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Articles 1 - 30 of 41
Full-Text Articles in Physics
Large Energy Gaps In Cac₆ From Tunneling Spectroscopy: Possible Evidence Of Strong-Coupling Superconductivity, Cihan Kurter, Lutfi Ozyuzer, Daniel Mazur, John F. Zasadzinski, Daniel Rosenmann
Large Energy Gaps In Cac₆ From Tunneling Spectroscopy: Possible Evidence Of Strong-Coupling Superconductivity, Cihan Kurter, Lutfi Ozyuzer, Daniel Mazur, John F. Zasadzinski, Daniel Rosenmann
Physics Faculty Research & Creative Works
Tunneling in CaC6 crystals reproducibly reveals superconducting gaps Δ of 2.3±0.2 meV that are ~40% larger than reported earlier. In an isotropic s -wave scenario, that puts CaC6 into the class of very strongly coupled superconductors, since 2Δ k Tc ~4.6, implying that soft Ca phonons are primarily involved in the superconductivity. This conclusion explains the relatively large Ca isotope effect found recently for CaC6, but it could also signal a strong anisotropy in the electron-phonon interaction.
Angular And Polarization Analysis Of X-Rays Emitted From Highly-Charged, Few-Electron Ions, Stephan Fritzsche, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker
Angular And Polarization Analysis Of X-Rays Emitted From Highly-Charged, Few-Electron Ions, Stephan Fritzsche, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker
Physics Faculty Research & Creative Works
The recent theoretical progress in studying the x-ray emission from highly-charged, few-electron ions is reviewed. These case studies show that relativistic, high-Z ions provide a unique tool for better understanding the interplay between the electron-photon and electron-electron interactions in strong fields. Most naturally, this interplay is probed by the radiative capture of a (quasi-) free electron into the bound states of projectile ions, and by varying the charge state and the energy of the projectiles. For the capture into initially hydrogen-and lithium-like ions, here we summarize the recent results for the angular distribution and polarization of the recombination photons as …
Zeeman Splitting And G Factor Of The 1s²2s²2p ²P3/2 And ²P1/2 Levels In Ar¹³⁺, R. Soria Orts, Jose R. Crespo Lopez-Urrutia, Hjalmar Bruhns, Antonio J. Gonzalez, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, Alain Lapierre, Hiroyuki Tawara, I. I. Tupitsyn, Joachim Hermann Ullrich, Andrey V. Volotka
Zeeman Splitting And G Factor Of The 1s²2s²2p ²P3/2 And ²P1/2 Levels In Ar¹³⁺, R. Soria Orts, Jose R. Crespo Lopez-Urrutia, Hjalmar Bruhns, Antonio J. Gonzalez, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, Alain Lapierre, Hiroyuki Tawara, I. I. Tupitsyn, Joachim Hermann Ullrich, Andrey V. Volotka
Physics Faculty Research & Creative Works
The Zeeman line components of the magnetic-dipole (M1) 1s2 2s2 2 P1/2 -2P3/2 transition in boronlike Ar13+ were experimentally resolved by high-precision emission spectroscopy using the Heidelberg electron beam ion trap. We determined the gyromagnetic (g) factors of the ground and first-excited levels to be g1/2 =0.663(7) and g3/2 =1.333(2), respectively. This corresponds to a measurement of the g factor of a relativistic electron in a bound non- S state of a multielectron ion with a 1.5 parts-per-thousand accuracy. The results are compared to theoretical calculations by means of the configuration …
Coincidence Angular Correlation In Electron Impact Single Or Double Ionisation Of Atoms And Molecules, E. M. Staicu-Casagrande, Adnan Naja, Xueguang Ren, Mohammed Nekkab, Fabrice Catoire, F. Mezdari, Azzeddine Lahmam-Bennani, Don H. Madison, Ochbadrakh Chuluunbaatar, Boghos B. Joulakian
Coincidence Angular Correlation In Electron Impact Single Or Double Ionisation Of Atoms And Molecules, E. M. Staicu-Casagrande, Adnan Naja, Xueguang Ren, Mohammed Nekkab, Fabrice Catoire, F. Mezdari, Azzeddine Lahmam-Bennani, Don H. Madison, Ochbadrakh Chuluunbaatar, Boghos B. Joulakian
Physics Faculty Research & Creative Works
Experimental results obtained with our multi-parameter multi-coincidence spectrometer are presented for the (e,3e) double ionisation of Ar and (e,2e) single ionisation of small molecules. The (e,3e) measurements are discussed in terms of competition between the two double ionisation processes present under the chosen kinematics, and qualitative conclusions are given. The results for the ionisation of H2 and the outer orbital of N2 are compared with the predictions of the most elaborate available theoretical models for description of the molecular ionisation process. Overall reasonable agreement is observed and tentative interpretations for the discrepancies are discussed.
