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 661 - 690 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Theoretical Fully Differential Cross Sections For Double-Charge-Transfer Collisions, Allison L. Harris, Jerry Peacher, Don H. Madison Aug 2010

Theoretical Fully Differential Cross Sections For Double-Charge-Transfer Collisions, Allison L. Harris, Jerry Peacher, Don H. Madison

Physics Faculty Research & Creative Works

We present a four-body model for double charge transfer, called the four-body double-capture model. This model explicitly treats all four particles in the collision, and we apply it here to fully differential cross sections (FDCSs) for proton+helium collisions. The effects of initial- and final-state electron correlations are studied, as well as the role of the projectile-nucleus interaction. We also present results for proton+helium single capture, as well as single-capture:double-capture ratios of FDCSs.

Go to article

Anomalously Elastic Intermediate Phase In Randomly Layered Superfluids, Superconductors, And Planar Magnets, Priyanka Mohan, Paul M. Goldbart, Rajesh Narayanan, John Toner, Thomas Vojta Aug 2010

Anomalously Elastic Intermediate Phase In Randomly Layered Superfluids, Superconductors, And Planar Magnets, Priyanka Mohan, Paul M. Goldbart, Rajesh Narayanan, John Toner, Thomas Vojta

Physics Faculty Research & Creative Works

We show that layered quenched randomness in planar magnets leads to an unusual intermediate phase between the conventional ferromagnetic low-temperature and paramagnetic high-temperature phases. In this intermediate phase, which is part of the Griffiths region, the spin-wave stiffness perpendicular to the random layers displays anomalous scaling behavior, with a continuously variable anomalous exponent, while the magnetization and the stiffness parallel to the layers both remain finite. Analogous results hold for superfluids and superconductors. We study the two phase transitions into the anomalous elastic phase, and we discuss the universality of these results, and implications of finite sample size as well …

Go to article

Doping Dependence Of Spin-Lattice Coupling And Two-Dimensional Ordering In Multiferroic Hexagonal Y₁₋ₓluₓmno₃ (0 ≤ X ≤ 1), Junghwan Park, Seongsu Lee, Misun Kang, Kwanghyun Jang, Changhee Lee, Sergey V. Streltsov, Vladimir V. Mazurenko, Maria V. Valentyuk, Julia E. Medvedeva, Takashi Kamiyama, Jegeun Park Aug 2010

Doping Dependence Of Spin-Lattice Coupling And Two-Dimensional Ordering In Multiferroic Hexagonal Y₁₋ₓluₓmno₃ (0 ≤ X ≤ 1), Junghwan Park, Seongsu Lee, Misun Kang, Kwanghyun Jang, Changhee Lee, Sergey V. Streltsov, Vladimir V. Mazurenko, Maria V. Valentyuk, Julia E. Medvedeva, Takashi Kamiyama, Jegeun Park

Physics Faculty Research & Creative Works

We have examined a complete phase diagram of Y1-x Lu xMnO3 with 0≤x≤1 by using bulk measurements and neutron-diffraction studies. With increasing Lu concentration, Curie-Weiss temperature and Neel temperature are found to increase continuously while the two-dimensional nature of short-range magnetic correlation persists even in the paramagnetic phase throughout the entire doping range. At the same time, the lattice constants and the unit-cell volume get contracted with Lu doping, i.e., chemical pressure effect. This decrease in the lattice constants and the unit-cell volume then leads naturally to an increased magnetic exchange interaction as found in our local …

Go to article

Polarization And Ellipticity Of High-Order Harmonics From Aligned Molecules Generated By Linearly Polarized Intense Laser Pulses, Anh-Thu Le, R. R. Lucchese, C. D. Lin Aug 2010

Polarization And Ellipticity Of High-Order Harmonics From Aligned Molecules Generated By Linearly Polarized Intense Laser Pulses, Anh-Thu Le, R. R. Lucchese, C. D. Lin

Physics Faculty Research & Creative Works

We present theoretical calculations for polarization and ellipticity of high-order harmonics from aligned N₂, CO₂, and O₂ molecules generated by linearly polarized lasers. Within the rescattering model, the two polarization amplitudes of the harmonics are determined by the photo-recombination amplitudes for photons emitted with polarization parallel or perpendicular to the direction of the same returning electron wave packet. Our results show clear species-dependent polarization states, in excellent agreement with experiments. We further note that the measured polarization ellipse of the harmonic furnishes the needed parameters for a "complete" experiment in molecules.

