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Articles 1891 - 1920 of 1942
Full-Text Articles in Physical Sciences and Mathematics
O++ In The Venusian Ionosphere, Jane L. Fox, G. A. Victor
O++ In The Venusian Ionosphere, Jane L. Fox, G. A. Victor
Physics Faculty Publications
It is shown that the revised photochemical theory for O++ in the earth's ionopshere, where double photoionization of O is the dominant source, is consistent with recent O++ measurements on Venus. A rate coefficient of 1.5 × 10−10 cm³ s−1 for O++ + O is obtained, and the possible importance of O++ chemistry on minor atomic ions and airglow emissions is explored.
Hall Effect At High Pressure In (Snxeu1-X)1.2mo6s8, Paul D. Hambourger, C. Y. Huang, H. L. Luo
Hall Effect At High Pressure In (Snxeu1-X)1.2mo6s8, Paul D. Hambourger, C. Y. Huang, H. L. Luo
Physics Faculty Publications
No abstract provided.
An Experiment In Discovery, Daniel J. Steck
An Experiment In Discovery, Daniel J. Steck
Physics Faculty Publications
No abstract provided.
Automation Of A Popular Monochromator, David C. Look, J. W. Farmer, R. N. Ely
Automation Of A Popular Monochromator, David C. Look, J. W. Farmer, R. N. Ely
Physics Faculty Publications
A wavelength‐scan and intensity‐control system for a widely‐used, high‐intensity monochromator is described. The wavelength scan is bidirectional and variable speed, and may be controlled manually or by TTL logic from a computer. The intensity control is effected by use of a programmable dc power supply and D–A converter. Various filters are described which allow an intensity of up to 2×1014 photons/cm2 s to be achieved in a 1 cm×3 cm area over a wavelength range 0.76–2.50 μm, at 0.07 μm bandwidth, with a single grating. (A lesser intensity is available to 3.4 μm.) This wide range is made …
Electron Irradiation Defects In N-Type Gaas, J. W. Farmer, David C. Look
Electron Irradiation Defects In N-Type Gaas, J. W. Farmer, David C. Look
Physics Faculty Publications
We have studied the production and annealing of defects produced by 1-MeV electron irradiation of n-type GaAs. Two of these defects lie at 0.15 and 0.31 eV from the conduction band, respectively; in addition, there is at least one acceptor much closer to the valence band. The carrier-removal rate depends upon sample purity but is independent of the irradiation flux. The removal rate is also highly dependent upon the position of the the Fermi level, an effect which is considered in some detail. At about 200°C, the defects recover in two stages, with the respective recovery rates given by λ …
Continental Drift, Tectonics, And Joshua, Joel W. Block
Continental Drift, Tectonics, And Joshua, Joel W. Block
Physics Faculty Publications
The Bible has served as a source of spiritual inspiration for many centuries. It has been used as a text in the academic disciplines of history, geography, archeology, literature, law, language, and health, as well as in theology. Yet this multipurpose manuscript has been virtually ignored as an earth science reference It is this writer's intent to demonstrate the Bible's value as a geological resource.
Characterization Of Phase Transitions In Vanadium Deuterides, R. L. Tober, Gust Bambakidis
Characterization Of Phase Transitions In Vanadium Deuterides, R. L. Tober, Gust Bambakidis
Physics Faculty Publications
No abstract provided.
Hall-Coefficient And Resistivity At High Pressure In 1t-Tas2, Paul D. Hambourger, F. J. Disalvo
Hall-Coefficient And Resistivity At High Pressure In 1t-Tas2, Paul D. Hambourger, F. J. Disalvo
Physics Faculty Publications
No abstract provided.
