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Physics Faculty Research & Creative Works

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Articles 511 - 540 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Phonon Lifetime Investigation Of Anharmonicity And Thermal Conductivity Of Uo₂ By Neutron Scattering And Theory, Judy W. Pang, William J. Buyers, Aleksandr V. Chernatynskiy, Mark D. Lumsden, Bennett C. Larson, Simon R. Phillpot Apr 2013

Phonon Lifetime Investigation Of Anharmonicity And Thermal Conductivity Of Uo₂ By Neutron Scattering And Theory, Judy W. Pang, William J. Buyers, Aleksandr V. Chernatynskiy, Mark D. Lumsden, Bennett C. Larson, Simon R. Phillpot

Physics Faculty Research & Creative Works

Inelastic neutron scattering measurements of individual phonon lifetimes and dispersion at 295 and 1200 K have been used to probe anharmonicity and thermal conductivity in UO2. They show that longitudinal optic phonon modes carry the largest amount of heat, in contrast to past simulations and that the total conductivity demonstrates a quantitative correspondence between microscopic and macroscopic phonon physics. We have further performed first-principles simulations for UO2 showing semiquantitative agreement with phonon lifetimes at 295 K, but larger anharmonicity than measured at 1200 K.

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Compact Object Coalescence Rate Estimation From Short Gamma-Ray Burst Observations, Carlo Enrico Petrillo, Alexander Dietz, Marco Cavaglia Apr 2013

Compact Object Coalescence Rate Estimation From Short Gamma-Ray Burst Observations, Carlo Enrico Petrillo, Alexander Dietz, Marco Cavaglia

Physics Faculty Research & Creative Works

Recent observational and theoretical results suggest that short-duration gamma-ray bursts (SGRBs) originate from the merger of compact binary systems of two neutron stars or a neutron star and a black hole. The observation of SGRBs with known redshifts allows astronomers to infer the merger rate of these systems in the local universe. We use data from the SWIFT satellite to estimate this rate to be in the range ∼500-1500 Gpc-3 yr-1. This result is consistent with earlier published results which were obtained through alternative approaches. We estimate the number of coincident observations of gravitational-wave signals with SGRBs …

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Comment On "Singly Ionizing 100-Mev/Amu C⁶⁺+He Collisions With Small Momentum Transfer", Michael Schulz, Robert Moshammer, Daniel Fischer, Joachim Hermann Ullrich Apr 2013

Comment On "Singly Ionizing 100-Mev/Amu C⁶⁺+He Collisions With Small Momentum Transfer", Michael Schulz, Robert Moshammer, Daniel Fischer, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

In a recent article, Kouzakov suggested that experimental resolution effects can be responsible for discrepancies between measured and calculated fully differential cross sections for the ionization of helium by fast C6+ impact. They further asserted that projectile-coherence effects have no influence on the measured cross sections. In this Comment, we reiterate that the experimental resolution can only explain part of the discrepancies. Furthermore, we note that the conclusion regarding the role of projectile coherence neglects potential interference between first- and higher-order transition amplitudes.

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Theoretical Study Of The Compton Effect With Correlated Three-Photon Emission: From The Differential Cross Section To High-Energy Triple-Photon Entanglement, Erik Loetstedt, Ulrich D. Jentschura Mar 2013

Theoretical Study Of The Compton Effect With Correlated Three-Photon Emission: From The Differential Cross Section To High-Energy Triple-Photon Entanglement, Erik Loetstedt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The three-photon Compton effect is studied. An incoming photon undergoes triple scattering off a free electron, which leads to the emission of three entangled photons. We investigate the properties of both the total cross section, assuming a low-energy cutoff for the detected photons, and the differential cross section. Particular emphasis is laid on evaluating polarization-resolved cross sections. The entanglement of the final three-photon state is analyzed.

