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Articles 35161 - 35190 of 36527

Full-Text Articles in Physical Sciences and Mathematics

Generalization Of The Rosen-Zener Model Of Noncrossing Interactions. Ii. Differential Cross Sections., T. R. Dinterman, John B. Delos Feb 1977

Generalization Of The Rosen-Zener Model Of Noncrossing Interactions. Ii. Differential Cross Sections., T. R. Dinterman, John B. Delos

Arts & Sciences Articles

The generalized Rosen-Zener model developed in the accompanying paper is used to calculate differential cross sections for a model noncrossing system, and the structure of the cross sections is explained in terms of the deflection functions. It is found that the angular threshold effects that are typical of potential-curve crossings do not appear in this noncrossing system.

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Generalization Of The Rosen-Zener Model Of Noncrossing Interactions. I. Total Cross Sections, T. R. Dinterman, John B. Delos Feb 1977

Generalization Of The Rosen-Zener Model Of Noncrossing Interactions. I. Total Cross Sections, T. R. Dinterman, John B. Delos

Arts & Sciences Articles

The formalism developed previously to study electronic transitions by the curve-crossing mechanism is used to obtain a general model for transitions which take place due to the strong coupling of curves which do not cross. This exactly solvable model is a generalization of a model developed by Rosen and Zener. The model is shown to give respectable agreement with exact calculations at low velocities, and to go to the correct resonant-charge-exchange limit at high velocities. Predictions of the model are shown to give good agreement with the measured total cross sections for charge exchange in the sytem Li+ + Na⇄Li+Na+.

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Influence Of Fringing Fields On The Field-Induced Quantum Beats Of Atomic Hydrogen, Gordon W. F. Drake Jan 1977

Influence Of Fringing Fields On The Field-Induced Quantum Beats Of Atomic Hydrogen, Gordon W. F. Drake

Physics Publications

Calculations are presented which include exactly the effects of fringing fields on the electric-field-induced quantum beats of atomic hydrogen. The results explain some recently observed phaseshifts of the quantum beats relative to the predictions of the 'sudden approximation'. The general features produced by finite rise-time and overshoot are discussed.

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Vector-Coupling Approach To Orbital And Spin-Dependent Tableau Matrix Elements In The Theory Of Complex Spectra, Gordon W. F. Drake, M. Schlesinger Jan 1977

Vector-Coupling Approach To Orbital And Spin-Dependent Tableau Matrix Elements In The Theory Of Complex Spectra, Gordon W. F. Drake, M. Schlesinger

Physics Publications

The power of the Young tableau scheme for labeling a complete spin-adapted basis set in the theory of complex spectra lies in one's ability to evaluate matrix elements of irreducible tensor operators directly in terms of the tableau labels and shapes. We show that the matrix-element rules stated by Harter for one-body operators can be easily derived from simple vector-coupling considerations. The graphical method of angular momentum analysis is used to derive closed-form expressions for the matrix elements of two-body operators. This study yields several interesting new relationships between spin-dependent operators and purely orbital operators. © 1977 The American Physical …

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Spin-Orbit Parameters By The Gelfand-Harter Method-A Test Calculation, J. Drake, Gordon W. F. Drake, M. Schlesinger Jan 1977

Spin-Orbit Parameters By The Gelfand-Harter Method-A Test Calculation, J. Drake, Gordon W. F. Drake, M. Schlesinger

Physics Publications

The spin-orbit parameters for the sextet states of the f5 configuration are computed using the Young-tableau techniques developed by Harter. The conceptual and computational advantages over traditional methods are discussed. © 1977 The American Physical Society.

