Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Physics Faculty Research & Creative Works

Discipline
Keyword
Publication Year

Articles 1261 - 1290 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Differential Double-Excitation Cross Sections In 50-150-Kev Proton-Helium Collisions, Michael Schulz, W. T. Htwe, A. D. Gaus, Jerry Peacher, Tibor Vajnai Mar 1995

Differential Double-Excitation Cross Sections In 50-150-Kev Proton-Helium Collisions, Michael Schulz, W. T. Htwe, A. D. Gaus, Jerry Peacher, Tibor Vajnai

Physics Faculty Research & Creative Works

We have measured projectile-energy-loss spectra for 50-, 100-, and 150-keV p+He collisions. From the data we obtained differential double-excitation cross sections as a function of projectile scattering angle. At 150 keV a pronounced peak structure was observed at about 0.7 mrad for double excitation to the (2p2) 1D and (2s2p) 1P states. Our data provide indications for the dominance of a first-order mechanism involving the electron-electron interaction in double excitation for 150 keV at small scattering angles. At lower projectile energies and larger scattering angles a second-order mechanism appears to be of the same order of …

Go to article

State Selective Scattering Angle Dependent Capture Cross Sections Measured By Cold Target Recoil Ion Momentum Spectroscopy, Volker Mergel, Reinhard Dorner, Joachim Hermann Ullrich, Ottmar Jagutzki, Sergio Lencinas, S. Nuttgens, Lutz Spielberger, Marc Unverzagt, C. Lewis Cocke, Ronald E. Olson, Michael Schulz, Udo Buck, E. Zanger, W. Theisinger, M. Isser, S. Geis, Horst Schmidt-Bocking Mar 1995

State Selective Scattering Angle Dependent Capture Cross Sections Measured By Cold Target Recoil Ion Momentum Spectroscopy, Volker Mergel, Reinhard Dorner, Joachim Hermann Ullrich, Ottmar Jagutzki, Sergio Lencinas, S. Nuttgens, Lutz Spielberger, Marc Unverzagt, C. Lewis Cocke, Ronald E. Olson, Michael Schulz, Udo Buck, E. Zanger, W. Theisinger, M. Isser, S. Geis, Horst Schmidt-Bocking

Physics Faculty Research & Creative Works

We have developed a new kind of recoil ion momentum spectroscopy technique, using a precooled supersonic gas jet target, to determine state selective, scattering angle dependent cross sections for swift ion-atom collisions ( 0. 25 , ..., , 1 MeV He2+ on He), by measuring the transverse and longitudinal momentum of the recoil ion. A longitudinal momentum resolution of ± 0.13 a. u. was achieved, about a factor of 30 better than ever obtained before, which enables a clear separation of K and L shell capture. In the transverse direction a resolution corresponding to a projectile scattering angle uncertainty …

Go to article

Electric-Field Enhancement Of Dielectronic Recombination From A Continuum Of Finite Bandwidth, J. Greg Story, Bernard J. Lyons, Thomas F. Gallagher Mar 1995

Electric-Field Enhancement Of Dielectronic Recombination From A Continuum Of Finite Bandwidth, J. Greg Story, Bernard J. Lyons, Thomas F. Gallagher

Physics Faculty Research & Creative Works

A small electric field is shown to increase the dielectronic recombination, via autoionizing Rydberg states, of an electron from a continuum of finite bandwidth. The continuum of finite bandwidth is a broad autoionizing state which is part of a series converging to a higher limit, and the field enhancement of the rate occurs because the field converts the nl Rydberg states to nk Stark states, increasing the number of contributing recombination paths. The experimental results are in excellent agreement with the predictions of an isolated resonance approximation treatment and show clearly both the positive effect of Stark mixing and the …

Go to article

Three-Body Final-State Momentum Distributions For Swift H⁺And He2+On He Collisions, R. Dömer, V. Mergel, Liu Zhaoyuan, J. Uilrich, L. Spielberger, Ronald E. Olson, H. Schmidt-Bocking Feb 1995

