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Physics Faculty Research & Creative Works

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Articles 601 - 630 of 1959

Full-Text Articles in Physical Sciences and Mathematics

Applicability Of The Position-Dependent Diffusion Approach To Localized Transport Through Disordered Waveguides, Pauf Neupane, Alexey Yamilov Jul 2015

Applicability Of The Position-Dependent Diffusion Approach To Localized Transport Through Disordered Waveguides, Pauf Neupane, Alexey Yamilov

Physics Faculty Research & Creative Works

In this work we show analytically and numerically that the localized regime of wave transport can be modeled as position-dependent diffusion with a diffusion coefficient that retains the memory of the source location. The dependence on the source diminishes when absorption is introduced.

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Erratum: Low-Energy Electron-Impact Ionization Of Argon: Three-Dimensional Cross Section (Physical Review A - Atomic, Molecular, And Optical Physics 85, 032702 (2012)), Xueguang Ren, Thomas Pfluger, Joachim Hermann Ullrich, Oleg I. Zatsarinny, Klaus Bartschat, Don H. Madison, Alexander Dorn Jul 2015

Erratum: Low-Energy Electron-Impact Ionization Of Argon: Three-Dimensional Cross Section (Physical Review A - Atomic, Molecular, And Optical Physics 85, 032702 (2012)), Xueguang Ren, Thomas Pfluger, Joachim Hermann Ullrich, Oleg I. Zatsarinny, Klaus Bartschat, Don H. Madison, Alexander Dorn

Physics Faculty Research & Creative Works

No abstract provided.

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Interference Effects For Intermediate Energy Electron-Impact Ionization Of H₂ And N₂ Molecules, Zehra Nur Ozer, Hari Chaluvadi, Don H. Madison, Mevlut Dogan Jul 2015

Interference Effects For Intermediate Energy Electron-Impact Ionization Of H₂ And N₂ Molecules, Zehra Nur Ozer, Hari Chaluvadi, Don H. Madison, Mevlut Dogan

Physics Faculty Research & Creative Works

We have studied electron impact ionization of H2 and N2 molecules at intermediate energies to look for possible two center interference effects experimentally and theoretically. Here we report a study of the interference factor I for 250 eV electron-impact ionization. The experimental measurements are performed using a crossed-beam-type electron-electron coincidence spectrometer and theoretical calculations are obtained using the Molecular Three Body Distorted Wave Approximation (M3DW). We found that the I-factor demonstrated strong evidence for two-center interference effects for both H2 and N2. We also found that the I-factor is more sensitive to projectile angular scans …

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Remarkably Robust And Correlated Coherence And Antiferromagnetism In (Ce₁₋ₓlaₓ)Cu₂Ge₂, Halyna Hodovanets, S. L. Bud'ko, W. E. Straszheim, V. Taufour, E. D. Mun, Hyunsoo Kim, R. Flint, P. C. Canfield Jun 2015

Remarkably Robust And Correlated Coherence And Antiferromagnetism In (Ce₁₋ₓlaₓ)Cu₂Ge₂, Halyna Hodovanets, S. L. Bud'ko, W. E. Straszheim, V. Taufour, E. D. Mun, Hyunsoo Kim, R. Flint, P. C. Canfield

Physics Faculty Research & Creative Works

We present magnetic susceptibility, resistivity, specific heat, and thermoelectric power measurements on (Ce1-xLax)Cu2Ge2 single crystals (0 ≤ x ≤ 1). With La substitution, the antiferromagnetic temperature TN is suppressed in an almost linear fashion and moves below 0.36 K, the base temperature of our measurements for x > 0.8. Surprisingly, in addition to robust antiferromagnetism, the system also shows low temperature coherent scattering below Tcoh up to ∼0.9 of La, indicating a small percolation limit ∼9% of Ce. Tcoh as a function of magnetic field was found to have different behavior …

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Imaging An Aligned Polyatomic Molecule With Laser-Induced Electron Diffraction, Michael G. Pullen, Benjamin Wolter, Anh-Thu Le, Matthias Baudisch, Michael Hemmer, Arne Senftleben, Claus Dieter Schroeter, Joachim Ullrich, Robert Moshammer, C. D. Lin, Jens Biegert Jun 2015

