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Articles 1 - 30 of 47
Full-Text Articles in Physics
Differential Electron Emission For Single And Multiple Ionization Of Argon By 500 Ev Positrons, Jared M. Gavin, Robert D. Dubois, O. G. De Lucio
Differential Electron Emission For Single And Multiple Ionization Of Argon By 500 Ev Positrons, Jared M. Gavin, Robert D. Dubois, O. G. De Lucio
Physics Faculty Research & Creative Works
Triply differential electron emission cross sections are measured for single ionization of argon by 500 eV positrons. Data are presented for coincidences between projectiles scattered into angles of 3° and electrons with emission energies less than 10 eV that are observed between 45 and 135° along the beam direction. For interpretation, these are compared to cosine squared representations of the binary and recoil lobes which are convoluted over experimental parameters. Singly differential electron emission data for double and triple ionization by positrons are also presented.
Two-Loop Bethe Logarithms For Non- S Levels, Ulrich D. Jentschura
Two-Loop Bethe Logarithms For Non- S Levels, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
Two-loop Bethe logarithms are calculated for excited P and D states in hydrogenlike systems, and estimates are presented for all states with higher angular momenta. These results complete our knowledge of the P and D energy levels in hydrogen at the order of α8 mec2, where me is the electron mass and c is the speed of light, and scale as Z6, where Z is the nuclear charge number. Our analytic and numerical calculations are consistent with the complete absence of logarithmic terms of order (απ)2 (Zα)6 ln [(Zα)-2] …
K Α₁ Radiation From Heavy, Heliumlike Ions Produced In Relativistic Collisions, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker, Stephan Fritzsche
K Α₁ Radiation From Heavy, Heliumlike Ions Produced In Relativistic Collisions, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker, Stephan Fritzsche
Physics Faculty Research & Creative Works
Bound-state transitions in few-electron, heavy ions following radiative electron capture are studied within the framework of the density matrix theory and the multiconfiguration Dirac-Fock approach. Special attention is paid to the K α1 (1 s1/2 2 p3/2 1.3PJ=1,2→1s21/2 1SJ=0) radiative decay of heliumlike uranium U90+ projectiles. This decay has recently been observed at the GSI facility in Darmstadt, giving rise to a surprisingly isotropic angular distribution, which is inconsistent with previous experiments and calculations based on a "one-particle" model. We show that the unexpected isotropy essentially results from …
Analysis Of Two-Dimensional Photoelectron Momentum Spectra And The Effect Of The Long-Range Coulomb Potential In Single Ionization Of Atoms By Intense Lasers, Zhangjin Chen, Toru Morishita, Anh-Thu Le, M. Wickenhauser, X. M. Tong, C. D. Lin
Analysis Of Two-Dimensional Photoelectron Momentum Spectra And The Effect Of The Long-Range Coulomb Potential In Single Ionization Of Atoms By Intense Lasers, Zhangjin Chen, Toru Morishita, Anh-Thu Le, M. Wickenhauser, X. M. Tong, C. D. Lin
Physics Faculty Research & Creative Works
Two-dimensional (2D) electron momentum distributions and energy spectra for multiphoton ionization of atoms by intense laser pulses, calculated by solving the time-dependent Schrödinger equation (TDSE) for different wavelengths and intensities, are compared to those predicted by the strong-field approximation (SFA). It is shown that the momentum spectra at low energies between the TDSE and SFA are quite different and the differences arise largely from the absence of a long-range Coulomb interaction in the SFA. We further found that the low-energy 2D momentum spectra from the TDSE exhibit ubiquitous fanlike features where the number of stripes is due to a single …
Quantum Dot Potentials: Symanzik Scaling, Resurgent Expansions, And Quantum Dynamics, Andrey S. Surzhykov, Michael Lubasch, Jean Zinn-Justin, Ulrich D. Jentschura
Quantum Dot Potentials: Symanzik Scaling, Resurgent Expansions, And Quantum Dynamics, Andrey S. Surzhykov, Michael Lubasch, Jean Zinn-Justin, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
This article is concerned with a special class of the "double-well- like" potentials that occur naturally in the analysis of finite quantum systems. Special attention is paid, in particular, to the so-called Fokker-Planck potential, which has a particular property: the perturbation series for the ground-state energy vanishes to all orders in the coupling parameter, but the actual ground-state energy is positive and dominated by instanton configurations of the form exp (-a g), where a is the instanton action. The instanton effects are most naturally taken into account within the modified Bohr-Sommerfeld quantization conditions whose expansion leads to the generalized perturbative …
Multiple Scattering Mechanisms In Simultaneous Projectile-Electron And Target-Electron Ejection In H⁻ + He Collisions, Michael Schulz, T. Ferger, Daniel Fischer, R. Moshammer, J. D. Ullrich
Multiple Scattering Mechanisms In Simultaneous Projectile-Electron And Target-Electron Ejection In H⁻ + He Collisions, Michael Schulz, T. Ferger, Daniel Fischer, R. Moshammer, J. D. Ullrich
Physics Faculty Research & Creative Works
We studied simultaneous electron ejection from both collision partners in 200-keV H-+He collisions in a kinematically complete experiment by measuring the fully momentum-analyzed recoil ions and both active electrons in coincidence. The data were analyzed in terms of Dalitz spectra, in which the momentum exchange between three particles is plotted simultaneously in a single spectrum. We found that the energy transfer occurs predominantly between the active electrons, but most of the momentum is exchanged in elastic scattering between the cores of the collision partners.