Three-Body Final-State Momentum Distributions For Swift H⁺And He2+On He Collisions, R. Dömer, V. Mergel, Liu Zhaoyuan, J. Uilrich, L. Spielberger, Ronald E. Olson, H. Schmidt-Bocking

Physics Faculty Research & Creative Works

The transverse and longitudinal momentum distributions of He+ions produced by 0.25-1MeV u-1H+ and He2+impact have been measured using a precooled supersonic gas jet target (cold-target recoil ion-momentum spectroscopy—coltrims). The transverse momentum of the recoil ions is mainly determined by the impact parameter. In the longitudinal direction the recoil ions are slightly backwardly directed. The width of the longitudinal momentum distribution is close to the electron momentum distribution in the initial state. This distribution gets much broader for larger transverse momentum transfer (i.e. smaller impact parameters). The experimental results are in good agreement with nCTMC calculations. © 1995 IOP Publishing Ltd.

Go to article

Neutron Investigations Of Novel Magnetic Phases, William B. Yelon Jan 1995

Neutron Investigations Of Novel Magnetic Phases, William B. Yelon

Physics Faculty Research & Creative Works

Recent years have seen a renewed search for Fe based permanent magnets, spurred by the discovery of Nd2Fe14B and interstitially modified rare-earth iron binaries. The insights derived from those compounds have suggested a number of routes to the development of such systems, including selective site substitution and combinations of site substitution and interstitial modification. Neutron diffraction is an essential component of this work, since it provides systematic information about the location of substitutional and interstitial atoms, and about the effects these changes have on the magnetic interactions in the systems of interest

Go to article

Measurements Of Fast Confined Alphas On Tftr, R. K. Fisher, J. M. Mcchesney, P. B. Parks, H. H. Duong, S. S. Medley, A. L. Roquemore, D. K. Mansfield, R. V. Budny, M. P. Petrov, Ronald E. Olson Jan 1995

Measurements Of Fast Confined Alphas On Tftr, R. K. Fisher, J. M. Mcchesney, P. B. Parks, H. H. Duong, S. S. Medley, A. L. Roquemore, D. K. Mansfield, R. V. Budny, M. P. Petrov, Ronald E. Olson

Physics Faculty Research & Creative Works

This Letter reports the first measurements of the fast confined α-particle energy distribution in a fusion plasma. The pellet charge exchange technique shows the fusion generated α's in the core of the Tokamak Fusion Test Reactor plasma slow down classically, and appear to be well confined. Preliminary indications are that stochastic ripple effects are responsible for steepening the energy distribution outside the plasma core (r/a0.35). Sawteeth mixing of fast α's is suggested in data during the post-beam-heating plasma decay. © 1995 The American Physical Society.

Go to article

Projectile Energy Loss In Multiply Ionizing Ion-Atom Collisions, Harald Schone, Reinhold S. Schuch, Sheldon Datz, Michael Schulz, Peter F. Dittner, J. P. Giese, Quentin C. Kessel, Herbert F. Krause, Philip D. Miller, Charles Randy Vane Jan 1995

Projectile Energy Loss In Multiply Ionizing Ion-Atom Collisions, Harald Schone, Reinhold S. Schuch, Sheldon Datz, Michael Schulz, Peter F. Dittner, J. P. Giese, Quentin C. Kessel, Herbert F. Krause, Philip D. Miller, Charles Randy Vane

Physics Faculty Research & Creative Works

The projectile energy loss for 7.5--25-MeV C6+,5+ and F6+ ions was measured for single collisions with He, Ne, Ar, and Kr as a function of the recoil-ion charge state and the projectile scattering. This energy loss was measured for collisions in which the projectile captured an electron and for those involving just direct ionization. We investigated and found a large average energy transfer (100--250 eV/electron) to the continuum electrons. A strong increase of the scattering angle with recoil-ion charge state was observed for both capture and direct ionization. The results imply that, for smaller impact parameters, higher recoil-ion …