Imaging An Aligned Polyatomic Molecule With Laser-Induced Electron Diffraction, Michael G. Pullen, Benjamin Wolter, Anh-Thu Le, Matthias Baudisch, Michael Hemmer, Arne Senftleben, Claus Dieter Schroeter, Joachim Ullrich, Robert Moshammer, C. D. Lin, Jens Biegert

Physics Faculty Research & Creative Works

Laser-induced electron diffraction is an evolving tabletop method that aims to image ultrafast structural changes in gas-phase polyatomic molecules with sub-Ångström spatial and femtosecond temporal resolutions. Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C-C and C-H bond lengths in aligned acetylene. Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160kHz mid-infrared few-cycle laser source with full three-dimensional electron-ion coincidence detection. Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules …

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Emerging Criticality In The Disordered Three-Color Ashkin-Teller Model, Qiong Zhu, Xin Wan, Rajesh Narayanan, José A. Hoyos, Thomas Vojta Jun 2015

Emerging Criticality In The Disordered Three-Color Ashkin-Teller Model, Qiong Zhu, Xin Wan, Rajesh Narayanan, José A. Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We study the effects of quenched disorder on the first-order phase transition in the two-dimensional three-color Ashkin-Teller model by means of large-scale Monte Carlo simulations. We demonstrate that the first-order phase transition is rounded by the disorder and turns into a continuous one. Using a careful finite-size-scaling analysis, we provide strong evidence for the emerging critical behavior of the disordered Ashkin-Teller model to be in the clean two-dimensional Ising universality class, accompanied by universal logarithmic corrections. This agrees with perturbative renormalization-group predictions by Cardy. As a byproduct, we also provide support for the strong-universality scenario for the critical behavior of …

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Erratum: Theoretical And Experimental (E,2e) Study Of Electron-Impact Ionization Of Laser-Aligned Mg Atoms [Physical Review A 90, 062707 (2014)], Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison Jun 2015

Erratum: Theoretical And Experimental (E,2e) Study Of Electron-Impact Ionization Of Laser-Aligned Mg Atoms [Physical Review A 90, 062707 (2014)], Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison

Physics Faculty Research & Creative Works

We have recently reported a theoretical and experimental study of electron-impact ionization of laser-aligned magnesium. Results were presented for both ionization of the ground state, as well as for laser-aligned atoms in the 3p state. For ionization from the 3p state, theoretical results were presented using the distorted wave Born (DWBA) and three-body distorted wave (3DW) approximations. Unfortunately, after publication we learned that the theoretical results were incorrect due to one of the arrays in the computer code dimensioned too small. The figures affected by this error are Figs. 3–5 in the original paper. The present Figs. 3–5 …

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Critical States Embedded In The Continuum, Milan Koirala, Alexey Yamilov, A. Basiri, Yaron Bromberg, Hui Cao, Tsampikos Kottos May 2015

Critical States Embedded In The Continuum, Milan Koirala, Alexey Yamilov, A. Basiri, Yaron Bromberg, Hui Cao, Tsampikos Kottos

Physics Faculty Research & Creative Works

Weintroduce a class of critical states which are embedded in the continuum (CSC) of a one-dimensional optical waveguide array with one non-Hermitian defect. These states are on the verge of being fractal and have real propagation constants. They emerge at a phase transition which is driven by the imaginary refractive index of the defective waveguide and it is accompanied by a mode segregation which reveals analogies with the Dicke super-radiance. Below this point the states are extended while above it they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states into …

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Tunable Negative Permeability In A Three-Dimensional Superconducting Metamaterial, Cihan Kurter, T. Lan, L. Sarytchev, Steven Mark Anlage May 2015

Tunable Negative Permeability In A Three-Dimensional Superconducting Metamaterial, Cihan Kurter, T. Lan, L. Sarytchev, Steven Mark Anlage

Physics Faculty Research & Creative Works

We report on highly tunable radio-frequency (rf) characteristics of a low-loss and compact three-dimensional (3D) metamaterial made of superconducting thin-film spiral resonators. The rf transmission spectrum of a single element of the metamaterial shows a fundamental resonance peak at ~24.95 MHz that shifts to a 25% smaller frequency and becomes degenerate when a 3D array of such elements is created. The metamaterial shows an in situ tunable narrow frequency band in which the real part of the effective permeability is negative over a wide range of temperature. This narrow frequency band gradually possesses near-zero and positive values for the real …

