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Physics Faculty Research & Creative Works

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Articles 1231 - 1260 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Three-Body Collision Dynamics For Single Ionization Of Helium By Protons And Antiprotons, C. J. Wood, Ronald E. Olson Apr 1996

Three-Body Collision Dynamics For Single Ionization Of Helium By Protons And Antiprotons, C. J. Wood, Ronald E. Olson

Physics Faculty Research & Creative Works

All momentum components of the three outgoing particles are calculated for 100 keV p and p- + He single-ionization collisions. Differential ejected electron cross sections are evaluated for a fixed collision plane defined by the incident momentum vector of the projectile and the final momentum vector of the He+ recoil ion. For proton impact the electron spectra display saddle-point ionization when the transverse recoil ion momentum is small, whereas the electrons are ejected in the backward direction for large transverse recoil ion momenta. The antiproton collisions primarily show backward ejected electrons. However, for the antiproton system there is a decided …

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Fine-Structure Effect For (E,2e) Collisions, Don H. Madison, V. D. Kravtsov, Stephenie J. Jones, Robert P. Mceachran Apr 1996

Fine-Structure Effect For (E,2e) Collisions, Don H. Madison, V. D. Kravtsov, Stephenie J. Jones, Robert P. Mceachran

Physics Faculty Research & Creative Works

For the case of inelastic electron-atom scattering, it has been known for some time that significant spin effects may be observed even if spin-dependent forces on the projectile can be ignored. These spin effects result from the Pauli principle and this phenomenon has become known as the fine-structure effect. Recently, the question of whether or not these same types of effects should be observed for atomic ionization has been considered and the initial indications are that significant spin asymmetries can also be expected for atomic ionization if the final ion satisfies LS coupling and the final J state of the …

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Critical Behavior Of A Quantum Spherical Model In A Random Field, Thomas Vojta, Michael Schreiber Apr 1996

Critical Behavior Of A Quantum Spherical Model In A Random Field, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We consider the influence of a quenched random field on the critical behavior of a quantum spherical model at the zero-temperature quantum phase transition. We find a complete solution of the model for arbitrary translationally invariant pair interactions. It turns out that the critical behavior for zero as well as finite temperatures is dominated by static random field fluctuations rather than by quantum or thermal fluctuations. Therefore the critical behavior close to the zero-temperature quantum phase transition is identical to that close to a finite-temperature transition. The system does not show a crossover from quantum to classical behavior.

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Doubly Differential Final-State Momentum Distributions Of The Ionization Products In Collision Of Bare Ions With Hydrogen, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, Ronald E. Olson Jan 1996

Doubly Differential Final-State Momentum Distributions Of The Ionization Products In Collision Of Bare Ions With Hydrogen, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, Ronald E. Olson

Physics Faculty Research & Creative Works

In this paper recoil-ion production cross sections are presented differential in recoil-ion longitudinal momentum and electron emission angle in ionization of atomic and molecular hydrogen by bare ion projectiles. A new formulation for constructing these double differential distributions from the measured electron double differential cross sections is used. A novel feature is the separation of two different branches of the recoil-ion longitudinal momentum distribution corresponding to soft and hard collision mechanisms of ionization. The single differential distributions have also been derived. © 1996 The American Physical Society.

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Imaging Of Saddle Point Electron Emission In Slow, R. Dörner, H. Khemliche, M. H. Prior, C. L. Cocke, J. A. Gary, Ronald E. Olson, V. Mergel, J. Ullrich, H. Schmidt-Böcking Jan 1996

Imaging Of Saddle Point Electron Emission In Slow, R. Dörner, H. Khemliche, M. H. Prior, C. L. Cocke, J. A. Gary, Ronald E. Olson, V. Mergel, J. Ullrich, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

The two-dimensional velocity distribution of electrons emitted in 5-15 keV p - He collisions has been measured for completely determined motion of the nuclei, that is, as a function of the impact parameter and in a well defined scattering plane. The electrons are emitted preferentially in the scattering plane and in the forward direction. The velocity distributions show sharp structures that vary strongly with impact parameter and projectile velocity. The results are compared to classical trajectory calculations. © 1996 The American Physical Society.