Go to article

Differential Cross Sections For Non-Sequential Double Ionization Of He By 52 Ev Photons From The Free Electron Laser In Hamburg, Flash, Moritz Kurka, Johannes Feist, Daniel A. Horner, Artem Rudenko, Yuhai Jiang, Kai Uwe Kuhnel, Lutz M. Foucar, Thomas N. Rescigno, Clyde William Mccurdy, Renate Pazourek, Stefan Nagele, Michael Schulz, Oliver Herrwerth, Matthias Lezius, Matthias F. Kling, Markus S. Schoffler, Ali Belkacem, Stefan Dusterer, Rolf Treusch, Barry I. Schneider, Lee A. Collins, Joachim Burgdorfer, Claus Dieter Schroter Jul 2010

Differential Cross Sections For Non-Sequential Double Ionization Of He By 52 Ev Photons From The Free Electron Laser In Hamburg, Flash, Moritz Kurka, Johannes Feist, Daniel A. Horner, Artem Rudenko, Yuhai Jiang, Kai Uwe Kuhnel, Lutz M. Foucar, Thomas N. Rescigno, Clyde William Mccurdy, Renate Pazourek, Stefan Nagele, Michael Schulz, Oliver Herrwerth, Matthias Lezius, Matthias F. Kling, Markus S. Schoffler, Ali Belkacem, Stefan Dusterer, Rolf Treusch, Barry I. Schneider, Lee A. Collins, Joachim Burgdorfer, Claus Dieter Schroter

Physics Faculty Research & Creative Works

Two-photon double ionization of He is studied at the Free Electron Laser in Hamburg (FLASH) by inspecting He2+ momentum (P-(He 2+)) distributions at 52 eV photon energy. We demonstrate that recoil ion momentum distributions can be used to infer information about highly correlated electron dynamics and find the first experimental evidence for 'virtual sequential ionization'. The experimental data are compared with the results of two calculations, both solving the time-dependent Schrodinger equation. We find good overall agreement between experiment and theory, with significant differences for cuts along the polarization direction that cannot be explained by the experimental resolution …

Go to article

Anderson Localization As Position-Dependent Diffusion In Disordered Waveguides, Ben Payne, Alexey Yamilov, Sergey E. Skipetrov Jul 2010

Anderson Localization As Position-Dependent Diffusion In Disordered Waveguides, Ben Payne, Alexey Yamilov, Sergey E. Skipetrov

Physics Faculty Research & Creative Works

We show that the recently developed self-consistent theory of Anderson localization with a position-dependent diffusion coefficient is in quantitative agreement with the supersymmetry approach up to terms of the order of 1/g 02 (with g0 the dimensionless conductance in the absence of interference effects) and with large-scale ab initio simulations of the classical wave transport in disordered waveguides, at least for g 0 ~ 0.5. In the latter case, agreement is found even in the presence of absorption. Our numerical results confirm that in open disordered media, the onset of Anderson localization can be viewed as position-dependent diffusion.