Two-Center Interference In P-H2 Electron-Transfer Collisions, Daniel Fischer, M. Gudmundsson, Kristian Stochkel, Zoltan Berenyi, Henrik Cederquist, Nicole Haag, Henrik A B Johansson, Sergey B. Levin, Peter Reinhed, Reinhold S. Schuch, Henning T. Schmidt
Two-Center Interference In P-H2 Electron-Transfer Collisions, Daniel Fischer, M. Gudmundsson, Kristian Stochkel, Zoltan Berenyi, Henrik Cederquist, Nicole Haag, Henrik A B Johansson, Sergey B. Levin, Peter Reinhed, Reinhold S. Schuch, Henning T. Schmidt
Physics Faculty Research & Creative Works
We report on measurements of transfer excitation in collisions of 0.3-1.3 MeV protons with spatially oriented H2 molecules. Evidences of two center interference are found in the angular distribution of the molecule after a transfer excitation process and directly in the projectile angular scattering distributions. These features can be explained in a way which is analogous to that for the interferences in Young's classical double slit experiment: The fast projectiles preferentially capture electrons close to either of the molecular nuclei, and thereby they change their momenta and de Broglie wavelengths. The waves emerging from the two 'slits' of the …
Matched Filtering And Parameter Estimation Of Ringdown Waveforms, Emanuele Berti, Jaime Cardoso, Vitor Cardoso, Marco Cavaglia
Matched Filtering And Parameter Estimation Of Ringdown Waveforms, Emanuele Berti, Jaime Cardoso, Vitor Cardoso, Marco Cavaglia
Physics Faculty Research & Creative Works
Using recent results from numerical relativity simulations of nonspinning binary black hole mergers, we revisit the problem of detecting ringdown waveforms and of estimating the source parameters, considering both LISA and Earth-based interferometers. We find that Advanced LIGO and EGO could detect intermediate-mass black holes of mass up to ∼103M⊙ out to a luminosity distance of a few Gpc. For typical multipolar energy distributions, we show that the single-mode ringdown templates presently used for ringdown searches in the LIGO data stream can produce a significant event loss ( > 10% for all detectors in a large interval of …
Analysis Of Two-Dimensional High-Energy Photoelectron Momentum Distributions In The Single Ionization Of Atoms By Intense Laser Pulses, Zhangjin Chen, Toru Morishita, Anh-Thu Le, C. D. Lin
Analysis Of Two-Dimensional High-Energy Photoelectron Momentum Distributions In The Single Ionization Of Atoms By Intense Laser Pulses, Zhangjin Chen, Toru Morishita, Anh-Thu Le, C. D. Lin
Physics Faculty Research & Creative Works
We analyzed the two-dimensional (2D) electron momentum distributions of high-energy photoelectrons of atoms in an intense laser field using the second-order strong field approximation (SFA2). The SFA2 accounts for the rescattering of the returning electron with the target ion to first order and its validity is established by comparing with results obtained by solving the time-dependent Schrödinger equation for short pulses. By analyzing the SFA2 theory, we confirmed that the yield along the back rescattered ridge in the 2D momentum spectra can be interpreted as due to the elastic scattering in the backward directions by the returning electron wave packet. …
Computing Quantum Phase Transitions, Thomas Vojta
Computing Quantum Phase Transitions, Thomas Vojta
Physics Faculty Research & Creative Works
This article first gives a concise introduction to quantum phase transitions, emphasizing similarities with and differences to classical thermal transitions. After pointing out the computational challenges posed by quantum phase transitions, a number of successful computational approaches is discussed. The focus is on classical and quantum Monte Carlo methods, with the former being based on the quantum-to classical mapping while the latter directly attack the quantum problem. These methods are illustrated by several examples of quantum phase transitions in clean and disordered systems.
