Digital Commons Network^™

A Simple Conceptual-Model For 2-Photon Absorption, Frank Moscatelli

Physics & Astronomy Faculty Works

The process of two‐photon excitation of atoms is explained by a simple conceptual model which takes into account virtual states of the atom as well as photon statistics. In addition to predicting the correct dependence of the two‐photon excitation probability on the intensity of incident light, the model also provides an explanation for a number of experimentally observed effects.

An Interplanetary Magnetic Field Dependent Model Of The Ionospheric Convection Electric Field, Jan Josef Sojka, C. E. Rasmussen, Robert W. Schunk

All Physics Faculty Publications

A mathematical model of the magnetospheric electric field imposed upon the ionosphere is presented. The model provides an interplanetary magnetic field (IMF) dependent description of the magnetospheric electric field at ionospheric altitudes for global ionospheric and thermospheric modelers. Although many theoretical and empirical ionospheric convection models have been published, none give both a quantitative and a general Kp, IMF (B_x , B_y , B_z) dependent description. The need for such a model is particularly pressing with the success of the Dynamic Explorer (DE) mission. As a result of this mission, extensive data sets of …

On The Existence Of Periodic And Eventually Periodic Solutions Of A Fluid Dynamic Forced Harmonic Oscillator, Charlie H. Cooke

Mathematics & Statistics Faculty Publications

For certain flow regimes, the nonlinear differential equation Y¨=F(Y)−G, Y≥0, G>0 and constant, models qualitatively the behaviour of a forced, fluid dynamic, harmonic oscillator which has been a popular department store attraction. The device consists of a ball oscillating suspended in the vertical jet from a household fan. From the postulated form of the model, we determine sets of attraction and exploit symmetry properties of the system to show that all solutions are either initially periodic, with the ball never striking the fan, or else eventually approach a periodic limit cycle, after a sufficient number of bounces away from …

Fock-Tani Transformation And A First-Order Theory Of Charge Transfer, P. C. Ojha, M. D. Girardeau, J. D. Gilbert, Jack C. Straton

Physics Faculty Publications and Presentations

A unitary (Fock-Tani) transformation of the second-quantized Hamiltonian breaks the interaction into its component parts, e.g., elastic scattering, inelastic scattering, rearrangement interaction, etc. The interaction for a particular process is ‘‘weaker’’ than the overall interaction; this is reflected in certain orthogonality corrections which appear in a perturbation expansion of the T-matrix element. As a result, the internuclear potential makes a negligible contribution of order m_e/m_p to the first-order amplitude for charge transfer. We find very good agreement with experimental and the best available theoretical results for the total cross section for the reaction p+H(1s)→H(1s)+p for …

Comments On The Raindrop Problem, I. Adawi

Physics Faculty Research & Creative Works

No abstract provided.

Resonant Charge Transfer In Symmetric Alkali-Ion Alkali-Atom Collisions, F. K. Men, M. Kimura, Ronald E. Olson

Physics Faculty Research & Creative Works

Resonant charge transfer in alkali-ion alkali-atom collisions is investigated by using the molecular-orbital expansion method incorporating the use of electron translation factors. Molecular wave functions and eigen energies are obtained by the pseudopotential method. Molecular properties, Re, De, and e, obtained in the present calculation are in good accord with other recent theoretical results, as well as spectroscopic measurements. Three-state close-coupling calculations reproduce the positions of the maxima and minima in the oscillatory structure seen experimentally in the resonant-charge-transfer cross sections for the Li2 + and Cs2 + systems. The magnitude of the total cross sections and their velocity dependence …

Energy Transfer Collisions Between Vibrationally Excited Molecular Nitrogen And Atoms, Laird D. Schearer

Physics Faculty Research & Creative Works

Chemiluminescent reactions between metastable states of molecular nitrogen and atoms are used to determine the vibrational temperatures of these Non radiating molecular systems. The excitation rates of Na, Mg, Cd, and Zn are used to obtain the vibrational temperature of N2(X 1Σ) and N2(A 3Σ) states in a fast-flowing nitrogen afterglow. The exponential dependence of the intensities of the emission from atoms excited by the energy transfer collisions on the energy of the level yields vibrational temperatures on the order of 3100 K. We also report the presence of apparent strong selection rules on the total spin of the system …

