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Articles 571 - 600 of 1959
Full-Text Articles in Physical Sciences and Mathematics
Astrophysical Implications Of The Binary Black Hole Merger Gw150914, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Astrophysical Implications Of The Binary Black Hole Merger Gw150914, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
The discovery of the gravitational-wave (GW) source GW150914 with the Advanced LIGO detectors provides the first observational evidence for the existence of binary black hole (BH) systems that inspiral and merge within the age of the universe. Such BH mergers have been predicted in two main types of formation models, involving isolated binaries in galactic fields or dynamical interactions in young and old dense stellar environments. The measured masses robustly demonstrate that relatively "heavy" BHs (≳25 M⊙) can form in nature. This discovery implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with …
First Low Frequency All-Sky Search For Continuous Gravitational Wave Signals, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
First Low Frequency All-Sky Search For Continuous Gravitational Wave Signals, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
In this paper we present the results of the first low frequency all-sky search of continuous gravitational wave signals conducted on Virgo VSR2 and VSR4 data. The search covered the full sky, a frequency range between 20 and 128 Hz with a range of spin-down between -1.0 x 10-10 and +1.5 x 10-11 Hz/s, and was based on a hierarchical approach. The starting point was a set of short fast Fourier transforms, of length 8192 s, built from the calibrated strain data. Aggressive data cleaning, in both the time and frequency domains, has been done in order to …
Observation Of Gravitational Waves From A Binary Black Hole Merger, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Observation Of Gravitational Waves From A Binary Black Hole Merger, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0x10-21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a …
Observing Gravitational-Wave Transient Gw150914 With Minimal Assumptions, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Observing Gravitational-Wave Transient Gw150914 With Minimal Assumptions, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
The gravitational-wave signal GW150914 was first identified on September 14, 2015, by searches for short-duration gravitational-wave transients. These searches identify time-correlated transients in multiple detectors with minimal assumptions about the signal morphology, allowing them to be sensitive to gravitational waves emitted by a wide range of sources including binary black hole mergers. Over the observational period from September 12 to October 20, 2015, these transient searches were sensitive to binary black hole mergers similar to GW150914 to an average distance of ∼600 Mpc. In this paper, we describe the analyses that first detected GW150914 as well as the parameter estimation …
Search Of The Orion Spur For Continuous Gravitational Waves Using A Loosely Coherent Algorithm On Data From Ligo Interferometers, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Search Of The Orion Spur For Continuous Gravitational Waves Using A Loosely Coherent Algorithm On Data From Ligo Interferometers, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
We report results of a wideband search for periodic gravitational waves from isolated neutron stars within the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational waves interact very weakly with matter, the search is unimpeded by dust and concentrations of stars. One search disk (A) is 6.87° in diameter and centered on 20h10m54.71s+33°33'25.29'', and the other (B) is 7.45° in diameter and centered on 8h35m20.61s-46°49'25.151''. We explored the frequency range of 50-1500 Hz and frequency derivative from 0 to -5 x 10 …
Neutron And Magnetic Studies Of La₀.₇Sr₀.₃Mn₁₋ₓcrₓo₃(X ≤ 0.7): A Homogeneous Charge-Ordered System, Thomas F. Creel, Jinbo Yang, Satish K. Malik, Sylvio Quezado, Oran Allan Pringle, William B. Yelon, William Joseph James