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Nuclear Spin-Lattice Relaxation And Activation Energies Of Tunnelling Methyl Groups, Peter A. Beckmann, S. Clough Jan 1977

Nuclear Spin-Lattice Relaxation And Activation Energies Of Tunnelling Methyl Groups, Peter A. Beckmann, S. Clough

Physics Faculty Research and Scholarship

The coupling of lattice vibrations with the rotational motion of hindered methyl groups is considered. It is shown that the apparent activation energy for methyl group rotation is determined at relatively high temperatures by the methyl group torsional energy splittings, but at low temperatures it depends on the frequencies of short-wavelength lattice modes which couple relatively strongly with methyl-group rotation. The temperature dependence of the proton spin lattice relaxation time from 6 to 50K is reported for three samples containing methyl groups whose tunnelling frequencies have previously been measured very precisely. They are 4-methyl-2,6-ditertiarybutylphenol (MDBP) and two deuterated derivatives. The …

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The Haupt Effect: Coupled Rotational And Dipolar Relaxation Of Methyl Groups, Peter A. Beckmann, S. Clough, J. W. Hennel, J. R. Hill Jan 1977

The Haupt Effect: Coupled Rotational And Dipolar Relaxation Of Methyl Groups, Peter A. Beckmann, S. Clough, J. W. Hennel, J. R. Hill

Physics Faculty Research and Scholarship

A theory is described for the dynamic proton dipolar polarization observed by Haupt (1972) in 4-methylpyridine following a sudden temperature change. The theory differs from that of Haupt in assuming that transitions which change the rotational quantum number of the 4-methyl group by +or-3 occur very rapidly, maintaining thermal equilibrium within each of the three subsets of rotational levels corresponding to the three methyl group proton spin symmetry species A, Ea and Eb. The difference of A and E species populations approaches the new equilibrium value slowly and exponentially, following the temperature jump, and generates dipolar polarization in the process. …

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Nuclear Spin Relaxation And Centrifugal Distortion Effects In Dilute Silane Gas, Peter A. Beckmann, E. E. Burnell Jan 1977

Nuclear Spin Relaxation And Centrifugal Distortion Effects In Dilute Silane Gas, Peter A. Beckmann, E. E. Burnell

Physics Faculty Research and Scholarship

We have measured the proton longitudinal spin relaxation rate in dilute gaseous silane (SiH4) between 10−2 and 1 amagats and are able to observe the influence of rotational Q branch centrifugal distortion transitions.

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Absolute Doubly Differential Cross Sections For Ejection Of Secondary Electrons From Gases By Electron Impact. I. 100- And 200-Ev Electrons On Helium, M. Eugene Rudd, R. D. Dubois Jan 1977

Absolute Doubly Differential Cross Sections For Ejection Of Secondary Electrons From Gases By Electron Impact. I. 100- And 200-Ev Electrons On Helium, M. Eugene Rudd, R. D. Dubois

M. Eugene Rudd Publications

We have measured absolute values of the cross sections for ejection of electrons from helium gas by 100- and 200-eV electrons. These cross sections were measured for emission angles from 10° to 150° and for electron energies from 3 eV to a value equal to the primary energy minus the ionization potential. The measurements were made using a static-gas target and an electrostatic analyzer. The resulting cross sections agree reasonably well with those of Opal, Peterson, and Beaty near 90°, but show the need for an adjustment of their angular distributions. Comparison with Born-approximation calculations of Manson et al. at …

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Energy And Angular Distribution Of Electrons Ejected From Argon By 5-Kev To 1.5-Mev Protons, T. L. Criswell, L. H. Toburen, M. Eugene Rudd Jan 1977

Energy And Angular Distribution Of Electrons Ejected From Argon By 5-Kev To 1.5-Mev Protons, T. L. Criswell, L. H. Toburen, M. Eugene Rudd

M. Eugene Rudd Publications

Cross sections, differential in emission energy and angle, have been measured for the ejection of electrons in collisions of H+ with argon gas targets. Incident-proton energies studied were from 5 keV to 1.5 MeV and electron emission angles ranged from 10° to 160°. Integration of the double-differential cross sections over emission angle and energy yield results in good agreement with direct measurement of total ionization cross sections. The electron distributions are compared to two plane-wave Born-approximation calculations, one using Hartree-Slater wave functions and the other using Hartree-Fock wave functions in the 3p-εd channel.