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Polarization And Interference Effects In Ionization Of Li By Ion Impact, Renate Hubele, Aaron C. Laforge, Michael Schulz, Johannes Goullon, Xincheng Wang, B. Najjari, Natalia Ferreira, Manfred Grieser, Vitor L B D De Jesus, Robert Moshammer, Katharina R. Schneider, Alexander B. Voitkiv, Daniel Fischer Mar 2013

Polarization And Interference Effects In Ionization Of Li By Ion Impact, Renate Hubele, Aaron C. Laforge, Michael Schulz, Johannes Goullon, Xincheng Wang, B. Najjari, Natalia Ferreira, Manfred Grieser, Vitor L B D De Jesus, Robert Moshammer, Katharina R. Schneider, Alexander B. Voitkiv, Daniel Fischer

Physics Faculty Research & Creative Works

We present initial-state selective fully differential cross sections for ionization of lithium by 24 MeV O8+ impact. The data for ionization from the 2s and 2p states look qualitatively different from each other and from 1s ionization of He. For ionization from the 2p state, to which in our study the mL=-1 substate predominantly contributes, we observe orientational dichroism and for 2s ionization pronounced interference which we trace back to the nodal structure of the initial-state wave function.

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Role Of Projectile Coherence In Close Heavy Ion-Atom Collisions, Katharina R. Schneider, Michael Schulz, Xincheng Wang, Aditya H. Kelkar, Manfred Grieser, Claude Krantz, Joachim Hermann Ullrich, Robert Moshammer, Daniel Fischer Mar 2013

Role Of Projectile Coherence In Close Heavy Ion-Atom Collisions, Katharina R. Schneider, Michael Schulz, Xincheng Wang, Aditya H. Kelkar, Manfred Grieser, Claude Krantz, Joachim Hermann Ullrich, Robert Moshammer, Daniel Fischer

Physics Faculty Research & Creative Works

We have measured fully differential cross sections for single ionization and transfer ionization (TI) in 16 MeV O7++He collisions. The impact parameters mostly contributing to single ionization are about an order of magnitude larger than for TI. Therefore, the projectile beam was much more coherent for the latter compared to the former process. The measured data suggest that, as a result, TI is significantly affected by interference effects which are not present in single ionization.

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Gravitationally Coupled Dirac Equation For Antimatter, Ulrich D. Jentschura Mar 2013

Gravitationally Coupled Dirac Equation For Antimatter, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The coupling of antimatter to gravity is of general interest because of conceivable cosmological consequences ("surprises") related to dark energy and the cosmological constant. Here, we revisit the derivation of the gravitationally coupled Dirac equation and find that the prefactor of a result given previously by Brill and Wheeler [Rev. Mod. Phys. 29, 465 (1957)] for the affine connection matrix is in need of a correction. We also discuss the conversion of the curved-space Dirac equation from the so-called "East-Coast" to the "West-Coast" convention, in order to bring the gravitationally coupled Dirac equation to a form where it can easily …

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Einstein@Home All-Sky Search For Periodic Gravitational Waves In Ligo S5 Data, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Feb 2013

Einstein@Home All-Sky Search For Periodic Gravitational Waves In Ligo S5 Data, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50,1 190] Hz and with frequency derivative range of ∼[-20,1.1] x 10-10 Hz s-1 for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we …

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Imaging The Anisotropic Nonlinear Meissner Effect In Nodal Yba ₂Cu₃O7-Δ Thin-Film Superconductors, Alexander P. Zhuravel, Behnood G. Ghamsari, Cihan Kurter, Philipp Jung, Stephen K. Remillard, John A. Abrahams, Alexander V. Lukashenko, Alexey V. Ustinov, Steven Mark Anlage Feb 2013

Imaging The Anisotropic Nonlinear Meissner Effect In Nodal Yba ₂Cu₃O7-Δ Thin-Film Superconductors, Alexander P. Zhuravel, Behnood G. Ghamsari, Cihan Kurter, Philipp Jung, Stephen K. Remillard, John A. Abrahams, Alexander V. Lukashenko, Alexey V. Ustinov, Steven Mark Anlage