Gravitational Diffraction Radiation, Vitor Cardoso, Marco Cavaglia, Mario Pimenta
Gravitational Diffraction Radiation, Vitor Cardoso, Marco Cavaglia, Mario Pimenta
Physics Faculty Research & Creative Works
We show that if the visible universe is a membrane embedded in a higher-dimensional space, particles in uniform motion radiate gravitational waves because of spacetime lumpiness. This phenomenon is analogous to the electromagnetic diffraction radiation of a charge moving near to a metallic grating. In the gravitational case, the role of the metallic grating is played by the inhomogeneities of the extra-dimensional space, such as a hidden brane. We derive a general formula for gravitational diffraction radiation and apply it to a higher-dimensional scenario with flat compact extra dimensions. Gravitational diffraction radiation may carry away a significant portion of the …
Volumes Of Critical Bubbles From The Nucleation Theorem, Gerald Wilemski
Volumes Of Critical Bubbles From The Nucleation Theorem, Gerald Wilemski
Physics Faculty Research & Creative Works
A corollary of the nucleation theorem due to Kashchiev [Nucleation: Basic Theory with Applications (Butterworth-Heinemann, Oxford, 2000)] allows the volume V* of a critical bubble to be determined from nucleation rate measurements. The original derivation was limited to one-component, ideal gas bubbles with a vapor density much smaller than that of the ambient liquid. Here, an exact result is found for multicomponent, nonideal gas bubbles. Provided a weak density inequality holds, this result reduces to Kashchiev's simple form which thus has a much broader range of applicability than originally expected. Limited applications to droplets are also mentioned, and the utility …
Exploring Relativistic Many-Body Recoil Effects In Highly Charged Ions, R. Soria Orts, Zoltan Harman, Jose R. Crespo Lopez-Urrutia, Anton N. Artemyev, Hjalmar Bruhns, Antonio J. Gonzalez, Ulrich D. Jentschura, Christoph H. Keitel, Alain Lapierre, Vladimir Sergeyevich Mironov, Vladimir M. Shabaev, Hiroyuki Tawara, I. I. Tupitsyn, Joachim Hermann Ullrich, Andrey V. Volotka
Exploring Relativistic Many-Body Recoil Effects In Highly Charged Ions, R. Soria Orts, Zoltan Harman, Jose R. Crespo Lopez-Urrutia, Anton N. Artemyev, Hjalmar Bruhns, Antonio J. Gonzalez, Ulrich D. Jentschura, Christoph H. Keitel, Alain Lapierre, Vladimir Sergeyevich Mironov, Vladimir M. Shabaev, Hiroyuki Tawara, I. I. Tupitsyn, Joachim Hermann Ullrich, Andrey V. Volotka
Physics Faculty Research & Creative Works
The relativistic recoil effect has been the object of experimental investigations using highly charged ions at the Heidelberg electron beam ion trap. Its scaling with the nuclear charge Z boosts its contribution to a measurable level in the magnetic-dipole (M1) transitions of B- and Be-like Ar ions. The isotope shifts of 36Ar versus 40Ar have been detected with sub-ppm accuracy, and the recoil effect contribution was extracted from the 1s22s22p 2P1/2-2P3/2 transition in Ar13+ and the 1s22s2p 3P1-3P2 transition …
Hyperspherical Close-Coupling Calculations For Electron-Capture Cross Sections In Low-Energy Ne¹⁰⁺ +H (1s) Collisions, P. Barragan, Anh-Thu Le, C. D. Lin
Hyperspherical Close-Coupling Calculations For Electron-Capture Cross Sections In Low-Energy Ne¹⁰⁺ +H (1s) Collisions, P. Barragan, Anh-Thu Le, C. D. Lin
Physics Faculty Research & Creative Works
We present total and partial electron-capture cross sections for Ne¹⁰⁺ +H (1s) collisions at energies from 0.01 eV to 1 keV using the hyperspherical close-coupling method. Good agreements with the previous calculations by the classical-trajectory Monte-Carlo method are found for total capture cross section, but not for partial cross sections, especially below about 200 eV/amu. We found that the total cross section is mainly due to the population of n=7 channels and only at energies above 50 eV/amu n = 5,6 channels begin to contribute to the total cross section.