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Double Ionization Of Helium And Neon For Fast Heavy-Ion Impact: Correlated Motion Of Electrons From Bound To Continuum States, R. Moshammer, J. Ullrich, H. Kollmus, W. Schmitt, M. Unverzagt, O. Jagutzki, V. Mergel, H. Schmidt-Böcking, R. Mann, C. J. Woods, Ronald E. Olson Jan 1996

Double Ionization Of Helium And Neon For Fast Heavy-Ion Impact: Correlated Motion Of Electrons From Bound To Continuum States, R. Moshammer, J. Ullrich, H. Kollmus, W. Schmitt, M. Unverzagt, O. Jagutzki, V. Mergel, H. Schmidt-Böcking, R. Mann, C. J. Woods, Ronald E. Olson

Physics Faculty Research & Creative Works

Double ionization of He and Ne by charged particle impact was explored in kinematically complete experiments measuring the final momenta of the two emerging electrons(Pfe1, Pfe2) and of the recoiling target ion PRf. The momentum transfer from the 3.6 MeV/u Se28+projectile to the electrons is found to be negligibly small. Thus distinct patterns observed in the Pfe1- versus - Pfe2spectra sensitively reflect the details of the electrons' correlated motion. Classical calculations reasonably describe the data only when the (e-e)interaction during the ionization reaction is included. © 1996 The American Physical Society.

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Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James Jan 1996

Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James

Physics Faculty Research & Creative Works

We have carried out neutron and magnetic studies on Nd2Fe17-xTx (T=Si, Mn) alloys. the unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. the Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric …

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Measurements Of Recoil And Projectile Momentum Distributions For 19-Mev [Formula Presented] + Ne Collisions, V. Frohne, S. Cheng, R. M. Ali, M. L.A. Raphaelian, C. L. Cocke, Ronald E. Olson Jan 1996

Measurements Of Recoil And Projectile Momentum Distributions For 19-Mev [Formula Presented] + Ne Collisions, V. Frohne, S. Cheng, R. M. Ali, M. L.A. Raphaelian, C. L. Cocke, Ronald E. Olson

Physics Faculty Research & Creative Works

The collision system of 19-MeV [Formula Presented] on Ne has been studied using recoil and projectile momentum spectroscopy. For each event, identified by final recoil and projectile charge state, the three-dimensional momentum vector of the recoil ion and the transverse momentum vector of the projectile ion were measured. The transverse momenta of the recoil and projectile ions were found to be equal in magnitude and opposite in direction, indicating that the transverse momentum exchange is dominated by interactions between the two ion cores. The transverse momentum distributions are well described by nCTMC calculations. The longitudinal momentum distributions of the recoil …

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High-Temperature Thermopower Of And Related Systems, D. Marsh, Paul Ernest Parris Jan 1996

High-Temperature Thermopower Of And Related Systems, D. Marsh, Paul Ernest Parris

Physics Faculty Research & Creative Works

We investigate theoretically the high-temperature Seebeck coefficient in LaMnO3 and related transition-metal-oxide perovskites. Our analysis employs a model for small polaron conduction that takes into account the electronic structure of the 3d orbitals of B-site transition-metal cations, yielding expressions for systems in which conduction occurs through the eg transition-metal manifold. Limiting forms for the Seebeck coefficient as a function of carrier concentration and site degeneracy are identified for strong and weak Coulomb interactions between electrons on the same and neighboring sites. Results are applied to an analysis of experimental data for LaMnO3, the La1-xCa …

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An Inline Optical Electron Polarimeter, K. W. Trantham, Timothy J. Gay, R. J. Vandiver Jan 1996

An Inline Optical Electron Polarimeter, K. W. Trantham, Timothy J. Gay, R. J. Vandiver

Physics Faculty Research & Creative Works

The design and operation of a simple inline optical electron polarimeter is presented. It is based on exchange excitation of ground state neon atoms. The electron polarization is determined from the degree of circular polarization of the subsequent 2p53p 3D3→2p53s 3P2 (6402 Å) fluorescence. This device can characterize both longitudinally and transversely polarized electron beams in a nondestructive fashion, and is inexpensive and easily constructed. © 1996 American Institute of Physics.