Neutron And Magnetic Studies Of La₀.₇Sr₀.₃Mn₁₋ₓcrₓo₃(X ≤ 0.7): A Homogeneous Charge-Ordered System, Thomas F. Creel, Jinbo Yang, Satish K. Malik, Sylvio Quezado, Oran Allan Pringle, William B. Yelon, William Joseph James
Physics Faculty Research & Creative Works
Structural and magnetic properties of La0.7Sr0.3Mn1-xCrxO3 (0 < x ≤ 0.7) have been studied in order to determine the effect of substitution of Cr3+ for Mn3+. The data consist of neutron and x-ray powder-diffraction and magnetization measurements. We previously suggested these systems transition from ferromagnetic to antiferromagnetic ordering with the intermediate concentrations containing coexisting ferromagnetic and antiferromagnetic domains. Upon further detailed examination, we find that the neutron data can be fit using a single homogeneous long-range magnetically ordered state and compositionally dependent charge ordering. The magnetic structures are controlled by the competition between Mn-Mn, Mn-Cr, and Cr-Cr interactions (double exchange and superexchange). The metal to …
Analytical Model For Calibrating Laser Intensity In Strong-Field-Ionization Experiments, Song-Feng. Zhao, Anh-Thu Le, Cheng Jin, Xu Wang, C. D. Lin
Analytical Model For Calibrating Laser Intensity In Strong-Field-Ionization Experiments, Song-Feng. Zhao, Anh-Thu Le, Cheng Jin, Xu Wang, C. D. Lin
Physics Faculty Research & Creative Works
The interaction of an intense laser pulse with atoms and molecules depends extremely nonlinearly on the laser intensity. Yet experimentally there still exists no simple reliable methods for determining the peak laser intensity within the focused volume. Here we present a simple method, based on an improved Perelomov-Popov-Terent'ev model, that would allow the calibration of laser intensities from the measured ionization signals of atoms or molecules. The model is first examined by comparing ionization probabilities (or signals) of atoms and several simple diatomic molecules with those from solving the time-dependent Schrödinger equation. We then show the possibility of using this …
Random Field Disorder At An Absorbing State Transition In One And Two Dimensions, Hatem Barghathi, Thomas Vojta
Random Field Disorder At An Absorbing State Transition In One And Two Dimensions, Hatem Barghathi, Thomas Vojta
Physics Faculty Research & Creative Works
We investigate the behavior of nonequilibrium phase transitions under the influence of disorder that locally breaks the symmetry between two symmetrical macroscopic absorbing states. In equilibrium systems such "random-field" disorder destroys the phase transition in low dimensions by preventing spontaneous symmetry breaking. In contrast, we show here that random-field disorder fails to destroy the nonequilibrium phase transition of the one- and two-dimensional generalized contact process. Instead, it modifies the dynamics in the symmetry-broken phase. Specifically, the dynamics in the one-dimensional case is described by a Sinai walk of the domain walls between two different absorbing states. In the two-dimensional case, …
Role Of Composition And Structure On The Properties Of Metal/Multifunctional Ceramic Interfaces, Fang Yin Lin, Aleksandr V. Chernatynskiy, Juan Claudio Nino, Jacob L. Jones, Richard G. Hennig, Susan Sinnott
Role Of Composition And Structure On The Properties Of Metal/Multifunctional Ceramic Interfaces, Fang Yin Lin, Aleksandr V. Chernatynskiy, Juan Claudio Nino, Jacob L. Jones, Richard G. Hennig, Susan Sinnott
Physics Faculty Research & Creative Works
The formation of intermetallic secondary phases, such as Pt3Pb, has been observed experimentally at PbTiO3/Pt and Pb(Zr,Ti)O3/Pt, or PZT/Pt, interfaces. Density functional theory calculations are used here to calculate the work of adhesion of these interfacial systems with and without the secondary intermetallic phase. The charge density maps of the interfaces reveal the electronic interactions at the interface and the impact of the secondary phase. In addition, Bader charge analysis provides a quantitative assessment of electron transfer from the perovskites to the Pt. Analysis of the band diagrams indicates an increase of the potential …