Young-Type Interference In (E, 2e) Ionization Of H₂, D. S. Milne-Brownlie, Matthew S. Foster, Junfang Gao, B. Lohmann, Don H. Madison
Young-Type Interference In (E, 2e) Ionization Of H₂, D. S. Milne-Brownlie, Matthew S. Foster, Junfang Gao, B. Lohmann, Don H. Madison
Physics Faculty Research & Creative Works
We have investigated the electron impact single ionization of the hydrogen molecule, with fully determined kinematics. The experimental and theoretical results are compared with He ionization under the same conditions. The results indicate that the ejected electron angular distribution for H2 is modified due to Young-type interference between ionization amplitudes for scattering from the two centers in the hydrogen molecule. The observable result is a suppression of the backward scattering (recoil) peak compared with the binary peak.
Quantum Electrodynamic Corrections To The Hyperfine Structure Of Excited S States, Ulrich D. Jentschura, Vladimir A. Yerokhin
Quantum Electrodynamic Corrections To The Hyperfine Structure Of Excited S States, Ulrich D. Jentschura, Vladimir A. Yerokhin
Physics Faculty Research & Creative Works
State-dependent quantum electrodynamic corrections are evaluated for the hyperfine splitting of nS states for arbitrary principal quantum number n. The calculations comprise both the self-energy and the vacuum-polarization correction of order α(Zα) 2 EF and the recoil correction of order (Zα)2 (m/M) EF. Higher-order corrections are summarized and partly reevaluated as well. Accurate predictions for hydrogen hyperfine splitting intervals of nS states with n=2,...,8 are presented. The results obtained are important due to steady progress in hydrogen spectroscopy for transitions involving highly excited S states.
Polarization-Operator Approach To Electron-Positron Pair Production In Combined Laser And Coulomb Fields, A. I. Milstein, Carsten Muller, Karen Z. Hatsagortsyan, Ulrich D. Jentschura, Christoph H. Keitel
Polarization-Operator Approach To Electron-Positron Pair Production In Combined Laser And Coulomb Fields, A. I. Milstein, Carsten Muller, Karen Z. Hatsagortsyan, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
The optical theorem is applied to the process of electron-positron pair creation in the superposition of a nuclear Coulomb and a strong laser field. We derive representations for the total production rate as twofold integrals, both for circular laser polarization and for the general case of elliptic polarization. Our approach allows us to obtain, by analytical means, the asymptotic behavior of the pair creation rate for various limits of interest. In particular, we consider pair production by two-photon absorption and show that, close to the energetic threshold of this process, the rate obeys a power law in the laser frequency …
(E,2e) Measurements On Xenon: Reexamination Of The Fine-Structure Effect, Radmila Panajotovic, Julian C A Lower, Erich Weigold, A. Prideaux, Don H. Madison
(E,2e) Measurements On Xenon: Reexamination Of The Fine-Structure Effect, Radmila Panajotovic, Julian C A Lower, Erich Weigold, A. Prideaux, Don H. Madison
Physics Faculty Research & Creative Works
The process of electron scattering from heavy target atoms is of considerable interest due to the enhanced role of relativistic effects and distortion of the electron trajectories resulting from the large value of nuclear charge. Here we present (e,2e) ionization measurements and distorted-wave Born approximation calculations for the scattering of spin-polarized electrons from xenon atoms in which the fine-structure levels of the residual ion are resolved. Comparison of measurements performed using a high-sensitivity toroidal analyzer spectrometer with the predictions of sophisticated calculations provide an improved understanding of the ionization dynamics of heavy target atoms and the treatment of electron exchange …
Two-Photon Excitation Dynamics In Bound Two-Body Coulomb Systems Including Ac Stark Shift And Ionization, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel, Nikolai N. Kolachevsky, Maximilian Herrmann, Peter Fendel, Marc P. Fischer, Th H. Udem, Ronald Holzwarth, Theodor Wolfgang Hansch, Marlan O. Scully, Girish S. Agarwal
Two-Photon Excitation Dynamics In Bound Two-Body Coulomb Systems Including Ac Stark Shift And Ionization, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel, Nikolai N. Kolachevsky, Maximilian Herrmann, Peter Fendel, Marc P. Fischer, Th H. Udem, Ronald Holzwarth, Theodor Wolfgang Hansch, Marlan O. Scully, Girish S. Agarwal
Physics Faculty Research & Creative Works
