Physical Sciences and Mathematics Commons^™

Projectile- And Target-Charge Dependent Effects In Ionizing Collisions Of H ⁺ And He 2+ With He, Ne And Ar Atoms, Timothy James Gay, M. W. Gealy, M. E. Rudd

Physics Faculty Research & Creative Works

The spectra of electrons emitted in collisions between H + and He 2+ projectiles and He, Ne and Ar targets at energies of 50 and 100 keV amu -1 have been studied. The data are in qualitative agreement with results of Irby el al., but are in disagreement with measurements of Bernardi et al. It is shown that the observed electron spectra have a dependence on both target-ion and projectile effective charge that can be understood qualitatively in terms of 'saddle-point' ionization. Several issues relevant to saddle-point ionization are discussed. © 1990 IOP Publishing Ltd.

Uniform Stationary-Phase Methods For Energy Spectra Resulting From Collisions In A Complex Potential: Penning And Associative Ionization Of He*(2³S)+He*(23s), Ronald James Bieniek, M. W. Muller, M. Movre

Physics Faculty Research & Creative Works

Heavy-particle collisions involving strong electronic coupling can be conveniently described by using a complex (optical) potential in the entrance channel. Uniform JWKB stationary-phase techniques are used to evaluate T-matrix elements for transitions where an electron is ejected. The semi-analytic expressions for the resulting electron energy spectra are no more difficult to implement than corresponding ones for totally real potentials. Numerical results are reported for Penning and associative ionization from sub thermal He*(23S)+He*(23S) collisions. These are in excellent agreement with fully quantal, complex-potential computations. The stationary-phase expressions for T-matrix elements and differential cross sections are employed to elucidate the rapid and …

Tunable Lasers At 1080 Nm For Helium Optical Pumping, Laird D. Schearer, Padetha Tin

Physics Faculty Research & Creative Works

We describe the current status of tunable, cw, solid-state lasers in the infrared region of the spectrum which may be tuned to the helium resonance transition near 1083 nm. The principal use for these laser devices is the optical pumping of ³He and ⁴He atoms via the 2³S₁ metastable state. The tunable lasers we have examined include Nd³⁺-doped YAlO₃, La_xNd_1-xMgAl₁₁O₁₉ (x ∼0.15), Nd:LiNbO₃, and Nd:silica glass fibers. Power outputs from these lasers range from a milliwatt to more than 1 W at …

A High Power, Tunable, Arc-Lamp Pumped Nd-Doped Lanthanum-Hexaluminate Laser, Padetha Tin, Laird D. Schearer

Physics Faculty Research & Creative Works

An LNA (Nd-doped lanthanum-hex aluminate) crystal has been pumped with a cw, krypton arc lamp in a commercial Nd:YAG cavity. The cw output power greater than 6 W is obtained in a 28-cm long, plane mirror cavity. The free-running wavelength is near 1083 nm and has a width of about 0.8 nm. Inserting a 0.25 mm thick, uncoated solid etalon in the cavity permits the laser output to be continuously tuned from 1082 to 1084 nm by tilting the etalon. The laser bandwidth is reduced to below 0.016 nm. Over 3 W are obtained at the helium resonance transition. The …

Single Transfer-Excitation Resonance Observed Via The Two-Photon Decay In He-Like Ge³⁰⁺, Paul H. Mokler, S. Reusch, A. Warczak, Zbigniew Stachura, T. Kambara, Alfred K. Muller, Reinhold S. Schuch, Michael Schulz

Physics Faculty Research & Creative Works

We measured the 2E1 decay of the 1s2s ¹S₀ →1s^{2 1}S₀ transition in He-like germanium for 12- to 19-MeV/u Ge³¹⁺ +H₂ collisions. The resonant population of the 2s2p ¹P₁ state by transfer excitation was isolated due to its cascading to the 1s2s ¹S₀ state. The experimental cross sections compare well with calculations using dielectronic recombination rates. The method gives the unique possibility to populate selectively the ¹S₀ state in heavy He-like ions.