Electron Impact Ionization Dynamics Of Para-Benzoquinone, D. B. Jones, E. Ali, C. G. Ning, J. Colgan, O. Ingólfsson, Don H. Madison, M. J. Brunger
Electron Impact Ionization Dynamics Of Para-Benzoquinone, D. B. Jones, E. Ali, C. G. Ning, J. Colgan, O. Ingólfsson, Don H. Madison, M. J. Brunger
Physics Faculty Research & Creative Works
Triple differential cross sections (TDCSs) for the electron impact ionization of the unresolved combination of the 4 highest occupied molecular orbitals (4b3g, 5b2u, 1b1g, and 2b3u) of para-benzoquinone are reported. These were obtained in an asymmetric coplanar geometry with the scattered electron being observed at the angles −7.5°, −10.0°, −12.5° and −15.0°. The experimental cross sections are compared to theoretical calculations performed at the molecular 3-body distorted wave level, with a marginal level of agreement between them being found. The character of the ionized orbitals, through calculated momentum profiles, provides some qualitative …
Control Of Mesoscopic Transport By Modifying Transmission Channels In Opaque Media, Raktim Sarma, Alexey Yamilov, Seng Fatt Liew, Mikhael Guy, Hui Cao
Control Of Mesoscopic Transport By Modifying Transmission Channels In Opaque Media, Raktim Sarma, Alexey Yamilov, Seng Fatt Liew, Mikhael Guy, Hui Cao
Physics Faculty Research & Creative Works
While controlling particle diffusion in a confined geometry is a popular approach taken by both natural and artificial systems, it has not been widely adopted for controlling light transport in random media, where wave interference effects play a critical role. The transmission eigenchannels determine not only light propagation through the disordered system but also the energy concentrated inside. Here, we propose and demonstrate an effective approach to modify these channels, whose structures are considered to be universal in conventional diffusive waveguides. By adjusting the waveguide geometry, we are able to alter the spatial profiles of the transmission eigenchannels significantly and …
Resonant Quantum Dynamics Of Few Ultracold Bosons In Periodically Driven Finite Lattices, Simeon I. Mistakidis, T. Wulf, A. Negretti, P. Schmelcher
Resonant Quantum Dynamics Of Few Ultracold Bosons In Periodically Driven Finite Lattices, Simeon I. Mistakidis, T. Wulf, A. Negretti, P. Schmelcher
Physics Faculty Research & Creative Works
The Out-Of-Equilibrium Dynamics Of Finite Ultracold Bosonic Ensembles In Periodically Driven One-Dimensional Optical Lattices Is Investigated. Our Study Reveals That The Driving Enforces The Bosons In Different Wells To Oscillate In-Phase And To Exhibit A Dipole-Like Mode. A Wide Range From Weak-To-Strong Driving Frequencies Is Covered And A Resonance-Like Behavior Of The Intra-Well Dynamics Is Discussed. In The Proximity Of The Resonance A Rich Intraband Excitation Spectrum Is Observed. The Single Particle Excitation Mechanisms Are Studied In The Framework Of Floquet Theory Elucidating The Role Of The Driving Frequency. The Impact Of The Interatomic Repulsive Interactions Is Examined In Detail …
Bounds On Large Extra Dimensions From The Simulation Of Black Hole Events At The Lhc, Shaoqi Hou, Benjamin Harms, Marco Cavaglia
Bounds On Large Extra Dimensions From The Simulation Of Black Hole Events At The Lhc, Shaoqi Hou, Benjamin Harms, Marco Cavaglia
Physics Faculty Research & Creative Works
If large extra dimensions exist, the Planck scale may be as low as a TeV and microscopic black holes may be produced in high-energy particle collisions at this energy scale. We simulate microscopic black hole formation at the Large Hadron Collider and compare the simulation results with recent experimental data by the Compact Muon Solenoid collaboration. The absence of observed black hole events in the experimental data allows us to set lower bounds on the Planck scale and various parameters related to microscopic black hole formation for a number (3 − 6) of extra dimensions. Our analysis sets lower bounds …
The Stripe 82 Massive Galaxy Project. I. Catalog Construction, Kevin Bundy, Alexie Leauthaud, Shun Saito, For Full List Of Authors, See Publisher's Website.
