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Articles 1 - 30 of 31
Full-Text Articles in Physical Sciences and Mathematics
Semiquantal Modeling Of Thermal Vibrational Relaxation Of Diatomic Molecules, Ronald James Bieniek, Steven J. Lipson
Semiquantal Modeling Of Thermal Vibrational Relaxation Of Diatomic Molecules, Ronald James Bieniek, Steven J. Lipson
Physics Faculty Research & Creative Works
Vibrationally excited molecules play an important role in the spectroscopy, energetics, and chemical behavior of a wide range of gaseous systems of scientific and applied interest. Unfortunately, many desired collisional relaxation rates have not yet been experimentally measured, and current theoretical methods are often inadequate or too cumbersome for practical application. We report a semiquantal two-parameter scaling method for predicting relaxation rates that is very simple to employ, and impressively fits the temperature and vibrational dependencies of quantum mechanical and experimental collisional relaxation rates for several diatomic molecules (e.g., N2, HF, OH, NO) over many orders of magnitude.
Angle-Resolved X-Ray Circular And Magnetic Circular Dichroisms: Definitions And Applications, Sy Y. Tong, X. Q. Guo, James G. Tobin, George Daniel Waddill
Angle-Resolved X-Ray Circular And Magnetic Circular Dichroisms: Definitions And Applications, Sy Y. Tong, X. Q. Guo, James G. Tobin, George Daniel Waddill
Physics Faculty Research & Creative Works
We introduce definitions of angle-resolved x-ray circular dichroism (ARXCD) and magnetic x-ray circular dichroism (ARMXCD). As defined, the much larger effect of circular dichroism (ARXCD) is separated from the smaller magnetic (ARMXCD) effect. In all materials, ARXCD is zero along mirror planes while nonzero elsewhere. ARMXCD is nonzero only in magnetic materials. The measurement and analysis of ARMXCD allow element specific surface magnetism and surface structure as well as their inter-relationship to be studied as functions of the outgoing electron's direction.
Breakdown Of Landau-Ginzburg-Wilson Theory For Certain Quantum Phase Transitions, Thomas Vojta, Dietrich Belitz, Rajesh S. Narayanan, Theodore R. Kirkpatrick
Breakdown Of Landau-Ginzburg-Wilson Theory For Certain Quantum Phase Transitions, Thomas Vojta, Dietrich Belitz, Rajesh S. Narayanan, Theodore R. Kirkpatrick
Physics Faculty Research & Creative Works
The quantum ferromagnetic transition of itinerant electrons is considered. It is shown that the Landau-Ginzburg-Wilson theory described by Hertz and others breaks down due to a singular coupling between fluctuations of the conserved order parameter. This coupling induces an effective long-range interaction between the spins of the form 1/r2d-1. It leads to unusual scaling behavior at the quantum critical point in 1 < d ≤ 3 dimensions, which is determined exactly.