Go to article

Scaled Vapor-To-Liquid Nucleation In A Lennard-Jones System, Barbara N. Hale, Mark Thomason Jul 2010

Scaled Vapor-To-Liquid Nucleation In A Lennard-Jones System, Barbara N. Hale, Mark Thomason

Physics Faculty Research & Creative Works

Scaling of the homogenous vapor-to-liquid nucleation rate, J, is observed in a model Lennard-Jones (LJ) system. The model uses Monte Carlo simulation-generated small cluster growth to decay rate constant ratios and the kinetic steady-state nucleation rate formalism to determine J at four temperatures below the LJ critical temperature, Tc. When plotted vs the scaled supersaturation, lnS/[Tc/T-1]3/2, the values of log J are found to collapse onto a single line. A similar scaling has been observed for the experimental nucleation rate data of water and toluene.

Go to article

Fivefold Differential Cross Sections For Ground-State Ionization Of Aligned H₂ By Electron Impact, Arne Senftleben, Ola A. Al-Hagan, Thomas Pfluger, Xueguang Ren, Don H. Madison, Alexander Dorn, Joachim Hermann Ullrich Jul 2010

Fivefold Differential Cross Sections For Ground-State Ionization Of Aligned H₂ By Electron Impact, Arne Senftleben, Ola A. Al-Hagan, Thomas Pfluger, Xueguang Ren, Don H. Madison, Alexander Dorn, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

We discuss the ionization of aligned hydrogen molecules into their ionic ground state by 200 eV electrons. Using a reaction microscope, the complete electron scattering kinematics is imaged over a large solid angle. Simultaneously, the molecular alignment is derived from postcollision dissociation of the residual ion. It is found that the ionization cross section is maximized for small angles between the internuclear axis and the momentum transfer. Fivefold differential cross sections (5DCSs) reveal subtle differences in the scattering process for the distinct alignments. We compare our observations with theoretical 5DCSs obtained with an adapted molecular three-body distorted wave model that …

Go to article

Astronomy's New Messengers: A Traveling Exhibit To Reach Out To A Young Adult Audience, Marco Cavaglia, Martin Hendry, Szabolocs Marka, David H. Reitze, Keith Riles Jul 2010

Astronomy's New Messengers: A Traveling Exhibit To Reach Out To A Young Adult Audience, Marco Cavaglia, Martin Hendry, Szabolocs Marka, David H. Reitze, Keith Riles

Physics Faculty Research & Creative Works

The Laser Interferometer Gravitational-wave Observatory exhibit Astronomy's New Messengers: Listening to the Universe with Gravitational Waves is traveling to colleges, universities, museums and other public institutions throughout the United States. In 2010, an extended version of this exhibit will appear in a New York City venue that is accessible to a large and diverse cross section of the general public. Astronomy's New Messengers primarily communicates with an adolescent and young adult audience, potentially inspiring them into the field of science. Acknowledging that this audience is traditionally a difficult one to attract, the exhibit publicly announces itself in a charismatic fashion …

Go to article

Order-Dependent Mappings: Strong-Coupling Behavior From Weak-Coupling Expansions In Non-Hermitian Theories, Jean Zinn-Justin, Ulrich D. Jentschura Jul 2010

Order-Dependent Mappings: Strong-Coupling Behavior From Weak-Coupling Expansions In Non-Hermitian Theories, Jean Zinn-Justin, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

A long time ago, it has been conjectured that a Hamiltonian with a potential of the form x 2+ivx 3, v real, has a real spectrum. This conjecture has been generalized to a class of the so-called PT symmetric Hamiltonians and some proofs have been given. Here, we show by numerical investigation that the divergent perturbation series can be summed efficiently by an order-dependent mapping (ODM) in the whole complex plane of the coupling parameter v 2, and that some information about the location of level-crossing singularities can be obtained in this way. Furthermore, we discuss to …

Go to article

Comment On "Coincidence Studies Of He Ionized By C⁶⁺, Au²⁴⁺, And Au⁵³⁺", Michael Schulz, Robert Moshammer, Daniel Fischer, Joachim Hermann Ullrich Jun 2010

Comment On "Coincidence Studies Of He Ionized By C⁶⁺, Au²⁴⁺, And Au⁵³⁺", Michael Schulz, Robert Moshammer, Daniel Fischer, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

In a recent article, McGovern [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA. 81.042704 81, 042704 (2010)] suggested that the normalization of our measured fully differential cross section for ionization of helium by Au53+ needs to be checked. In this comment we confirm that the normalization of the published data is correct. Furthermore, we point out that, for a conclusive comparison between experiment and theory, an accurate inclusion of the experimental resolution using correct experimental parameters in the calculation is important.