Erratum: Dipole Moment And Potential Energy Functions Of The X ¹∑+ And A1∑+ States Of Nah. (The Journal Of Chemical Physics (1984) 80 (356)), W. T. Zemke, Ronald E. Olson, K. K. Verma, W. C. Stwalley, B. Liu

Physics Faculty Research & Creative Works

No abstract provided.

Nuclear Magnetic Resonance Spectroscopy And Relaxation In Molecular Solids Containing Isopropyl Groups. Part 2—The Large Two-Phase Temperature Region In 1,4-Di-Isopropylbenzene, Peter A. Beckmann

Physics Faculty Research and Scholarship

We report a proton n.m.r. study of the large, long-lived two-phase temperature region in 1,4-di-isopropylbenzene (DIB). The proton spectra are characterized by a narrow line superimposed on a 42 kHz broad line. The narrow line shows the chemical shift structure of DIB. When the sample is in the solid state the narrow lines are sharp (<30 Hz) near the melting point of 256 K and they broaden to ca.1.5 kHz at ca. 170 K where they disappear. A variety of selective and non-selective Zeeman relaxation experiments as well as a Goldman–Shen exchange experiment were performed. It is concluded that the two sets of spins do not communicate on any timescale shorter …

Electron Transitions In Multiply-Charged Ion-Helium Collisions, M. Lou Mckenzie

Masters Theses

"A classical model for He using the Classical Trajectory Monte Carlo method is developed to study multiply charged ions colliding with He at intermediate energies. Reactions studied are single and double electron capture and ionization and electron capture-ionization for projectile charge states q = +1 to +50. The dominant collision process is single ionization. Charge exchange is found to be a two-electron process, where one electron is ionized and one is captured by the projectile. We find our calculations to be in good agreement with available experimental data, supporting our interpretations of the collision mechanisms"-- Abstract, p. iii

The Homodyne Interferometer And Its Use In Finding The Optical Properties Of Graphite, Steven Randle Frey

Masters Theses

"An interferometer based on the principle of homodyning can be used to measure the reflectance of solid samples at microwave frequencies. These measurements provide the low frequency values needed for a Kramers-Kronig analysis. This analysis yields the complex dielectric function, e₁⁺ ie₂, and complex index of refraction, n + ik, of the solid. 2 This interferometer was tested on a pressed pellet sample of powdered Dixon 200-10 graphite and yielded satisfactory results. Also investigated were two different methods of signal modulation: mechanical chopping and a rotating wire grid polarizer" Abstract, p. ii

Ar+ In The Terrestrial Ionosphere, Jane L. Fox

Physics Faculty Publications

The Ar⁺ densities in the terrestrial ionosphere are computed for both low and high solar activity models. The reaction N₂⁺(υ > 0) + Ar → N₂+ Ar⁺ is found to be a significant source of Ar⁺, nearly equal to photoionization and electron impact ionization in the high solar activity model. Peak densities of Ar⁺ of 11 cm⁻³ near 190 km and 22 cm⁻³ near 220 km are predicted for the low and high solar activity models. It is suggested that a simultaneous measurement of Ar⁺ and Ar densities …

Electron Capture And Loss For 2.5-200-Mev 16s13++He Collisions, M. W. Clark, E. M. Bernstein, J. A. Tanis, W. G. Graham, Robert H. Mcfarland, T. J. Morgan, B. M. Johnson, K. W. Jones, M. Meron

Physics Faculty Research & Creative Works

Electron capture and loss cross sections have been measured for highly charged (q=13+) sulfur ions with energies 2.5-200 MeV colliding with helium. Electron capture varies by nearly six orders of magnitude over the energy range investigated, while electron loss varies by only about a factor of 2. The capture cross sections are in reasonable agreement with classical and empirical scaling rules, while the loss cross sections agree well with the plane-wave Born approximation. © 1986 The American Physical Society.