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Saturated Superfluid 4he Film Flow: Characteristic Oscillations Induced By Persistent Circulation, Robert Hallock, R. K. Galkiewicz Jan 1977

Saturated Superfluid 4he Film Flow: Characteristic Oscillations Induced By Persistent Circulation, Robert Hallock, R. K. Galkiewicz

Robert Hallock

We report observations of characteristic reservoir oscillations induced by persistent circulation in saturated 4He films for several different geometries. The shape of the oscillation structure appears to be in qualitative agreement with the predictions of Campbell. Within the constraints imposed by theoretical approximations and uncertainties in the experimental parameters, the quantitative agreement is satisfactory.

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Compton's 'Crucial Test' - Theoretical Preconceptions And Experimental Interpretation, Roger H. Stuewer Jan 1977

Compton's 'Crucial Test' - Theoretical Preconceptions And Experimental Interpretation, Roger H. Stuewer

Journal of the Minnesota Academy of Science

Arthur Holly Compton, as a result of his own research and confidence in the validity of classical electrodynamics, was convinced in 1921 that homogeneous x-rays and gamma rays could be affected in only two possible ways when passing through matter: either they gave rise to "truly scattered" radiation of the same wavelength as that of the incident rays, or they excited "fluorescent" radiation of a longer wavelength. When Compton was led to carry out experiments using homogeneous x-rays and actually found secondary radiation of longer wavelength, he regarded his result as a crucial test between the "truly scattered" and the …

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Atomic Numbers Revalued, Frank H. Meyer Jan 1977

Atomic Numbers Revalued, Frank H. Meyer

Journal of the Minnesota Academy of Science

As a general physical theory, the Reciprocal System of D.B. Larson covers all physical fields, including atomic physics . Inasmuch as all of the conclusions reached in the theoretical development are derived entirely by deduction from the basic postulates of this system, the conclusions provide information that is completely independent of observation. The theoretical development indicates that the Mosely atomic number mathematical formula is quite right, and the Rutherford-Bohr-Mosely nuclear atom physical interpretation of atomic number is seriously wrong. The discrete units constituting atoms evidently are not neutrons and electrically charged particles. Nor are atoms made up of parts, a …

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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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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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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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The Nitrogen Dayglow On Mars, Jane L. Fox, Alexander Dalgarno, E. R. Constantinides, G. A. Victor Jan 1977

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.

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Radiative Transition Probabilities Of The 1S2P22P And 1S2P22D States Of The Lithium Isoelectronic Sequence, Jane L. Fox, Alexander Dalgarno Jan 1977

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. …

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Positron Annihilation In Copper, K. White, W. H. Rickles, Thomas Listerman Jan 1977

Positron Annihilation In Copper, K. White, W. H. Rickles, Thomas Listerman

Physics Faculty Publications

No abstract provided.

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A Geomagnetic Survey Of Greene County, Ohio, V. E. D. Obot, Paul J. Wolfe Jan 1977

A Geomagnetic Survey Of Greene County, Ohio, V. E. D. Obot, Paul J. Wolfe

Physics Faculty Publications

No abstract provided.

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Four-Color And Hβ Photometry Of Stars In Ngc 7654 And M25, Edward G. Schmidt Jan 1977

Four-Color And Hβ Photometry Of Stars In Ngc 7654 And M25, Edward G. Schmidt

Edward Schmidt Publications

Four-color and Hβ photometry has been obtained of stars in the galactic clusters NGC 7654 and M25. An analysis of these data shows variable extinction in both clusters. The distance modnlus of NGC 7654 is found to be 10m.99 ± 0.2 and that of M25 is 8m.68 ± 0.1.