Go to article

Counterintuitive Consequence Of Heating In Strongly-Driven Intrinsic Junctions Of Bi₂Sr₂Cacu₂O8+Δ Mesas, Cihan Kurter, Lutfi Ozyuzer, Thomas Proslier, John F. Zasadzinski, David G. Hinks, Kenneth E. Gray Jun 2010

Counterintuitive Consequence Of Heating In Strongly-Driven Intrinsic Junctions Of Bi₂Sr₂Cacu₂O8+Δ Mesas, Cihan Kurter, Lutfi Ozyuzer, Thomas Proslier, John F. Zasadzinski, David G. Hinks, Kenneth E. Gray

Physics Faculty Research & Creative Works

Anomalously high and sharp peaks in the conductance of intrinsic Josephson junctions in Bi2 Sr2 CaCu2 O 8+δ (Bi2212) mesas have been commonly interpreted as superconducting energy gaps but here we show they are a result of strong self-heating. This conclusion follows directly from a comparison to the equilibrium gap measured by tunneling in single break junctions on equivalent crystals. As the number of junctions in the mesa, N, and thus heating increase, the peak voltages decrease and the peak width abruptly sharpens for N≥12. Clearly these widely variable features vs N cannot all represent the equilibrium …

Go to article

Miniaturized Superconducting Metamaterials For Radio Frequencies, Cihan Kurter, John A. Abrahams, Steven Mark Anlage Jun 2010

Miniaturized Superconducting Metamaterials For Radio Frequencies, Cihan Kurter, John A. Abrahams, Steven Mark Anlage

Physics Faculty Research & Creative Works

We have developed a low-loss, ultrasmall radio frequency (rf) metamaterial operating at ~76 MHz. This miniaturized medium is made up of planar spiral elements with diameter as small as ~λ/658 (λ is the free space wavelength), fashioned from Nb thin films on quartz substrates. The transmission data are examined below and above the superconducting transition temperature of Nb for both a single spiral and a one dimensional array. The validity of the design is tested through numerical simulations and good agreement is found. We discuss how superconductors enable such a compact design in the rf with high loaded-quality factor (in …

Go to article

Phase Transitions Of The Generalized Contact Process With Two Absorbing States, Man Young Lee, Thomas Vojta Jun 2010

Phase Transitions Of The Generalized Contact Process With Two Absorbing States, Man Young Lee, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the generalized contact process with two absorbing states in one space dimension by means of large-scale Monte Carlo simulations. Treating the creation rate of active sites between inactive domains as an independent parameter leads to a rich phase diagram. In addition to the conventional active and inactive phases we find a parameter region where the simple contact process is inactive, but an infinitesimal creation rate at the boundary between inactive domains is sufficient to take the system into the active phase. Thus, the generalized contact process has two different phase transition lines. The point separating them shares some …

Go to article

First Mediterranean Conference On Classical And Quantum Gravity (Mccqg 2009): Preface, Spyros Basilakos, Mariano Cadoni, Marco Cavaglia, Theodosios Christodoulakis, Elias C. Vagenas Jun 2010

First Mediterranean Conference On Classical And Quantum Gravity (Mccqg 2009): Preface, Spyros Basilakos, Mariano Cadoni, Marco Cavaglia, Theodosios Christodoulakis, Elias C. Vagenas

Physics Faculty Research & Creative Works

No abstract provided.