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Single Ionization Of He By Low-Velocity Protons And [Formula Presented]: Ejected Electron Momentum Distributions, S. D. Kravis, M. Abdallah, C. L. Cocke, C. D. Lin, M. Stockli, B. Walch, Y. D. Wang, Ronald E. Olson, V. D. Rodríguez, W. Wu, M. Pieksma, N. Watanabe Jan 1996

Single Ionization Of He By Low-Velocity Protons And [Formula Presented]: Ejected Electron Momentum Distributions, S. D. Kravis, M. Abdallah, C. L. Cocke, C. D. Lin, M. Stockli, B. Walch, Y. D. Wang, Ronald E. Olson, V. D. Rodríguez, W. Wu, M. Pieksma, N. Watanabe

Physics Faculty Research & Creative Works

A technique for electron spectroscopy which yields full two-dimensional momentum distributions for continuum electrons has been used to study ejected electrons from single ionization of He by [Formula Presented] and proton projectiles at low velocities. Projectile velocities of 1.63, 1.38, and 1.16 a.u. for [Formula Presented] and 2.39, 1.71, 1.15,. 85, and 0.63 a.u. for protons were used. All spectra show much broader distributions along the beam than transverse to the beam. For the case of proton bombardment, the spectra are strongly influenced by both target and projectile potentials, maximizing near the velocity of the saddle in the potential between …

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Quantum Version Of A Spherical Model: Crossover From Quantum To Classical Critical Behavior, Thomas Vojta Jan 1996

Quantum Version Of A Spherical Model: Crossover From Quantum To Classical Critical Behavior, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate a quantum version of the spherical model which is obtained from the classical Berlin-Kac spherical model by a simple canonical quantization scheme. We find a complete solution of the model for short-range as well as for long-range interactions. At finite temperatures the critical behavior is the same as in the classical spherical model whereas at zero temperature we find a quantum phase transition characterized by new critical exponents. Based on a functional-integral representation of the partition function the free energy of the model is shown to be equivalent to that of the nonlinear σ model in the limit …

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Optical Electron Polarimetry With Heavy Noble Gases, Timothy James Gay, J. E. Furst, K. W. Trantham, W. M.K.P. Wijayaratna Jan 1996

Optical Electron Polarimetry With Heavy Noble Gases, Timothy James Gay, J. E. Furst, K. W. Trantham, W. M.K.P. Wijayaratna

Physics Faculty Research & Creative Works

We have measured the polarization of fluorescence emitted by the noble gases He, Ne, Ar, Kr, and Xe following impact excitation by polarized electrons. In He, the [Formula Presented]P→[Formula Presented]S transition was studied; in the heavy noble gases the [Formula Presented](n+1)p[Formula Presented]→[Formula Presented](n+1)s[Formula Presented] transitions were analyzed. We investigated these transitions as candidates for efficient optical electron polarimetry and found that, because of their larger excitation cross sections and analyzing power, the heavy noble gases are superior to He, which had been used previously as a polarimetric target. Several issues with regard to the implementation and accuracy of optical electron …

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Collective Behavior Of Electrons Emitted In Multiply Ionizing Collisions Of 5.9 Mev/U U⁶⁵⁺ With Ne, M. Unverzagt, R. Moshammer, W. Schmitt, Ronald E. Olson, P. Jardin, V. Mergel, J. Ullrich, H. Schmidt-Böcking Jan 1996

Collective Behavior Of Electrons Emitted In Multiply Ionizing Collisions Of 5.9 Mev/U U⁶⁵⁺ With Ne, M. Unverzagt, R. Moshammer, W. Schmitt, Ronald E. Olson, P. Jardin, V. Mergel, J. Ullrich, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

The collective behavior of up to six target electrons emitted in a single collision of 5.9 MeV/u U65+ with Ne was investigated using high-resolution recoil-ion momentum spectroscopy. With an increasing number of ejected electrons the recoil ions are increasingly scattered into the backward direction, providing evidence that the electrons are emitted into the forward hemisphere. Their mean longitudinal sum energy varies from about 5 eV for single ionization up to 1.1 keV for Ne6+. Experimental recoil-ion momentum distributions are in excellent agreement with results of classical many-particle calculations. © 1996 The American Physical Society.

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Effective-Medium Theory For The Electric-Field Dependence Of The Hopping Conductivity Of Disordered Solids, Paul Ernest Parris, B. D. Bookout Jan 1996

Effective-Medium Theory For The Electric-Field Dependence Of The Hopping Conductivity Of Disordered Solids, Paul Ernest Parris, B. D. Bookout

Physics Faculty Research & Creative Works

We derive a general effective-medium theory for describing biased diffusion on a bond-disordered lattice in the presence of an external driving field. In our theory, the effective medium associated with a disordered d-dimensional lattice is characterized, for each value of the applied field, by 2d independent parameters describing, respectively, the net drift velocity vv and the diffusion constant Dvv describing the spread of a carrier packet about its mean value, for each of the d crystal axes. The theory correctly predicts the velocity transition occurring in an exactly soluble model studied by Derrida and, in contrast to other …

