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Physics Faculty Research & Creative Works

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Articles 1501 - 1530 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Angular Differential And Total Cross Sections For The Excitation Of Atomic Hydrogen To Its N=2 Level By 25-150-Kev Hydrogen Molecular Ions, Jerry Peacher, Paul J. Martin, Denver G. Seely, Judith E. Aldag, Thomas J. Kvale, E. Redd, D. M. Blankenship, V. C. Sutcliffe, John T. Park Aug 1984

Angular Differential And Total Cross Sections For The Excitation Of Atomic Hydrogen To Its N=2 Level By 25-150-Kev Hydrogen Molecular Ions, Jerry Peacher, Paul J. Martin, Denver G. Seely, Judith E. Aldag, Thomas J. Kvale, E. Redd, D. M. Blankenship, V. C. Sutcliffe, John T. Park

Physics Faculty Research & Creative Works

Experimentally and theoretically determined differential and total cross sections are reported for excitation of atomic hydrogen to its n=2 level by 25-150-keV hydrogen molecular ions. The differential cross sections decrease 3-4 orders of magnitude over the measured center-of-mass scattering-angular range from 0 to 4.5 mrad. The results of a first Born approximation and two other theoretical calculations based upon the Glauber approximation are presented and compared with the experimental results. Both calculations based on the Glauber approximation agree fairly well with the experimental results. The Born approximation agrees moderately well with the experimental results at the very small scattering angles …


Full Second-Order Distorted-Wave Calculation Without Approximations For Atomic Excitation By Electron Impact, Don H. Madison Jul 1984

Full Second-Order Distorted-Wave Calculation Without Approximations For Atomic Excitation By Electron Impact, Don H. Madison

Physics Faculty Research & Creative Works

A new technique has been developed for evaluating second-order distorted-wave amplitudes for atomic excitation without making any approximations. By this technique, second-order amplitudes with arbitrary distorted waves and arbitrary Green's functions in the interaction can be evaluated with comparable difficulty. The utility of the method is demonstrated through a practical calculation of the second-order distorted-wave approximation for electron excitation of the 2p state of hydrogen.


Homogeneous Nucleation Rate For Water, Donald E. Hagen, James L. Kassner Apr 1984

Homogeneous Nucleation Rate For Water, Donald E. Hagen, James L. Kassner

Physics Faculty Research & Creative Works

Homogeneous nucleation rate data for water extending over an exceptionally large domain of rate (J), supersaturation ratio (S), and temperature (T) was recently published. Because it spans a large J-S-T surface, this data constitutes a good test of nucleation theory. Here classical nucleation theory is used to analyze this data. By adjusting only the sticking coefficient, we are able to obtain a good fit between theory and experiment. It was necessary to include an increase in the water molecular density associated with the finite water compressibility.


Elastic Differential Cross Sections For Small-Angle Scattering Of 25-, 40-, And 60-Kev Protons By Atomic Hydrogen, Eduard P. Rille, Jerry Peacher, E. Redd, Thomas J. Kvale, Denver G. Seely, D. M. Blankenship, Ronald E. Olson, John T. Park Feb 1984

Elastic Differential Cross Sections For Small-Angle Scattering Of 25-, 40-, And 60-Kev Protons By Atomic Hydrogen, Eduard P. Rille, Jerry Peacher, E. Redd, Thomas J. Kvale, Denver G. Seely, D. M. Blankenship, Ronald E. Olson, John T. Park

Physics Faculty Research & Creative Works

Elastic angular differential cross sections for small-angle scattering of protons by atomic hydrogen have been measured. The technique utilized unambigously distinguishes the elastically and inelastically scattered ions. The cross sections fall monotonically by 3 orders of magnitude in the angular range from 0.5 to 3.0 mrad, in the center-of-mass system. The experimental data obtained are in very good agreement with a multistate calculation and in fair agreement with both our Glauber-approximation and classical-trajectory Monte Carlo results.


Additional Remarks To The Schrödinger Spin‐Exchange Ferromagnet, Harry A. Brown Jan 1984

Additional Remarks To The Schrödinger Spin‐Exchange Ferromagnet, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.