Electron Emission From Both Target And Projectile In C⁺ + He Collisions, C. O. Reinhold, D. R. Schultz, Ronald E. Olson, L. H. Toburen, R. (Robert) D. Dubois

Physics Faculty Research & Creative Works

The first classical trajectory Monte Carlo calculation of the electronic spectra arising from both target and projectile ionization is presented and compared with experimental measurements of the differential cross section for electrons emitted in C++He collisions. The theoretical treatment is based on an independent-electron model in which the interactions between the electrons are approximated by quantum model potentials. Good agreement is obtained between theory and experiment and structures appearing in the measurements can be explained in terms of the electron emission from either, or both, target and projectile. Further, the relative importance of the electron capture to the continuum and …

Coincident Charge State Production In F⁶⁺+Ne Collisions, D. R. Schultz, Ronald E. Olson, C. O. Reinhold

Physics Faculty Research & Creative Works

Total cross sections are presented for the production of various stages of multiple ionization of the target in coincidence with the final projectile charge state for collisions of F⁶⁺ with Ne at 10 and 15 MeV. In particular, the current measurements are compared with the results of a classical trajectory Monte Carlo method in which electrons are included explicitly on both target and projectile (nCTMC) and with those based on the conventional independent electron model (IEM). It is shown by the good agreement with experiment that the nCTMC model simultaneously represents well the ionization, charge transfer and excitation channels …

Theoretical Description Of The Binary Peak In Clothed Ion-Atom Collisions, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

The impulse or binary encounter approximation for ion-atom collisions is extended to treat the non-Coulomb interaction between a clothed projectile ion and the target electrons. This model is shown to reproduce the unexplained enhancement of the zero-degree binary peak for partially stripped ions over that for Equi velocity fully stripped ions that has recently been observed experimentally in F^q++H₂, He collisions. Very good agreement is obtained between theory and experiment and, furthermore, this model is used to illuminate the underlying dynamics which leads to the observed enhancement. © 1990 IOP Publishing Ltd.

Angular Distribution Of Auger Electrons Emitted Through The Resonant Transfer And Excitation Process Following O⁵⁺+He Collisions, Malika Benhenni, Stephen M. Shafroth, J. K. Swenson, Michael Schulz, J. P. Giese, Harald Schone, Charles Randy Vane, Peter F. Dittner, Sheldon Datz

Physics Faculty Research & Creative Works

This Letter reports the first measurements of the angular distribution of Auger electrons emitted from the decay of the (1s2s2p²)³D O^4+** doubly excited state formed predominantly through resonant transfer and excitation (RTE) in collisions of 13-MeV O⁵⁺ projectiles with He. The (1s2s2p²)³D angular distribution is strongly peaked along the beam direction, in agreement with recent calculations of the RTE angle-dependent impulse approximation. Furthermore, interference effects between the RTE and the elastic target direct-ionization channels are observed.

Evidence For A Crossover From Multiple Trapping To Percolation In The High-Temperature Electrical Conductivity Of Mn-Doped Lacroo₃, Ryne P. Raffaelle, Harlan U. Anderson, Don M. Sparlin, Paul Ernest Parris

Materials Science and Engineering Faculty Research & Creative Works

We explain the deep electrical conductivity minimum near x=0.05 in the perovskite-type ceramic LaCr_1-xMn_xO₃ as a crossover between two different regimes of hopping conduction. At low Mn concentrations the diffusion of small polarons among Cr ions is limited by multiple trapping at energetically lower Mn sites. At higher concentrations a percolating path of Mn sites forms and direct transport between Mn ions dominates the conduction process.

Robot Pedagogics: The Adaptation, Analysis, And Computer Control Of A Model Manipulator, Edward T. Hammerand, Chung You Ho

Computer Science Technical Reports

The subject of robotics is addressed by many different fields, among them computer science, electrical engineering, and mechanical engineering. This work is an attempt to bring together all of these aspects from the perspective of a computer science background. Different techniques are considered and reconciled with one another in the analytical area, while detail and explanation are added in all areas that were not previously available. In addition, geometrical interpretations arc presented for concepts that have heretofore been presented only in the form of equations.

