Physical Sciences and Mathematics Commons^™

The Momentum Of The Photon, K F. Ratcliff, David Peak

All Physics Faculty Publications

No abstract provided.

Β-Delayed Proton Decay Of 9c, David D. Allred, John E. Esterl, J. C. Hardy, R. G. Sextro, Joseph Cerny

Faculty Publications

The delayed-proton spectrum following the β decay of 9C (t1/2=126.5±1.0 msec) was found to consist primarily of a continuum extending from 13 to 1.5 MeV, the latter being the lowest energy observed. In addition to the previously observed peaks at 9.28 and 12.30 MeV (C.M.), possible peaks between 3 and 7 MeV have been tentatively identified.

Research Project For Undergraduates: Ionic Thermoconductivity In Dielectrics, Richard M. Fuller, Robert Fuller

Robert G. Fuller Publications

Research projects for undergraduates should satisfy several conditions with regards to the physical insight, experimental manipulation, data analyses, and time for the experimental run that are required of the students. These conditions are satisfied by the study of dipole relaxations in dielectric materials using the method of ionic thermocurrents (ITC). ITC can be used to determine the concentration, activation energy, and relaxation time of dipoles in a dielectric. The necessary equipment and some possible research projects are discussed.

Electrical Sensor Of Plane Coordinates, George S. Hurst, James E. Parks

Physics and Astronomy Faculty Patents

An inexpensive electrical sensor of plane coordinates employs juxtaposed sheets of conducting material having electrical equipotential lines extending across each sheet and arranged normal to each other. A probe upon touching each sheet at a selected intersection of the equipotential lines causes separate signals to be applied to one or more conventional information-indicating units.

Cellular Absorbed Dose Spectrometer (Cads) Data Reduction And Analysis., John T. Cervini

Physics & Astronomy ETDs

A detailed description of a space qualified linear energy transfer (LET) spectrometer is presented. The Cellular Absorbed Dose Spectrometer (CADS) is a prototype instrument which was launched on March 17, 1969 into an elliptical orbit. Its purpose was to obtain the first successful LET measurements in space; and, thereby provide additional data to assess the biological hazards of the near earth space environment, especially during periods of in­creased solar activity.

The physical processes that take place in the CADS in­strument are discussed, and a definition of linear energy transfer is given, as well as its relation to dE/dx. The performance …

Nuclear-Magnetic-Resonance Measurement Of The Conduction-Electron G Factor In Cdte, David C. Look, D. L. Moore

Physics Faculty Publications

The effective g factor g^* of conduction electrons in degenerate CdTe has been determined by using measurements of the Cd¹¹³ nuclear spin-lattice relaxation time T₁ and the Knight shift K. It is shown that the magnitude of g^* is given by the Korringa product T₁TK²=C(g^*)², where C is a known constant and T is the absolute temperature, and that the sign of g^* is given by the sign of K for a spherically symmetric conduction band. The measured value, g^*=-1.1±0.1, is within the range allowed …

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 …

Schottky Defects In Alkali Halides, Paul D. Schulze, John R. Hardy

John R. Hardy Papers

The method of lattice statics and the deformation-dipole model have been applied to Schottky defects in ionic crystals in approximations higher than zero order. For an isolated vacancy, all host-lattice-ion potential energy functions for short-ranged repulsive and Coulomb-defect forces were expanded to terms quadratic in the displacements and dipole moments, and the resulting forces were allowed to act on the first and/or second neighbors to the vacancy. The zero-order Coulomb force was allowed to act on the remainder of the host-lattice ions past first and/or second neighbors. The vacancy and Schottky-pair-formation energies in the 12 Na, K, Rb halides have …

A Study Of The Kinetics Of Light Induced Modulation Of Absorption In Zinc Selenide, Herbert Seth Berman

Master's Theses

No abstract provided.

Nuclear Quadrupole Coupling Of B-12 In A Single Be Crystal, R. L. Williams Jr., Richard C. Haskell, Leon Madansky

All HMC Faculty Publications and Research

Quadrupole resonance lines of β-unstable 12B have been distinctly resolved in a single crystal of Be, and have behaved properly under field reversal and variation of the angle θ between crystal c axis and external magnetic field.