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Luminous Red Galaxies In Clusters: Central Occupation, Spatial Distributions And Miscentring, Hanako Hoshino, Alexie Leauthaud, Shun Saito, For Full List Of Authors, See Publisher's Website. Apr 2015

Luminous Red Galaxies In Clusters: Central Occupation, Spatial Distributions And Miscentring, Hanako Hoshino, Alexie Leauthaud, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Luminous red galaxies (LRG) from the Sloan Digital Sky Survey are among the best understood samples of galaxies and are employed in a broad range of cosmological studies. In this paper, we study how LRGs occupy massive haloes via counts in clusters and reveal several unexpected trends. Using the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) cluster catalogue, we derive the central occupation of LRGs as a function richness. We show that clusters contain a significantly lower fraction of central LRGs than predicted from the two-point correlation function. At halo masses of 1014.5 M⊙, we find Ncen = …

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Target Electron Ionization In Li²⁺-L-Li Collisions: A Multi-Electron Perspective, Maciej Dominik Piewanowski, Laszlo Gulyas, Marko W. Horbatsch, Johannes Goullon, Natalia Ferreira, Renate Hubele, Vitor L B D De Jesus, H. Lindenblatt, Katharina R. Schneider, Michael Schulz, Michael Schuricke, Z. Song, Shaofeng Zhang, Daniel Fischer, Tom Kirchner Apr 2015

Target Electron Ionization In Li²⁺-L-Li Collisions: A Multi-Electron Perspective, Maciej Dominik Piewanowski, Laszlo Gulyas, Marko W. Horbatsch, Johannes Goullon, Natalia Ferreira, Renate Hubele, Vitor L B D De Jesus, H. Lindenblatt, Katharina R. Schneider, Michael Schulz, Michael Schuricke, Z. Song, Shaofeng Zhang, Daniel Fischer, Tom Kirchner

Physics Faculty Research & Creative Works

Target electron removal in Li2+-Li collisions at 2290 keV/amu is studied experimentally and theoretically for ground and excited lithium target configurations. It is shown that in outer-shell ionization a single-electron process plays the dominant part. However, the K-shell ionization results are more difficult to interpret. According to our calculations, the process is shown to be strongly single-particle like. On one hand, a high resemblance between theoretical single-particle ionization and exclusive inner-shell ionization is demonstrated, and contributions from multi-electron processes are found to be weak. On the other hand, it is indicated by the discrepancy between experimental and single-particle …

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Classical Description Of H(1s) And H* (N=2) For Cross-Section Calculations Relevant To Charge-Exchange Diagnostics, N. D. Cariatore, Sebastian Otranto, Ronald E. Olson Apr 2015

Classical Description Of H(1s) And H* (N=2) For Cross-Section Calculations Relevant To Charge-Exchange Diagnostics, N. D. Cariatore, Sebastian Otranto, Ronald E. Olson

Physics Faculty Research & Creative Works

In this work, we introduce a classical trajectory Monte Carlo (CTMC) methodology, specially conceived to provide a more accurate representation of charge-exchange processes between highly charged ions and H(1s) and H* (n=2). These processes are of particular relevance in power fusion reactor programs, for which charge-exchange spectroscopy has become a useful plasma diagnostics tool. To test the methodology, electron-capture reactions from these targets by C6+,N7+, and O8+ are studied at impact energies in the 10-150keV/amu range. State-selective cross sections are contrasted with those predicted by the standard microcanonical formulation of the CTMC method, the CTMC …

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Total Projectile Electron Loss Cross Sections Of U28+ Ions In Collisions With Gaseous Targets Ranging From Hydrogen To Krypton, G. Weber, M. O. Herdrich, Robert D. Dubois, P. M. Hillenbrand, H. Beyer Mar 2015

Total Projectile Electron Loss Cross Sections Of U28+ Ions In Collisions With Gaseous Targets Ranging From Hydrogen To Krypton, G. Weber, M. O. Herdrich, Robert D. Dubois, P. M. Hillenbrand, H. Beyer

Physics Faculty Research & Creative Works

Beam lifetimes of stored U28+ ions with kinetic energies of 30 and 50 MeV/u, respectively, were measured in the experimental storage ring of the GSI accelerator facility. By using the internal gas target station of the experimental storage ring, it was possible to obtain total projectile electron loss cross sections for collisions with several gaseous targets ranging from hydrogen to krypton from the beam lifetime data. The resulting experimental cross sections are compared to predictions by two theoretical approaches, namely the CTMC method and a combination of the DEPOSIT code and the RICODE program.