Double Excitation Of He By Fast Ions, J. P. Giese, Michael Schulz, J. K. Swenson, Harald Schone, Malika Benhenni, S. L. Varghese, Charles Randy Vane, Peter F. Dittner, Stephen M. Shafroth, Sheldon Datz

Physics Faculty Research & Creative Works

Autoionization of He atoms following double excitation by electrons, protons, C^Q+ (Q=4-6), and F^Q+ (Q=7-9) ions has been studied. The electron-emission yields from the doubly excited 2s²(¹S), 2s2p(¹P), and 2p²(¹P) states were measured at the reduced projectile energy of 1.5 MeV/nucleon for observation angles between 10°and 60°. The results indicate excitation to the 2s²(¹S) and 2p²(¹D) states increases as approximately Q³, while excitation to the 2s2p(¹P) state varies as approximately Q², where Q is …

Mössbauer-Effect, Magnetic, And Neutron-Diffraction Study Of Nafep₂O₇, R. C. Mercader, L. Terminiello, Gary J. Long, D. G. Reichel, K. Dickhaus, R. Zysler, R. Sanchez, M. Tovar

Chemistry Faculty Research & Creative Works

Neutron-diffraction, magnetic-susceptibility, specific-heat, and Mössbauer-effect studies of NaFeP₂O₇ reveal that it is a normal Heisenberg isotropic three-dimensional antiferromagnetic material with a Néel temperature of 29.0 K. NaFeP₂O₇ has the monoclinic P2₁/c magnetic space group, which is the same as the nuclear crystallographic space group. The easy axis of magnetization lies in the monoclinic ac plane at an angle of 21.0° from the c axis. The specific-heat measurements reveal a λ-type anomaly at 28.7(2) K. A molecular-field model analysis indicates that the intrasublattice magnetic exchange coupling J_aa=J_bb=-0.37 cm-1, whereas …

Observation Of Velocity-Tuned Multiphoton Doppleron Resonances In Laser-Cooled Atoms, Jeffrey J. Tollett, Jian Chen, J. Greg Story, N. W M Ritchie, Curtis C. Bradley, Randall G. Hulet

Physics Faculty Research & Creative Works

An atomic beam of Li was transversely cooled using an intense standing-wave radiation field. A dramatic change in the transverse velocity distribution was observed. Structure in the resulting velocity distribution was found to be due to velocity-tuned multiphoton Doppleron resonances. The force due to seven-photon resonances is clearly resolved in the data. The data are in good agreement with theoretical predictions.

Oscillations In Lotka-Volterra Systems Of Chemical Reactions, Roger H. Hering

Mathematics and Statistics Faculty Research & Creative Works

For a chemical reaction system modeled by x =k₁Ax -k₂x² -k₃xy +k₄y², y =k₃xy -k₄y² -k₅y +k₆B, it is shown that for each positive choice of parameters k₁A, B there exists a unique stationary state which is globally asymptotically stable in the positive quadrant. A criterion for the non-existence of periodic solutions is given for the generalized Lotka-Volterra system:x = f(x)h(x, y), y. © 1990 J.C. Baltzer AG, Scientific Publishing Company.

Parallel Implementation Of A Recursive Least Squares Neural Network Training Method On The Intel Ipsc/2, James Edward Steck, Bruce M. Mcmillin, K. Krishnamurthy, M. Reza Ashouri, Gary G. Leininger

Computer Science Faculty Research & Creative Works

An algorithm based on the Marquardt-Levenberg least-square optimization method has been shown by S. Kollias and D. Anastassiou (IEEE Trans. on Circuits Syst. vol.36, no.8, p.1092-101, Aug. 1989) to be a much more efficient training method than gradient descent, when applied to some small feedforward neural networks. Yet, for many applications, the increase in computational complexity of the method outweighs any gain in learning rate obtained over current training methods. However, the least-squares method can be more efficiently implemented on parallel architectures than standard methods. This is demonstrated by comparing computation times and learning rates for the least-squares method implemented …

Coupled-Channel Optical Calculation Of Electron-Hydrogen Scattering: The Distorted-Wave Optical Potential, Igor Bray, Don H. Madison, Ian E. Mccarthy

Physics Faculty Research & Creative Works

The coupled-channel optical method solves a set of coupled momentum-space integral equations for a finite set of reaction channels. The remaining channels, including the target continuum, are described by the polarization potential operator, which formally depends on the full three-body state vectors for these channels. The distorted-wave optical potential makes the distorted-wave Born approximation for these state vectors, using exact target states. No other approximation is made. Calculations and comparison with experiment are reported for total ionization cross sections and asymmetries, total excitation cross sections, entrance-channel phenomena, and the coupled 1s,2s,2p channels, at a range of energies.