Physical Consequences Of Anomalies In Nonlocal Potential Problems, L. L. Foldy, James A. Lock
Physical Consequences Of Anomalies In Nonlocal Potential Problems, L. L. Foldy, James A. Lock
Physics Faculty Publications
An s-wave two-body separable potential may give rise to several phenomena which are absent for nonsingular local potentials. We examine the physical implications of a well known example of such phenomena, the continuum bound state, as well as of two lesser known anomalies, the so-called positive energy spurious state and negative energy bound states with improper long-range behavior. By examining these anomalies in light of Levinson's theorem, Wigner's phase shift inequality, and the effect of a perturbation on the anomalous states by their insertion in a three-body scattering situation, we find in agreement with previous studies that the continuum bound …
Type Conversion In Electron‐Irradiated Gaas, J. W. Farmer, David C. Look
Type Conversion In Electron‐Irradiated Gaas, J. W. Farmer, David C. Look
Physics Faculty Publications
The unambiguous type conversion of GaAs by electron irradiation is reported here for the first time. Several high‐quality n‐type vapor‐phase epitaxial layers (ρ?3 Ω cm and μ?7000 cm2/V sec at 300 K) were converted by 1‐MeV electrons to high‐quality p‐type layers (ρ?30 Ω cm and μ?400 cm2/V sec). Temperature‐dependent Hall‐effect data show energy levels at 0.5, 0.3, and about 0.1 eV above the valence band. Evidence is presented to indicate that the failure of some of our samples (and, perhaps, other samples reported in the literature) to convert to low‐r …
Electronic Structure Calculation Of Icosahedral B-12, R. P. Wagner, Gust Bambakidis
Electronic Structure Calculation Of Icosahedral B-12, R. P. Wagner, Gust Bambakidis
Physics Faculty Publications
No abstract provided.
Ionization, Luminosity, And Heating Of The Upper Atmosphere Of Mars, Jane L. Fox, Alexander Dalgarno
Ionization, Luminosity, And Heating Of The Upper Atmosphere Of Mars, Jane L. Fox, Alexander Dalgarno
Physics Faculty Publications
A model based upon Viking data is constructed of the Martian atmosphere, and a comprehensive quantitative discussion is given of the measurements of the ultraviolet dayglow. A detailed assessment is made of the heating of the neutral and ionized components of the atmosphere arising from the absorption of ultraviolet solar radiation.
Electrical Resistivity Studies Of Order-Disorder Phenomena In V2h And V2d, Gust Bambakidis, M. W. Pershing, R. C. Bowman
Electrical Resistivity Studies Of Order-Disorder Phenomena In V2h And V2d, Gust Bambakidis, M. W. Pershing, R. C. Bowman
Physics Faculty Publications
No abstract provided.
Electron Transport In Se-Doped Lt-Tas2, Paul D. Hambourger, F. J. Disalvo
Electron Transport In Se-Doped Lt-Tas2, Paul D. Hambourger, F. J. Disalvo
Physics Faculty Publications
No abstract provided.
Role Of Low-Energy Two-Body Virtual States In Three-Particle Scattering Situations, James A. Lock
Role Of Low-Energy Two-Body Virtual States In Three-Particle Scattering Situations, James A. Lock
Physics Faculty Publications
A model three-particle scattering situation consisting of a projectile incident on a target bound to a residual core was considered under the assumptions that there was a low-energy virtual state in the projectile-target channel, that the projectile and core did not interact, and that the projectile-target and target-core interactions were s-wave separable interactions. When the appropriate Faddeev equations were solved by inversion, an enhancement was found in the three-body elastic cross section for virtual state energies less than or comparable to the target-core binding energy. This enhancement was determined to be kinematical in origin.