Triple-Differential Cross Sections For Target Ionization With Simultaneous Projectile Detachment In 200-Kev H⁻ + He Collisions, T. Ferger, Michael Schulz, Daniel Fischer, B. Najjari, R. Moshammer, J. D. Ullrich
Triple-Differential Cross Sections For Target Ionization With Simultaneous Projectile Detachment In 200-Kev H⁻ + He Collisions, T. Ferger, Michael Schulz, Daniel Fischer, B. Najjari, R. Moshammer, J. D. Ullrich
Physics Faculty Research & Creative Works
We have performed a kinematically complete experiment for target ionization with simultaneous projectile detachment (TIPD) in 200-keV H− + He collisions. From the data we extracted triple-differential cross sections (TDCSs) for each electron separately. These TDCSs closely resemble corresponding data for single ionization by charged-particle impact. Surprisingly, the contributions from higher-order processes to TIPD, proceeding through two independent interactions of each electron with the core of the respective other collision partner, are found to be somewhat larger than the first-order process proceeding through the electron-electron interaction.
Qcd And Spin Effects In Black Hole Air Showers, Marco Cavaglia, Arunava Roy
Qcd And Spin Effects In Black Hole Air Showers, Marco Cavaglia, Arunava Roy
Physics Faculty Research & Creative Works
In models with large extra dimensions, black holes may be produced in high-energy particle collisions. We revisit the physics of black hole formation in extensive air showers from ultrahigh-energy cosmic rays, focusing on collisional QCD and black hole emissivity effects. New results for rotating black holes are presented. Monte Carlo simulations show that QCD effects and black hole spin produce no observable signatures in air showers. These results further confirm that the main characteristics of black hole-induced air showers do not depend on the fine details of micro-black-hole models.
Analysis Of Experimental Data For Ion-Impact Single Ionization Of Helium With Monte Carlo Event Generators Based On Quantum Theory, M. Dürr, B. Najjari, Michael Schulz, A. Dorn, R. Moshammer, A. B. Voitkiv, J. Ullrich
Analysis Of Experimental Data For Ion-Impact Single Ionization Of Helium With Monte Carlo Event Generators Based On Quantum Theory, M. Dürr, B. Najjari, Michael Schulz, A. Dorn, R. Moshammer, A. B. Voitkiv, J. Ullrich
Physics Faculty Research & Creative Works
Recent multiply differential experimental data taken with reaction microscopes severely challenge predictions of quantum mechanical few-body models. Here, we report on a thorough analysis of all known possible experimental resolution effects and their influence on the extracted cross sections. Using a Monte Carlo event generator to simulate true events on the basis of quantum calculations allows us to consistently incorporate all aspects of the experimental resolution of the reaction microscope. We study the effect of the instrumental function in single ionization of helium by 3.6 MeV/u Au53+ and 100 MeV/u C6+ ions and find it to significantly modify the simulated …
Theoretical Analysis Of Dynamic Chemical Imaging With Lasers Using High-Order Harmonic Generation, Van-Hoang Le, Anh-Thu Le, Rui-Hua Xie, C. D. Lin
Theoretical Analysis Of Dynamic Chemical Imaging With Lasers Using High-Order Harmonic Generation, Van-Hoang Le, Anh-Thu Le, Rui-Hua Xie, C. D. Lin
Physics Faculty Research & Creative Works
We report theoretical investigations of the tomographic procedure suggested by Itatani et al. [Nature (London) 432, 867 (2004)] for reconstructing highest occupied molecular orbitals (HOMOs) using high-order harmonic generation (HHG). Due to the limited range of harmonics from the plateau region, we found that even under the most favorable assumptions, it is still very difficult to obtain accurate HOMO wave functions using the tomographic procedure, but the symmetry of the HOMOs and the internuclear separation between the atoms can be accurately extracted, especially when lasers of longer wavelengths are used to generate the HHG. Since the tomographic procedure relies on …
Triply Differential Ionization Of Ar By 500 Ev Positron And Electron Impact, O. G. De Lucio, Jared M. Gavin, Robert D. Dubois
Triply Differential Ionization Of Ar By 500 Ev Positron And Electron Impact, O. G. De Lucio, Jared M. Gavin, Robert D. Dubois
Physics Faculty Research & Creative Works
Coincidences between recoil ions-ejected electrons and recoil ions-scattered projectiles have been used to study the kinematics of electron and positron impact ionization. Triply Differential (TDCS) data for 500 eV positron and electron impact on Ar are presented here as function of scattering angle for a given range of energy losses. Binary and recoil interactions can be distinguished allowing us to determine the relative intensity between those interactions. Preliminary integration of the data indicate an enhancement of the binary region for positron interaction while for electron impact the intensity of the recoil and binary interactions is comparable.