The Stripe 82 Massive Galaxy Project. I. Catalog Construction, Kevin Bundy, Alexie Leauthaud, Shun Saito, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
The Stripe 82 Massive Galaxy Catalog (S82-MGC) is the largest-volume stellar mass-limited sample of galaxies beyond z ≈ 0.1 constructed to date. Spanning 139.4 deg2, the S82-MGC includes a mass-limited sample of 41,770 galaxies with log M*/M⊙ ≳ 11.2 to z ≈ 0.7, sampling a volume of 0.3 Gpc3, roughly equivalent to the volume of the Sloan Digital Sky Survey-I/II (SDSS-I/II) z < 0.15 main sample. The catalog is built on three pillars of survey data: the SDSS Stripe 82 Coadd photometry which reaches r-band magnitudes of ∼23.5 AB, Y JHK photometry at depths of 20th magnitude (AB) from the UK Infrared Deep Sky Survey Large Area Survey, and over 70,000 spectroscopic galaxy redshifts from the SDSS-I/II and the Baryon Oscillation Spectroscopic Survey. We describe the catalog construction and verification, the production of 9-band matched aperture photometry, tests of existing and newly estimated photometric redshifts required to supplement spectroscopic redshifts for 55% of the log M*/M⊙ ≳ 11.2 sample, and geometric masking. We provide near-IR based stellar mass estimates and compare these to previous estimates. All catalog products are made publicly available. The S82-MGC …
Using Geometry To Manipulate Long-Range Correlation Of Light Inside Disordered Media, Raktim Sarma, Alexey Yamilov, Pauf Neupane, Hui Cao
Using Geometry To Manipulate Long-Range Correlation Of Light Inside Disordered Media, Raktim Sarma, Alexey Yamilov, Pauf Neupane, Hui Cao
Physics Faculty Research & Creative Works
We demonstrate an effective approach of modifying the long-range spatial correlation for light propagating inside random photonic waveguides by varying the shape of the waveguide. The functional form of spatial correlation is no longer universal in the regime of diffusive transport and becomes shape dependent due to the nonlocal nature of wave propagation. The spatial dependence of the correlation may become asymmetric for light incident from opposite ends of the waveguide. This work opens the door to control nonlocal effects in mesoscopic transport of waves by tailoring the geometry of random systems. .
Infinite-Noise Criticality: Nonequilibrium Phase Transitions In Fluctuating Environments, Thomas Vojta, José A. Hoyos
Infinite-Noise Criticality: Nonequilibrium Phase Transitions In Fluctuating Environments, Thomas Vojta, José A. Hoyos
Physics Faculty Research & Creative Works
We study the effects of time-varying environmental noise on nonequilibrium phase transitions in spreading and growth processes. Using the examples of the logistic evolution equation as well as the contact process, we show that such temporal disorder gives rise to a distinct type of critical points at which the effective noise amplitude diverges on long time scales. This leads to enormous density fluctuations characterized by an infinitely broad probability distribution at criticality. We develop a real-time renormalization-group theory that provides a general framework for the effects of temporal disorder on nonequilibrium processes. We also discuss how general this exotic critical …
Reconstruction Of Two-Dimensional Molecular Structure With Laser-Induced Electron Diffraction From Laser-Aligned Polyatomic Molecules, Chao Yu, Hui Wei, Xu Wang, Anh-Thu Le, Ruifeng Lu, C. D. Lin
Reconstruction Of Two-Dimensional Molecular Structure With Laser-Induced Electron Diffraction From Laser-Aligned Polyatomic Molecules, Chao Yu, Hui Wei, Xu Wang, Anh-Thu Le, Ruifeng Lu, C. D. Lin
Physics Faculty Research & Creative Works
Imaging the transient process of molecules has been a basic way to investigate photochemical reactions and dynamics. Based on laser-induced electron diffraction and partial one-dimensional molecular alignment, here we provide two effective methods for reconstructing two-dimensional structure of polyatomic molecules. We demonstrate that electron diffraction images in both scattering angles and broadband energy can be utilized to retrieve complementary structure information, including positions of light atoms. With picometre spatial resolution and the inherent femtosecond temporal resolution of lasers, laser-induced electron diffraction method offers significant opportunities for probing atomic motion in a large molecule in a typical pump-probe measurement.