V/2 Electrons In H++H Ionizing Collisions, Ronald E. Olson

Physics Faculty Research & Creative Works

Classical-trajectory Monte Carlo calculations are used to determine the velocity and angular dependence of the electron ionized in the H++HH++H++e- collision. The energy range studied is 40200 keV. At energies E60 keV, ionized electrons with velocities that are near one-half (v/2) the relative velocity v of the collision dominate the electron spectra. At higher energies the maximum position of the ionized electrons shifts and is found centered about the target nucleus. © 1986 The American Physical Society.

The Three‐Spin Box Product Interaction, Harry A. Brown

Physics Faculty Research & Creative Works

The three‐spin interaction in the form of a box product, σ1 x σ2 · σ3, is investigated including additional interaction terms in the Hamiltonian in the forms \document class{article}\page style{empty}\begin{document}$ \sum\limits_i {\sigma _{iz},} \sum\limits_{ij} {\sigma _{iz} \sigma _{jz}} $\end{document}, and πiσiz. With the relative strengths considered as parameters, the thermodynamic properties are evaluated as a function of temperature and show considerable variety. Both second‐ and first‐order phase transitions are found. Copyright © 1986 WILEY‐VCH Verlag GmbH & Co. KGaA

Lna: A New Cw Nd Laser Tunable Around 1.05 And 1.08 Μm, Laird D. Schearer, Michele Leduc, Daniel Vivien, Anne Marie Lejus, Jeanine Thery

Physics Faculty Research & Creative Works

We have investigated the CW laser properties of the lanthamide hexa-aluminate La0.9Nd0.1MgAl11O19 at room temperature. When a I cm long crystal is pumped by an Ar⁺ laser (514 nm) or a Kr⁺ laser (752 nm), CW emission is obtained with slope efficiencies of 10 and 26 percent, respectively. A four-plate Lyot filter in the cavity forces the LNA crystal to oscillate in either of the two major bands centered at 10 820 A (tuning range 80 A) and 10 545 A (tuning range 35 Å). Copyright © 1986 by The Institute of Electrical and Electronics Engineers, Inc.

General Features Of The Aerosol Observed In The Guinean Savannah At The Level Of The Itcz Influence Of The Drought, F. Désalmand, R. Serpolay, Josef Podzimek

Physics Faculty Research & Creative Works

The stagnation and mixing of various air masses at the level of the ITCZ in the dry season, together with the absence of rain, favor, in the Guinean savannah, the formation of a well-aged and homogeneous aerosol made up of very active mixed nuclei. When the drought increases, the aerosol always remains an aged one, i.e. absence of particles with radius r < 0.02 μm, no nucleation mode. However, different properties show a younger and less homogeneous aerosol, i.e. very high counts in all the categories of particles (the concentration of nuclei activated at the supersaturation S {reversed tilde equals} 0.32% reaches 9960 cm-3), poor correlations between the concentrations of various groups of particles and no fog. When the fires are frequent and spread all over the savannah, a permanent addition of new particles to the local background aerosol (due to a complicated circulation) prevents the ageing of the aerosol that is observed during the usual drought with a moderate extension of bushfires. © 1986.

Multiple-Electron Capture And Ionization In Collisions Of Highly Stripped Ions With Ar Atoms, A. M̈Ller, B. Schuch, W. Groh, E. Salzborn, H. F. Beyer, P. H. Mokler, Ronald E. Olson

Physics Faculty Research & Creative Works

Multiple-vacancy production in Ar atoms by 1.4-MeV/u highly stripped ion impact is studied. From a recoil-ionprojectile-ion coincidence experiment charge-state distributions of Ar ions were obtained distinguishing between pure ionization and capture of up to three electrons by N6+,7+, Fe12+,15+,20+,21+, Kr18+, Gd37+, and U30+,36+,41+,44+,4 8+ ions. With increasing projectile charge state the relative abundances of multiply charged recoil ions increase. However, for high-charge-state projectiles, the relative fractions of recoil ions for concomitant electron capture and ionization are found to be independent of projectile charge or species. To interpret the data, classical trajectory Monte Carlo calculations have been made assuming the applicability …