Non-Linear Oscillation, Automodulation And Anelasticity, Tetsuro Suzuki, Manfred Wuttig Jan 1984

Non-Linear Oscillation, Automodulation And Anelasticity, Tetsuro Suzuki, Manfred Wuttig

Physics Faculty Research & Creative Works

The auto modulation observed in the course of internal friction is discussed as a special example of the universal nature of non-linear oscillations. Universal features of non-linear oscillations are the requirement of energy supply or negative damping and the period doubling route to chaos. The negative damping responsible for the auto modulation is described in terms of the soliton model for twinning deformation. © 1984 The Japan Society of Applied Physics.


A Three-Spin Interaction Model, Harry A. Brown Jan 1984

A Three-Spin Interaction Model, Harry A. Brown

Physics Faculty Research & Creative Works

A three-spin interaction in the form of a box product, σ1 x σ2 · σ3, is considered. The thermodynamic behavior is investigated using an effective field theory. A second-order phase transition is found and the magnetization and energy per spin appear to be very similar to those of an ordinary Heisenberg ferromagnet. © 1984.


Electron-Ion Recombination In Gas Mixtures Of Helium, Nitrogen, And Carbon Dioxide, Ian M. Littlewood, M. C. Cornell, Kaare J. Nygaard Jan 1984

Electron-Ion Recombination In Gas Mixtures Of Helium, Nitrogen, And Carbon Dioxide, Ian M. Littlewood, M. C. Cornell, Kaare J. Nygaard

Physics Faculty Research & Creative Works

A study has been conducted to determine the electron-ion recombination rates in gas mixtures of helium, nitrogen, and carbon dioxide. Measurements were made as functions of electric field strength, gas pressure, and gas composition. In gas mixtures containing only nitrogen and carbon dioxide, the rates were dependent on pressure. This dependence is interpreted as being due to the separate effects of two- and three-body recombination processes. No pressure dependence was observed for mixtures containing helium. In such mixtures, two-body recombination appears to be dominant. Moreover, the addition of relatively low concentrations of helium to the discharge leads to a dramatic …


Dipole Moment And Potential Energy Functions Of The X ¹Σ + And A 1Σ+ States Of Nah, W. T. Zemke, Ronald E. Olson, K. K. Verma, W. C. Stwalley, B. Liu Jan 1984

Dipole Moment And Potential Energy Functions Of The X ¹Σ + And A 1Σ+ States Of Nah, W. T. Zemke, Ronald E. Olson, K. K. Verma, W. C. Stwalley, B. Liu

Physics Faculty Research & Creative Works

Calculated radiative transition probabilities between all vibrational levels in the X 1Σ+ state (υ=0-21) and in the A 1Σ+ state (υ=0-32) of NaH are given. In addition, the calculated spontaneous emission lifetimes for vibrational- rotational levels (J=0,1) and the calculated dipole moments for these same levels are given. The calculations use new hybrid potential energy curves based on Rydberg-Klein-Rees (RKR) and ab initio potential curves. The RKR curve for the X state is new. The calculations use new ab initio dipole moment functions of internuclear distance. © 1984 American Institute of Physics.


Resonant Electron Transfer And Excitation In Two-, Three-, And Four- Electron Caq +20 And Vq +23 Ions Colliding With Helium, J. A. Tanis, E. M. Bernstein, W. G. Graham, M. P. Stockli, M. Clark, Robert H. Mcfarland, T. J. Morgan, K. H. Berkner, A. S. Schlachter, J. W. Stearns Jan 1984

Resonant Electron Transfer And Excitation In Two-, Three-, And Four- Electron Caq +20 And Vq +23 Ions Colliding With Helium, J. A. Tanis, E. M. Bernstein, W. G. Graham, M. P. Stockli, M. Clark, Robert H. Mcfarland, T. J. Morgan, K. H. Berkner, A. S. Schlachter, J. W. Stearns

Physics Faculty Research & Creative Works

Significant new evidence is reported for resonant transfer and excitation in ion-atom collisions. This process, which is analogous to dielectronic recombination, occurs when a target electron is captured simultaneously with the excitation of the projectile followed by photon emission. Strong resonant behavior with structure, in agreement with theoretical calculations, is observed in the cross section for projectile K x rays coincident with single electron capture for 100-360-MeV Ca16+,17+,18+20 and 180-460-MeV V19+,20+,21+23 ions colliding with helium. © 1984 The American Physical Society.