Go to article

The Light Ion Pulsed Power Induction Accelerator For Etf, Ronald E. Olson, M. G. Mazarakis, C. L. Olson, D. L. Smith, L. F. Bennett Jan 1995

The Light Ion Pulsed Power Induction Accelerator For Etf, Ronald E. Olson, M. G. Mazarakis, C. L. Olson, D. L. Smith, L. F. Bennett

Physics Faculty Research & Creative Works

The light ion Engineering Test Facility (ETF) driver concept, based on Hermes III and RHEPP technologies, is a scaled-down version of the LMF design incorporating repetition rate capabilities of up to 10 Hz. The preconceptual design presented here provides 250 TW peak power to the ETF target during 8 ns, equal to 2 MJ total ion beam energy. Linear inductive voltage addition driving a self-magnetically insulated transmission line (MITL) is utilized to generate the 36 MV peak voltage needed for lithium ion beams. The ~3 MA ion current is achieved by utilizing many accelerating modules in parallel. Since the current …

Go to article

Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James Jan 1995

Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James

Physics Faculty Research & Creative Works

ErNi5-xCox alloys were prepared by RF induction melting and analyzed using neutron powder diffraction. Rietveld analysis neutron diffraction data indicates the unit cell volume increases with Co content while the a and c lattice parameters show different dependencies on the composition. the Co atoms show higher affinity for the 3g sites than for the 2c sites. the Co sublattice tends to couple antiferromagnetically to the Er sublattice. the easy magnetization direction is along the c axis.

Go to article

Energy Spread And Ion Current Measurements Of Several Ion Sources, A. D. Gaus, W. T. Htwe, J. A. Brand, Timothy James Gay, Michael Schulz Dec 1994

Energy Spread And Ion Current Measurements Of Several Ion Sources, A. D. Gaus, W. T. Htwe, J. A. Brand, Timothy James Gay, Michael Schulz

Physics Faculty Research & Creative Works

Energy spread and extracted current measurements are presented for five different types of ion sources: hot cathode, cold cathode, magnetron, microwave, and electron cyclotron resonance (ECR). The measurements were performed with a 45° parallel-plate energy analyzer with a resolution of better than 0.5 eV at 500 eV incident energy. Energy spreads ranged from 0.5 to 4 eV, while total extracted beam currents ranged from 2 to 30 μA. Beam currents due specifically to protons, 3He++ ions, and H +2 ions are also presented. The ECR and magnetron sources gave the best overall performance. These, along with the energy analyzer, are …

Go to article

Comment On "Critical Behavior Of The Coulomb Glass", Thomas Vojta, Michael Schreiber Nov 1994

Comment On "Critical Behavior Of The Coulomb Glass", Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

No abstract provided.

Go to article

Cosmological And Wormhole Solutions In Low-Energy Effective String Theory, Mariano Cadoni, Marco Cavaglia Nov 1994

Cosmological And Wormhole Solutions In Low-Energy Effective String Theory, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We derive and study a class of cosmological and wormhole solutions of low-energy effective string field theory. We consider a general four-dimensional string effective action where moduli of the compactified manifold and the electromagnetic field are present. The cosmological solutions of the two-dimensional effective theory obtained by dimensional reduction of the former are discussed. In particular we demonstrate that the two-dimensional theory possesses a scale-factor duality invariance. Eucidean four-dimensional instantons describing the nucleation of the baby universes are found and the probability amplitude for the nucleation process given.