Rotational Effects In The Vuv Continuum Of H2, H. Schmoranzer, T. Noll, T. Noll, E. Roueff, H. Abgrall, Ronald James Bieniek

Physics Faculty Research & Creative Works

The effects of rotation-vibration interaction and of rotational coupling between the B 2p 1Σu+ and C 2p 1Πu electronic states on the B-X continuum of H2 were investigated spectroscopically using monochromatized synchrotron radiation for selective excitation of rovibronic states. The perturbed continuum intensities observed for the first time agree well with close-coupling calculations also performed. © 1990 IOP Publishing Ltd.

A Direct Access Method Using A Neural Network Model, John William Meyer, George Winston Zobrist

Computer Science Technical Reports

One of the concerns in computer science involves optimizing usage of machines to make them more efficient and cost effective. One item of particular concern is the use of secondary storage devices, devices that store data other than in the main memory of the computer to which it is attached. The times for searching for data on these devices consistently proves to be a contributing factor in inefficient computer usage.

One data access method that avoids searching when possible is the hashing method. A function is defined to return the record number of a record based on its key field. …

Input Data Pattern Encoding For Neural Net Algorithms, Hyeoncheol Kim, George Winston Zobrist

Computer Science Technical Reports

First, a brief overview of neural networks and their applications are described, including the BAM (Bidirectional Associative Memory) model.

A bucket-weight-matrix scheme is proposed, which is a data pattern encoding method that is necessary to transform a set of real-world numbers into neural network state numbers without losing the pattern property the set has. The scheme is designed as a neural net so that it can be combined with other data processing neural nets. The net itself can be used as a bucket-sorting net also. This shows that traditional data structure problems can be an area that neural networks may …

Algorithms And Probabilistic Bounds For The Chromatic Number Of Random Composite Graphs, Jack L. Oakes, Billy E. Gillett

Computer Science Technical Reports

The composite graph coloring problem (CGCP) is a generalization of the standard graph coloring problem (SGCP). Associated with each vertex is a positive integer called its chromaticity. The chromaticity of a vertex specifies the number of consecutive colors which must be assigned to it.

An exact algorithm for solving the CGCP is presented. The algorithm is a generalization of the vertex-sequential with dynamic reordering approach for the SGCP. It is shown that the method is as effective on composite graphs as its counterpart is on standard graphs. Let X̅(CG_np) and X̅(SG_np) denote, respectively, the mean chromatic …

Effect Of Second-Order Exchange In Electron-Hydrogen Scattering, Don H. Madison, Igor Bray, Ian E. Mccarthy

Physics Faculty Research & Creative Works

The electron-hydrogen scattering problem has been a nemesis to theoretical atomic physicists due to the fact that even the most sophisticated of theoretical calculations, both perturbative and nonperturbative, do not agree with experiment. The current opinion is that the perturbative approach cannot be used for this problem since recent second-order calculations are not in agreement with the experimental data and higher-order calculations are deemed impractical However, these second-order calculations neglected second-order exchange. We have now added exchange to the second-order calculation and have found that the primary source of disagreement between experiment and theory for intermediate energies is attributable not …

Polar-Liquid, Derivatized Cyclodextrin Stationary Phases For The Capillary Gas Chromatography Separation Of Enantiomers, Daniel W. Armstrong, Weiyong Li, Chau Dung Chang, Josef Pitha

Chemistry Faculty Research & Creative Works

A new class of hydrophilic, relatively polar liquid, cyclodextrin (CD) derivatives have been used as highly selective chiral stationary phases (CSPs) for capillary gas chromatography (GC). Several possible requirements for liquidity In CD derivatives are discussed. O-(S)-2-Hydroxypropyl derivatives of α-, β-, and γ-cyclodextrlns were synthesized, exclusively characterized, permethylated, and evaluated for enantloselectlvity. Seventy pairs of enantiomers were resolved. They represent a wide variety of structural types and classes of compounds including chlral alkyl amines, amino alcohols, epoxides, pyrans, furans, sugars, dlols, esters, ketones, bicyclic compounds, alcohols, and so on. Many of these compounds were not aromatic and cannot be resolved …

A Fast O(K) Multicast Message Routing Algorithm, Thomas J. Sager, Bruce M. Mcmillin

Computer Science Technical Reports

In many multicomputer applications is it necessary for one node to send an identical message to many nodes. One to many communications are called multicasts. Although broadcasts (one to all) and unicasts (one to one) have been widely implemented, multicasts, in spite of their importance to efficient use of multicomputer systems, have not received much attention.

