, Kaare J. Nygaard, Yu Bong Hahn
Total Electron Impact Ionization Cross Section In Rubidium From Threshold To 250 Ev, Kaare J. Nygaard, Yu Bong Hahn
Physics Faculty Research & Creative Works
A study of ionization in rubidium has been made in a crossed atom-electron beam apparatus. At an electron energy of about 10 eV there is a maximum in the cross section corresponding to the maximum probability for removal of the 5s valence electron. At 16.5 eV we have observed a new peak that is caused by the mechanism of autoionization. For energies below 30 eV there is a good agreement, both in shape and magnitude, between the present measurements and the empirical formula of Lotz. The over-all uncertainty in the measurements is ± 12% which is mostly accounted for by …
Absolute Differential Elastic- And Inelastic-Scattering Cross Sections In 25-140 Kev He+ + He Collisions, Victor Pol, Walter Kauppila, John T. Park
Absolute Differential Elastic- And Inelastic-Scattering Cross Sections In 25-140 Kev He+ + He Collisions, Victor Pol, Walter Kauppila, John T. Park
Physics Faculty Research & Creative Works
Data obtained as energy-loss spectra at angles from 0 to 7.3x10-3 rad (c.m.) with typical energy-loss resolution of 0.7 eV and angular resolution of 2x10-3 rad (c.m.) were used to calculate average differential cross sections dσdΩav for elastic scattering, direct excitation of the individual He(n=2) states, and direct excitation of the He+(n=2) states. The total cross section for excitation of the He(n=2) states obtained by integrating the differential cross sections was found to be 20x10-18 cm2 at 25 keV (lab) decreasing to 7x10-18 cm2 at 140 keV. At incident lab energies below 100 keV the He(2S2) and He(2P3) states dominate …
Penning Ionization Of Zn And Cd By Noble-Gas Metastable Atoms, L. A. Riseberg, William F. Parks, Laird D. Schearer
Penning Ionization Of Zn And Cd By Noble-Gas Metastable Atoms, L. A. Riseberg, William F. Parks, Laird D. Schearer
Physics Faculty Research & Creative Works
The Penning-ionization cross sections for He, Ne, Ar, and Kr metastable atoms with Zn and Cd have been measured in a pulsed afterglow. Within the framework of existing theories we have determined those parameters which are of importance in collisions of this type. We find that our data are internally consistent if the cross sections are proportional to the cube of the "hard-sphere" radii and the effects of selection rules are included. A theoretical basis for this dependence is suggested. © 1973 The American Physical Society.
Note On The Poisson Distribution, I. Adawi
Note On The Poisson Distribution, I. Adawi
Physics Faculty Research & Creative Works
No abstract provided.
Laser Scattering Measurements Of Droplet Growth In Binary Mixtures. Ii. H2o And Argon H2o And Helium, M. A. Viettit, Burton Schuster
Laser Scattering Measurements Of Droplet Growth In Binary Mixtures. Ii. H2o And Argon H2o And Helium, M. A. Viettit, Burton Schuster
Physics Faculty Research & Creative Works
Water droplet growth rates in a Wilson cloud chamber were measured in Ar-H2O and He-H2O media. These rates were determined in the size range 0.45-10.0 u.m by detection of oscillations in the intensity of polarized light from a He-Ne laser source scattered at 30° by the droplet population. Pressure and initial temperature were measured in the chamber for use in the computation of three droplet growth theories for comparison to experiment. Experiments were conducted in supersaturations ranging from 1.04 to 3.45.
General Theory Of Diffusion-Controlled Reactions, Gerald Wilemski, Marshall Fixman
General Theory Of Diffusion-Controlled Reactions, Gerald Wilemski, Marshall Fixman
Physics Faculty Research & Creative Works
A formal mathematical description of diffusion-controlled bimolecular reactions is presented. The theory is completely general with respect to the kinds of reaction processes that may be considered. Besides the presentation of the general formalism, the paper also contains several examples illustrating the application of the theory to a simple many-particule system for simple catalytic bimolecular reactions, including fluorescence quenching. The manner in which approximate solutions may be obtained is also outlined.