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Upper-Tropospheric Aerosol Sampled During Project Fire Ifo Ii, Donald E. Hagen, Josef Podzimek, Max B. Trueblood Dec 1995

Upper-Tropospheric Aerosol Sampled During Project Fire Ifo Ii, Donald E. Hagen, Josef Podzimek, Max B. Trueblood

Physics Faculty Research & Creative Works

Aerosols can play a role in the cloud formation process through the heterogeneous nucleation mechanism, and in turn, once formed, cirrus clouds can impact the ambient aerosol through scavenging and other collection mechanisms. University of Missouri aerosol sampling facilities were employed on aircraft for in situ collection and characterization of the particulates near cirrus cloud level. Tandem differential mobility analyzer and impactor techniques were used to measure aerosol size distribution, hydration capability, and particle composition information. Evidence of aerosol layering was observed near the tropospause, and there was a tendency toward depletion of the ambient aerosol at both ends of …

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Coherent Excitation Of The Singlet-Triplet Mixed 1s4f State Of Helium, Jingbo Wang, J. F. Williams, Andris T. Stelbovics, John E. Furst, Don H. Madison Oct 1995

Coherent Excitation Of The Singlet-Triplet Mixed 1s4f State Of Helium, Jingbo Wang, J. F. Williams, Andris T. Stelbovics, John E. Furst, Don H. Madison

Physics Faculty Research & Creative Works

In this paper, we present a detailed theoretical description for the coherent electron-impact excitation, the subsequent time evolution, and the cascading decay process of the singlet-triplet mixed 1s4f state of helium. The excitation amplitude and phase of each sublevel of this state are related to measurable coincidence intensities and polarizations of the emitted photons. It is found that the intensity and polarization of the emitted photons are time modulated due to the singlet and triplet mixing in the 1s4f state.

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Comparison Of Branching Ratio And Sum-Rule Analyses Of Magnetic Circular Dichroism In X-Ray-Absorption Spectroscopy, James G. Tobin, George Daniel Waddill, Alan F. Jankowski, Philip A. Sterne, David P. Pappas Sep 1995

Comparison Of Branching Ratio And Sum-Rule Analyses Of Magnetic Circular Dichroism In X-Ray-Absorption Spectroscopy, James G. Tobin, George Daniel Waddill, Alan F. Jankowski, Philip A. Sterne, David P. Pappas

Physics Faculty Research & Creative Works

Two localized picture methods of analyzing the magnetic circular dichroism in x-ray absorption will be applied to experimental results: the branching ratio (BR) and sum rule (SR) approaches. A derivation of the BR formulas and detailed comparison to the SR expressions will be made, including error estimations. The BR approach will be seen to be a limiting case form of the SR spin-moment expression and provide a simple picture of the underlying physics in magnetic x-ray circular dichroism absorption in 3d magnetic materials.

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Floquet Description Of Multiphoton Processes In Li, D. I. Duncan, J. Greg Story, Thomas F. Gallagher Sep 1995

Floquet Description Of Multiphoton Processes In Li, D. I. Duncan, J. Greg Story, Thomas F. Gallagher

Physics Faculty Research & Creative Works

We have made several different types of measurements of the three-photon ionization of Li produced by 3-ps laser pulses and describe the results using a Floquet picture. Over the photon frequency range 15 000 to 15 800 cm-1, Li represents a strongly coupled three-state system with the 2s ground state coupled to the 2p and 3d states by one and two photons, respectively. Energy analysis of the photoelectrons allows the measurement of the intensity dependent shift of the 2s Floquet state during the laser pulse. The shift shows a strong frequency dependence that is not predicted by first-order …

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Polarized Light Emission In Kev He²⁺ + Na(3s) Collisions, S. Schippers, P. Boduch, J. Van Buchem, F. W. Bliek, R. Hoekstra, R. Morgenstem, Ronald E. Olson Aug 1995

Polarized Light Emission In Kev He²⁺ + Na(3s) Collisions, S. Schippers, P. Boduch, J. Van Buchem, F. W. Bliek, R. Hoekstra, R. Morgenstem, Ronald E. Olson

Physics Faculty Research & Creative Works

We investigated l- and m-distributions of He u (n = 4) states formed during 213.3 keV amu'1 He2+ + Na(3s) collisions by measuring profiles and the linear polarization of the He u (4→ 3) emission. We found that at these energies capture into He+(4f) dominates over capture into other He+(4i) states. Over the indicated energy range the polarization of the4He u (4 → 3) photon emission increases from 0.2 to 0.3 indicating a strong alignment of the captured projectile charge cloud along the intemuclear axis. Due to the non-zero nuclear spin the polarization is up to 10% lower when using3He2+ …