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Negative-Quench-Induced Excitation Dynamics For Ultracold Bosons In One-Dimensional Lattices, Simeon I. Mistakidis, L. Cao, P. Schmelcher Mar 2015

Negative-Quench-Induced Excitation Dynamics For Ultracold Bosons In One-Dimensional Lattices, Simeon I. Mistakidis, L. Cao, P. Schmelcher

Physics Faculty Research & Creative Works

The Nonequilibrium Dynamics Following A Quench Of Strongly Repulsive Bosonic Ensembles In One-Dimensional Finite Lattices Is Investigated By Employing Interaction Quenches And/or A Ramp Of The Lattice Potential. Both Sudden And Time-Dependent Quenches Are Analyzed In Detail. For The Case Of Interaction Quenches We Address The Transition From The Strong Repulsive To The Weakly Interacting Regime, Suppressing In This Manner The Heating Of The System. The Excitation Modes Such As The Cradle Process And The Local Breathing Mode Are Examined Via Local Density Observables. In Particular, The Cradle Mode Is Inherently Related To The Initial Delocalization And, Following A Negative …

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Directed Search For Gravitational Waves From Scorpius X-1 With Initial Ligo Data, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Mar 2015

Directed Search For Gravitational Waves From Scorpius X-1 With Initial Ligo Data, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present results of a search for continuously emitted gravitational radiation, directed at the brightest low-mass x-ray binary, Scorpius X-1. Our semicoherent analysis covers 10 days of LIGO S5 data ranging from 50-550 Hz, and performs an incoherent sum of coherent F-statistic power distributed amongst frequency-modulated orbital sidebands. All candidates not removed at the veto stage were found to be consistent with noise at a 1% false alarm rate. We present Bayesian 95% confidence upper limits on gravitational-wave strain amplitude using two different prior distributions: a standard one, with no a priori assumptions about the orientation of Scorpius X-1; …

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Kinematically Complete Study Of Low-Energy Electron-Impact Ionization Of Neon: Internormalized Cross Sections In Three-Dimensional Kinematics, Xueguang Ren, Sadek Amami, Oleg Zatsarinny, Thomas Pflüger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn Mar 2015

Kinematically Complete Study Of Low-Energy Electron-Impact Ionization Of Neon: Internormalized Cross Sections In Three-Dimensional Kinematics, Xueguang Ren, Sadek Amami, Oleg Zatsarinny, Thomas Pflüger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn

Physics Faculty Research & Creative Works

Low-energy (E0 0=65eV) electron-impact single ionization of Ne (2p) has been investigated to thoroughly test state-of-the-art theoretical approaches. The experimental data were measured using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission energies ranging from 2 to 8 eV, and projectile scattering angles ranging from 8.5⁰ to 20.0⁰. The experimental triple-differential cross sections are internormalized across all measured scattering angles and ejected energies. The experimental data are compared to predictions from a hybrid second-order distorted-wave Born plus R-matrix approach, the distorted-wave Born approximation with the inclusion of postcollision interaction (PCI), …

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Symmetric Solitonic Excitations Of The (1 + 1)-Dimensional Abelian-Higgs Classical Vacuum, F. K. Diakonos, Garyfallia C. Katsimiga, X. N. Maintas, C. E. Tsagkarakis Feb 2015

Symmetric Solitonic Excitations Of The (1 + 1)-Dimensional Abelian-Higgs Classical Vacuum, F. K. Diakonos, Garyfallia C. Katsimiga, X. N. Maintas, C. E. Tsagkarakis

Physics Faculty Research & Creative Works

We study the classical dynamics of the Abelian-Higgs model in (1 + 1) space-time dimensions for the case of strongly broken gauge symmetry. In this limit the wells of the potential are almost harmonic and sufficiently deep, presenting a scenario far from the associated critical point. Using a multiscale perturbation expansion, the equations of motion for the fields are reduced to a system of coupled nonlinear Schrödinger equations. Exact solutions of the latter are used to obtain approximate analytical solutions for the full dynamics of both the gauge and Higgs field in the form of oscillons and oscillating kinks. Numerical …