Go to article

Doubly Differential Spectra Of Scattered Protons In Ionization Of Atomic Hydrogen, Michael Schulz, A. C. Laforge, K. N. Egodapitiya, J. S. Alexander, A. Hasan, M. F. Ciappina, A. C. Roy, R. Dey, A. Samolov, A. L. Godunov May 2010

Doubly Differential Spectra Of Scattered Protons In Ionization Of Atomic Hydrogen, Michael Schulz, A. C. Laforge, K. N. Egodapitiya, J. S. Alexander, A. Hasan, M. F. Ciappina, A. C. Roy, R. Dey, A. Samolov, A. L. Godunov

Physics Faculty Research & Creative Works

We have measured and calculated doubly differential cross sections for ionization of atomic hydrogen using 75-keV proton impact for fixed projectile energy losses as a function of scattering angle. This collision system represents a pure three-body system and thus offers an accurate test of the theoretical description of the few-body dynamics without any complications presented by electron correlation in many-electron targets. Comparison between experiment and several theoretical models reveals that the projectile-target nucleus interaction is best described by the operator of a second-order term of the transition amplitude. Higher-order contributions in the projectile-electron interaction, on the other hand, are more …

Go to article

Magnetic Transition In The Rare Earth Intermetallic Compound [Formula Omitted]: Heat Capacity And Neutron Diffraction Studies, R. Nirmala, A. V. Morozkin, Jagat Lamsal, William B. Yelon, S. K. Malik May 2010

Magnetic Transition In The Rare Earth Intermetallic Compound [Formula Omitted]: Heat Capacity And Neutron Diffraction Studies, R. Nirmala, A. V. Morozkin, Jagat Lamsal, William B. Yelon, S. K. Malik

Physics Faculty Research & Creative Works

Polycrystalline Ce5Ge4 compound (orthorhombic Sm5Ge4 -type structure, space group Pnma, No. 62) orders ferromagnetically at ~12 K (Tc). Low field dc magnetization and ac magnetic susceptibility data reveal presence of competing magnetic interactions below Tc. Heat capacity of Ce5Ge4 in zero applied field indicates a second order transition with a peak centered at 11 K. Powder neutron diffraction studies confirm the existence of a commensurate magnetic order in this compound at 10 K without a change of crystal structure. the Ce moments lie in the ab plane and the moment …

Go to article

Investigating Two-Photon Double Ionization Of D₂ By Xuv-Pump-Xuv-Probe Experiments, Yuhai Jiang, Artem Rudenko, Jhon Fredy Perez-Torres, Oliver Herrwerth, Lutz M. Foucar, Moritz Kurka, Kai Uwe Kuhnel, M. Toppin, Etienne Plesiat, Felipe Morales, Fernando Javier Martin, Matthias Lezius, Matthias F. Kling, Till Jahnke, Reinhard Dorner, Jose Luis Sanz-Vicario, Jeroen Van Tilborg, Ali Belkacem, Michael Schulz, Kiyoshi Ueda, Stefan Dusterer, Rolf Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich May 2010

Investigating Two-Photon Double Ionization Of D₂ By Xuv-Pump-Xuv-Probe Experiments, Yuhai Jiang, Artem Rudenko, Jhon Fredy Perez-Torres, Oliver Herrwerth, Lutz M. Foucar, Moritz Kurka, Kai Uwe Kuhnel, M. Toppin, Etienne Plesiat, Felipe Morales, Fernando Javier Martin, Matthias Lezius, Matthias F. Kling, Till Jahnke, Reinhard Dorner, Jose Luis Sanz-Vicario, Jeroen Van Tilborg, Ali Belkacem, Michael Schulz, Kiyoshi Ueda, Stefan Dusterer, Rolf Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

We used a split-mirror setup attached to a reaction microscope at the free-electron laser in Hamburg (FLASH) to perform an XUV-pump-XUV-probe experiment by tracing the ultrafast nuclear wave-packet motion in the D2 +(1sσg) with <10 fs time resolution. Comparison with time-dependent calculations shows excellent agreement with the measured vibrational period of 22±4 fs in D2+, points to the importance of accurately knowing the internuclear distance-dependent ionization probability, and paves the way to control sequential and nonsequential two-photon double-ionization contributions.

