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Angular-Differential Studies Of Excitation In Quasi-One-Electron Collisions At "High" Energy, E. Redd, Timothy Gay, D. M. Blankenship, John T. Park, Jerry Peacher, Denver G. Seely

Physics Faculty Research & Creative Works

Qualitative differences have been observed between two types of "quasi-one-electron" collision systems. We have studied valence-electron excitation at "high" energy (relative collision velocities up to 0.5 a.u.) in the Mg⁺+He and Na⁺+H collision systems, and find that while Mg⁺+He collisions are dominated by "direct" excitation, the Na⁺+H collisions exhibit significant "molecular" excitation, even at the highest velocities. This behavior can be understood in terms of the molecular structure of the respective collision complexes, and the energy separation between the ground and first excited states of the valence electron.

Angular-Differential Studies Of Excitation In Quasi-Oneelectron Collisions At "High" Energy, E. Redd, Timothy J. Gay, D. M. Blakenship, J. T. Park, J. L. Peacher, D. G. Seely

Timothy J. Gay Publications

Qualitative differences have been observed between two types of "quasi-one-electron" collision systems. We have studied valence-electron excitation at "high" energy (relative collision velocities up to 0.5 a.u.) in the Mg⁺+He and Na⁺+H collision systems, and find that while Mg⁺+He collisions are dominated by "direct" excitation, the Na⁺+H collisions exhibit significant "molecular" excitation, even at the highest velocities. This behavior can be understood in terms of the molecular structure of the respective collision complexes, and the energy separation between the ground and first excited states of the valence electron.

The Effects Of A Mandatory Early Shutdown Of Maine Yankee, Maine State Planning Office

Maine Collection

The Effects of a Mandatory Early Shutdown of Maine Yankee

Maine State Planning Office - Richard Silkman, Director (September 1987).

Contents: Introduction / Legal Issues / Economic Issues / Health and Environmental Issues / Conclusions / Appendices

High Acceptor Production Rate In Electron-Irradiated N-Type Gaas - Impact On Defect Models, David C. Look

Physics Faculty Publications

Defect production rates have been studied in electron-irradiated GaAs by temperature-dependent Hall-effect (TDR) measurements. The TDH results agree well with deep level transient spectroscopy (DLTS) results for the wen-known electron traps E1, E2, and E3, but conclusively demonstrate a much higher production rate (4 ± 1 cm^-1) of acceptors below E3 than the total of all other DLTS traps. These findings strongly affect current defect models, and, e.g., are consistent with the existence of Ga sublattice damage, not seen before.

Energy-Transfer Theory For The Classical Decay Rates Of Molecules At Rough Metallic Surfaces, P.T. Leung, Thomas F. George

Physics Faculty Publications and Presentations

The problem of the decay rates for molecules at rough metallic surfaces is considered, where the classical electromagnetic energy-transfer theory of Chance, Prock, and Silbey for a flat surface is generalized to the case of a rough boundary. A dynamical theory is constructed through the combination of the Sommerfeld antenna theory and the integral equation formalism of Maxwell's equations at rough boundaries established mainly by Maradudin, Mills, and Agarwal. Perturbative solutions are obtained and numerical results are given with reference to a shallow sinusoidal grating surface. The results, when compared with those obtained previously from the application of the image …

N-Level Quantum Systems With Su(2) Dynamic Symmetry, Foek T. Hioe

Physics Faculty/Staff Publications

We present an analytic solution of the coherent evolution of a laser-driven N-level quantum system that possesses an SU(2) dynamic symmetry.

Contributions Of Higher Partial Waves To The Elastic Scattering Amplitude For Various Long Range Interactions, J M. Wadehra, Sultana N. Nahar

Physics and Astronomy Faculty Research Publications

The contributions of higher partial waves to the elastic scattering amplitude are dominated by long-range interactions which fall off as r^(−n) as r→∞. Closed-form expressions for the contributions of higher partial waves (2l>n-3) to the scattering amplitude for various long-range interactions (n ranging from 3 to 8) are presented.

Theoretical Studies Of Electron Transfer In Metal Dimers: Xy+→X+Y, Where X, Y=Be, Mg, Ca, Zn, Cd, Robert J. Cave, David V. Baxter, William A. Goddard Iii, John D. Baldeschwieler

All HMC Faculty Publications and Research

The electronic matrix element responsible for electron exchange in a series of metal dimers was calculated using ab initio wave functions. The distance dependence is approximately exponential for a large range of internuclear separations. A localized description, where the two nonorthogonal structures characterizing the electron localized at the left and right sites are each obtained self‐consistently, is found to provide the best description of the electron exchange process. We find that Gaussian basis sets are capable of predicting the expected exponential decay of the electronic interactions even at quite large internuclear distances.