Bremsstrahlung In Α Decay Reexamined, H. Boie, Heiko Scheit, Ulrich D. Jentschura, F. Kock, M. Lauer, A. I. Milstein, Ivan S. Terekhov, Dirk Schwalm
Bremsstrahlung In Α Decay Reexamined, H. Boie, Heiko Scheit, Ulrich D. Jentschura, F. Kock, M. Lauer, A. I. Milstein, Ivan S. Terekhov, Dirk Schwalm
Physics Faculty Research & Creative Works
A high-statistics measurement of bremsstrahlung emitted in the α decay of 210Po has been performed, which allows us to follow the photon spectra up to energies of ~500keV. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasiclassical approximation as well as with the exact quantum mechanical calculation. It is shown that, due to the small effective electric dipole charge of the radiating system, a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the α particle and the emitted photon.
Signatures Of Black Holes At The Lhc, Marco Cavaglia, Romulus Godang, Lucien M. Cremaldi, Donald J. Summers
Signatures Of Black Holes At The Lhc, Marco Cavaglia, Romulus Godang, Lucien M. Cremaldi, Donald J. Summers
Physics Faculty Research & Creative Works
Signatures of black hole events at CERN's Large Hadron Collider are discussed. Event simulations are carried out with the Fortran Monte Carlo generator CATFISH. Inelasticity effects, exact field emissivities, color and charge conservation, corrections to semiclassical black hole evaporation, gravitational energy loss at formation and possibility of a black hole remnant are included in the analysis.
Laser-Assisted Bremsstrahlung For Circular And Linear Polarization, Stephan Schnez, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Laser-Assisted Bremsstrahlung For Circular And Linear Polarization, Stephan Schnez, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
We numerically evaluate the cross sections for spontaneous bremsstrahlung emission in a laser field for both circular and linear laser polarization, in a regime where the classical ponderomotive energies for the considered laser intensities are considerably larger than the rest mass of the electron. A fully relativistic quantum-electrodynamic approach using the Volkov solutions of an electron in an external field and Dirac-Volkov propagators for the intermediate electrons is applied. We compare circular to linear polarization and point out several interesting features of the laser-dressed cross sections. Regularizations in both electron and photon propagators are required. Specifically, imaginary mass and energy …
Doubly Differential Single And Multiple Ionization Of Krypton By Electron Impact, O. G. De Lucio, Jared M. Gavin, Robert D. Dubois
Doubly Differential Single And Multiple Ionization Of Krypton By Electron Impact, O. G. De Lucio, Jared M. Gavin, Robert D. Dubois
Physics Faculty Research & Creative Works
Differential measurements for single and multiple ionization of Kr by 240 and 500 eV electron impact are presented. Using a pulsed extraction field, Kr+, Kr2+, and Kr3+ ions were measured in coincidence with scattered electrons for energy losses up to 120 eV and scattering angles between 16° and 90°. Scaling properties of the doubly differential cross sections (DDCS) are investigated as a function of energy loss, scattering angle, and momentum transfer. It is shown that scaling the DDCS as outlined by Kim and Inokuti and plotting them versus a parameter consisting of the momentum transfer divided by the square root …
Few-Photon Multiple Ionization Of Ne And Ar By Strong Free-Electron-Laser Pulses, Robert Moshammer, Yuhai Jiang, L. Foucar, Artem Rudenko, Th. Ergler, Claus Dieter Schroter, S. Ludemann, Karl Zrost, Daniel Fischer, J. Titze, Till Jahnke, Markus S. Schoffler, Th Weber, Reinhard Dorner, Theo J.M. Zouros, Alexander Dorn, T. Ferger, Kai Uwe Kuhnel, S. Dusterer, R. Treusch, Paul Radcliffe, Elke Plonjes, Joachim Hermann Ullrich
Few-Photon Multiple Ionization Of Ne And Ar By Strong Free-Electron-Laser Pulses, Robert Moshammer, Yuhai Jiang, L. Foucar, Artem Rudenko, Th. Ergler, Claus Dieter Schroter, S. Ludemann, Karl Zrost, Daniel Fischer, J. Titze, Till Jahnke, Markus S. Schoffler, Th Weber, Reinhard Dorner, Theo J.M. Zouros, Alexander Dorn, T. Ferger, Kai Uwe Kuhnel, S. Dusterer, R. Treusch, Paul Radcliffe, Elke Plonjes, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
Few-photon multiple ionization of Ne and Ar atoms by strong vacuum ultraviolet laser pulses from the free-electron laser at Hamburg was investigated differentially with the Heidelberg reaction microscope. The light-intensity dependence of Ne2+ production reveals the dominance of nonsequential two-photon double ionization at intensities of I< 6 x 1012W/cm2 and significant contributions of three-photon ionization as I increases. Ne2+ recoil-ion-momentum distributions suggest that two electrons absorbing "instantaneously" two photons are ejected most likely into opposite hemispheres with similar energies.