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Electron Emission From Foils Induced By Heavy-Ion Collisions, R. A. Sparrow, Ronald E. Olson, D. Schneider Aug 1995

Electron Emission From Foils Induced By Heavy-Ion Collisions, R. A. Sparrow, Ronald E. Olson, D. Schneider

Physics Faculty Research & Creative Works

Absolute double differential yield per ion has been calculated for forward and backward electron emission produced by collisions of highly charged uranium ions with carbon foils of varying thicknesses. A Monte Carlo method has been developed which employs multiple ionization of the carbon and subsequent energy and angular straggling of freed electrons through the foil. A comparison with experimental double differential electron emission yields shows general agreement. Calculated total electron emission is in agreement with experiment at 44 fig cm-2 as well as the results of Rothard et el. In addition, the radial distribution of energy deposited by the electrons …

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Polarized Light Emission In Kev He ²⁺+Na(3s) Collisions, S. Schippers, P. Boduch, J. Van Buchem, F. W. Bliek, R. Hoekstra, R. Morgenstern, Ronald E. Olson Aug 1995

Polarized Light Emission In Kev He ²⁺+Na(3s) Collisions, S. Schippers, P. Boduch, J. Van Buchem, F. W. Bliek, R. Hoekstra, R. Morgenstern, Ronald E. Olson

Physics Faculty Research & Creative Works

We investigated l- and m-distributions of He Pi (n=4) states formed during 2-13.3 keV amu -1 He 2++Na(3s) collisions by measuring profiles and the linear polarization of the He Pi (4 to 3) emission. We found that at these energies capture into He +(4f) dominates over capture into other He +(4l) states. Over the indicated energy range the polarization of the 4He Pi (4 to 3) photon emission increases from 0.2 to 0.3 indicating a strong alignment of the captured projectile charge cloud along the internuclear axis. Due to the non-zero nuclear spin the polarization is up to 10% lower …

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Instability Of The R³Xs¹ Vacuum In Low-Energy Effective String Theory, Mariano Cadoni, Marco Cavaglia Aug 1995

Instability Of The R³Xs¹ Vacuum In Low-Energy Effective String Theory, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We present and discuss a Euclidean solution of the low-energy effective string action that can be interpreted as a semiclassical decay process of the ground state of the theory.

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Coulomb Gap At Finite Temperatures, Masoud Sarvestani, Michael Schreiber, Thomas Vojta Aug 1995

Coulomb Gap At Finite Temperatures, Masoud Sarvestani, Michael Schreiber, Thomas Vojta

Physics Faculty Research & Creative Works

The Coulomb glass, a model of interacting localized electrons in a random potential, exhibits a soft gap, the Coulomb gap, in the single-particle density of states (DOS) g(ε,T) close to the chemical potential µ. In this paper we investigate the Coulomb gap at finite temperatures T by means of a Monte Carlo method. We find that the Coulomb gap fills with increasing temperature. In contrast to previous results the temperature dependence is, however, much stronger than g(µ,T)~TD-1 as predicted analytically. It can be described by power laws with the exponents 1.75 ± 0.1 for the two-dimensional model and 2.7 …

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Binary Nucleation Kinetics. Ii. Numerical Solution Of The Birth-Death Equations, Barbara Ellen Wyslouzil, Gerald Wilemski Jul 1995

Binary Nucleation Kinetics. Ii. Numerical Solution Of The Birth-Death Equations, Barbara Ellen Wyslouzil, Gerald Wilemski

Physics Faculty Research & Creative Works

We numerically solve the complete set of coupled differential equations describing transient binary nucleation kinetics for vapor-to-liquid phase transitions. We investigate binary systems displaying both positive and negative deviations from ideality in the liquid phase and obtain numerical solutions over a wide range of relative rates of monomer impingement. We emphasize systems and conditions that either have been or can be investigated experimentally. In almost every case, we find behavior consistent with Stauffer's idea that the major particle flux passes through the saddle point with an orientation angle that depends on the rates of monomer impingement. When this is true, …

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Binary Nucleation Kinetics. I. Self-Consistent Size Distribution, Gerald Wilemski, Barbara Ellen Wyslouzil Jul 1995

Binary Nucleation Kinetics. I. Self-Consistent Size Distribution, Gerald Wilemski, Barbara Ellen Wyslouzil