Minimal traffic multicasting is equivalent to the minimal Steiner tree problem and is known to be NP-complete. Therefore, a heuristic polynomial time approximation must be used; but, to take advantage of advances in second generation multicomputer hardware such as wormhole routing, a distributed multicast …

Computational Complexity Of Geometric Symmetry Detection In Graphs, Joseph Manning

Computer Science Technical Reports

Constructing a visually informative drawing of an abstract graph is a problem of considerable practical importance, and has recently been the focus of much investigation. Displaying symmetry has emerged as one of the foremost criteria for achieving good drawings. Linear-time algorithms are already known for the detection and display of symmetry in trees, outerplanar graphs, and embedded planar graphs. The central results of this paper show that for general graphs, however, detecting the presence of even a single axial or rotational symmetry is NP-complete. A number of related results are also established, including the #P-completeness of counting the axial or …

Reversing Enantioselectivity In Capillary Gas Chromatography With Polar And Nonpolar Cyclodextrin Derivative Phases, Daniel W. Armstrong, Weiyong Li, Josef Pitha

Chemistry Faculty Research & Creative Works

No abstract provided.

Molecular Mobility In A Model Polymer Composite, Joan Ethel Gambogi

Masters Theses

"The adsorption of aminoalkysilane coupling agents onto silica surfaces and the interaction of these functional silanes with a bismaleimide and an epoxy resin has been studied using solid-state NMR techniques. ¹³C CP-MAS was used to confirm the bonding between the silence and bismaleimide (BMI) resin and elucidate the nature of the crosslinking reaction of BMI. Deuterated coupling agents were synthesized and adsorbed on silica surfaces. The motional dynamics were probed using deuterium solid-echo NMR. It was determined that the motion of the alky portion of the coupling agents was consistent with gauche migrations (gtt ↔ tig) and pair gauche …

Subshell Electron Capture In Collisions Of Fully Stripped Ions With He And H2 At Intermediate Energies, L. Meng, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

Classical phase-space models of the hydrogen molecule and helium are utilized to study shell and subshell electron-capture processes in collisions of fully stripped ions on charge states from 1 to 15 with H2 and He at intermediate impact energies (20200 keV/amu). Autoionization after double electron capture is approximated and is found to be an important channel for high projectile charges. The resulting (n,l) distributions for proton impact of He and H₂ as well as total capture cross sections are found to be in very good agreement with experimental data. l distributions for high projectile charges are also analyzed for …

Experimental And Theoretical Study Of The Electron Spectra In 66.7350-Kev/U C++He Collisions, L. H. Toburen, R. (Robert) D. Dubois, C. O. Reinhold, D. R. Schultz, Ronald E. Olson

Physics Faculty Research & Creative Works

Measurements of the differential and total cross sections for production of free electrons are reported for collisions of 66.7350-keV/u C+ ions with He. The experimental data are compared with theoretical calculations that include electron emission from both target and projectile using the classical-trajectory Monte Carlo method and the independent-electron approximation. Good agreement is observed between theory and experiment, and structures appearing in the electron spectra can be explained in terms of either, or both, target and projectile ionization. © 1990 The American Physical Society.

A Study Of The Hydration Properties Of Selected Laser Dye Aerosols Including Continuous-Flow Parallel Plate And Alternating-Gradient Thermal Diffusion Cloud Chamber Measurements In The High Supersaturation Regime, Donald E. Hagen, Max B. Trueblood, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Hydration Behavior of Aerosols made Up of Various Fluorescent Dyes when Exposed to Water Saturation or Supersaturated Conditions Has Been Studied. Critical Supersaturation Spectra Are Reported. the Dyes Are Found to Behave as High Molecular Weight Ionic Compounds that Obey Kohler Theory. their Relevant Kohler Parameters Are Measured. This Study Makes Use of and Compares Results from the Isothermal Hazecontinuous-Flowand Alternating-Gradient Thermal Diffusion Cloud Chambers. the Ability of the Continuous-Flow Thermal Diffusion Chamber to Operate Correctly at High Supersaturations is Shown. © 1990 Elsevier Science Publishing Co., Inc.