Ionization Of H And He+ By Electrons And Positrons Colliding At Near-Threshold Energies, A. E. Wetmore, Ronald E. Olson

Physics Faculty Research & Creative Works

Ionization cross sections for the four combinations of electrons and positrons on H and He+ have been calculated at energies near the threshold for ionization using the classical trajectory Monte Carlo method. In addition, charge-exchange (positronium formation) cross sections have been calculated for the positron-impact collisions. The ionization cross sections compare well with the predictions of the Wannier and Klar models and experimental observations. Our results indicate that the Wannier-type threshold behavior may extend to higher energies than was previously thought. In addition, we have calculated two of the collision parameters, the angle and the relative separation between the escaping …

Deuteron Zeeman Relaxation Of Cd4 In The Isotropic Liquid, The Liquid Crystalline, And The Solid State Of Several Substances, Peter A. Beckmann, Myer Bloom, E. Elliott Burnell

Physics Faculty Research and Scholarship

Measurement of deuteron Zeeman relaxation rates of CD₄ dissolved in benzene, hexane, and the liquid crystals MBBA, EBBA, and Merck ZLI‐1132 and in pure CD₄ gas as a function of temperature at 30.7 and 61.4 MHz shows that the CD₄ is uniformly dispersed in the liquid solvents but resides in gas pockets when the solvents are in the solid state. Effects of centrifugal distortion were observed in the gas phase. The relaxation rate was found to be nearly independent of solvent, temperature, and pressure for the methane–liquid mixtures. This result is explained in terms of the extended …

An Approximate Variational Method For Improved Thermodynamics Of Molecular Fluids, M. S. Shaw, J. D. Johnson, John D. Ramshaw

Physics Faculty Publications and Presentations

For a certain class of thermodynamic perturbation theories, a generalization of the Gibbs-Bogoliubov inequality holds through second order of perturbation theory and for a subset of terms the inequality is true to infinite order. Using this approximate variational principle, a perturbation theory is chosen for which the Helmholtz free energy of the reference system is minimized under the constraint that the first order term is identically zero. We apply these ideas to the determination of effective spherical potentials that accurately reproduce the thermodynamics of nonspherical molecular potentials. For a diatomic-Lennard-Jones (DLJ) potential with l ∕σ = 0.793, the resulting spherical …

Nonadiabatic Theory Of Fine-Structure Branching Cross Sections For Na-He, Na-Ne, And Na-Ar Optical Collisions, Linda L. Vahala, P. S. Julienne, Mark D. Havey

Electrical & Computer Engineering Faculty Publications

The nonadiabatic close-coupled theory of atomic collisions in a radiation field is generalized to include electron spin and is used to consider the weak-field Na–rare-gas (RG) optical collision Na(²S_1/2)+RG+nhν μNa(²P_j)+RG+(n-1)hν. The effects of detuning and incident energy on the branching into the atomic Na 3p²P_3/2 and 3p²P_1/2 states are examined. The cross sections σ(j) are found to have a strong asymmetry between red and blue detuning as well as a complex threshold and resonance structure dependence on energy. A partial cross-section analysis …

Conductivity And Photoconductivity Mechanisms Of Iron And Magnesium Doped Lithium Niobate, Joseph Francis Kirchhoff

Masters Theses

Various compositions of lithium niobate crystals were observed to have an electrical conductivity given by 2.3 x 10³ exp(-1.21/kT) Ω^-1 m^-1 between 200 and 3 15°C. This implies that in this temperature range, all such crystals exhibit comparable carrier concentration and mobility. A model based on intrinsic conductivity is presented which adequately agrees with experiment. In addition, a model is presented by which electronic photoconductivity can be predicted by evaluating the trapping cross-section associated with Fe³⁺ ions dependent upon their lattice sites"-- Abstract, p. ii