Physics Faculty Research & Creative Works

We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact self-resonant spiral structure, excited near resonance in the radio-frequency range, and scanned with a focused laser beam perturbation. At low temperatures, direction-dependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal …

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Picturing Electron Capture To The Continuum In The Transfer Ionization Of Intermediate-Energy He²⁺ Collisions With Argon, Ruitian Zhang, Xinwen Ma, Shaofeng Zhang, Xiaolong Zhu, Susmitha Akula, Don H. Madison, Bingsheng Li, Dongbin Qian, Wentian Feng, Dalong Guo, Huiping Liu, Shuncheng Yan, Pengju Zhang, Shenyue Xu, Ximeng Chen Jan 2013

Picturing Electron Capture To The Continuum In The Transfer Ionization Of Intermediate-Energy He²⁺ Collisions With Argon, Ruitian Zhang, Xinwen Ma, Shaofeng Zhang, Xiaolong Zhu, Susmitha Akula, Don H. Madison, Bingsheng Li, Dongbin Qian, Wentian Feng, Dalong Guo, Huiping Liu, Shuncheng Yan, Pengju Zhang, Shenyue Xu, Ximeng Chen

Physics Faculty Research & Creative Works

Electron emission occurring in transfer ionization for He2+ collisions with argon has been investigated using cold target recoil ion momentum spectroscopy. The double differential cross sections for electron capture to the continuum of the projectile (cusp-shaped electrons) are presented for collision energies from 17.5 to 75 keV/u. For an energy of 30 keV/u, we find a maximum in the experimental ratio of the cusp-shaped electron yield to the total electron yield. This result is explained in terms of the velocity matching between the projectile ion and the electron initially bound to the target. One of the important issues for …

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Search For Gravitational Waves From Binary Black Hole Inspiral, Merger, And Ringdown In Ligo-Virgo Data From 2009-2010, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jan 2013

Search For Gravitational Waves From Binary Black Hole Inspiral, Merger, And Ringdown In Ligo-Virgo Data From 2009-2010, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We report a search for gravitational waves from the inspiral, merger and ringdown of binary black holes (BBH) with total mass between 25 and 100 solar masses, in data taken at the LIGO and Virgo observatories between July 7, 2009 and October 20, 2010. The maximum sensitive distance of the detectors over this period for a (20,20)M⊙ coalescence was 300 Mpc. No gravitational wave signals were found. We thus report upper limits on the astrophysical coalescence rates of BBH as a function of the component masses for nonspinning components, and also evaluate the dependence of the search sensitivity on …

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High Harmonic Spectroscopy Of The Cooper Minimum In Molecules, M. C. H. Wong, Anh-Thu Le, A. F. Alharbi, A. E. Boguslavskiy, R. R. Lucchese, J.-P. Brichta, C. D. Lin, V. R. Bhardwaj Jan 2013

High Harmonic Spectroscopy Of The Cooper Minimum In Molecules, M. C. H. Wong, Anh-Thu Le, A. F. Alharbi, A. E. Boguslavskiy, R. R. Lucchese, J.-P. Brichta, C. D. Lin, V. R. Bhardwaj

Physics Faculty Research & Creative Works

The Cooper minimum (CM) has been studied using high harmonic generation solely in atoms. Here, we present detailed experimental and theoretical studies on the CM in molecules probed by high harmonic generation using a range of near-infrared light pulses from λ = 1.3 to 1.8 µm. We demonstrate the CM to occur in CS₂ and CCl₄ at ~42 and ~40 eV, respectively, by comparing the high harmonic spectra with the known partial photoionization cross sections of different molecular orbitals, confirmed by theoretical calculations of harmonic spectra. We use CM to probe electron localization in Cl-containing molecules (CCl₄, CH₂Cl₂, and trans …