Infrared Spectral Detectivity Of Cr‐Doped Gaas, David C. Look
Infrared Spectral Detectivity Of Cr‐Doped Gaas, David C. Look
Physics Faculty Publications
The room‐temperature spectral detectivity of Cr‐doped GaAs has been examined in the impurity excitation region out to 1.7 μ, a range which includes the wavelengths of several important lasers as well as low‐loss optical fibers. The results include values of D∗ greater than 1011 cm Hz1/2/W in the photoconductive mode, and 1010 cm Hz1/2/W in the photomagnetoelectric mode. Small carrier lifetimes, ∼10−8 sec, offer the potential of high‐speed operation; however, the measured response times are much larger, ∼10−3–10−2 sec, because of very high input impedances. Formulas are presented to …
Isospin Forbidden And Allowed Reactions 16O(Α,Α0)160 And 160(Α,Γ)20Ne, Daniel J. Steck
Isospin Forbidden And Allowed Reactions 16O(Α,Α0)160 And 160(Α,Γ)20Ne, Daniel J. Steck
Physics Faculty Publications
Six 20Ne levels have been investigated in detail via the 16O+α channel between 6.9≤Eα≤10.2 MeV. Level parameters for states at Ex(20Ne)=10.264±0.008, 11.077±0.008, 11.259±0.008, 11.552±0.008,12.237±0.008, and 12.390±0.008 MeV have been extracted from γ decay properties and phase shift analysis of the elastic scattering. With the exception of the 11.552 and 12.39 MeV states, these levels display primarily TT=0 states, several other weak γ decaying resonances were observed at 11.97 ± 0.04, 12.05 ± 0.04, and 12.49 ± 0.02 MeV but were not studied in detail. Charge dependent matrix elements (4-120 …
Interpretation Emphasis In Exploration Geophysics, Paul J. Wolfe, Benjamin H. Richard
Interpretation Emphasis In Exploration Geophysics, Paul J. Wolfe, Benjamin H. Richard
Physics Faculty Publications
No abstract provided.
Magnetoresistance Of 1t-Tase2, Paul D. Hambourger, F. J. Disalvo
Magnetoresistance Of 1t-Tase2, Paul D. Hambourger, F. J. Disalvo
Physics Faculty Publications
No abstract provided.
Impurity Photomagnetoelectric Effect: Application To Semi-Insulating Gaas, David C. Look
Impurity Photomagnetoelectric Effect: Application To Semi-Insulating Gaas, David C. Look
Physics Faculty Publications
The theories of the photomagnetoelectric (PME) and photoconductivity (PC) effects in semiconductors are extended to include unequal excitation rates of holes and electrons, as might be expected from impurity photo-excitation. The results are applied to two semi-insulating Cr-doped GaAs crystals, which exhibit mixed conductivity. It is seen that the PC and PME effects give complementary information on the holes and electrons. In the impurity excitation region the PME current responds strongly to changes in the absorption coefficient, and provides a convenient way to study this quantity.
The Electrical Characterization Of Semi‐Insulating Gaas: A Correlation With Mass‐Spectrographic Analysis, David C. Look
The Electrical Characterization Of Semi‐Insulating Gaas: A Correlation With Mass‐Spectrographic Analysis, David C. Look
Physics Faculty Publications
The room‐temperature electrical properties of 28 semi‐insulating GaAs crystals have been determined by using a mixed‐conductivity analysis. It is shown that for most of these samples, such an analysis gives good accuracy for the electron mobility μn and electron concentration n, but poorer accuracy for the hole mobility μp, hole concentration p, and intrinsic concentration ni. The intrinsic concentration is determined at 296 °K to be ni ≈ (1.7±0.4) ×106 cm−3, which compares favorably with the theoretical value deduced from the band gap and the effective masses. From a …
Astronomy And The Bible: Joshua's Long Day, Joel W. Block
Astronomy And The Bible: Joshua's Long Day, Joel W. Block
Physics Faculty Publications
The Bible has served as a multipurpose text for thousands of years. However, the Bible has been ignored in the area of astronomy. Several teaching points can be demonstrated using the Bible stories and modern astronomical principles.