Theory Of The Seebeck Coefficient In Lacro₃ And Related Perovskite Systems, D. B. Marsh, Paul Ernest Parris
Theory Of The Seebeck Coefficient In Lacro₃ And Related Perovskite Systems, D. B. Marsh, Paul Ernest Parris
Physics Faculty Research & Creative Works
We consider the Seebeck coefficient in LaCrO3 and related transition-metal-oxide perovskites using a model for electronic conduction based on the electronic structure of the 3d orbitals of the B-site transition-metal cations. Relations for the Seebeck coefficient are presented for those perovskite systems in which electronic conduction is through the t2g states of the B-site transition-metal cations. High- and low-temperature limits for the Seebeck coefficient are identified for the cases of both strong and weak magnetic coupling between electron spins. In these high- and low-temperature limits, the Seebeck coefficient is determined as a function of carrier concentration. Results are …
Higher-Order Binding Corrections To The Lamb Shift Of 2p States, Ulrich D. Jentschura, Krzysztof Pachucki
Higher-Order Binding Corrections To The Lamb Shift Of 2p States, Ulrich D. Jentschura, Krzysztof Pachucki
Physics Faculty Research & Creative Works
We present an improved calculation of higher-order corrections to the one-loop self-energy of 2P states in hydrogenlike systems with small nuclear charge Z. The method is based on a division of the integration with respect to the photon energy into a high- and a low-energy part. The high-energy part is calculated by an expansion of the electron propagator in powers of the Coulomb field. The low-energy part is simplified by the application of a Foldy-Wouthuysen transformation. This transformation leads to a clear separation of the leading contribution from the relativistic corrections and removes higher-order terms. The method is applied to …
Relation Between Charge-Dipole Interactions And The Sqrt(E)-Dependent Mobility In Molecularly Doped Polymers, Paul Ernest Parris
Relation Between Charge-Dipole Interactions And The Sqrt(E)-Dependent Mobility In Molecularly Doped Polymers, Paul Ernest Parris
Physics Faculty Research & Creative Works
Time-of-flight measurements on a wide variety of molecularly-doped polymers reveal carrier mobilities that exhibit an exponential dependence on the square root of the applied electric field. Recent attempts to explain the observed field dependence have focused on the role played by spatial and energetic disorder. It as also been conjectured that the charge-dipole interactions often identified as the source of energetic disorder could be of sufficient range to lead to correlations in the energies of neighboring hopping sites. We have analytically explored the effect of such correlations on high field carrier transport in random potentials, and discuss how particular features …
Neutron Diffraction Structural Study Of Ce₂Fe₁₇₋ₓgaₓ, H. Luo, Z. Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow
Neutron Diffraction Structural Study Of Ce₂Fe₁₇₋ₓgaₓ, H. Luo, Z. Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow
Physics Faculty Research & Creative Works
Six samples of Ce2Fe17-xGax with nominal Ga content x equal to 0, 0.3, 0.5, 0.7, 1.0, 2.0 have been studied by powder neutron diffraction at room temperature. Both crystalline and magnetic refinements have been carried out. All six samples adopt the Th2Zn17-type rhombohedral structure. The only additional phase found is α-iron. Gallium atoms are found to have high affinity for the iron 18h site, and are absent from the 9d and 18f sites. The Ga substitution for Fe leads to an expansion of both the a and c axes. The Curie …
Anisotropy And Polarization In Charge Changing Collisions Of C⁴⁺ With Na(3s) And Laser Aligned Na(3p), S. Schippers, R. Hoekstra, R. Morgenstern, Ronald E. Olson
Anisotropy And Polarization In Charge Changing Collisions Of C⁴⁺ With Na(3s) And Laser Aligned Na(3p), S. Schippers, R. Hoekstra, R. Morgenstern, Ronald E. Olson
Physics Faculty Research & Creative Works
Absolute cross sections for C3+(6→5) emission at 465.7 nm after collisions of C4+ ions with ground state Na(3s) and laser excited aligned Na(3p) atoms are measured over the collision energy range of 3-7 keV amu-1. For Na(3s) polarizations are observed by measuring the linear polarization of the emitted light. In these collisions the polarization is found to be 0.33 and almost independent of the collision energy. Cross sections for collisions with the Na(3p) target are up to five times larger than for collisions with Na(3s). Slightly larger cross sections are measured when the laser excited Na(3p) target is Π-aligned as …
Charge-Dipole Model For The Universal Field Dependence Of Mobilities In Molecularly Doped Polymers, David H. Dunlap, Paul Ernest Parris, Vasudev M. Kenkre
Charge-Dipole Model For The Universal Field Dependence Of Mobilities In Molecularly Doped Polymers, David H. Dunlap, Paul Ernest Parris, Vasudev M. Kenkre
Physics Faculty Research & Creative Works
Using the general result that the mobility μ, of charge carriers driven in a spatially correlated random potential by an electric field E can be expressed in terms of the Laplace transform of a particular correlation function related to the random potential, we demonstrate that the exponential dependence of μ on √E universally observed in molecularly doped polymers arises naturally from the interaction of charge carriers with randomly distributed permanent dipoles.