Go to article

Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓalₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow Nov 1994

Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓalₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow

Physics Faculty Research & Creative Works

Aluminum-substituted Nd2Fe17-xAlx solid solutions with x=2.30, 4.44, 6.13, 8.00, and 9.40 have been studied by neutron diffraction and Mössbauer spectroscopy. A Rietveld analysis of the neutron scattering indicates that the aluminum atoms have a high initial affinity for the 18h site, show a high affinity for the 6c site at high aluminum concentrations, and are absent from the 9d site at all aluminum concentrations. The Mössbauer spectra show a maximum in both the maximum and weighted average hyperfine field for x≅2. This indicates that the lattice expansion which occurs with aluminum substitution is sufficient, at …

Go to article

Quantum Electromagnetic Wormholes And Geometrical Description Of The Electric Charge, Marco Cavaglia Oct 1994

Quantum Electromagnetic Wormholes And Geometrical Description Of The Electric Charge, Marco Cavaglia

Physics Faculty Research & Creative Works

I present and discuss a class of solutions of the Wheeler-DeWitt equation describing wormholes generated by coupling of gravity to the electromagnetic field for Kantowski-Sachs and Bianchi type-I spacetimes. Since the electronic charge can be viewed as electric lines of force trapped in a finite region of spacetime, these solutions can be interpreted as the quantum corresponding to the Einstein-Rosen-Misner-Wheeler electromagnetic geon.

Go to article

Neutron-Diffraction And Mössbauer Effect Study Of The Tb₂Fe₁₇₋ₓalₓ Solid Solutions, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Gary J. Long, Zhong Bo Hu, William B. Yelon, Fernande Grandjean, D. P. Middleton, K. H. J. Buschow Sep 1994

Neutron-Diffraction And Mössbauer Effect Study Of The Tb₂Fe₁₇₋ₓalₓ Solid Solutions, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Gary J. Long, Zhong Bo Hu, William B. Yelon, Fernande Grandjean, D. P. Middleton, K. H. J. Buschow

Physics Faculty Research & Creative Works

The magnetic properties of a series of Tb2Fe17-xAlx solid solutions, with nominal x compositions of 0, 2, 3, 4, 5, 6, 7, and 8, have been studied by neutron diffraction and Mössbauer spectroscopy. Neutron-diffraction data indicate that the compounds all crystallize with the Th2Zn17 structure and that the aluminum atoms are excluded from the 9d site and show a distinct preference for the 6c site only for an aluminum content greater than 6. The unit-cell volume increases by approximately 1% per aluminum atom substituted in the formula unit. The magnetic moment per …

Go to article

Differential Double Excitation Cross Sections In Proton-Helium Collisions Studied By Energy-Loss Spectroscopy, W. T. Htwe, Tibor Vajnai, M. Barnhart, A. D. Gaus, Michael Schulz Sep 1994

Differential Double Excitation Cross Sections In Proton-Helium Collisions Studied By Energy-Loss Spectroscopy, W. T. Htwe, Tibor Vajnai, M. Barnhart, A. D. Gaus, Michael Schulz

Physics Faculty Research & Creative Works

We have measured ion energy-loss spectra for 150 keV proton-helium collisions as a function of the projectile scattering angle. From the data we obtained double excitation cross sections differential in the proton scattering angle as well as the ratios of both double excitation and single ionization to single excitation. In these ratios pronounced peak structures are observed at about 0.7 mrad. Two alternative interpretations of these peak structures are offered: They may be due to binary collisions between the projectile and the target electrons, or they could be a manifestation of an interference between different transition amplitudes leading to the …

Go to article

He²⁺-He Collisions: One-Electron Capture And Target-Ion Excitation, H. O. Folkerts, F. W. Bliek, L. Meng, Ronald E. Olson, R. Morgenstern, M. V. Von Hellermann, H. P. Summers, R. Hoekstra Aug 1994

He²⁺-He Collisions: One-Electron Capture And Target-Ion Excitation, H. O. Folkerts, F. W. Bliek, L. Meng, Ronald E. Olson, R. Morgenstern, M. V. Von Hellermann, H. P. Summers, R. Hoekstra