Radiative Orbital Electron Capture By The Atomic Nucleus, Krzysztof Pachucki, Ulrich D. Jentschura, Marek M. Pfutzner
Radiative Orbital Electron Capture By The Atomic Nucleus, Krzysztof Pachucki, Ulrich D. Jentschura, Marek M. Pfutzner
Physics Faculty Research & Creative Works
The rate for the photon emission accompanying orbital 1S electron capture by the atomic nucleus is recalculated. While a photon can be emitted by the electron or by the nucleus, the use of the length gauge significantly suppresses the nuclear contribution. Our calculations resolve the long standing discrepancy of theoretical predictions with experimental data for ΔJ=2 forbidden transitions. We illustrate the results by comparison with the data established experimentally for the first forbidden unique decays of 41Ca and 204Tl.
Ionization And Ionization-Excitation Of Helium To The N=1-4 States Of He⁺ By Electron Impact, Susan M. Bellm, Julian C A Lower, Klaus Bartschat, Xiaoxu Guan, Daniel Weflen, Matthew S. Foster, Allison L. Harris, Don H. Madison
Ionization And Ionization-Excitation Of Helium To The N=1-4 States Of He⁺ By Electron Impact, Susan M. Bellm, Julian C A Lower, Klaus Bartschat, Xiaoxu Guan, Daniel Weflen, Matthew S. Foster, Allison L. Harris, Don H. Madison
Physics Faculty Research & Creative Works
We present experimental and theoretical results for the electron-impact-induced ionization of ground-state helium atoms. Using a high-sensitivity toroidal electron spectrometer, we measured cross-section ratios for transitions leading to the first three excited states of the residual helium ion relative to the transition leaving the ion in the ground state. Measurements were performed for both symmetric- and asymmetric-energy-sharing kinematics. By presenting results as a ratio, a direct comparison can be made between theoretical and experimental predictions without recourse to normalization. The experimental data are compared to theoretical predictions employing various first-order models and a second-order hybrid distorted-wave + convergent R matrix …
Gravitational Larmor Formula In Higher Dimensions, Vitor Cardoso, Marco Cavaglia, Jun-Quo Guo
Gravitational Larmor Formula In Higher Dimensions, Vitor Cardoso, Marco Cavaglia, Jun-Quo Guo
Physics Faculty Research & Creative Works
The Larmor formula for scalar and gravitational radiation from a pointlike particle is derived in any even higher-dimensional flat spacetime. General expressions for the field in the wave zone and the energy flux are obtained in closed form. The explicit results in four and six dimensions are used to illustrate the effect of extra dimensions on linear and uniform circular motion. Prospects for detection of bulk gravitational radiation are briefly discussed.