New Thin-Film Tunnel Triode Using Amorphous Semiconductors, Pavel Smejtek, R. F. Shaw, H. Fritzsche, M. Silver, S. Holmberg, S. R. Ovshinsky

Physics Faculty Publications and Presentations

A new thin‐film tunnel triode is discussed which uses a p‐type amorphous film to achieve amplification of injected current from a tunnel cathode. It is not only the basis for a new semiconductor device but also suggests a novel method for measuring electrical properties of semiconductors.

Electronic Properties Of Fe2+ In Cubic Kmgf3 From Mössbauer Spectroscopy, Richard B. Frankel, J. Chappert, J. R. Regnard, A. Misetich, C. R. Abeledo

Physics

Iron-doped KMgF₃ single crystals have been studied by Mössbauer spectroscopy of Fe⁵⁷. Single lines due to Fe²⁺ and Fe³⁺ are observed at room temperature. For TK, the Fe²⁺ line splits into a quadrupole doublet with a splitting ΔE_Q=0.44±0.02 mm/sec. Comparison with a random-strain model due to Ham yields a value of 120 cm^-1 for the position of the first excited spin-orbit split level. Magnetic hyperfine structure in external magnetic fields at low temperature is observed and analysis yields a value of -495 ±30 kOe for the corepolarization hyperfine field …

Scattering Spin 1/2 Particles By Nuclei, Pui-Wah Cheng

Masters Theses

No abstract provided.

Solutions Of The Two-State Potential-Curve-Crossing Problem, John B. Delos, W. R. Thorson

Arts & Sciences Articles

A general theory of the two-state curve-crossing problem has been developed, with a complete solution of an accurate model for "close" crossings (including numerical computations for strong coupling). Results clarify the position of the Landau-Zener approximation and its improvements by Nikitin and others, provide a general way of extending these approximations into regions often treated incorrectly (including the high-energy limit), and can be readily adapted to simple, rapid calculations.

Potential-Barrier Effects In Photoabsorption. I. General Theory, Anthony F. Starace

Anthony F. Starace Publications

This paper combines parts of the theories of spectroscopy, collisions, and autoionization to provide a unified framework for a quantitative theory of experimental data on 4d-shell photoabsorption in rare earths. The calculations by atomic theory are intended for tentative application to solids. The theory should also apply to 3p-shell photoabsorption in the transition metals and to other cases where the effect of a potential barrier is crucial. A prescription is given for the ab initio numerical calculation of total and partial photoabsorption cross sections, as well as of the profiles, energies, and widths of resonances. A …

Potential-Barrier Effects In Photoabsorption. Iii. Application To 4D-Shell Photoabsorption In Lanthanum, J.L. Dehmer, Anthony F. Starace

Anthony F. Starace Publications

An exploratory calculation of the photoabsorption cross section near the 4d ionization threshold of lanthanum metal is carried out. The level structure of the configuration 4d⁹4f is found to be altered by interaction with the continuum configuration 4d⁹εf. The Fano profile of the resonance above threshold is calculated, as are the oscillator strengths of the discrete states below threshold. Our results provide the ground work for more detailed calculations.

Elastic Scattering Of Low-Energy Electrons At 180° In Co2, Paul Burrow, L. Sanche

Paul Burrow Publications

A technique is described for the study of electrons which are elastically scattered from a gas target into a small solid angle centered at 180° with respect to the direction of the incident electron beam. The method is applied to electron scattering from CO₂. Information is obtained concerning the nature of the compound state in the 4-eV region.

Studies Of Bistable Fluid Devices For Particle Flow Control, Gerald H. Hogland

Dissertations and Theses

This study was directed toward the development of a bistable wall attachment Flip-Flop device which was capable of directionally controlling particle flow. The particles were transported by a fluid stream which under the influence of wall attachment. The dominant criteria in the development of the device was the achievement of the highest recovery of particles at the active output, without destroying the wall attachment of the fluid stream The experiment was conducted in several distinct stages; each of which was concerned with at least one aspect of wa1l attachment or particle flow. Results derived from one test were used to …

Raman-Active Resonance Modes, Overtones, And Anharmonicity In Nacl:Cu+, B.N. Ganguly, Roger D. Kirby, M.V. Klein, G.P. Montgomery Jr.