Fermi-Surface Topology Of 2h-Tase2 At 4.2k, Paul D. Hambourger
Fermi-Surface Topology Of 2h-Tase2 At 4.2k, Paul D. Hambourger
Physics Faculty Publications
The magnetoresistance of single-crystal 2H-TaSe2 in the commensurate charge-density-wave state has been measured at 4.2 K in magnetic fields up to 48 kG. The results indicate that the Fermi surface supports open orbits parallel to the [0001] direction for all orientations of magnetic field in the (0001) plane. No evidence of open orbits in other directions was observed.
The Nitrogen Dayglow On Mars, Jane L. Fox, Alexander Dalgarno, E. R. Constantinides, G. A. Victor
The Nitrogen Dayglow On Mars, Jane L. Fox, Alexander Dalgarno, E. R. Constantinides, G. A. Victor
Physics Faculty Publications
The ultraviolet dayglow spectrum arising from emission of N2 in the Mars atmosphere is predicted. The intensities are such that a high-resolution spectrum should readily reveal the presence of N2 at the abundances suggested by the Viking experiments.
Radiative Transition Probabilities Of The 1S2P22P And 1S2P22D States Of The Lithium Isoelectronic Sequence, Jane L. Fox, Alexander Dalgarno
Radiative Transition Probabilities Of The 1S2P22P And 1S2P22D States Of The Lithium Isoelectronic Sequence, Jane L. Fox, Alexander Dalgarno
Physics Faculty Publications
A Z-expansion procedure is used to obtain eigenvalues and eigenfunctions for the 1s22p2Po, 1s2p22P, and 1s2p22D states of the lithium sequence. Expansions in inverse powers of the nuclear charge Z are obtained also for the dipole-matrix elements and oscillator strengths of the 1s22p2Po-1s2p22P and 1s22p2Po-1s2p22D transitions, valid for Z > 3. …
Positron Annihilation In Copper, K. White, W. H. Rickles, Thomas Listerman
Positron Annihilation In Copper, K. White, W. H. Rickles, Thomas Listerman
Physics Faculty Publications
No abstract provided.
A Geomagnetic Survey Of Greene County, Ohio, V. E. D. Obot, Paul J. Wolfe
A Geomagnetic Survey Of Greene County, Ohio, V. E. D. Obot, Paul J. Wolfe
Physics Faculty Publications
No abstract provided.
Search For Volume Anomaly In Paramagnetic Zrzn2, Paul D. Hambourger
Search For Volume Anomaly In Paramagnetic Zrzn2, Paul D. Hambourger
Physics Faculty Publications
No abstract provided.
Multiple Rainbows From Single Drops Of Water And Other Liquids, Jearl D. Walker
Multiple Rainbows From Single Drops Of Water And Other Liquids, Jearl D. Walker
Physics Faculty Publications
The scattering of light by spherical drops and the theory of rainbows are reviewed in detail to predict the angular positions of rainbows from single drops. The angular positions of the first 13 rainbows of water, observed from a drop suspended in a student spectrometer, were compared to these theoretical positions. Since the rainbows were dependent on the refractive index, the positions shifted with drops of other fluids having other refractive indices. Light corn syrup yielded 11 rainbows, including the 17th-order one. The light emerging from the drops was white except for the multicolors of the rainbows and the faint …
Hall-Effect Measurements In Cd-Implanted Gaas, B. K. Shin, David C. Look, Y. S. Park, J. E. Ehret
Hall-Effect Measurements In Cd-Implanted Gaas, B. K. Shin, David C. Look, Y. S. Park, J. E. Ehret
Physics Faculty Publications
Cadmium ions were implanted in GaAs crystals at 135 keV to doses ranging from 1012 to 1016 ion/cm2 at room temperature. Sheet‐resistivity and Hall‐effect measurements were carried out as a function of temperature, 4.2–300°K, after annealings at 700, 800, or 900°C in an Ar ambient. The sample surfaces were protected with pyrolytically deposited Si3N4. Significant p‐type conduction was observed when samples with doses ≳1013cm−2 were annealed at ≳700°C. For doses below 1014 cm−2 nearly complete electrical activity was attained after an 800–900°C anneal. The Cd profiles were …