Comparison Of Experimental And Theoretical Electron-Impact-Ionization Triple-Differential Cross Sections For Ethane, Esam Ali, Kate Nixon, Andrw Murray, Chuangang Ning, James Colgan, Don H. Madison
Comparison Of Experimental And Theoretical Electron-Impact-Ionization Triple-Differential Cross Sections For Ethane, Esam Ali, Kate Nixon, Andrw Murray, Chuangang Ning, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We have recently examined electron-impact ionization of molecules that have one large atom at the center, surrounded by H nuclei (H2O, NH3, CH4). All of these molecules have ten electrons; however, they vary in their molecular symmetry. We found that the triple-differential cross sections (TDCSs) for the highest occupied molecular orbitals (HOMOs) were similar, as was the character of the HOMO orbitals which had a p-type "peanut" shape. In this work, we examine ethane (C2H6) which is a molecule that has two large atoms surrounded by H nuclei, so that …
Possible Evidence Of 3ʳᵈ And 4th Order Interactions Contributions To Double Ioni- Zation Of Helium By Protons And Antiprotons, A. C.F. Santos, Robert D. Dubois, S. T. Manson
Possible Evidence Of 3ʳᵈ And 4th Order Interactions Contributions To Double Ioni- Zation Of Helium By Protons And Antiprotons, A. C.F. Santos, Robert D. Dubois, S. T. Manson
Physics Faculty Research & Creative Works
Published cross sections for double ionization of helium by protons and antiprotons are analyzed in terms of the traditional interference between 1st and 2nd amplitudes. Between 3 and 10 a.u., the velocity dependence implies a dominant 2nd order interaction. For slower collisions it is shown that the velocity dependences are consistent with 3rd and 4th order interactions becoming important with these interactions having negative coefficients.
Discharge Properties Of Macroscopic Glass Capillaries After Irradiation By Low Intensity Low Energy Single Charged Ar Ions, E. Giglio, Robert D. Dubois, K. Tokési
Discharge Properties Of Macroscopic Glass Capillaries After Irradiation By Low Intensity Low Energy Single Charged Ar Ions, E. Giglio, Robert D. Dubois, K. Tokési
Physics Faculty Research & Creative Works
The discharge properties of a macroscopic cylindrically shaped glass capillary, initially charged by a 1 keV Ar+ beam tilted by 5° with respect to the capillary axis is studied. Our experimental observations were compared to our Monte Carlo simulation, highlighting the importance of the surface conductivity.
Classical Dynamics Of The Abelian Higgs Model From The Critical Point And Beyond, Garyfallia C. Katsimiga, F. K. Diakonos, X. N. Maintas
Classical Dynamics Of The Abelian Higgs Model From The Critical Point And Beyond, Garyfallia C. Katsimiga, F. K. Diakonos, X. N. Maintas
Physics Faculty Research & Creative Works
We present two different families of solutions of the U(1)-Higgs model in a (1. +. 1) dimensional setting leading to a localization of the gauge field. First we consider a uniform background (the usual vacuum), which corresponds to the fully higgsed-superconducting phase. Then we study the case of a non-uniform background in the form of a domain wall which could be relevantly close to the critical point of the associated spontaneous symmetry breaking. For both cases we obtain approximate analytical nodeless and nodal solutions for the gauge field resulting as bound states of an effective Pöschl-Teller potential created by the …
First Evidence Of Interference Effects In The Ionization Of N₂ Molecule, Zehra Nur Ozer, Hari Chaluvadi, Mevlut Dogan, James Colgan, Don H. Madison
First Evidence Of Interference Effects In The Ionization Of N₂ Molecule, Zehra Nur Ozer, Hari Chaluvadi, Mevlut Dogan, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We will present an experimental and theoretical investigation of triple differential cross sections for electron- impact ionization of nitrogen molecules at intermediate energies. A discussion of interference effects contained in the theoretical and experimental interference factors will be presented.