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Rounding Of A First-Order Quantum Phase Transition To A Strong-Coupling Critical Point, Fawaz Hrahsheh, Jose A. Hoyos, Thomas Vojta Dec 2012

Rounding Of A First-Order Quantum Phase Transition To A Strong-Coupling Critical Point, Fawaz Hrahsheh, Jose A. Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the effects of quenched disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong-disorder renormalization group, we demonstrate that quenched disorder rounds the first-order quantum phase transition to a continuous one for both weak and strong coupling between the colors. In the strong-coupling case, we find a distinct type of infinite-randomness critical point characterized by additional internal degrees of freedom. We investigate its critical properties in detail and find stronger thermodynamic singularities than in the random transverse field Ising chain. We also discuss the implications for higher spatial …

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Acoustic Scale From The Angular Power Spectra Of Sdss-Iii Dr8 Photometric Luminous Galaxies, Hee-Jong Seo, Shirley Ho, Martin White, Antonio J. Cuesta, Ashley J. Ross, Shun Saito, For Full List Of Authors, See Publisher's Website. Dec 2012

Acoustic Scale From The Angular Power Spectra Of Sdss-Iii Dr8 Photometric Luminous Galaxies, Hee-Jong Seo, Shirley Ho, Martin White, Antonio J. Cuesta, Ashley J. Ross, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872, 921 galaxies over ~10,000 deg2 between 0.45 < z < 0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, to derive the location of Baryon acoustic oscillations (BAOs) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale DA(z)/rs = 9.212+0.416-0.404 at z = 0.54, and therefore DA (z) = 1411 ± 65 Mpc at z = 0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance DA(z) is 1.4σ higher than what is expected for the concordance ΛCDM, in accordance to the trend of other spectroscopic BAO measurements for …

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Laser-Induced Electron Diffraction For Probing Rare Gas Atoms, Junliang Xu, Cosmin I. Blaga, Anthony D. Dichiara, Emily Sistrunk, Kaikai Zhang, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin, Pierre Agostini, Louis F. Dimauro Dec 2012

Laser-Induced Electron Diffraction For Probing Rare Gas Atoms, Junliang Xu, Cosmin I. Blaga, Anthony D. Dichiara, Emily Sistrunk, Kaikai Zhang, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin, Pierre Agostini, Louis F. Dimauro

Physics Faculty Research & Creative Works

Recently, using midinfrared laser-induced electron diffraction (LIED), snapshots of a vibrating diatomic molecule on a femtosecond time scale have been captured [C.I. Blaga et al., Nature (London) 483, 194 (2012)]. In this Letter, a comprehensive treatment for the atomic LIED response is reported, a critical step in generalizing this imaging method. Electron-ion differential cross sections (DCSs) of rare gas atoms are extracted from measured angular-resolved, high-energy electron momentum distributions generated by intense midinfrared lasers. Following strong-field ionization, the high-energy electrons result from elastic rescattering of a field-driven wave packet with the parent ion. For recollision energies [greater or equal] 100eV, …

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Disordered Bosons In One Dimension: From Weak- To Strong-Randomness Criticality, Fawaz Hrahsheh, Thomas Vojta Dec 2012

Disordered Bosons In One Dimension: From Weak- To Strong-Randomness Criticality, Fawaz Hrahsheh, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte Carlo simulations. For weak disorder, we find the transition to be in the same universality class as the superfluid-Mott insulator transition of the clean system. The nature of the transition changes for stronger disorder. Beyond a critical disorder strength, we find nonuniversal, disorder-dependent critical behavior. We compare our results to recent perturbative and strong-disorder renormalization group predictions. We also discuss experimental implications as well as extensions of our results to other systems.