Molecular Lifetimes In The Presence Of Periodically Roughened Metallic Surfaces, P.T. Leung, Z. C. Wu, Daniel A. Jelski, Thomas F. George

Physics Faculty Publications and Presentations

The lifetimes of molecules located close to a sinusoidal grating surface are studied within a classical phenomenological model. The contribution of surface roughness to the molecular decay rate is attributed to the discrepancy between the experiments of Rossetti and Brus and the theory of Chance, Prock, and Silbey. It is found that surface roughness can either enhance or diminish the flat-surface value for the decay rate depending on the emitting frequency, molecule-surface distance, and the molecular orientation.

Length-Independent Voltage Fluctuations In Small Devices, A. Benoit, C. P. Umbach, R. B. Laibowitz, Richard A. Webb

Faculty Publications

Conductance fluctuations in one-dimensional lines of length L shorter than the phase-coherence length L_φ are not universal but diverge as L^-2. Using the Onsager relations and voltage additivity, we show that the voltage fluctuations are independent of the distance between voltage probes. The antisymmetric (Hall-type) contribution to the voltage fluctuations is constant for all values of L. Measurements of the voltage fluctuations and correlation function between different regions in Au and Sb lines confirm these results.

University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker

Physics Faculty Research & Creative Works

The Graduate Center for Cloud Physics Research at UMR has developed a cloud simulation facility to study phenomena occurring in terrestrial clouds and fogs. The facility consists of a pair of precision cooled-wall expansion chambers along with extensive supporting equipment. The smaller of these chambers, described in this article, is fully operational, and is capable of simulating a broad range of in-cloud thermodynamic conditions. It is currently being used to study water drop growth and evaporation for drops nucleated (activated) on well-characterized aerosol particles. Measurements have been made not only for continuous expansions (simulated updraft) but also for cyclic conditions, …

Variational Principles Of Fluid Mechanics And Electromagnetism: Imposition And Neglect Of The Lin Constraint, Ross Roundy Allen Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Variational principles in classical fluid mechanics and electromagnetism have sprinkled the literature since the eighteenth century. Even so, no adequate variational principle in the Eulerian description of matter was had until 1968 when an Eulerian variational principle was introduced which reproduces Euler's equation of fluid dynamics. Although it successfully produces the appropriate equation of motion for a perfect fluid, the variational principle requires imposition of a constraint which was not fully understood at the time the variational principle was introduced. That constraint is the Lin constraint. The Lin constraint has subsequently been utilized by a number of authors who have …

Reduced-Mass Fock-Tani Representations For A+ + (B+C-) --> (A+C-) + B+ And First-Order Results For {Abc} = {Ppe, Epe, Μpμ, Μdμ, And Μtμ}, Jack C. Straton

Physics Faculty Publications and Presentations

The Fock-Tani transformation in the Jacobi three ⟶ two-body reduced-mass system is carried out and the first-order T matrix is found to be identical to that for the full three-body transformation. The Fock-Tani transformation in the reduced-mass system in which particle b is fixed at the origin is found to give a first-order T matrix with an error of m_c /m_b in the initial momentum wave function. First-order differential and total cross sections are calculated for a⁺ + (b⁺c^-)⟶(a⁺c^-) + b⁺ where |abc|= { …

Mössbauer Study Of Spin Reorientation In Y1.8Er0.2Fe14B, M. Abe , Sy_Hwang Liou, C.L. Chien, N.C. Koon, B.N. Das, E. Callen

Sy-Hwang Liou Publications

Fe⁵⁷ Mössbauer spectra were taken from 300 K down to 4.2 K for two single-crystal samples of Y_1.8Er_0.2Fe₁₄B, one cut with its [001] axis normal to the surface, the other with its diagonal of [100], [010], and [001] axes normal to the surface. The former sample has shown that the angle between the Fe spin and the [001] increases continuously below ~90 K. This qualitatively agrees with the spin reorientation (i.e., the easy axis of magnetization rotates away from the [001] toward [100] on cooling below ~90 K) which have already been observed …

Radiosensitivity Parameters For Neoplastic Transformations In C3h10t1/2 Cells, M. P. R. Waligorski, G. L. Sinclair, Robert Katz

Robert Katz Publications

We have evaluated radiosensitivity parameters for cellular transformation from published experimental data on neoplastic transformations induced in C3H10T1/2 cells by BEVALAC ions. The measured RBE values are well reproduced by a track theory calculation using sets of m-target parameters with either m = 2 or m = 3, suggesting a quadratic or cubic extrapolation to low doses of γ rays. Using track theory one is thus able to predict transformation frequencies in those cells after an arbitrary radiation field, under known or assumed conditions of exposure, in a manner shown earlier for cellular survival. Extension of these calculations to interpret …

Excitation Of The Isobaric Analog State Of ¹⁶⁵Ho By Pion Single-Charge Exchange, William J. Fickinger

Faculty Scholarship

Forward-angle differential cross sections for the 165Ho(π+,π0)165Er(IAS) reaction have been measured at Tπ=98.0, 163.2, and 228.3 MeV in the angular range & ≲14°. The shapes of the angular distributions at 98.0 and 163.2 MeV are compared to predictions arising from the strong absorption model of pion single-charge exchange scattering. Extrapolated 0° cross sections are compared with trends previously established with mostly spherical and near-spherical nuclei. The measurement demonstrates the possibility of using the (π+,π0) reaction for studying neutron density deformations in oriented 165Ho.