Physics Faculty Research & Creative Works

Using the principle of detailed balance, we derive a new self-consistency requirement, termed the kinetic product rule, relating the evaporation coefficients and equilibrium cluster distribution for a binary system. We use this result to demonstrate and resolve an inconsistency for an idealized Kelvin model of nucleation in a simple binary mixture. We next examine several common forms for the equilibrium distribution of binary clusters based on the capillarity approximation and ideal vapor behavior. We point out fundamental deficiencies for each expression. We also show that each distribution yields evaporation coefficients that formally satisfy the new kinetic product rule but are …

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Generalization Of The Schwartz-Soffer Inequality For Correlated Random Fields, Thomas Vojta, Michael Schreiber Jul 1995

Generalization Of The Schwartz-Soffer Inequality For Correlated Random Fields, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We investigate the influence of spatial correlations between the values of the random field on the critical behavior of random-field lattice models and derive a generalized version of the Schwartz-Soffer inequality for the averages of the susceptibility and its disconnected part. At the critical point this leads to a modification of the Schwartz-Soffer exponent inequality for the critical exponents η and η- describing the divergences of the susceptibility and its disconnected part, respectively. It now reads η- ≤ 2η-2y where 2y describes the divergence of the random-field correlation function in Fourier space. As an example we exactly calculate …

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The Kelvin Equation And Self-Consistent Nucleation Theory, Gerald Wilemski Jul 1995

The Kelvin Equation And Self-Consistent Nucleation Theory, Gerald Wilemski

Physics Faculty Research & Creative Works

Issues of self-consistency are reviewed for several unary equilibrium size distributions based on the capillarity approximation. Some apparent difficulties of interpretation are resolved. In terms of the kinetic approach to nucleation theory, the influence of self-consistency on the nucleation rate is shown to arise entirely from differences in the dimer evaporation rates for nearly all versions of classical theory. The nucleation rate behavior of the Kelvin model is explored. In this model, the Kelvin equation is used to prescribe all cluster evaporation rates. Nucleation rates predicted by the Kelvin model are quantitatively similar to those of the self-consistent classical (SCC) …

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Observation Of Postcollision Effects In The Scattered Projectile Spectra For Ionizing Proton-Helium Collisions, Tibor Vajnai, A. D. Gaus, Joachim A. Brand, W. T. Htwe, Don H. Madison, Ronald E. Olson, Jerry Peacher, Michael Schulz May 1995

Observation Of Postcollision Effects In The Scattered Projectile Spectra For Ionizing Proton-Helium Collisions, Tibor Vajnai, A. D. Gaus, Joachim A. Brand, W. T. Htwe, Don H. Madison, Ronald E. Olson, Jerry Peacher, Michael Schulz

Physics Faculty Research & Creative Works

We have measured and calculated doubly differential single ionization cross sections as a function of the scattering angle and the projectile energy loss for 50 to 150 keV proton-helium collisions. These cross sections show unexpected structures as a function of both the energy loss and the scattering angle, which are interpreted as due to the postcollision interaction. Although the effects of postcollision interactions have previously been observed in electron spectra, this is the first observation of such effects for the scattered protons.

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Target Dependence Of Binary Encounter Electron Peak Anomalies In Collisions Of Partially Stripped Heavy Ions With Molecular Hydrogen And Noble Gases, W. Wolff, J. Wang, H. E. Wolft, J. L. Shinpaugh, Ronald E. Olson, D. H. Jakubassa-Amundsen, S. Lencinas, U. Bechthold, R. Herrmann, H. Schmidt-Bocking Apr 1995

Target Dependence Of Binary Encounter Electron Peak Anomalies In Collisions Of Partially Stripped Heavy Ions With Molecular Hydrogen And Noble Gases, W. Wolff, J. Wang, H. E. Wolft, J. L. Shinpaugh, Ronald E. Olson, D. H. Jakubassa-Amundsen, S. Lencinas, U. Bechthold, R. Herrmann, H. Schmidt-Bocking

Physics Faculty Research & Creative Works

A systematic search was performed for the manifestation of quantum interference effects in the shape and angular distribution of the binary-encounter electron peak in collisions of partially stripped, or structured, heavy ions with noble gases and molecular hydrogen. The ionic species investigated were Cu5+,19+, I7+,23+, Au11+,29+ and U13+, all at the same nominal velocity equivalent to 0.6 MeV amu-1. Experimental double-differential cross sections for secondary electron emission in the binary encounter energy region are compared with a simple model based on the elastic scattering of quasi-free target electrons in the projectile field as well as with results of impulse approximation …

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