Go to article

All-Sky Search For Gravitational-Wave Bursts In The First Joint Ligo-Geo-Virgo Run, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. May 2010

All-Sky Search For Gravitational-Wave Bursts In The First Joint Ligo-Geo-Virgo Run, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present results from an all-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed by three different analysis algorithms over the frequency band 50-6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days. No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined …

Go to article

Ch₃Ch₂Od/D₂O Binary Condensation In A Supersonic Laval Nozzle: Presence Of Small Clusters Inferred From A Macroscopic Energy Balance, Shinobu Tanimura, Barbara E. Wyslouzil, Gerald Wilemski Apr 2010

Ch₃Ch₂Od/D₂O Binary Condensation In A Supersonic Laval Nozzle: Presence Of Small Clusters Inferred From A Macroscopic Energy Balance, Shinobu Tanimura, Barbara E. Wyslouzil, Gerald Wilemski

Physics Faculty Research & Creative Works

We determined the heat released in the condensing flow of a CH3 CH2 OD/ D2 O /carrier gas mixture (EtOD/ D2 O for brevity) through a supersonic Laval nozzle by integrating the equations for supersonic flow with condensation, using the static pressure, temperature, and mole fractions of EtOD and D2 O monomers [S. Tanimura, B. E. Wyslouzil, M. S. Zahniser, J. Chem. Phys. 127, 034305 (2007)] as inputs. by considering the depletion of the monomer species, the deviation of the pressure from the isentropic value, and the heat released, we estimated that ∼10% of the EtOD molecules are present as …

Go to article

Triply Differential Single Ionization Of Argon: Charge Effects For Positron And Electron Impact, Sebastian Otranto, Ronald E. Olson, O. G. De Lucio, Robert D. Dubois Apr 2010

Triply Differential Single Ionization Of Argon: Charge Effects For Positron And Electron Impact, Sebastian Otranto, Ronald E. Olson, O. G. De Lucio, Robert D. Dubois

Physics Faculty Research & Creative Works

Triply differential single ionization of Ar by 200 eV positron and electron impact is measured and calculated. For an unequivocal test of kinematic differences, fully differential ejected electron angular distributions are measured using the same experimental apparatus and conditions for both positron and electron impact. The binary/recoil intensity ratios are shown to significantly differ for the two projectiles. These data are used to test theoretical calculations.

Go to article

Infinite Randomness And Quantum Griffiths Effects In A Classical System: The Randomly Layered Heisenberg Magnet, Priyanka Mohan, Rajesh Narayanan, Thomas Vojta Apr 2010

Infinite Randomness And Quantum Griffiths Effects In A Classical System: The Randomly Layered Heisenberg Magnet, Priyanka Mohan, Rajesh Narayanan, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the phase transition in a three-dimensional classical Heisenberg magnet with planar defects, i.e., disorder perfectly correlated in two dimensions. By applying a strong-disorder renormalization group, we show that the critical point has exotic infinite-randomness character. It is accompanied by strong power-law Griffiths singularities. We compute various thermodynamic observables paying particular attention to finite-size effects relevant for an experimental verification of our theory. We also study the critical dynamics within a Langevin equation approach and find it extremely slow. At the critical point, the autocorrelation function decays only logarithmically with time while it follows a nonuniversal power law in …

Go to article

Electronic Structure And Volume Effect On Thermoelectric Transport In P -Type Bi And Sb Tellurides, Minsik Park, Junghwan Song, Julia E. Medvedeva, Miyoung Kim, Ingee Kim, Arthur J. Freeman Apr 2010