Molecular-State Cross-Section Calculations For H+Csh-+Cs+, Ronald E. Olson, M. Kimura, H. Sato Jan 1984

Molecular-State Cross-Section Calculations For H+Csh-+Cs+, Ronald E. Olson, M. Kimura, H. Sato

Physics Faculty Research & Creative Works

Pseudopotential molecular-structure calculations have been used to obtain the seven lowest 1 and 1 states of CsH. These states and their associated radial and rotational coupling terms have been used to calculate the cross sections for H-+Cs+ ion-pair production in H+Cs(6s) and H+Cs*(6p) collisions at energies from 0.1 to 10 keV. The ion-ion mutual neutralization cross section, H-+Cs+ H+Cs, is also presented. The cross-section calculations were done with the perturbed-stationary-state method, modified to include two-electron translation factors. The ion-pair production cross section for ground-state reactants is in good agreement with experiment; collisions of H with excited Cs*(6p) show an order-of-magnitude …


The Homogeneous Nucleation Of Nonane, G. W. Adams, John L. Schmitt, R. A. Zalabsky Jan 1984

The Homogeneous Nucleation Of Nonane, G. W. Adams, John L. Schmitt, R. A. Zalabsky

Physics Faculty Research & Creative Works

The homogeneous nucleation rate of n-nonane has been measured as a function of temperature and supersaturation ratio in a precision fast-expansion chamber. The measured nucleation rate ranges from 102 to 105 drops/cm3 over the temperature range 215-270 K. The results have been compared to the classical theory and to the classical theory with the RKC replacement factor. The RKC theory functional form is the basis for an empirical rate equation to fit the data. A full listing of the thermodynamic constants used for the reduction of the data is given. © 1984 American Institute of Physics.


Electron Drift Velocities In Gas Mixtures Of He, N2, And Co 2, Michael C. Cornell, Ian M. Littlewood, Howard L. Brooks, Kaare J. Nygaard Dec 1983

Electron Drift Velocities In Gas Mixtures Of He, N2, And Co 2, Michael C. Cornell, Ian M. Littlewood, Howard L. Brooks, Kaare J. Nygaard

Physics Faculty Research & Creative Works

An electron swarm experiment has been used to obtain electron drift velocities in the He:CO2:N2 mixtures 0:1:1, 3:1:2, and 3:1:1. The E/N range of 3 to 57 Td was studied with total gas pressure varied from 50 to 200 Torr. These particular mixtures have not been previously studied experimentally. Good agreement is observed between theoretical calculations and experimental data.


Isotope Effect And Momentum-Transfer Scaling In The Elastic-Scattering Differential Cross Sections For Hydrogen-Isotope Collision Systems, Eduard P. Rille, Jerry Peacher, Denver G. Seely, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park Dec 1983

Isotope Effect And Momentum-Transfer Scaling In The Elastic-Scattering Differential Cross Sections For Hydrogen-Isotope Collision Systems, Eduard P. Rille, Jerry Peacher, Denver G. Seely, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park

Physics Faculty Research & Creative Works

A projectile-dependent isotope effect was found for the elastic-scattering differential cross sections in the hydrogen-isotope collision systems. All four differential cross sections lie on a common curve if they are divided by the square of the reduced mass and plotted against momentum transfer. The experimental results are in satisfactory agreement with a simple Glauber-approximation calculation.


Two- And Three-Body Electron-Ion Recombination In Carbon Dioxide, Ian M. Littlewood, M. C. Cornell, B. K. Clark, Kaare J. Nygaard Dec 1983

Two- And Three-Body Electron-Ion Recombination In Carbon Dioxide, Ian M. Littlewood, M. C. Cornell, B. K. Clark, Kaare J. Nygaard

Physics Faculty Research & Creative Works

The electron-ion recombination rate in carbon dioxide was measured as a function of electric field strength and gas pressure. The separate effects of two- and three-body recombination was observed, and the respective rate constants obtained. The results indicate that three-body recombination is dominant at low field strengths for gas pressures above 1 atm, whereas two-body recombination is dominant at high field strengths.