Fragmentation Of Molecules By Fast Ion Impact, Christina Dimopoulou, Nicole Haag, Robert Moshammer, Pablo Daniel Fainstein, Alexander Dorn, M. Durr, Daniel Fischer, Joachim Hermann Ullrich
Fragmentation Of Molecules By Fast Ion Impact, Christina Dimopoulou, Nicole Haag, Robert Moshammer, Pablo Daniel Fainstein, Alexander Dorn, M. Durr, Daniel Fischer, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
Single ionization of simple molecules, e.g. H2, CO2, by fast charged particle impact has been studied using a reaction microscope. By measuring the momenta of the emitted electron and the recoil ionic fragment in coincidence, channel-selective low-energy electron spectra have been recorded. The experimental cross sections will be presented, compared with the predictions of state-of-the-art CDW-EIS calculations and discussed in terms of molecular effects such as (i) autoionization and predissociation channels, (ii) interference patterns resulting from the two-center geometry of the diatomic molecule, in analogy to Young's double-slit experiment and (iii) dependence of the electron emission …
Correlation And Quantum Electrodynamic Effects On The Radiative Lifetime And Relativistic Nuclear Recoil In Ar¹³⁺ And Ar¹⁴⁺ Ions, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, Alain Lapierre, R. Soria Orts, Jose R. Crespo Lopez-Urrutia, Hiroyuki Tawara, Joachim Hermann Ullrich, Anton N. Artemyev, I. I. Tupitsyn, Andrey V. Volotka, Vladimir M. Shabaev
Correlation And Quantum Electrodynamic Effects On The Radiative Lifetime And Relativistic Nuclear Recoil In Ar¹³⁺ And Ar¹⁴⁺ Ions, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, Alain Lapierre, R. Soria Orts, Jose R. Crespo Lopez-Urrutia, Hiroyuki Tawara, Joachim Hermann Ullrich, Anton N. Artemyev, I. I. Tupitsyn, Andrey V. Volotka, Vladimir M. Shabaev
Physics Faculty Research & Creative Works
The radiative lifetime and mass isotope shift of the 1s22s22p 2P3/2 - 2P1/2 M1 transition in Ar13+ ions have been determined with high accuracies using the Heidelberg electron beam ion trap. This fundamentally relativistic transition provides unique possibilities for performing precise studies of correlation and quantum electrodynamic effects in many-electron systems. The lifetime corresponding to the transition has been measured with an accuracy of the order of one per thousand. Theoretical calculations predict a lifetime that is in significant disagreement with this high-precision experimental value. Our mass shift calculations, based on …
Effects Of Configuration Interaction On The Alignment Of Beryllium-Like Ions, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker, Stephan Fritzsche
Effects Of Configuration Interaction On The Alignment Of Beryllium-Like Ions, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker, Stephan Fritzsche
Physics Faculty Research & Creative Works
The radiative electron capture into (initially) lithium-like ions is studied within the framework of the density matrix approach. Special attention is paid to the magnetic sublevel population of the residual ionic states which is described by a set of alignment parameters. Detailed calculations of these parameters have been performed for the capture into the 1s2 2s 3d3/2 Jf2 level of high-Z ions along the beryllium isoelectronic sequence. We devote special attention to the modifications in the many-electron case as opposed to singleelectron systems. The electron correlation leads to an enhancement of the alignment, which becomes more …
Entrainment And Stimulated Emission Of Auto-Oscillators In An Acoustic Cavity, Richard L. Weaver, Oleg I. Lobkis, Alexey Yamilov
Entrainment And Stimulated Emission Of Auto-Oscillators In An Acoustic Cavity, Richard L. Weaver, Oleg I. Lobkis, Alexey Yamilov
Physics Faculty Research & Creative Works
We report theory, measurements and numerical simulations on nonlinear piezoelectric ultrasonic devices with stable limit cycles. The devices are shown to exhibit behavior familiar from the theory of coupled auto-oscillators. Frequency of auto-oscillation is affected by the presence of an acoustic cavity as these spontaneously emitting devices adjust their frequency to the spectrum of the acoustic cavity. Also, the auto-oscillation is shown to be entrained by an applied field; the oscillator synchronizes to an incident wave at a frequency close to the natural frequency of the limit cycle. It is further shown that synchronization occurs here with a phase that …
Quantum-Theory Based Event Generator For The Analysis Of Kinematically Complete Experiments, M. Dürr, B. Najjari, Michael Schulz, A. Dorn, R. Moshammer, J. Ullrich
Quantum-Theory Based Event Generator For The Analysis Of Kinematically Complete Experiments, M. Dürr, B. Najjari, Michael Schulz, A. Dorn, R. Moshammer, J. Ullrich
Physics Faculty Research & Creative Works
The 'reaction microscope', an electron-ion coincidence momentum imaging spectrometer, represents a unique technique to measure multiply differential ionization cross sections for ionic projectiles. Observed discrepancies with theory for singly ionizing collision of 3.6 MeV/u Au53+ and 100 MeV/u C6+ ions severely challenge theoretical models. We present a method based on event-generators, which allows to consistently incorporate instrumental effects into theory. The result of the convolution procedure suggests, that the observed discrepancies are not a result of the experimental resolution, but are of true physical nature.