Physics Faculty Research & Creative Works

By means of photon emission spectroscopy the authors have studied state selective one-electron capture and target-ion excitation in collisions of He2+ with He. The collision energy has been varied from 1 to 75 keV amu-1. Four-body classical trajectory Monte Carlo calculations have been performed in the energy range of 50-300 keV amu-1. In the energy range where experiment and theory overlap there is in general fair agreement, although the l-distributions within a principal quantum shell exhibit differences. At energies below 50 keV amu-1 the experiments confirm the results of atomic orbital calculations, presented in an accompanying paper by Fritsch (1994). …

Go to article

Effect Of Carrier Gas Pressure On Condensation In A Supersonic Nozzle, Barbara Ellen Wyslouzil, Gerald Wilemski, M. G. Beals, Michael B. Frish Aug 1994

Effect Of Carrier Gas Pressure On Condensation In A Supersonic Nozzle, Barbara Ellen Wyslouzil, Gerald Wilemski, M. G. Beals, Michael B. Frish

Physics Faculty Research & Creative Works

Supersonic nozzle experiments were performed with a fixed water or ethanol vapor pressure and varying amounts of nitrogen to test the hypothesis that carrier gas pressure affects the onset of condensation. Such an effect might occur if nonisothermal nucleation were important under conditions of excess carrier gas in the atmospheric pressure range, as has been suggested by Ford and Clement [J. Phys. A 22, 4007 (1989)]. Although a small increase was observed in the condensation onset temperature as the stagnation pressure was reduced from 3 to 0.5 atm, these changes cannot be attributed to any nonisothermal effects. The pulsed nozzle …

Go to article

Landau-Zener Treatment Of Intensity-Tuned Multiphoton Resonances Of Potassium, J. Greg Story, D. I. Duncan, Thomas F. Gallagher Aug 1994

Landau-Zener Treatment Of Intensity-Tuned Multiphoton Resonances Of Potassium, J. Greg Story, D. I. Duncan, Thomas F. Gallagher

Physics Faculty Research & Creative Works

When exposed to intense light of ~580 nm, the ground state of K shifts up in energy, passing through two photon resonances with Rydberg states, and finally crossing the two-photon ionization limit. We have used laser pulses of varying duration to study the nature of the population transfer from the ground state to the excited state due to the intensity-tuned resonances encountered during the rising edge of the pulse. A dynamic Floquet approach in which the resonances are treated as avoided crossings of the Floquet energy levels is used to model the population transfer and gives excellent agreement with the …

Go to article

Neutron-Diffraction Study Of Γ-Fe At High Pressure, Oran Allan Pringle, Rafael Calvo, R. E. Parra Aug 1994

Neutron-Diffraction Study Of Γ-Fe At High Pressure, Oran Allan Pringle, Rafael Calvo, R. E. Parra

Physics Faculty Research & Creative Works

Face-centered-cubic iron (γ-Fe) coherently precipitated in a single crystal of Cu has been studied by neutron diffraction at high pressures up to 0.9 GPa and in the temperature range from about 5 to 110 K. It undergoes antiferromagnetic ordering at 67±2 K at ambient pressure. The ordering temperature TN monotonically decreases with increasing pressure following a relation TN(K)=67-12.8p - 11.1p2 - 6.17p3, where p is in units of GPa. The change of TN in γ-Fe is discussed in terms of the volume change caused by pressurization or by alloying.