Separated Resonances In Simultaneous Capture And Excitation Of S¹⁵⁺ In H₂ Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch

Physics Faculty Research & Creative Works

We have measured cross sections for the correlated emission of two K x rays following the collision of hydrogenlike sulfur ions with H₂ in the energy range between 70 and 160 MeV. The observation of the two correlated x rays is interpreted as a resonant capture of a target electron accompanied by simultaneous excitation of the projectile in the collision (RTE). By our distinguishing between Kα and Kβ lines, contributions from KLL and KLn (n≥M) resonances could be determined independently.

On A Moving Boundary Problem Of Transitional Ballistics, Jen-Ing G. Hwang

Mathematics & Statistics Theses & Dissertations

A major problem which arises in computer simulation of the firing of a gun weapon is the development of numerical schemes which effectively account for the physics of projectile motion. The chief difficulty is that away from the projectile the calculation is ordinarily accomplished on a fixed numerical grid, whereas due to projectile movement some cells of the grid near the projectile undergo volume changes as the calculation proceeds. A local finite volume scheme is developed which accounts for the expansion or compression of cells fore-and-aft of the projectile. Through the process of numerical experiment, the effectiveness of the scheme …

A Study Of The Direct Capture Process Of Protons By 27Al, Rozana Hussain

Masters Theses

An experimental investigation of the 27Al(p,γ)²⁸Si reaction was made for protons in the energy range 550- to 1785-keV and at angles of 0, 20, 55, 90 and 118 degrees. Four angular distributions at E_p = 845-, 1055-, 1135-, and 1618-keV were selected for detailed study. These angular distributions were fit with theoretical calculations employing a directcapture model. These fits permitted the extraction of spectroscopic factors for the population of the first excited-state in ²⁸Si by proton transfer.

Science And Society Test X: Energy Conservation, David W. Hafemeister

Physics

United States energy consumption has remained essentially constant at about 80 exajoules/year (75 quads/year) since the oil embargo of 1973–1974, while the GNP in constant dollars has increased by about 30%. This article will discuss the physics behind some of these improvements in end-use efficiency in such areas as: (i) buildings (scaling laws, "free-heat,'' superinsulated houses, thermal storage in large buildings, off-peak cooling), (ii) solar energy (passive, photovoltaics), (iii) utility load management ("smart meters,'' capital recovery fees, voltage control), (iv) appliances (life-cycle costs, refrigerators), and (v) lighting (isotopic enhancement).

Inactivation Of Dry Enzymes And Viruses By Energetic Heavy Ions, M. P. R. Waligorski, Kim Sun Loh, Robert Katz

Robert Katz Publications

A newly developed corrected formula for the radial distribution of dose (RDD) has been used to calculate cross sections for the inactivation of dry enzymes and viruses by heavy ions ranging from ⁴₂He to ⁴⁰₁₈ Ar of energies ca. 10 MeV/a.m.u., spanning a range of LET of ca. 5–2,000 Me V cm² g^–1. In comparison with earlier “point-target” calculations of Butts and Katz where a linear range-energy relationship for electrons (δ-rays) was used, and with “extended-target” calculations of Zhang, Dunn, and Katz, where a power range-energy law and an “uncorrected” RDD formula …

Two-Dimensional Polymer Melts, Rolfe G. Petschek

Faculty Scholarship

We discuss the asymptotic highmolecular-weight behavior of flexible, weakly repulsive polymer chains in melts, both through an analogy to an O(n) model of magnets and directly. We show that such polymers are slightly expanded in two dimensions so that in the limit of very high molecular weight, polymers interpenetrate strongly and the fraction of the monomers belonging to a polymer within the radius of gyration of that polymer tends to zero logarithmically. The molecular-weight or length-scale dependence of the radius of gyration, osmotic pressure, and end-end scattering function is given. The range of parameters for which this behavior is expected …

Multicritical Susceptibility Sum Rules, Miron Kaufman, Michael Ma

Physics Faculty Publications

Asymptotically close to the Nth-order multicritical point of an N-phase system, there are N-1 sum rules involving the mean-field susceptibilities measured in each of the coexisting phases. These sum rules provide the experimentalist a convenient and stringent test of the theory. In particular, they facilitate the detection of nonclassical effects, especially valuable for N>3 where the fluctuation effect is dominated by the classical contribution for three-dimensional systems.