Charge Transfer And Ionisation Processes Involving Multiply Charged Ions In Collision With Atomic Hydrogen, D. J.W. Hardie, Ronald E. Olson Dec 1983

Charge Transfer And Ionisation Processes Involving Multiply Charged Ions In Collision With Atomic Hydrogen, D. J.W. Hardie, Ronald E. Olson

Physics Faculty Research & Creative Works

Total cross sections are presented for the charge transfer reaction Xq++H(1s) to X(q-1)+H+ and ionization process Xq++H(1s) to Xq++H+-e-. Here Xq+ is a fully or partially stripped ion. The collision energy range lies between 25-200 keV amu-1. Cross sections are also given for charge transfer into particular ionic n states and n, l states for energies of 25 and 50 keV amu-1, where Xq+=H+, He 2+, C6+, O8+. The calculations were performed by the classical trajectory Monte Carlo method of Olson and …


Electron Capture Cross Sections For Tih⁴⁺, H. Sato, M. Kimura, A. E. Wetmore, Ronald E. Olson Dec 1983

Electron Capture Cross Sections For Tih⁴⁺, H. Sato, M. Kimura, A. E. Wetmore, Ronald E. Olson

Physics Faculty Research & Creative Works

Electron capture cross sections have been computed for Ti4++H to Ti3++H+ and Ti3++H+ to Ti4++H, where the reactants were in their ground states. The energy range investigated was 0.1 to 10 keV amu-1. The impact parameter perturbed-stationary-state method incorporating electron translation factors were used to calculate the cross sections. The molecular wavefunctions were generated using the pseudo-potential method. At 1 keV amu-1 ( nu rel=4.4*107 cm s-1), representative electron capture cross sections for the Ti4++H and Ti3++H+ reactions are 2*10-15 cm 2 and 1*10-17 cm2, respectively. An …


Reactive Scattering Cell For Atomic Hydrogen And Deuterium, John T. Park, E. Redd, T. J. Kvale, E. Rille Dec 1983

Reactive Scattering Cell For Atomic Hydrogen And Deuterium, John T. Park, E. Redd, T. J. Kvale, E. Rille

Physics Faculty Research & Creative Works

A design for a high-temperature reactive scattering cell for atomic hydrogen and atomic deuterium is described. At approximately 2700 K a dissociation of the molecular target species of over 95% has been obtained. The lifetime of 340 h of operation is sufficient for precision, long-time, differential cross-section measurements.


Composition Of The Critical Nucleus In Multicomponent Vapor Nucleation, Gerald Wilemski Oct 1983

Composition Of The Critical Nucleus In Multicomponent Vapor Nucleation, Gerald Wilemski

Physics Faculty Research & Creative Works

No abstract provided.


Study Of Prenucleation Ion Clusters: Correlation Between Ion Mobility Spectra And Size Distributions, Sung-Ho Suck Salk, Donald E. Hagen, James L. Kassner Jul 1983

Study Of Prenucleation Ion Clusters: Correlation Between Ion Mobility Spectra And Size Distributions, Sung-Ho Suck Salk, Donald E. Hagen, James L. Kassner

Physics Faculty Research & Creative Works

Additional studies regarding our earlier electrothermodynamic theory are presented. Comparisons to recent expansion cloud chamber ion mobility measurements are made, indicating general agreement with observations. This theory predicts more stable and ordered structure for prenucleation ion-water cluster systems than accounted for by the classical Thomson's theory. In the limiting case of the dielectric constant ε = 1, our monopole electrostatic energy term contributed by the foreign ion center precisely converges to that of Thomson. Predicted ion cluster size distributions are found to correlate well with ion cluster size spectra obtained from the ion mobility measurements of hydrated ion clusters and …


Momentum-Transfer Scaling In Hydrogen-Isotope Collision Systems, Eduard P. Rille, Jerry Peacher, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park Jun 1983

Momentum-Transfer Scaling In Hydrogen-Isotope Collision Systems, Eduard P. Rille, Jerry Peacher, Thomas J. Kvale, E. Redd, D. M. Blankenship, John T. Park

Physics Faculty Research & Creative Works

The differential cross sections for excitation of atomic hydrogen isotopes to their n=2 states by proton or deutron impact are found to follow a simple scaling relationship. The momentum-transfer-scaled differential excitation cross sections, for a projectile velocity of 1.26 a.u., produce one differential cross-section curve for all four possible hydrogen-isotope collision systems. The experimental results are in excellent agreement with our Glauber-approximation calculations.