Go to article

Critical Correlations And Susceptibilities In The Random-Field Spherical Model, Thomas Vojta, Michael Schreiber Jul 1994

Critical Correlations And Susceptibilities In The Random-Field Spherical Model, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We investigate the behavior of the correlation function and the susceptibility of the random-field spherical model at the critical point. In particular we calculate the critical exponents η and η- describing the divergences of the susceptibility and its disconnected part, respectively. In the case of short-range interactions we obtain η=η-=0. For power-law interactions Uij~rij-σ we find η=1/2η-=D+2-σ (for D<σ

Go to article

Differential Transfer Ionization Cross Sections For 50175-Kev Proton-Helium Collisions, S. W. Bross, S. M. Bonham, A. D. Gaus, Jerry Peacher, Tibor Vajnai, Michael Schulz, Horst Schmidt-Bocking Jul 1994

Differential Transfer Ionization Cross Sections For 50175-Kev Proton-Helium Collisions, S. W. Bross, S. M. Bonham, A. D. Gaus, Jerry Peacher, Tibor Vajnai, Michael Schulz, Horst Schmidt-Bocking

Physics Faculty Research & Creative Works

We have measured coincidences between neutralized projectiles and He recoil ions for 50175-keV proton-helium collisions. From the data we obtained transfer ionization (TI) cross sections differential in the projectile scattering angle. Laboratory scattering angles range from 0 to 2.0 mrad. The experimental method allowed separation of the postcollision charge states of the target atoms. The ratio of the cross sections for TI to the sum of TI and single capture, F, is presented as a function of projectile scattering angle. Comparison is made to previous measurements of this ratio where data is available. The differential cross sections are compared to …

Go to article

A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of Nd₂Fe₁₅Ga₂ And The Tb₂Fe₁₇₋ₓgaₓ Solid Solutions, Zhong Bo Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean Jul 1994

A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of Nd₂Fe₁₅Ga₂ And The Tb₂Fe₁₇₋ₓgaₓ Solid Solutions, Zhong Bo Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean

Physics Faculty Research & Creative Works

An x-ray diffraction study of the substitution of gallium in Tb 2Fe17 to form the Tb2Fe17-xGax solid solutions indicates that the compounds adopt the rhombohedral Th2Zn17 structure. The unit cell volume and the a-axis lattice parameter increase linearly with increasing gallium content. The c-axis lattice parameter increases linearly from x=0 to 6 and then decreases between x=7 and 8. Magnetic studies show the Curie temperature increases by ~150° above that of Tb2Fe17 to reach a maximum between x=3 and 4, and then decreases with further increases in …

Go to article

Projectile And Electron Spectra Resulting From Positron-Argon Collisions, R. A. Sparrow, Ronald E. Olson Jun 1994

Projectile And Electron Spectra Resulting From Positron-Argon Collisions, R. A. Sparrow, Ronald E. Olson

Physics Faculty Research & Creative Works

A three-body classical trajectory Monte-Carlo calculation is used to evaluate the differential cross sections for the ejected electron, as well as the projectile scattering for 50, 100 and 150 eV e++Ar0 electron removal collisions. In the ionized eleciron spectra both the electron capture to the continuum (ecc) and binary peak structures are observed. The theoretical ecc peak is diffuse and shifted to lower energies than expected from simple arguments. The calculated double differential cross sections for electron ejection have been compared to experiment, When the experimental apparatus function of Moxom et al is used to convolute the theoretical spectra, good …

Go to article

State-Selective Electron Capture In He²⁺-H2 Collisions, L. Meng, Ronald E. Olson, H. O. Folkerts, R. Hoekstra Jun 1994

State-Selective Electron Capture In He²⁺-H2 Collisions, L. Meng, Ronald E. Olson, H. O. Folkerts, R. Hoekstra

Physics Faculty Research & Creative Works

A classical phase-space model of the hydrogen molecule which includes both electrons and nuclear centers is utilized to study state selective electron capture for collisions with alpha particles at intermediate impact energies (30-200 keV amu‑1), The calculations are performed within the framework of the classical trajectory Monte Carlo method. The direct one-electron transfer process and the transfer ionization reaction which becomes increasingly important at the higher impact energies are directly included in the cross section determinations. Photon emission spectroscopy experiments were conducted to obtain line emission cross sections for capture to the He+(np) states, n = 2-5, for energies from …

Go to article

Anisotropic Wormhole: Tunneling In Time And Space, Marco Cavaglia, Vittorio De Alfaro, Fernado De Felice Jun 1994

Anisotropic Wormhole: Tunneling In Time And Space, Marco Cavaglia, Vittorio De Alfaro, Fernado De Felice

Physics Faculty Research & Creative Works

We discuss the structure of a gravitational Euclidean instanton obtained through coupling of gravity to electromagnetism. This Euclidean solution can be interpreted as a tunneling to a hyperbolic space (baby universe) or alternatively as a static wormhole that joins two asymptotically flat spaces of a Reissner-Nordström type solution.

