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Full-Text Articles in Physics
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 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 …
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
Adsorption Of Rare Gas Atoms On Xenon, Donald E. Hagen
Adsorption Of Rare Gas Atoms On Xenon, Donald E. Hagen
Physics Faculty Research & Creative Works
The problem of adsorption of rare gas atoms on solids is treated for the case of submonolayer films. An energy spectrum calculation method which is suitable for band structure or heat capacity calculations is discussed. It is particularly useful for adsorbate-substrate systems in the region intermediate between "tight binding" and "plane wave" behavior. The method employs a technique introduced by Kohn and Luttinger of using the eigenfunctions corresponding to a particular point in the Brillouin zone as a basis set. The cases of He and Ne adsorbed on Xe are discussed.
An Inexpensive Electrical Vacuum Feedthrough, D. R. Kastelein, Richard A. Anderson, Kaare J. Nygaard
An Inexpensive Electrical Vacuum Feedthrough, D. R. Kastelein, Richard A. Anderson, Kaare J. Nygaard
Physics Faculty Research & Creative Works
No abstract provided.
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.
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.
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 …
Excited-Ion Lifetimes Using Penning-Ionizing Collisions, William F. Parks, Laird D. Schearer
Excited-Ion Lifetimes Using Penning-Ionizing Collisions, William F. Parks, Laird D. Schearer
Physics Faculty Research & Creative Works
We show that in the Penning-ionizing collision He(23S1)+X→He(11S0)+(X+)*+e the precession of the Hem spin at its Larmor frequency forces the J polarization of the Penning ion to rotate at the same frequency but shifted in phase. The tangent of the phase shift is proportional to the lifetime of the ionic state and presents a unique method for measuring excited-ion lifetimes. © 1972 The American Physical Society.