Electronic Structure And Volume Effect On Thermoelectric Transport In P -Type Bi And Sb Tellurides, Minsik Park, Junghwan Song, Julia E. Medvedeva, Miyoung Kim, Ingee Kim, Arthur J. Freeman

Physics Faculty Research & Creative Works

Thermoelectric transport properties (Seebeck coefficient, S, and electrical conductivity, σ) of p -type Bi and Sb tellurides are investigated using a first-principles all-electron density-functional approach. We demonstrate that the carrier concentration, band gap, and lattice constants have an important influence on the temperature behavior of S and that the volume expansion by 5.5% in Sb2Te3 results in an increase in S by 33μV/K at 300 K. We argue that in addition to the electronic structure characteristics, the volume also affects the value of S and hence should be considered as an origin of the experimental observations that …

Go to article

Theoretical Study Of Photoelectron Angular Distributions In Single-Photon Ionization Of Aligned N₂ And Co₂, Cheng Jin, Anh-Thu Le, Song-Feng Zhao, R. R. Lucchese, C. D. Lin Mar 2010

Theoretical Study Of Photoelectron Angular Distributions In Single-Photon Ionization Of Aligned N₂ And Co₂, Cheng Jin, Anh-Thu Le, Song-Feng Zhao, R. R. Lucchese, C. D. Lin

Physics Faculty Research & Creative Works

We calculate photoelectron angular distributions (PADs) resulting from single-photon (43 eV) ionization of molecules that have been transiently aligned with a short laser pulse. The total ionization cross sections of N₂ and CO₂ vs the time delay between the aligning laser pulse and the soft x-ray photon are calculated and compared to experimental results reported by I. Thomann et al. [J. Phys. Chem. A 112, 9382 (2008)]. We present the PADs from these aligned molecules in the laboratory frame which can be compared directly with future experiments from aligned N₂ and CO₂. The alignment dependence of single-photon ionization, multiphoton ionization, …

Go to article

Tuning The Properties Of Complex Transparent Conducting Oxides: Role Of Crystal Symmetry, Chemical Composition, And Carrier Generation, Julia E. Medvedeva, Chaminda L. Hettiarachchi Mar 2010

Tuning The Properties Of Complex Transparent Conducting Oxides: Role Of Crystal Symmetry, Chemical Composition, And Carrier Generation, Julia E. Medvedeva, Chaminda L. Hettiarachchi

Physics Faculty Research & Creative Works

The electronic properties of single- and multication transparent conducting oxides (TCOs) are investigated using first-principles density-functional approach. A detailed comparison of the electronic band structure of stoichiometric and oxygen deficient In2 O3, α, and β -Ga2 O3, rock salt and wurtzite ZnO, and layered InGaZnO4 reveals the role of the following factors which govern the transport and optical properties of these TCO materials: (i) the crystal symmetry of the oxides, including both the oxygen coordination and the long-range structural anisotropy; (ii) the electronic configuration of the cation(s), specifically, the type of orbital(s)- s, …

Go to article

Electron-Impact-Ionization Cross Sections Of H₂ For Low Outgoing Electron Energies From 1 To 10 Ev, Ola A. Al-Hagan, Andrew James Murray, Christian V. Kaiser, James Colgan, Don H. Madison Mar 2010

Electron-Impact-Ionization Cross Sections Of H₂ For Low Outgoing Electron Energies From 1 To 10 Ev, Ola A. Al-Hagan, Andrew James Murray, Christian V. Kaiser, James Colgan, Don H. Madison

Physics Faculty Research & Creative Works

Theoretical and experimental fully differential cross sections are presented for electron-impact ionization of molecular hydrogen in a plane perpendicular to the incident beam direction. The experimental data exhibit a maximum for 1-eV electrons detected 180° apart and a minimum for 10-eV electrons. We investigate the different physical effects which cause back-to-back scattering and demonstrate that, over the energy range from 10 to 1 eV, a direct transition is observed from a region where Wannier threshold physics is essentially unimportant to where it completely dominates.