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Clustering Of Sloan Digital Sky Survey Iii Photometric Luminous Galaxies: The Measurement, Systematics, And Cosmological Implications, Shirley Ho, Antonio J. Cuesta, Hee-Jong Seo, Roland De Putter, Ashley J. Ross, Martin White, Nikhil Padmanabhan, Shun Saito, For Full List Of Authors, See Publisher's Website. Dec 2012

Clustering Of Sloan Digital Sky Survey Iii Photometric Luminous Galaxies: The Measurement, Systematics, And Cosmological Implications, Shirley Ho, Antonio J. Cuesta, Hee-Jong Seo, Roland De Putter, Ashley J. Ross, Martin White, Nikhil Padmanabhan, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The Sloan Digital Sky Survey (SDSS) surveyed 14,555 deg2, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between z = 0.45 and z = 0.65, constructed from the SDSS using methods described in Ross et al. This data set spans 11,000 deg2 and probes a volume of 3 h-3 Gpc3, making it the largest volume ever used for galaxy clustering measurements. We describe in detail the construction of the survey window function and various systematics affecting our measurement. …

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Quantum Dynamics In Atomic-Fountain Experiments For Measuring The Electric Dipole Moment Of The Electron With Improved Sensitivity, Benedikt J. Wundt, Charles T. Munger, Ulrich D. Jentschura Nov 2012

Quantum Dynamics In Atomic-Fountain Experiments For Measuring The Electric Dipole Moment Of The Electron With Improved Sensitivity, Benedikt J. Wundt, Charles T. Munger, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

An improved measurement of the electron electric dipole moment (EDM) appears feasible using groundstate alkali atoms in an atomic fountain in which a strong electric field, which couples to a conceivable EDM, is applied perpendicular to the fountain axis. In a practical fountain, the ratio of the atomic tensor Stark shift to the Zeeman shift is a factor μ ~ 100.We expand the complete time-evolution operator in inverse powers of this ratio; complete results are presented for atoms of total spin F = 3, 4, and 5. For a specific set of entangled hyperfine sublevels (coherent states), potential systematic errors …

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Monte Carlo Simulations Of The Clean And Disordered Contact Process In Three Dimensions, Thomas Vojta Nov 2012

Monte Carlo Simulations Of The Clean And Disordered Contact Process In Three Dimensions, Thomas Vojta

Physics Faculty Research & Creative Works

The absorbing-state transition in the three-dimensional contact process with and without quenched randomness is investigated by means of Monte Carlo simulations. In the clean case, a reweighting technique is combined with a careful extrapolation of the data to infinite time to determine with high accuracy the critical behavior in the three-dimensional directed percolation universality class. In the presence of quenched spatial disorder, our data demonstrate that the absorbing-state transition is governed by an unconventional infinite-randomness critical point featuring activated dynamical scaling. The critical behavior of this transition does not depend on the disorder strength, i.e., it is universal. Close to …

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Swift Follow-Up Observations Of Candidate Gravitational-Wave Transient Events, P. A. Evans, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2012

Swift Follow-Up Observations Of Candidate Gravitational-Wave Transient Events, P. A. Evans, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them …

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Theory Of High Harmonic Generation For Probing Time-Resolved Large-Amplitude Molecular Vibrations With Ultrashort Intense Lasers, Anh-Thu Le, Toru Morishita, R. R. Lucchese, C. D. Lin Nov 2012

Theory Of High Harmonic Generation For Probing Time-Resolved Large-Amplitude Molecular Vibrations With Ultrashort Intense Lasers, Anh-Thu Le, Toru Morishita, R. R. Lucchese, C. D. Lin

Physics Faculty Research & Creative Works

We present a theory that incorporates the vibrational degrees of freedom in a high-order harmonic generation (HHG) process with ultrashort intense laser pulses. In this model, laser-induced time-dependent transition dipoles for each fixed molecular geometry are added coherently, weighted by the laser-driven time-dependent nuclear wave packet distribution. We show that the nuclear distribution can be strongly modified by the HHG driving laser. The validity of this model is first checked against results from the numerical solution of the time-dependent Schrödinger equation for a simple model system. We show that in combination with the established quantitative rescattering theory this model is …