Structural Studies Of Low Temperature Ice Iₕ Using A Central Force Potential Model, Peter W. Deutsch, Barbara N. Hale, Richard C. Ward, Donald A. Reago Jr. Apr 1983

Structural Studies Of Low Temperature Ice Iₕ Using A Central Force Potential Model, Peter W. Deutsch, Barbara N. Hale, Richard C. Ward, Donald A. Reago Jr.

Physics Faculty Research & Creative Works

The revised central force potentials of Stillinger and Rahman [J. Chem. Phys. 68, 666 (1978)] are used to study the binding energy, structure, and multipole moments of a periodic ice Ih sample with a unit cell of 192 water molecules. The initial configuration for the unit cell has each oxygen in a wurtzite structure and intramolecular H-O-H angles symmetrically positioned in the tetrahedral O-O-O angles. Hydrogens are placed such that the total dipole moment for the unit cell is zero and the diagonal quadrupole moments are small (≲ 10-28 esu cm2). Subject to these restrictions, a …


Exciton Trapping And Sensitized Luminescence: A Generalized Theory For All Trap Concentrations, Vasudev M. Kenkre, Paul Ernest Parris Mar 1983

Exciton Trapping And Sensitized Luminescence: A Generalized Theory For All Trap Concentrations, Vasudev M. Kenkre, Paul Ernest Parris

Physics Faculty Research & Creative Works

The generalized-master-equation theory of sensitized luminescence in molecular crystals is extended to cover arbitrary guest concentrations by making use of a recently introduced formalism. Central to the formalism is a quantity termed the ν function, which is an ensemble average of the sum of host propagators over guest-influenced host sites. A variety of experimentally relevant sensitized luminescence observables, such as the host (and guest) luminescence intensity, the quantum yields, and the energy-transfer rates are simply related to the ν function. It is shown how the latter can be calculated for exciton motion possessing an arbitrary degree of coherence, dimensionality, and …


Homogeneous Nucleation Rate Measurements For Water Over A Wide Range Of Temperature And Nucleation Rate, Ronald C. Miller, Robert J. Anderson, James L. Kassner, Donald E. Hagen Mar 1983

Homogeneous Nucleation Rate Measurements For Water Over A Wide Range Of Temperature And Nucleation Rate, Ronald C. Miller, Robert J. Anderson, James L. Kassner, Donald E. Hagen

Physics Faculty Research & Creative Works

An expansion cloud chamber was used to measure the homogeneous nucleation rate for water over a wide range of temperature from 230-290 K and nucleation rates of 1-106 drops cm-3 s-1. The comprehensive and extensive nature of this data allows a much more detailed comparison between theory and experiment than has previously been possible. The expansion chamber technique employs continuous pressure measurement and an adiabatic pulse of supersaturation to give the time history of supersaturation and temperature during the nucleation. The resulting drop concentration is determined using photographic techniques. The experimental observations are presented in tabular …


Ion-Atom Differential Cross Sections At Intermediate Energies, Ronald E. Olson Jan 1983

Ion-Atom Differential Cross Sections At Intermediate Energies, Ronald E. Olson

Physics Faculty Research & Creative Works

The classical-trajectory Monte Carlo method has been used to calculate H++H(1s) electron-capture and ionization differential cross sections in the range 25-200 keV. The results indicate the importance of including excited product states to describe the small-angle electron-capture scattering. Angular scattering of the electron removed by the ionization process has been studied as a function of ejected-electron velocity ve. The classical calculations are in reasonable agreement with coupled-channel results of Shakeshaft [Phys. Rev. A 18, 1930 (1978)] as to the "electron capture to the continuum" (ECC) component of the ionization process where this term is defined as the ejected electron being …


Ion Scattering From State-Selected Rydberg Atoms, G. A. Kohring, A. E. Wetmore, Ronald E. Olson Jan 1983