Low-Energy (E₀ = 65 Ev) Electron-Impact Ionization Of Neon: Internormalized Triple-Differentical Cross Sections In 3d Kinematics, Xueguang Ren, Sadek M. Amami, Oleg I. Zatsarinny, Thomas Pfluger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn
Low-Energy (E₀ = 65 Ev) Electron-Impact Ionization Of Neon: Internormalized Triple-Differentical Cross Sections In 3d Kinematics, Xueguang Ren, Sadek M. Amami, Oleg I. Zatsarinny, Thomas Pfluger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn
Physics Faculty Research & Creative Works
We present a combined experimental and theoretical study on the low-energy (E0 = 65 eV) electron- impact ionization of neon. The experimental data are compared to predictions from a hybrid second-order distorted-wave Born plus R-matrix approach (DWB2-RM), the distorted-wave Born approximation with inclusion of post-collision interaction (DWBA-PCI), a three-body distorted-wave approach (3DW), and a B-spline R-matrix (BSR) with pseudostates approach. Excellent agreement is found between experiment and the 3DW and BSR theories. The importance of PCI effects is clearly visible in this low-energy electron-impact ionization process.
Theoretical And Experimental Study Of (E,2e) Ionization Of The Co₂ (1ΠG) Molecule At 250 Ev, Mevlut Dogan, Zehra Nur Ozer, Murat Yavuz, Osman Alwan, Adnan Naja, Boghos B. Joulakian, Esam S M Ali, Chuangang Ning, Don H. Madison
Theoretical And Experimental Study Of (E,2e) Ionization Of The Co₂ (1ΠG) Molecule At 250 Ev, Mevlut Dogan, Zehra Nur Ozer, Murat Yavuz, Osman Alwan, Adnan Naja, Boghos B. Joulakian, Esam S M Ali, Chuangang Ning, Don H. Madison
Physics Faculty Research & Creative Works
Triple differential cross sections (TDCSs) of the electron-impact ionization of carbon dioxide are measured in the coplanar asymmetric geometry, with incident electron energy value of 250eV, and ejected electron of 37eV. We will report the experimental results in comparison with the theoretical calculations of the M3DW and TCC (type 5) calculations.
Coplanar Asymmetric Angles And Symmetric Energy Sharing Triple Differential Cross Sections For 200 Ev Electron-Impact Ionization Of Ar (3p), Zehra Nur Ozer, Sadek M. Amami, Onur Varol, Murat Yavuz, Mevlut Dogan, Don H. Madison
Coplanar Asymmetric Angles And Symmetric Energy Sharing Triple Differential Cross Sections For 200 Ev Electron-Impact Ionization Of Ar (3p), Zehra Nur Ozer, Sadek M. Amami, Onur Varol, Murat Yavuz, Mevlut Dogan, Don H. Madison
Physics Faculty Research & Creative Works
We have measured triple differential cross sections (TDCSs) for electron-impact ionization of the 3p shell of Ar at 200 eV incident electron energy. The experiments have been performed in coplanar asymmetric energy sharing geometry. The experimental results are compared with the theoretical models of three body distorted wave (3DW) and distorted wave Born approximation (DWBA).
Polyatomic Molecular Structure Retrieval Using Laser-Induced Electron Diffraction, Michael G. Pullen, Benjamin Wolter, Anh-Thu Le, Matthias Baudisch, Michael Hemmer, Arne Senftleben, M. Sclafani, Claus Dieter Schroeter, Joachim Ullrich, Robert Moshammer, C. D. Lin, Jens Biegert
Polyatomic Molecular Structure Retrieval Using Laser-Induced Electron Diffraction, Michael G. Pullen, Benjamin Wolter, Anh-Thu Le, Matthias Baudisch, Michael Hemmer, Arne Senftleben, M. Sclafani, Claus Dieter Schroeter, Joachim Ullrich, Robert Moshammer, C. D. Lin, Jens Biegert
Physics Faculty Research & Creative Works
Laser-induced electron diffraction is a developing dynamical imaging technique that is already able to probe molecular dynamics at few-femtosecond temporal resolutions and has the potential to reach the sub-femtosecond level. Here we provide the recipe for the extension of the technique to polyatomic molecules and we demonstrate the method by extracting the structure of aligned and anti-aligned acetylene (C₂H₂). We show that multiple bond lengths can be simultaneously imaged at high accuracy including elusive hydrogen containing bonds. Our results open the door to the investigation of larger complex molecules and the realization of a true molecular movie.