Structural And Topological Contributions To The Electronic Properties Of Inhomogeneous Media (Fractal, Electrode, Impedance), Michael Kramer

Dissertations, Theses, and Capstone Projects

Recent theoretical developments in the theory of inhomogeneous media have enabled Physicists to explore various properties of random composites. We demonstrate how these techniques can be applied to the treatment of electrochemical systems, specifically porous structures. A Random Network Model is introduced to represent the porous electrode immersed in electrolyte, and using numerical simulation the a.c. impedance behavior of the system is explored. We explore how various compositional and structural parameters contribute to the electrical properties of the system. The topology of our model is analyzed, and the effect of fractal structures on impedance behavior is considered. To examine the …

Static And Dynamic Properties Of Polystyrene In Good Solvents: Ethylbenzene And Tetrahydrofuran, K. Venkataswamy, Alexander M. Jamieson, Rolfe G. Petschek

Faculty Scholarship

We report static and dynamic light scattering studies of polystyrenes of narrow molecular weight distribution in ethylbenzene (EtPh) and tetrahydrofuran (THF) as solvents. These experiments generate values for z-average radius of gyration, (Rg)₂, weight-average second osmotic virial coefficient, A₂, z-average translational diffusion coefficients, (Dt)z, and hence the diffusion virial coefficients, kD, and the z-average of the inverse frictional radius, 〈Rf-1〉z. The results show that while for a specific molecular weight the 〈Rg〉z values in THF are similar to our experimental values in ethylbenzene and to literature values in benzene or toluene, the A2 values, as well as hydrodynamic radii, are …

Biological Effects Of Heavy Ions From The Standpoint Of Target Theory, Robert Katz

Robert Katz Publications

The biological effect of heavy ions is best described through the action cross section, as a function of the end-point of interest and the charge and speed of the ion. In track theory this is called the “ion-kill" cross section, for it is the effect produced by a single heavy ion and its delta rays. As with nuclear emulsions the biological track structure passes from the grain count regime to the track width regime to the thindown region with an increase in LET. With biological cells, as with any detector capable of storing sub-lethal damage, with low LET irradiation the …

Angular And Energy Dependence Of Cross Sections For Ejection Of Electrons From Water Vapor. I. 50-2000-Ev Electron Impact, M. A. Bolorizadeh, M. Eugene Rudd

M. Eugene Rudd Publications

We have measured the angular and energy distribution of the absolute cross sections for ejection of electrons from water vapor by electrons incident at 50-2000 eV. The angular range was 15° to 150° and the range of secondary electron energies was from 2 eV to an energy equal to the primary energy minus the first ionization potential. Electron energies were analyzed with a parallel-plate electrostatic analyzer with a resolution of 1.1%. Generally good agreement is obtained with the data of Opal et al. [J. Chem. Phys. 55, 4100 (1971)l at 500 eV except at the extremes of their angular range. …

Magnetite And Magnetotaxis In Bacteria And Algae, Richard B. Frankel

Physics

We are using Mössbauer spectroscopy and magnetic measurements in conjunction with electrochemical, pH and optical spectroscopic measurements to study the mechanisms of iron containing core of these proteins.

Biological Effects Of Static Magnetic Fields, Richard B. Frankel

Physics

No abstract provided.

A Study Of Electron-Ion And Ion-Ion Recombination In Atmospheric Gas Discharges, Michael Corbin Cornell

Doctoral Dissertations

"In separate experiments, the electron-ion recombination rate, Y_ei, has been measured in CO₂ and in mixtures of He, CO₂, and N₂; and the ion-ion recombination rate, Y_ii, has been measured in SF6 and in mixtures of SF₆ and CH₄. The rate constant was determined by analyzing the rising edge of the discharge current pulse. Measurements were made as functions of reduced electric field strength, gas pressure, and gas composition.

In the electron-ion recombination study, Y_ei in CO₂ and in mixtures containing N₂ and CO_{2 …}