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Gravitational Correction To Vacuum Polarization, Ulrich D. Jentschura Feb 2015

Gravitational Correction To Vacuum Polarization, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We consider the gravitational correction to (electronic) vacuum polarization in the presence of a gravitational background field. The Dirac propagators for the virtual fermions are modified to include the leading gravitational correction (potential term) which corresponds to a coordinate-dependent fermion mass. The mass term is assumed to be uniform over a length scale commensurate with the virtual electron-positron pair. The on-mass shell renormalization condition ensures that the gravitational correction vanishes on the mass shell of the photon, i.e., the speed of light is unaffected by the quantum field theoretical loop correction, in full agreement with the equivalence principle. Nontrivial corrections …

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Benchmarking Accurate Spectral Phase Retrieval Of Single Attosecond Pulses, Hui Wei, Anh-Thu Le, Toru Morishita, Chao Yu, C. D. Lin Feb 2015

Benchmarking Accurate Spectral Phase Retrieval Of Single Attosecond Pulses, Hui Wei, Anh-Thu Le, Toru Morishita, Chao Yu, C. D. Lin

Physics Faculty Research & Creative Works

A single extreme-ultraviolet (XUV) attosecond pulse or pulse train in the time domain is fully characterized if its spectral amplitude and phase are both determined. The spectral amplitude can be easily obtained from photoionization of simple atoms where accurate photoionization cross sections have been measured from, e.g., synchrotron radiations. To determine the spectral phase, at present the standard method is to carry out XUV photoionization in the presence of a dressing infrared (IR) laser. In this work, we examine the accuracy of current phase retrieval methods (PROOF and iPROOF) where the dressing IR is relatively weak such that photoelectron spectra …

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Nodal To Nodeless Superconducting Energy-Gap Structure Change Concomitant With Fermi-Surface Reconstruction In The Heavy-Fermion Compound Cecoin₅, Hyunsoo Kim, M. A. Tanatar, R. Flint, C. Petrovic, Rongwei Hu, B. D. White, I. K. Lum, M. B. Maple, R. Prozorov Jan 2015

Nodal To Nodeless Superconducting Energy-Gap Structure Change Concomitant With Fermi-Surface Reconstruction In The Heavy-Fermion Compound Cecoin₅, Hyunsoo Kim, M. A. Tanatar, R. Flint, C. Petrovic, Rongwei Hu, B. D. White, I. K. Lum, M. B. Maple, R. Prozorov

Physics Faculty Research & Creative Works

The London penetration depth λ(T) was measured in single crystals of Ce1-xRxCoIn5, R = La, Nd, and Yb down to Tmin ≈ 50mK (Tc/Tmin ∼ 50) using a tunnel-diode resonator. In the cleanest samples Δλ(T) is best described by the power law Δλ(T) α Tn, with n ∼ 1, consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of Tc; however, the effects on Δλ(T) differ. While La and Nd substitution leads to …

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Narrow-Band Search Of Continuous Gravitational-Wave Signals From Crab And Vela Pulsars In Virgo Vsr4 Data, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jan 2015

Narrow-Band Search Of Continuous Gravitational-Wave Signals From Crab And Vela Pulsars In Virgo Vsr4 Data, 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 a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational-wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed assuming both that polarization parameters are completely unknown …

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Searching For Stochastic Gravitational Waves Using Data From The Two Colocated Ligo Hanford Detectors, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jan 2015

Searching For Stochastic Gravitational Waves Using Data From The Two Colocated Ligo Hanford Detectors, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Searches for a stochastic gravitational-wave background (SGWB) using terrestrial detectors typically involve cross-correlating data from pairs of detectors. The sensitivity of such cross-correlation analyses depends, among other things, on the separation between the two detectors: the smaller the separation, the better the sensitivity. Hence, a colocated detector pair is more sensitive to a gravitational-wave background than a noncolocated detector pair. However, colocated detectors are also expected to suffer from correlated noise from instrumental and environmental effects that could contaminate the measurement of the background. Hence, methods to identify and mitigate the effects of correlated noise are necessary to achieve the …