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Search For Gravitational Waves Associated With Gamma-Ray Bursts During Ligo Science Run 6 And Virgo Science Runs 2 And 3, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Oct 2012

Search For Gravitational Waves Associated With Gamma-Ray Bursts During Ligo Science Run 6 And Virgo Science Runs 2 And 3, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results of a search for gravitational waves associated with 154 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments in 2009-2010, during the sixth LIGO science run and the second and third Virgo science runs. We perform two distinct searches: a modeled search for coalescences of either two neutron stars or a neutron star and black hole, and a search for generic, unmodeled gravitational-wave bursts. We find no evidence for gravitational-wave counterparts, either with any individual GRB in this sample or with the population as a whole. For all GRBs we place lower bounds on the …

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Random Fields At A Nonequilibrium Phase Transition, Hatem Barghathi, Thomas Vojta Oct 2012

Random Fields At A Nonequilibrium Phase Transition, Hatem Barghathi, Thomas Vojta

Physics Faculty Research & Creative Works

We study nonequilibrium phase transitions in the presence of disorder that locally breaks the symmetry between two equivalent macroscopic states. In low-dimensional equilibrium systems, such random-field disorder is known to have dramatic effects: it prevents spontaneous symmetry breaking and completely destroys the phase transition. In contrast, we show that the phase transition of the one-dimensional generalized contact process persists in the presence of random-field disorder. The ultraslow dynamics in the symmetry-broken phase is described by a Sinai walk of the domain walls between two different absorbing states. We discuss the generality and limitations of our theory, and we illustrate our …

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Evidence Of Electron Saddle Swap Oscillations In Angular Differential Ion-Atom Charge Exchange Cross Sections, S. Otranto, I. Blank, Ronald E. Olson, R. Hoekstra Sep 2012

Evidence Of Electron Saddle Swap Oscillations In Angular Differential Ion-Atom Charge Exchange Cross Sections, S. Otranto, I. Blank, Ronald E. Olson, R. Hoekstra

Physics Faculty Research & Creative Works

State selective charge exchange processes in 1-10keV/amu Ne8++Na(3s) collisions were measured by means of the magneto-optical trap recoil-ion momentum spectroscopy technique and compared to classical trajectory Monte Carlo calculations. We find that for electron capture to n-levels >= 10, the transverse momentum distributions exhibit an oscillatory structure which is very sensitive to the impact energy. Our theoretical analysis suggests that this feature is a direct consequence of the number of swaps the electron undergoes across the potential energy saddle during the charge exchange process. © 2012 IOP Publishing Ltd.

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Ion-Lithium Collision Dynamics Studied With A Laser-Cooled In-Ring Target, Daniel Fischer, Dominik Globig, Johannes Goullon, Manfred Grieser, Renate Hubele, Vitor L B D De Jesus, Aditya H. Kelkar, Aaron C. Laforge, H. Lindenblatt, Deepankar S. Misra, B. Najjari, Katharina R. Schneider, Michael Schulz, Martin Sell, Xincheng Wang Sep 2012

Ion-Lithium Collision Dynamics Studied With A Laser-Cooled In-Ring Target, Daniel Fischer, Dominik Globig, Johannes Goullon, Manfred Grieser, Renate Hubele, Vitor L B D De Jesus, Aditya H. Kelkar, Aaron C. Laforge, H. Lindenblatt, Deepankar S. Misra, B. Najjari, Katharina R. Schneider, Michael Schulz, Martin Sell, Xincheng Wang

Physics Faculty Research & Creative Works

We present a novel experimental tool allowing for kinematically complete studies of break-up processes of laser-cooled atoms. This apparatus, the 'MOTReMi,' is a combination of a magneto-optical trap (MOT) and a reaction microscope (ReMi). Operated in an ion-storage ring, the new setup enables us to study the dynamics in swift ion-atom collisions on an unprecedented level of precision and detail. In the inaugural experiment on collisions with 1.5MeV/amu O8 +-Li the pure ionization of the valence electron as well as the ionization-excitation of the lithium target was investigated.