Go to article

Channel Closing In Multiphoton Ionization Of Mg, J. Greg Story, D. I. Duncan, Thomas F. Gallagher May 1994

Channel Closing In Multiphoton Ionization Of Mg, J. Greg Story, D. I. Duncan, Thomas F. Gallagher

Physics Faculty Research & Creative Works

Experimental data are presented showing the channel closing of four-photon ionization of Mg. It is shown that, for circularly polarized light, the ionization versus intensity spectra exhibit sharp breaks from the normal I4 intensity dependence at the critical intensity where the channel closing occurs. Above the critical intensity, the population of Rydberg states which survives the laser pulse is observed. The residual Rydberg population is found to be greatly reduced for linearly polarized light due to the relatively large probability of ionization of the low-angular-momentum Rydberg states. The data are in good agreement with a model which includes averaging …

Go to article

Spin-Resolved (E,2e) Coincidences For Heavy Rare-Gas Targets, Stephenie J. Jones, Don H. Madison, G. Friedrich Hanne Apr 1994

Spin-Resolved (E,2e) Coincidences For Heavy Rare-Gas Targets, Stephenie J. Jones, Don H. Madison, G. Friedrich Hanne

Physics Faculty Research & Creative Works

It has been well established that the Coulomb force alone can produce spin-dependent effects for electron-impact excitation of heavy rare-gas atoms if the incident electrons are spin polarized and the final J state of the atom is resolved. This effect has become known as the fine-structure effect. Here we demonstrate that the same type of effect may be expected for electron-impact ionization.

Go to article

Coherence Parameters For Electron Capture In H⁺ + He Collisions, C. J. Lundy, Ronald E. Olson, D. R. Schultzi, J. P. Pascale Mar 1994

Coherence Parameters For Electron Capture In H⁺ + He Collisions, C. J. Lundy, Ronald E. Olson, D. R. Schultzi, J. P. Pascale

Physics Faculty Research & Creative Works

The classical trajectory Monte Carlo method is used to calculate coherence parameters for electron capture to H(n = 2, 3 and 4) in 30 to 250 keV H+ + He collisions. The parameters evaluated are the x- and z-components of the dipole moment (D) and the z-component of the perihelion velocity of the captured electron (L x A). The calculated integral values are found to be in reasonable agreement with available experimental results. Components of the dipole moment and (L x A) were also evaluated as a function of projectile scattering angle. Here, rapid variations of the parameters are observed …

Go to article

Correlated Two-Electron Wave Functions Of Any Symmetry, Christopher Bottcher, David R. Schultz, Don H. Madison Mar 1994

Correlated Two-Electron Wave Functions Of Any Symmetry, Christopher Bottcher, David R. Schultz, Don H. Madison

Physics Faculty Research & Creative Works

Using a procedure originally due to Hylleraas, a convenient expansion in coupled spherical harmonics which terminates in a very small number of terms is applied to the treatment of fully correlated two-electron wave functions of any symmetry (total angular momentum, parity, and spin). Coupled equations satisfied by these wave functions are derived which are well adapted to computation and which we discretize on a numerical lattice utilizing the basis-spline collocation method. Use of this method which relies on very flexible basis functions is intended to facilitate subsequently the consideration of time-dependent rearrangments such as autoionization, photoionization, and electron-impact excitation and …

Go to article

First Prev Next Last