Production Of Metastable Ions In Cesium-Atom-Electron Collisions, Kaare J. Nygaard, Yu Bong Hahn
Production Of Metastable Ions In Cesium-Atom-Electron Collisions, Kaare J. Nygaard, Yu Bong Hahn
Physics Faculty Research & Creative Works
The structure in the total electron-impact ionization cross section in cesium can be partially accounted for by the mechanisms of autoionization and excitation ionization of 5p electrons. For electron energies above 17 eV a large fraction of the ions are metastable and can de detected by Auger emission from a metal surface. The experiment was performed in a cesium-atom-electron crossed-beam apparatus, and the metastable ions were counted with a channel electron multiplier. The metastable-ion count rate was a factor of 100 higher than that due to photons from atomic and ionic transitions. We have measured the over-all excitation function for …
Chemical Shift Parameters For Shallow Donors In Semiconductors, Edward Boyd Hale
Chemical Shift Parameters For Shallow Donors In Semiconductors, Edward Boyd Hale
Physics Faculty Research & Creative Works
A model for a shallow donor impurity in a semiconductor is used to calculate two relationships and several conditions involving the chemical shift parameters. The model is based on the standard effective mass form for the donor electron wave function, the existence of a potential in the chemical cell which may be real, pseudo, or rather general in nature, and a few somewhat restrictive approximations. The parameters, Δ, δ and Λ are theoretically calculated and are shown to be related if the approximations are valid. These parameters determine the 1S multiplet level structure and it is shown how properties of …
Gaas Laser Experiments For The Undergraduate Laboratory, R. E. Robert, Daniel J. Jones, Kaare J. Nygaard
Gaas Laser Experiments For The Undergraduate Laboratory, R. E. Robert, Daniel J. Jones, Kaare J. Nygaard
Physics Faculty Research & Creative Works
No abstract provided.
On The Effect Of Cesium In Photoionization Laser Plasmas, Kaare J. Nygaard
On The Effect Of Cesium In Photoionization Laser Plasmas, Kaare J. Nygaard
Physics Faculty Research & Creative Works
A number of photoionization mechanisms and how they can be used to generate large-volume laser plasmas are discussed. Reaction rates for two-step photoionization of the cesium atoms as well as formation of molecular ions (Cs2+) are estimated. The necessary cross-section data were obtained from related research in thermionic energy converters. © 1973, IEEE. All rights reserved.
Channeltron Gain In Magnetic Fields, Yu Bong Hahn, Robert E. Hebner, Daniel R. Kastelein, Kaare J. Nygaard
Channeltron Gain In Magnetic Fields, Yu Bong Hahn, Robert E. Hebner, Daniel R. Kastelein, Kaare J. Nygaard
Physics Faculty Research & Creative Works
The gain and total count rate of electron channel multipliers depend strongly on applied magnetic fields. We report experimental results for Channeltrons operated in magnetic fields of up to 300 G, and find that the applied voltage must be increased to about 4000 V to maintain a sufficiently high gain. Slightly higher count rates are observed if the magnetic field is parallel to the plane of the Channeltron, as compared to perpendicular to that plane. © 1972 The American Institute of Physics.
System For Data Acquisition From High Voltage Terminals, George W. York, John T. Park, James J. Miskinis, David H. Crandall, Victor Pol
System For Data Acquisition From High Voltage Terminals, George W. York, John T. Park, James J. Miskinis, David H. Crandall, Victor Pol
Physics Faculty Research & Creative Works
An inexpensive data acquisition system has been designed to provide high voltage isolation for data acquisition in analog, digital, and pulse modes. The telemetry system uses GaAs light sources, fiber optics, and phototransistors to accomplish the data transmission. Prewired logic boards have been adapted to accomplish the timing and logic functions. Seven decades of digital data are transmitted error free, pulse data can be transmitted at rates up to 1 MHz, and analog data are transmitted with 0.05% full scale accuracy. © 1972 The American Institute of Physics.