Reconciliation Of Measured Fully Differential Single Ionization Data With The First Born Approximation Convoluted With Elastic Scattering, Michael Schulz, M. Dürr, B. Najjari, R. Moshammer, J. D. Ullrich
Reconciliation Of Measured Fully Differential Single Ionization Data With The First Born Approximation Convoluted With Elastic Scattering, Michael Schulz, M. Dürr, B. Najjari, R. Moshammer, J. D. Ullrich
Physics Faculty Research & Creative Works
An analysis of experimental fully differential data for single ionization in 100 MeV/amu C6++He collisions is reported. We present a convolution of the first Born approximation with elastic scattering by using an event generator technique. Furthermore, the calculation is convoluted with all known experimental resolutions. Our analysis shows that elastic scattering is a viable explanation for surprising structures observed in the fully differential cross sections outside the scattering plane. Furthermore, it may even explain discrepancies in the “recoil peak” frequently observed for both ion and electron impact.
Evidence Of Dynamical Spin Shielding In Ce From Spin-Resolved Photoelectron Spectroscopy, James G. Tobin, S. W. Yu, Takashi Komesu, B. W. Chung, Simon A. Morton, George Daniel Waddill
Evidence Of Dynamical Spin Shielding In Ce From Spin-Resolved Photoelectron Spectroscopy, James G. Tobin, S. W. Yu, Takashi Komesu, B. W. Chung, Simon A. Morton, George Daniel Waddill
Physics Faculty Research & Creative Works
Using Fano effect measurements upon polycrystalline Ce, we have observed a phase reversal between the spectral structure at the Fermi edge and the other 4f derived feature near a binding energy of 2 eV. The Fano effect is the observation of spin polarized photoelectron emission from nonmagnetic materials, under chirally selective excitation, such as circularly polarized photons. The observation of phase reversal between the two peaks is a direct experimental proof of Kondo shielding in Ce, confirming the predictions of Gunnarsson and Shoenhammer, albeit with a small modification.
Normal Transport At Positive Temperatures In Classical Hamiltonian Open Systems, P. Lafitte, Paul Ernest Parris, Stephan De Bièvre
Normal Transport At Positive Temperatures In Classical Hamiltonian Open Systems, P. Lafitte, Paul Ernest Parris, Stephan De Bièvre
Physics Faculty Research & Creative Works
We study the transport properties of classical Hamiltonian models describing the motion of an unconfined particle coupled to vibrational degrees of freedom in thermal equilibrium at zero or positive temperature. We identify and discuss conditions under which, in such systems, the particle has a well-defined diffusion constant and mobility. We will in particular point out some marked differences with the situation where the particle is confined and described with a Caldeira-Leggett model. We will more specifically report on results obtained in a classical version of the Holstein molecular crystal model, speculate on their relevance in the corresponding quantum system and …
Evaluation Of Laser-Assisted Bremsstrahlung With Dirac-Volkov Propagators, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Evaluation Of Laser-Assisted Bremsstrahlung With Dirac-Volkov Propagators, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
We study spontaneous bremsstrahlung emission in a highly intense laser field. In this regime the interaction with the laser field has to be treated nonperturbatively by using the relativistic formalism including Dirac-Volkov propagators, while the interaction with the Coulomb field and the bremsstrahlung radiation can be treated in first-order perturbation theory. For the intermediate electron state a fully laser-dressed propagator is used, including radiative corrections to avoid singularities on the mass shell. We find that the use of the Dirac-Volkov propagator is crucial to obtain correct numerical results. The cross section of the process is evaluated for laser intensities of …