Go to article

Determination Of Structure Parameters In Strong-Field Tunneling Ionization Theory Of Molecules, Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T. F. Jiang, C. D. Lin Mar 2010

Determination Of Structure Parameters In Strong-Field Tunneling Ionization Theory Of Molecules, Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T. F. Jiang, C. D. Lin

Physics Faculty Research & Creative Works

In the strong field molecular tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)], the ionization rate depends on the asymptotic wave function of the molecular orbital from which the electron is removed. The orbital wave functions obtained from standard quantum chemistry packages in general are not good enough in the asymptotic region. Here we construct a one-electron model potential for several linear molecules using density functional theory. We show that the asymptotic wave function can be improved with an iteration method and after one iteration accurate asymptotic wave functions and structure parameters are determined. With …

Go to article

Positron And Electron Impact Double Ionization Of Argon: How 1st- And 2nd-Order Mechanisms Influence The Differential Electron Emission, Robert D. Dubois, O. G. De Lucio, J. Gavin Feb 2010

Positron And Electron Impact Double Ionization Of Argon: How 1st- And 2nd-Order Mechanisms Influence The Differential Electron Emission, Robert D. Dubois, O. G. De Lucio, J. Gavin

Physics Faculty Research & Creative Works

Double-to-single-ionization ratios for electron emission as a function of the angle are measured for 200, 500, and 1000 eV positron and electron impact on argon. Both the sign of the projectile charge and the impact energy are shown to influence the angular dependences. by combining these ratios for positron and electron impact, information about how first- and second-order double-ionization mechanisms interfere and contribute to the total differential electron emission at different collision velocities is obtained. © 2010 EPLA.

Go to article

Quantum Griffiths Phase In The Weak Itinerant Ferromagnetic Alloy Ni₁₋ₓvₓ, Sara Ubaid-Kassis, Thomas Vojta, Almut Schroeder Feb 2010

Quantum Griffiths Phase In The Weak Itinerant Ferromagnetic Alloy Ni₁₋ₓvₓ, Sara Ubaid-Kassis, Thomas Vojta, Almut Schroeder

Physics Faculty Research & Creative Works

We present magnetization (M) data of the d-metal alloy Ni1-xVx at vanadium concentrations close to xx ~ 11.4% where the onset of long-range ferromagnetic (FM) order is suppressed to zero temperature. Above xc, the temperature (T) and magnetic field (H) dependencies of the magnetization are best described by simple nonuniversal power laws. the exponents of M/H ~ T γ and M ~ Hα are related by 1-γ=α for wide temperature (10c to γ<0.1 for x=15%. This behavior is not compatible with either classical or quantum critical behavior in a clean 3D FM. Instead it closely follows the predictions for a quantum Griffiths phase associated with a quantum phase transition in a disordered metal. Deviations at the lowest temperatures hint at a freezing of large clusters and the onset of a cluster glass phase.

Go to article

Astronomy's New Messengers: A Traveling Exhibit On Gravitational-Wave Physics, Marco Cavaglia, Martin Hendry, Szabolcs Marka, David H. Reitze, Keith Riles Feb 2010

Astronomy's New Messengers: A Traveling Exhibit On Gravitational-Wave Physics, Marco Cavaglia, Martin Hendry, Szabolcs Marka, David H. Reitze, Keith Riles

Physics Faculty Research & Creative Works

The Laser Interferometer Gravitational-wave Observatory exhibit Astronomy's New Messengers: Listening to the Universe with Gravitational Waves is traveling to colleges, universities, museums and other public institutions throughout the United States. Astronomy's New Messengers primarily communicates with an adolescent and young adult audience, potentially inspiring them into the field of science. Acknowledging that this audience is traditionally a difficult one to attract, the exhibit publicly announces itself in a charismatic fashion to reach its principal goals of broadening the community of people interested in science and encouraging interest in science among young people.

Go to article

First Prev Next Last