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Eclipsing Systems In Star Structures. Iii. Early-Type Contact System Bh Centauri, Kam-Ching Leung, Donald P. Schneider Jan 1977

Eclipsing Systems In Star Structures. Iii. Early-Type Contact System Bh Centauri, Kam-Ching Leung, Donald P. Schneider

Department of Physics and Astronomy: Faculty Publications

Close to 1000 photoelectric observations of BH Cen in the yellow, blue, and ultraviolet regions were analyzed. The period found was 0.791616 days. The depths of minima were about equal, and were more than 1 magnitude! A photometric solution was derived with the Wilson and Devinney model. The binary is an overcontact system with primary and secondary masses equal to 10 M?. Based on its membership in IC 2944 and the size of the primary radius, BH Cen may be another example of a zero-age contact system.

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Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Functional-Derivative Approach, John D. Ramshaw Jan 1977

Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Functional-Derivative Approach, John D. Ramshaw

Physics Faculty Publications and Presentations

In a previous article [J. Chem. Phys. 57, 2684 (1972)] sufficient conditions were established for the existence of the dielectric constant ɛ in rigid-dipole fluids. One of these conditions was an unrealistic restriction on the angular dependence of the direct correlation function c (12) at short range. Here it is shown that this restriction can be removed without altering the previous conclusions. Consequently, ɛ rigorously exists if c (12) depends only upon relative positions and orientations of molecules 1 and 2, and becomes asymptotic to -φd(12)/kT at long range, where φd(12) is the dipole-dipole potential. The development is based upon …

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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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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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Electron And Ion Temperatures—A Comparison Of Ground-Based Incoherent Scatter And Ae-C Satellite Measurements, R F. Benson, P Bauer, L H. Brace, Herbert C. Carlson, J Hagen, W B. Hanson, W R. Hoegy, M R. Torr, R H. Wand, Vincent B. Wickwar Jan 1977

Electron And Ion Temperatures—A Comparison Of Ground-Based Incoherent Scatter And Ae-C Satellite Measurements, R F. Benson, P Bauer, L H. Brace, Herbert C. Carlson, J Hagen, W B. Hanson, W R. Hoegy, M R. Torr, R H. Wand, Vincent B. Wickwar

All Physics Faculty Publications

The Atmosphere Explorer-C satellite (AE-C) is uniquely suited for correlative studies with ground-based stations because its on-board propulsion system enables a desired ground station overflight condition to be maintained for a period of several weeks. It also provides the first low-altitude (below 260 km) comparison of satellite and incoherent scatter electron and ion temperatures. More than 40 comparisons of remote and in situ measurements were made by using data from AE-C and four incoherent scatter stations (Arecibo, Chatanika, Millstone Hill, and St. Santin). The results indicate very good agreement between satellite and ground measurements of the ion temperature, the average …

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The Plasma Line Revisited As An Aeronomical Diagnostic: Suprathermal Electrons, Solar Euv, Electron‐Gas Thermal Balance, Herbert C. Carlson, Vincent B. Wickwar, G P. Mantas Jan 1977

The Plasma Line Revisited As An Aeronomical Diagnostic: Suprathermal Electrons, Solar Euv, Electron‐Gas Thermal Balance, Herbert C. Carlson, Vincent B. Wickwar, G P. Mantas

All Physics Faculty Publications

Spectra of plasma wave intensities (kTp) in the ionosphere over Arecibo are calculated and compared with those from observations of the plasma line intensity. This approach involving directly observed quantities avoids the uncertainties that have plagued past comparisons with photoelectron theory. In addition, careful comparisons in physically relevant segments of the spectra show that any significant increase in the magnitude of the solar EUV flux would lead to a contradiction of the observed plasma wave intensities. Further, the comparisons indicate that resolution of the thermal electron‐gas heat balance problem must be sought through better heat transfer rates (e.g., …

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Property And Tort In Nuclear Law Today, Kazimierz Grzybowski, William Dobishinski Jan 1977

Property And Tort In Nuclear Law Today, Kazimierz Grzybowski, William Dobishinski

Faculty Scholarship

No abstract provided.

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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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