Eikonal Approximation For Coupled Equations For Multichannel Scattering, Rung T. Ling, Joseph C.Y. Chen, Jerry Peacher, Kenneth M. Watson
Eikonal Approximation For Coupled Equations For Multichannel Scattering, Rung T. Ling, Joseph C.Y. Chen, Jerry Peacher, Kenneth M. Watson
Physics Faculty Research & Creative Works
It is well known that the Glauber approximation for scattering amplitudes is obtained by applying the eikonal approximation to the Fourier transform of the transition operator. The eikonal approximation can also be applied to the coupled equations of scattering obtained by the expansion of the state function in terms of a suitable set of functions. The scattering amplitude can thus be obtained by solving the set of eikonal coupled equations. The latter approach is analyzed for a special class of channel-coupling potentials. The first-order approximation to the derived eikonal coupled equations is the eikonal Born approximation. Numerical illustrations in this …
Molecular Model For Prenucleation Water Clusters, P. L. M. Plummer, Barbara N. Hale
Molecular Model For Prenucleation Water Clusters, P. L. M. Plummer, Barbara N. Hale
Physics Faculty Research & Creative Works
A molecular model applicable to prenucleation water clusters is described. As an illustration the model is applied to water clusters having clathrate-like structures composed of five-menibered rings. This work was motivated by the apparent inadequacies of the corrected liquid drop model which (in addition to applying bulk properties to small clusters) predicts nucleation rates which may be as much as 1017 larger than experiment. We present the "energy of formation" at a temperature of 277°K for our molecular model for clusters ranging in size from 5 to 57 molecules. These results agree qualitatively with experiment and, we believe, provide …
A Study Of Phosphorus Adsorption And Desorption Kinetics On Silicon (111) Surfaces, L. E. Davis, L. L. Levenson, J. J. Melles
A Study Of Phosphorus Adsorption And Desorption Kinetics On Silicon (111) Surfaces, L. E. Davis, L. L. Levenson, J. J. Melles
Physics Faculty Research & Creative Works
Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) methods were used to characterize the (111) surface of Si wafers before and after the deposition of P2 molecules. Before deposition, the well-known Si(111)-7 LEED pattern was easily obtained by thermal cleaning at 1200 °C. Cleaning was done by electron bombardment in a vacuum chamber with a base pressure of ∼ 10-10 Torr. After cleaning, AES showed that about 10-2 atomic layer of carbon was the only surface contaminant. The sensitivity of our cylindrical AES apparatus for phosphorus was about 10-3 atomic layer. We found that ∼5x10-2 atomic layer of …
A Correction To Classical Homogeneous Nucleation Theory For Polar Molecules Exhibiting An Electric Double Layer At The Liquid Surface, Daniel R. White, James L. Kassner
A Correction To Classical Homogeneous Nucleation Theory For Polar Molecules Exhibiting An Electric Double Layer At The Liquid Surface, Daniel R. White, James L. Kassner
Physics Faculty Research & Creative Works
An oriented dipole surface layer is added to the classical liquid drop model of nucleation to account for the surface behavior of substances having polar nonsymmetrical molecules. The preliminary treatment of the change in free energy as given by Abraham is modified to include Fletcher's exponential decay of the degree of orientation. An additional correction for the excess binding energy due to the presence of a foreign molecule in the prenucleation cluster is included to account for the inflections observed in the experimental results of Allen and Kassner. The resulting free energy of formation is combined with the kinetic treatment …
Collisional Excitation Of N+ At 50 Kev, D. H. Crandall, G. York, V. Pol, John T. Park
Collisional Excitation Of N+ At 50 Kev, D. H. Crandall, G. York, V. Pol, John T. Park
Physics Faculty Research & Creative Works
The excitation spectrum of N+ has been observed by examining the energy lost by a 50- keV N+ beam passing through a He target. The spectrum exhibits dramatic features with large cross sections. Determination of the approximate ratio of metastable to ground-state ions in the primary ion beam has permitted measurement of excitation cross sections from both ground-state and metastable N+ ions colliding with He target atoms. © 1972 The American Physical Society.
Application Of The Weiss Molecular Field Theory To The B‐Site Spinel, W. E. Holland, Harry A. Brown
Application Of The Weiss Molecular Field Theory To The B‐Site Spinel, W. E. Holland, Harry A. Brown
Physics Faculty Research & Creative Works
A molecular field treatment of the B‐site spinel was used to determine the ordering temperatures and the asymptotic Curie temperature in terms of the exchange integrals. The theory was developed from a 16‐sublattice model and took into account interactions between an atom and its nearest to fourth‐nearest neighbors. Experimental values of the ordering temperatures and the asymptotic Curie temperature were then used to determine the exchange integrals for the systems Hg1−xCdx Cr2 S4, CdCr2S4(1−y)Se4y, and Zn1−xCdxCr2Se4. Copyright © 1972 WILEY‐VCH Verlag GmbH & Co. KGaA
Thomson's E/M Experiment Revisited, Michael Glascock, Don M. Sparlin
Thomson's E/M Experiment Revisited, Michael Glascock, Don M. Sparlin
Physics Faculty Research & Creative Works
The objective of this experiment is to familiarize the student with the impulse theorem, electron dynamics, and magnetic field contours. He is challenged to obtain accurate as well as precise measurements with suboptimum apparatus through correct analysis. He also investigates the influence of various systematic errors using model calculations on a small computer. © 1972, American Association of Physics Teachers. All rights reserved.