Binary Nucleation Kinetics. Iii. Transient Behavior And Time Lags, Barbara Ellen Wyslouzil, Gerald Wilemski
Binary Nucleation Kinetics. Iii. Transient Behavior And Time Lags, Barbara Ellen Wyslouzil, Gerald Wilemski
Physics Faculty Research & Creative Works
Transient binary nucleation is more complex than unary because of the bidimensionality of the cluster formation kinetics. To investigate this problem qualitatively and quantitatively, we numerically solved the birth-death equations for vapor-to-liquid phase transitions. Our previous work [J. Chem. Phys 103, 1137 (1995)] showed that the customary saddle point and growth path approximations are almost always valid in steady state gas phase nucleation and only fail if the nucleated solution phase is significantly nonideal. The current work demonstrates that in its early transient stages, binary nucleation rarely, if ever, occurs via the saddle point. This affects not only the number …
Structural And Magnetic Studies On Prba2fe3o8, V. P.S. Awana, Latika Menon, S. K. Malik, Apurva Mehta, Sanjay Mishra, William B. Yelon
Structural And Magnetic Studies On Prba2fe3o8, V. P.S. Awana, Latika Menon, S. K. Malik, Apurva Mehta, Sanjay Mishra, William B. Yelon
Physics Faculty Research & Creative Works
It is known that Fe moments order antiferromagnetically with Néel temperature, TN, above 700 K in RBa2Fe3O7-δ with R=Y and Eu, and Pr moments order antiferromagnetically in PrBa2Cu3,O7-δ, with TN of 17 K. We have synthesized PrBa2Fe3O8 to study the ordering of Pr and Fe moments. From X-ray and neutron diffraction studies, this compound is found to crystallize in the tetragonal structure (space group P4/mmm). 57Fe Mössbauer studies show a complex hyperfine split pattern at 77 K, but a doublet superimposed on a six-line pattern at 300 K implying that some of the Fe moments order magnetically between 77 and …
A Classical Analysis Of Proton Collisions With Ground-State And Excited, Aligned Sodium Targets, C. J. Lundy, Ronald E. Olson
A Classical Analysis Of Proton Collisions With Ground-State And Excited, Aligned Sodium Targets, C. J. Lundy, Ronald E. Olson
Physics Faculty Research & Creative Works
The dependence of electron capture and ionization processes on the pre-collision electronic distribution is examined for the systems H+ + Na(3s, 3pΣ, 3pΠ) primarily in the energy range 1-15 keV. Populations of the capture and ionization channels as well as the coherence of the post-collision electronic distribution of the capture product are formulated using the classical trajectory Monte Carlo (CTMC) method. Total capture and ionization cross sections arising from initially aligned Na(3p) targets exhibit transient behaviour near the velocity-matching energy of 5.7 keV. This observation is described in terms of anisotropy parameters; anisotropy effects are also analysed for the capture …
State-Selective Electron Capture In Low Velocity Multiply Charged Ion, Helium Collisions, A. Cassimi, S. Duponchel, X. Flechard, P. Jardin, P. Sortais, D. Hennecart, Ronald E. Olson
State-Selective Electron Capture In Low Velocity Multiply Charged Ion, Helium Collisions, A. Cassimi, S. Duponchel, X. Flechard, P. Jardin, P. Sortais, D. Hennecart, Ronald E. Olson
Physics Faculty Research & Creative Works
Recoil ion momentum spectroscopy has been applied to study low energy, state-selective single electron capture by highly charged projectiles. The specific systems investigated are fully stripped 6.82 keV/u Ne10+ 6.82 keV/u Ar18+ on He. Measurements of the He+ recoil ion longitudinal momenta are used to determine the final n-state dependence of the captured electron. Simultaneous measurement of the transverse momenta of the recoil ion yields information about the impact parameter dependence of the reaction and the reaction window for electron capture. © 1996 The American Physical Society.