Evidence For Unnatural-Parity Contributions To Electron-Impact Ionization Of Laser-Aligned Atoms, G. S. J. Armstrong, J. Colgan, M. S. Pindzola, S. Amami, Don H. Madison, J. Pursehouse, K. L. Nixon, A. J. Murray
Evidence For Unnatural-Parity Contributions To Electron-Impact Ionization Of Laser-Aligned Atoms, G. S. J. Armstrong, J. Colgan, M. S. Pindzola, S. Amami, Don H. Madison, J. Pursehouse, K. L. Nixon, A. J. Murray
Physics Faculty Research & Creative Works
Recent measurements have examined the electron-impact ionization of excited-state laser-aligned Mg atoms. In this work we show that the ionization cross section arising from the geometry where the aligned atom is perpendicular to the scattering plane directly probes the unnatural parity contributions to the ionization amplitude. The contributions from natural parity partial waves cancel exactly in this geometry. Our calculations resolve the discrepancy between the nonzero measured cross sections in this plane and the zero cross section predicted by distorted-wave approaches. We demonstrate that this is a general feature of ionization from p-state targets by additional studies of ionization from …
Anharmonic Properties In Mg₂X (X= C, Si, Ge, Sn, Pb) From First-Principles Calculations, Aleksandr V. Chernatynskiy, Simon R. Phillpot
Anharmonic Properties In Mg₂X (X= C, Si, Ge, Sn, Pb) From First-Principles Calculations, Aleksandr V. Chernatynskiy, Simon R. Phillpot
Physics Faculty Research & Creative Works
Thermal conductivity reduction is one of the potential routes to improve the performance of thermoelectric materials. However, detailed understanding of the thermal transport of many promising materials is still missing. In this paper, we employ electronic-structure calculations at the level of density functional theory to elucidate thermal transport properties of the Mg2X (X=C, Si, Ge, Sn, and Pb) family of compounds, which includes Mg2Si, a material already identified as a potential thermoelectric. All these materials crystallize into the same antifluorite structure. Systematic trends in the anharmonic properties of these materials are presented and examined. Our calculations …
Ultrarelativistic Decoupling Transformation For Generalized Dirac Equations, J. H. Noble, Ulrich D. Jentschura
Ultrarelativistic Decoupling Transformation For Generalized Dirac Equations, J. H. Noble, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
The Foldy-Wouthuysen transformation is known to uncover the nonrelativistic limit of a generalized Dirac Hamiltonian, lending an intuitive physical interpretation to the effective operators within Schrö dinger-Pauli theory. We here discuss the opposite, ultrarelativistic limit which requires the use of a fundamentally different expansion where the leading kinetic term in the Dirac equation is perturbed by the mass of the particle and other interaction (potential) terms, rather than vice versa. The ultrarelativistic decoupling transformation is applied to free Dirac particles (in the Weyl basis) and to high-energy tachyons, which are faster-than-light particles described by a fully Lorentz-covariant equation. The effective …
Muonic Bound Systems, Virtual Particles, And Proton Radius, Ulrich D. Jentschura
Muonic Bound Systems, Virtual Particles, And Proton Radius, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
The proton radius puzzle questions the self-consistency of theory and experiment in light muonic and electronic bound systems. Here we summarize the current status of virtual particle models as well as Lorentz-violating models that have been proposed in order to explain the discrepancy. Highly charged one-electron ions and muonic bound systems have been used as probes of the strongest electromagnetic fields achievable in the laboratory. The average electric field seen by a muon orbiting a proton is comparable to hydrogenlike uranium and, notably, larger than the electric field in the most advanced strong-laser facilities. Effective interactions due to virtual annihilation …