Ion Scattering From State-Selected Rydberg Atoms, G. A. Kohring, A. E. Wetmore, Ronald E. Olson

Physics Faculty Research & Creative Works

Classical-trajectory Monte Carlo calculations have been performed for collisions of protons with state-selected hydrogenic Rydberg atoms. The examples investigated were Rydberg atoms in the n=10, l=9 level with ml=0 and 9. The collision velocity range was 0.1 to 1.0 a.u. (2.2x107 to 2.2x108 cm/s). The ionization cross sections were found to be relatively insensitive to changes in the ml levels. However, the charge-transfer cross sections showed considerable enhancement if the Rydberg electron is orientated in a plane which is parallel to the direction of the incident projectile. © 1983 The American Physical Society.


Molecular Treatment Of Charge Transfer In Li+ +Ca Collisions, M. Kimura, H. Sato, Ronald E. Olson Jan 1983

Molecular Treatment Of Charge Transfer In Li+ +Ca Collisions, M. Kimura, H. Sato, Ronald E. Olson

Physics Faculty Research & Creative Works

The perturbed-stationary-state method, appended with electron translation factors, has been applied to charge transfer in Li+ +Ca collisions for energies from 0.1 to 20 keV/amu. The Born-Oppenheimer wave functions and eigenvalues were generated using the pseudopotential technique, which reduced the many-electron system to a simpler two-electron problem. The molecular ground-state X +1 is calculated to be bound and has the potential-well parameters Re=6.20a0, De=1.11 eV, e=235 cm-1, and Be=0.263 cm-1. From the scattering computations, a representative value for the charge-transfer cross section is 4x10-15 cm2 at 5 keV/amu. The cross section decreases rapidly as the energy is reduced below 1 …


On The Schrödinger Spin‐Exchange Ferromagnet, Harry A. Brown Jan 1983

On The Schrödinger Spin‐Exchange Ferromagnet, Harry A. Brown

Physics Faculty Research & Creative Works

The thermodynamic behavior of a ferromagnet whose interactions are described by the Schrödinger spin‐exchange operator is investigated. The transition temperatures, magnetization, susceptibility, exchange energy, heat capacity, and entropy are calculated for general spin and lattice coordination number using the constant‐coupling approximation. Both first‐ and second‐order phase transitions are found. Comparison with some results of the high‐temperature expansion method shows some qualitative agreement. Copyright © 1983 WILEY‐VCH Verlag GmbH & Co. KGaA


Universal Stationary-Phase Treatment Of Far-Wing And Excimer Spectral Line Shapes, Ronald James Bieniek, T. J. Streeter Jan 1983

Universal Stationary-Phase Treatment Of Far-Wing And Excimer Spectral Line Shapes, Ronald James Bieniek, T. J. Streeter

Physics Faculty Research & Creative Works

When two atoms are in proximity, their resonance lines are broadened because of the formation of molecular potentials, between which photon transitions can occur. The level of experimental refinement in measuring excimer and collisional far-wing spectra calls for interpretive theoretical methods that accurately treat the observed structure in line shapes. Of particular interest are satellites and undulations, for they can give much information on intermolecular potentials. We derive an expression for T-matrix elements, based on JWKB wave functions and stationary-phase techniques, that is universally applicable to situations with one, two, or more Condon points. Each transition point is treated individually, …


Thermal Decomposition Kinetics Of Iodine‐Doped Polyacetylene In Vacuum, J. ‐E Osterholm, H. Yasuda, L. L. Levenson Jan 1983

Thermal Decomposition Kinetics Of Iodine‐Doped Polyacetylene In Vacuum, J. ‐E Osterholm, H. Yasuda, L. L. Levenson

Physics Faculty Research & Creative Works

The thermal stability of iodine‐doped polyacetylene films, (CHIy)x, has been studied by means of electrical conductivity measurements, measurements on weight loss, and mass spectrometric analysis of desorbing species. When heated between room temperature and 125°C in vacuum, these films proved to be of poor thermal stability, being unstable at temperatures above 20°C. During the thermal treatments, molecular iodine desorbs from the films, resulting in an appreciable dopant weight loss with accompanying decrease in the electrical conductivity. The decomposition process does not follow simple kinetics. Copyright © 1983 John Wiley & Sons, Inc.