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The Role Of Multiple Electron Capture In The X-Ray Emission Process Following Charge Exchange Collisions With Neutral Targets, Sebastian Otranto, N. D. Cariatore, Ronald E. Olson Jan 2015

The Role Of Multiple Electron Capture In The X-Ray Emission Process Following Charge Exchange Collisions With Neutral Targets, Sebastian Otranto, N. D. Cariatore, Ronald E. Olson

Physics Faculty Research & Creative Works

In this work we theoretically study photonic spectra that follow charge exchange processes between highly charged ions and neutral argon and CO targets. The range of collision energies studied is 5 eV/amu-10 keV/amu, covering typical EBIT-traps and Solar Wind energies. Our studies are based on multiple electrons schemes within the classical trajectory Monte Carlo method. Electrons are sorted with the sequential binding energies for the target under consideration. The role played by the multiple electron capture process for the different collision systems under consideration is explicitly analyzed and its contribution separated as arising from double radiative decay and autoionizing multiple …

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One-Loop Dominance In The Imaginary Part Of The Polarizability: Application To Blackbody And Noncontact Van Der Waals Friction, Ulrich D. Jentschura, Grzegorz Lach, Maarten Dekieviet, Krzysztof Pachucki Jan 2015

One-Loop Dominance In The Imaginary Part Of The Polarizability: Application To Blackbody And Noncontact Van Der Waals Friction, Ulrich D. Jentschura, Grzegorz Lach, Maarten Dekieviet, Krzysztof Pachucki

Physics Faculty Research & Creative Works

Phenomenologically important quantum dissipative processes include blackbody friction (an atom absorbs counterpropagating blueshifted photons and spontaneously emits them in all directions, losing kinetic energy) and noncontact van der Waals friction (in the vicinity of a dielectric surface, the mirror charges of the constituent particles inside the surface experience drag, slowing the atom). The theoretical predictions for these processes are modified upon a rigorous quantum electrodynamic treatment, which shows that the one-loop "correction" yields the dominant contribution to the off-resonant, gauge-invariant, imaginary part of the atom's polarizability at room temperature, for typical atom-surface interactions. The tree-level contribution to the polarizability dominates …

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Long-Range Atom-Wall Interactions And Mixing Terms: Metastable Hydrogen, Ulrich D. Jentschura Jan 2015

Long-Range Atom-Wall Interactions And Mixing Terms: Metastable Hydrogen, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We investigate the interaction of metastable 2S hydrogen atoms with a perfectly conducting wall, including parity-breaking S-P mixing terms (with full account of retardation). The neighboring 2P1/2 and 2P3/2 levels are found to have a profound effect on the transition from the short-range, nonrelativistic regime, to the retarded form of the Casimir-Polder interaction. The corresponding P state admixtures to the metastable 2S state are calculated. We find the long-range asymptotics of the retarded Casimir-Polder potentials and mixing amplitudes for general excited states, including a fully quantum electrodynamic treatment of the dipole-quadrupole mixing term. The decay width of the …

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Critical States Embedded In The Continuum, Milan Koirala, Alexey Yamilov, A. Basiri, Yaron Bromberg, Hui Cao, Tsampikos Kottos Jan 2015

Critical States Embedded In The Continuum, Milan Koirala, Alexey Yamilov, A. Basiri, Yaron Bromberg, Hui Cao, Tsampikos Kottos

Physics Faculty Research & Creative Works

We introduce a class of critical states which are embedded in the continuum (CSC) of a one-dimensional optical waveguide array with one non-Hermitian defect. These states are on the verge of being fractal and have real propagation constants. They emerge at a phase transition which is driven by the imaginary refractive index of the defective waveguide and it is accompanied by a mode segregation which reveals analogies with the Dicke super-radiance. Below this point the states are extended while above it they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states …

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Composition-Dependent Structural And Transport Properties Of Amorphous Transparent Conducting Oxides, Rabi Khanal, D. Bruce Buchholz, Robert P. Chang, Julia E. Medvedeva Jan 2015

Composition-Dependent Structural And Transport Properties Of Amorphous Transparent Conducting Oxides, Rabi Khanal, D. Bruce Buchholz, Robert P. Chang, Julia E. Medvedeva