Roger Kirby Publications

The existence of an impurity-activated E_g resonance mode in NaCl:Cu⁺ has been suggested by several previous experiments. Raman data presented here reveal this resonance directly and also reveal the three components of the first overtone of the 23.5-cm^-1 infrared resonance mode. The frequencies of the E_g resonance and the E_g component of the overtone are shifted as a result of a strong anharmonic coupling. Their line shapes and strengths are considerably altered by an interference between the Raman amplitudes. A reasonable fit to the data has been obtained using a simple theory.

Eigenvalues Of The 2p3pp3 And 2p3dd1,3 Bound States Of The Helium Isoelectronic Sequence, H. Doyle, M. Oppenheimer, Gordon W. F. Drake

Physics Publications

The 1Z expansion method is used to calculate the eigenvalues of the 2p3pP3 and 2p3dD1,3 states of the helium isoelectronic sequence. The results are compared to variational calculations for neutral helium. Wavelengths are predicted for a number of transitions originating in doubly excited states of the heliumlike ions up to Fe xxv. The results for neutral helium are compared to recent beam-foil experiments and alternative line identifications are made. The predicted wavelength for the 2p3dD3-2p2P3 transition is 3014, in close agreement with the line observed by Berry et al. at 3012 ± 2. © 1972 The American Physical Society.

Relativistic Corrections To Radiative Transition Probabilities, Gordon W. F. Drake

Physics Publications

The rate of spontaneous emission of radiation by a loosely bound composite system is calculated from quantum electrodynamics correct through terms of relative order α2Z2. Recent criticisms by Feinberg and Sucher of the semiclassical method of deriving the higher-order radiation coupling terms are discussed. It is proved that the Breit interaction remains valid in the presence of radiation emission and that the semiclassical and quantum-electrodynamic methods of deriving the higher-order coupling terms always yield the same results to relative order α2Z2. We discuss in particular relativistic corrections to allowed and spin-forbidden electric dipole transitions and the 1s2s S13-1s2 S01 magnetic …

Radiative Transition Rates From The 2p3p P3 And 2p3d D1,3 States Of The Helium Isoelectronic Sequence, Gordon W. F. Drake

Physics Publications

The Hylleraas-Scherr-Knight variation-perturbation method is applied to the calculation of oscillator strengths for the dominant transitions from the metastable 2p3p P3 and 2p3d D1,3 states of helium and the heliumlike ions. The results explain the absence of the 1s2pP3-2p3pP3 transition of He i from recent beam-foil excitation spectra. © 1972 The American Physical Society.

Observation Of A Broad Resonance In The 23S Excitation Of Helium By Electron Impact, G. B. Crooks, R. D. Dubois, D. E. Golden, M. Eugene Rudd

M. Eugene Rudd Publications

We have observed a broad P-wave resonance at about 50 eV primary energy in the angular distribution of electrons scattered after excitation of the 2³S state of helium. The resonance has a width of about 15 eV and affects the differential excitation cross section by more than 3 orders of magnitude. It is suggested that this resonance is associated with the temporary formation of triply excited states of the negative helium ion.

Strong, Quasiperiodic Dependence Of Autoionization Shape Parameters On Projectile Energy In H+ + He Collisions, F. D. Schowengerdt, M. Eugene Rudd

M. Eugene Rudd Publications

Profiles of the 2s² (¹S) autoionizing state in He have been observed in the ejected-electron spectrum of H⁺ + He for small angles of ejection and for H⁺ energies of 6 to 150 keV. The shape parameter q shows an increasing dependence on projectile energy as the angle of ejection is decreased, with strong, quasiperiodic oscillations appearing at 10°.

Detection Of Energetic Heavy Ions, Robert Katz, S. C. Sharma, Mehdi Homayoonfar

Robert Katz Publications

The delta-ray theory of track structure, applied earlier to such 1-or-more hit detection systems as the inactivation of dry enzymes and viruses, the NaI(Tl) scintillation counter, and nuclear emulsion, is extended to the silver activated phosphate glass dosimeter, the LiF thermoluminescent dosimeter, the creation of free radicals in solid biological substances, solid and liquid organic scintillators, and the ferrous sulfate (Fricke) dosimeter. The response of these systems to both gamma-rays and heavy ions is characterized by two parameters: 1) D_γ³⁷, the dose of gamma-rays at which 37% of the sensitive elements remain unaffected by the radiation, and …

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.

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

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.

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.

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 …