Transport Anisotropy And Percolation In The Two-Dimensional Random-Hopping Model, Kalyan P. Kundu, Paul Ernest Parris, Philip W. Phillips

Physics Faculty Research & Creative Works

We consider hopping transport on an anisotropic two-dimensional square lattice. The displacements parallel to one axis are governed by uniform, nearest-neighbor hopping rates c, while the displacements parallel to the other axis are governed by static but spatially fluctuating rates w_n. Adapting a new class of generating functions recently introduced for the random-trapping problem, we are able to obtain expressions for the mean-square displacement in the fluctuating direction through an exact decoupling of the effects due to displacements in the uniform direction. The resulting expressions for the low-frequency diffusion coefficient D(ε) are exact in the limits c →0 …

Fourier Transform Of The Product Of N One-Center Hydrogenic Orbitals, Jack C. Straton

Physics Faculty Publications and Presentations

Integrating the radial part of the Fourier transform of the product of N hydrogenic orbitals results in an associated Legendre function that can be reduced to a finite series of elementary functions. This transform is found to depend on a polynomial in the wave vector k divided by a binomial in k² raised to a power that is the sum of principle quantum numbers. This form facilitates the analytical reduction of integrals arising from orthogonalization corrections in atomic processes. Transforms for the product of orbital pairs (1s,1s) through (1s,3d) are given …

Equivalence Of Donor And Acceptor Fits Of Temperature-Dependent Carrier-Concentration Data, David C. Look, J. R. Sizelove

Physics Faculty Publications

It is shown that the usual charge-balance analysis of temperature-dependent carrier-concentration data cannot distinguish between the donor and acceptor behavior of a center which is emitting carriers to a particular band, even though the statistics are different in the two cases. Other data, such as mobility or analytical results are needed to make the distinction.

Variational Treatment Of A Harmonic Oscillator Coupled To A Dissipative Heat Bath, Paul Ernest Parris, Robert J. Silbey

Physics Faculty Research & Creative Works

We consider the problem of a single quantum oscillator coupled linearly to a heat bath of independent harmonic modes. An exact solution is presented for the system-oscillator observables of interest. The exact results are then used to evaluate the utility of a variational approach to the problem that has proven useful recently in elucidating the dynamics of dissipatively coupled systems. We find that the variational approach does provide a good description for most, but not all, observables of interest. Both the exact and the variational treatment demonstrate the important role played by the low-frequency bath modes in determining qualitative features …

Recoil-Ion Production From Zero-Impact-Parameter H+-Ar And H+-Kr Collisions At 20-70 Kev, Akio Itoh, M. Eugene Rudd

M. Eugene Rudd Publications

Recoil ions emitted at 70° from H⁺-Ar and at 50° and 70° from H+-Kr collisions at 20-70 keV were analyzed by an electrostatic spectrometer. Ions selected in this way result from collisions at very small, essentially zero, impact parameters. Charge states up to 6 + were identified in the spectrum. The cross section for each charge state was measured. The data indicate that these close collisions produce a larger fraction of ions in high charge states than more distant collisions.

Hemispherical Emissivity Of V, Nb, Ta, Mo, And W From 300 To 1000 K, S. X. Cheng, P. Cebe, L. M. Hanssen, D. Mark Riffe, A. J. Sievers

All Physics Faculty Publications

The hemispherical emissivities of five transition elements, V, Nb, Ta, Mo, and W, have been measured from 300 to 1000 K, complementing earlier higher-temperature results. These low-temperature data, which are similar, are fitted to a Drude model in which the room-temperature parameters have been obtained from optical measurements and the temperature dependence of the dc resistivity is used as input to calculate the temperature dependence of the emissivity. A frequency-dependent free-carrier relaxation rate is found to have a similar magnitude for all these elements. For temperatures larger than 1200 K the calculated emissivity is always greater than the measured value, …

Optical And Radar Characterization Of A Short-Lived Auroral Event At High Latitude, A Vallance-Jones, R L. Gattinger, P Shih, J W. Meriwether, Vincent B. Wickwar, J D. Kelly

All Physics Faculty Publications

Observations of optical emission intensities and incoherent scatter radar returns in the magnetic zenith were compared in a study carried out at Sondre Stromfjord (Λ = 76.1°) in Greenland. The results were used to test the consistency of a theoretical model of ion chemistry and optical emissions in aurora and to explore the accuracy of relations between optical measurements and the average energy of the incident electrons. The incident primary electron spectrum and its temporal variation were inferred from zenith electron density profiles from the radar. The inferred primary energy spectrum at the peak intensity of the event approximated a …