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Erratum: Search For Gravitational Waves From Binary Black Hole Inspiral, Merger, And Ringdown (Physical Review D - Particles, Fields, Gravitation And Cosmology (2011) 83 (122005)), J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Sep 2012

Erratum: Search For Gravitational Waves From Binary Black Hole Inspiral, Merger, And Ringdown (Physical Review D - Particles, Fields, Gravitation And Cosmology (2011) 83 (122005)), J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Since the publication we have discovered two errors in the calculation of upper limits on binary black hole (BBH) coalescence rates inferred from the nondetection of gravitational waves. The errors caused systematic biases of opposite signs and different sizes in the 90% confidence rate limits; when errors are corrected, the resulting limits are a factor 3 to 5 smaller than those quoted. Here we give a brief description of the errors and report their impacts on the upper limit results.

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Non-Fermi Liquid Transport And "Universal" Ratios In Quantum Griffiths Phases, David Nozadze, Thomas Vojta Sep 2012

Non-Fermi Liquid Transport And "Universal" Ratios In Quantum Griffiths Phases, David Nozadze, Thomas Vojta

Physics Faculty Research & Creative Works

We use the semi-classical Boltzmann equation to investigate transport properties such as electrical resistivity, thermal resistivity, thermopower, and the Peltier coefficient of disordered metals close to an antiferromagnetic quantum phase transition. In the quantum Griffiths phase, the electrons are scattered by spin-fluctuations in the rare regions. This leads to singular temperature dependencies not just at the quantum critical point, but in the entire Griffiths phase. We show that the resulting non-universal power-laws in transport properties are controlled by the same Griffiths exponent λ which governs the thermodynamics. λ takes the value zero at the quantum critical point and increases throughout …

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Quantum Electrodynamic Corrections To The G Factor Of Helium P States, Mariusz Puchalski, Ulrich D. Jentschura Aug 2012

Quantum Electrodynamic Corrections To The G Factor Of Helium P States, Mariusz Puchalski, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The Landég factor describes the response of an atomic energy level to an external perturbation by a uniform and constant magnetic field. In the case of many-electron systems, the leading term is given by the interaction μ B(L- +2S- )•B- , where L- and S- are the orbital and spin angular momentum operators, respectively, summed over all electrons. For helium, a long-standing experimental-theoretical discrepancy for P states motivates a re-evaluation of the higher order terms which follow from relativistic quantum theory and quantum electrodynamics (QED). The tensor structure of relativistic corrections involves scalar, vector, and symmetric and antisymmetric tensor …

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Percolation Transition In Quantum Ising And Rotor Models With Sub-Ohmic Dissipation, Manal Al-Ali, Jose Abel Hoyos, Thomas Vojta Aug 2012

Percolation Transition In Quantum Ising And Rotor Models With Sub-Ohmic Dissipation, Manal Al-Ali, Jose Abel Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the influence of sub-Ohmic dissipation on randomly diluted quantum Ising and rotor models. The dissipation causes the quantum dynamics of sufficiently large percolation clusters to freeze completely. As a result, the zero-temperature quantum phase transition across the lattice percolation threshold separates an unusual super-paramagnetic cluster phase from an inhomogeneous ferromagnetic phase. We determine the low-temperature thermodynamic behavior in both phases, which is dominated by large frozen and slowly fluctuating percolation clusters. We relate our results to the smeared transition scenario for disordered quantum phase transitions, and we compare the cases of sub-Ohmic, Ohmic, and super-Ohmic dissipation.

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Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Aaron Laforge, Kisra Egodapitiya, Sachin Sharma, Michael Schulz Aug 2012

Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Aaron Laforge, Kisra Egodapitiya, Sachin Sharma, Michael Schulz

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.

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