Physics Faculty Research & Creative Works

Structural properties of amorphous In-based oxides, In-X-O with X=Zn, Ga, Sn, or Ge, are investigated using ab initio molecular dynamics liquid-quench simulations. The results reveal that indium retains its average coordination of 5.0 upon 20% X fractional substitution for In, whereas X cations satisfy their natural coordination with oxygen atoms. This finding suggests that the carrier generation is primarily governed by In atoms, in accord with the observed carrier concentration in amorphous In-O and In-X-O. At the same time, the presence of X affects the number of six-coordinated In atoms as well as the oxygen sharing between the InO6 …

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Computational Discovery Of Lanthanide Doped And Co-Doped Y₃Al₅O₁₂ For Optoelectronic Applications, Kamal Kumar Choudhary, Aleksandr V. Chernatynskiy, Kiran Mathew, Eric W. Bucholz, Simon R. Phillpot, Susan Sinnott, Richard G. Hennig Jan 2015

Computational Discovery Of Lanthanide Doped And Co-Doped Y₃Al₅O₁₂ For Optoelectronic Applications, Kamal Kumar Choudhary, Aleksandr V. Chernatynskiy, Kiran Mathew, Eric W. Bucholz, Simon R. Phillpot, Susan Sinnott, Richard G. Hennig

Physics Faculty Research & Creative Works

We systematically elucidate the optoelectronic properties of rare-earth doped and Ce co-doped yttrium aluminum garnet (YAG) using hybrid exchange-correlation functional based density functional theory. The predicted optical transitions agree with the experimental observations for single doped Ce:YAG, Pr:YAG, and co-doped Er,Ce:YAG. We find that co-doping of Ce-doped YAG with any lanthanide except Eu and Lu lowers the transition energies; we attribute this behavior to the lanthanide-induced change in bonding environment of the dopant atoms. Furthermore, we find infrared transitions only in case of the Er, Tb, and Tm co-doped Ce:YAG and suggest Tm,Ce:YAG and Tb,Ce:YAG as possible functional materials for …

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Electron- And Photon-Impact Ionization Of Furfural, D. B. Jones, E. Ali, K. L. Nixon, P. Limão-Vieira, M.-J. Hubin-Franskin, J. Delwiche, C. G. Ning, J. Colgan, Andrew J. Murray, Don H. Madison, M .J. Brunger Jan 2015

Electron- And Photon-Impact Ionization Of Furfural, D. B. Jones, E. Ali, K. L. Nixon, P. Limão-Vieira, M.-J. Hubin-Franskin, J. Delwiche, C. G. Ning, J. Colgan, Andrew J. Murray, Don H. Madison, M .J. Brunger

Physics Faculty Research & Creative Works

The He(i) photoelectron spectrum of furfural has been investigated, with its vibrational structure assigned for the first time. The ground and excited ionized states are assigned through ab initio calculations performed at the outer-valence Green's function level. Triple differential cross sections (TDCSs) for electron-impact ionization of the unresolved combination of the 4a" + 21a' highest and next-highest occupied molecular orbitals have also been obtained. Experimental TDCSs are recorded in a combination of asymmetric coplanar and doubly symmetric coplanar kinematics. The experimental TDCSs are compared to theoretical calculations, obtained within a molecular 3-body distorted wave framework that employed either an orientation …

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Understanding Higher-Order Nonlocal Halo Bias At Large Scales By Combining The Power Spectrum With The Bispectrum, Shun Saito, Tobias Baldauf, For Full List Of Authors, See Publisher's Website. Dec 2014

Understanding Higher-Order Nonlocal Halo Bias At Large Scales By Combining The Power Spectrum With The Bispectrum, Shun Saito, Tobias Baldauf, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Understanding the relation between underlying matter distribution and biased tracers such as galaxies or dark matter halos is essential to extract cosmological information from ongoing or future galaxy redshift surveys. At sufficiently large scales such as the baryon acoustic oscillation (BAO) scale, a standard approach for the bias problem on the basis of the perturbation theory (PT) is to assume the "local bias" model in which the density field of biased tracers is deterministically expanded in terms of matter density field at the same position. The higher-order bias parameters are then determined by combining the power spectrum with higher-order statistics …

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