Neutron Diffraction And Magnetic Studies Of Rfe₁₂₋ₓtₓcY (R=Y,Er; T=V,Ti,Mo) Alloys, Z. Hu, William B. Yelon, X. D. Zhang, William Joseph James
Neutron Diffraction And Magnetic Studies Of Rfe₁₂₋ₓtₓcY (R=Y,Er; T=V,Ti,Mo) Alloys, Z. Hu, William B. Yelon, X. D. Zhang, William Joseph James
Physics Faculty Research & Creative Works
RFe12-xTxCy, (R=Y,Er; T=V,Ti,Mo) alloys were prepared by rf induction melting and analyzed using neutron powder diffraction and superconducting quantum interference device (SQUID) measurements. Rietveld analysis of the neutron diffraction data indicates that V, Ti, and Mo atoms all prefer the 8i sites. The refined amount of carbon atoms found in the interstitial sites from neutron diffraction data is significantly less than the nominal carbon content. All samples have the easy direction along the c axis. The Er sublattice couples to the Fe sublattice antiferromagnetically. The average Fe site moments range from 1.3 to 2.8 …
Neutron Diffraction Studies Of Ndₙfeₘ₋ₓ₋YVₓalY [(N,M)=(1,12), (2,17), (3,29)], Z. Hu, William B. Yelon, William Joseph James
Neutron Diffraction Studies Of Ndₙfeₘ₋ₓ₋YVₓalY [(N,M)=(1,12), (2,17), (3,29)], Z. Hu, William B. Yelon, William Joseph James
Physics Faculty Research & Creative Works
Several NdnFem-x-yVxAly [(n,m)=(1,12), (2,17), (3,29)] samples were prepared and analyzed using neutron powder diffraction. Rietveld analysis of the neutron diffraction data indicates that the V and Al substituents take those sites with similar environments in all three phases, as observed in our previous study of Ti-substituted compounds. It was confirmed that the diffraction data of the 3:29 compound can be better refined using the A2/m space group than using the P21/c space group. The SQUID measurements show that all samples have Curie temperatures well above room temperature. The neutron diffraction results …
Site Affinity Of Substituents In Nd₂Fe₁₇₋ₓtₓ (T=Cu,Zr,Nb,Ti,V) Alloys, William B. Yelon, Z. Hu, William Joseph James, G. K. Marasinghe
Site Affinity Of Substituents In Nd₂Fe₁₇₋ₓtₓ (T=Cu,Zr,Nb,Ti,V) Alloys, William B. Yelon, Z. Hu, William Joseph James, G. K. Marasinghe
Physics Faculty Research & Creative Works
In order to understand the magnetic properties of the substituted rare-earth-iron alloys, it is especially important to know the location of the substitutional atoms within the iron lattice. The site distributions of some nontransition-metal substituents in the substituted Nd2Fe17-xTx alloys have previously been reported. Here we report the site distributions of some transition-metal substituents (Cu,Zr,Nb,Ti,V) in the Nd2Fe17-xTx alloys and compare them with those of the nontransition-metal substituted compounds. Rietveld analysis of neutron powder diffraction data indicates that the nontransition-metal substituents show very similar site affinity at low substituent content. …
Three-Body Collision Dynamics For Single Ionization Of Helium By Protons And Antiprotons, C. J. Wood, Ronald E. Olson
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 …
Critical Behavior Of A Quantum Spherical Model In A Random Field, Thomas Vojta, Michael Schreiber
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.
Fine-Structure Effect For (E,2e) Collisions, Don H. Madison, V. D. Kravtsov, Stephenie J. Jones, Robert P. Mceachran
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 …
Effective-Medium Theory For The Electric-Field Dependence Of The Hopping Conductivity Of Disordered Solids, Paul Ernest Parris, B. D. Bookout
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 …
Quantum Version Of A Spherical Model: Crossover From Quantum To Classical Critical Behavior, Thomas Vojta
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 …
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
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 …
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
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.
High-Temperature Thermopower Of And Related Systems, D. Marsh, Paul Ernest Parris
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 …
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
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 …
An Inline Optical Electron Polarimeter, K. W. Trantham, Timothy J. Gay, R. J. Vandiver
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.
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
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.
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
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.
Optical Electron Polarimetry With Heavy Noble Gases, Timothy James Gay, J. E. Furst, K. W. Trantham, W. M.K.P. Wijayaratna
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 …
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
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.