One of the dominant systematic effects that shift resonance lines in high-precision measurements of two-photon transitions is the dynamic (ac) Stark shift. For suitable laser frequencies, the ac Stark shift acquires an imaginary part which corresponds to the rate of resonant one-photon ionization of electrons into a continuum state. At the current level of spectroscopic accuracy, the underlying time-dependent quantum dynamics governing the atomic two-photon excitation process must be well understood, and related considerations are the subject of the present paper. In order to illustrate the basic mechanisms in the transient regime, we investigate an analytically solvable model scenario for …
Benchmarking High-Field Few-Electron Correlation And Qed Contributions In Hg⁷⁵⁺ To Hg⁷⁸⁺ Ions. I. Experiment, Antonio J. Gonzalez, Jose R. Crespo Lopez-Urrutia, Jean Pierre Braun, Gunter Brenner, Hjalmar Bruhns, Alain Lapierre, Vladimir Sergeyevich Mironov, R. Soria Orts, Hiroyuki Tawara, Michael Trinczek, Joachim Hermann Ullrich, Anton N. Artemyev, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, James H. Scofield, I. I. Tupitsyn
Benchmarking High-Field Few-Electron Correlation And Qed Contributions In Hg⁷⁵⁺ To Hg⁷⁸⁺ Ions. I. Experiment, Antonio J. Gonzalez, Jose R. Crespo Lopez-Urrutia, Jean Pierre Braun, Gunter Brenner, Hjalmar Bruhns, Alain Lapierre, Vladimir Sergeyevich Mironov, R. Soria Orts, Hiroyuki Tawara, Michael Trinczek, Joachim Hermann Ullrich, Anton N. Artemyev, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, James H. Scofield, I. I. Tupitsyn
Physics Faculty Research & Creative Works
The photorecombination of highly charged few-electron mercury ions Hg75+ to Hg78+ has been explored with the Heidelberg electron beam ion trap. By monitoring the emitted x rays (65-76 keV) and scanning the electron beam energy (45-54 keV) over the KLL dielectronic recombination (DR) region, the energies of state-selected DR resonances were determined to within ±4 eV (relative) and ±14 eV (absolute). At this level of experimental accuracy, it becomes possible to make a detailed comparison to various theoretical approaches and methods, all of which include quantum electrodynamic (QED) effects and finite nuclear size contributions (for a 1s electron, …
Benchmarking High-Field Few-Electron Correlation And Qed Contributions In Hg⁷⁵⁺ To Hg⁷⁸⁺ Ions. Ii. Theory, Zoltan Harman, I. I. Tupitsyn, Anton N. Artemyev, Ulrich D. Jentschura, Christoph H. Keitel, Jose R. Crespo Lopez-Urrutia, Antonio J. Gonzalez, Hiroyuki Tawara, Joachim Hermann Ullrich
Benchmarking High-Field Few-Electron Correlation And Qed Contributions In Hg⁷⁵⁺ To Hg⁷⁸⁺ Ions. Ii. Theory, Zoltan Harman, I. I. Tupitsyn, Anton N. Artemyev, Ulrich D. Jentschura, Christoph H. Keitel, Jose R. Crespo Lopez-Urrutia, Antonio J. Gonzalez, Hiroyuki Tawara, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
Theoretical resonance energies for KLL dielectronic recombination into He-, Li-, Be-, and B-like Hg ions are calculated by various means and discussed in detail. We apply the multiconfiguration Dirac-Fock and the configuration interaction Dirac-Fock-Sturmian methods, and quantum electrodynamic many-body theory. The different contributions such as relativistic electron interaction, quantum electrodynamic contributions, and finite nuclear size and mass corrections are calculated and their respective theoretical uncertainties are estimated. Our final results are compared to experimental data from the preceding paper. The comparison of theoretical values with the experimental energies shows a good overall agreement for most transitions and illustrates the significance …
Evidence Of Two-Center Interference In High-Order Harmonic Generation From Co₂, Anh-Thu Le, Xiao-Min Tong, C. D. Lin
Evidence Of Two-Center Interference In High-Order Harmonic Generation From Co₂, Anh-Thu Le, Xiao-Min Tong, C. D. Lin
Physics Faculty Research & Creative Works
Two recent pump-probe experiments on the high-order harmonic generation (HHG) from partially aligned CO₂ molecules have shown that the HHG yields versus the ionization rates as functions of the pump-probe delay time exhibit inverted modulation. The inversion has been attributed to the quantum interference in the recombination process from the two oxygen centers. Using the Lewenstein model to calculate HHG from fixed CO₂ molecules and taking into account the partial alignment of the molecules versus the time delay, we interpret that the inversion is due to the degree of overlap between the partially aligned molecules and the angular dependence of …
Radiative Electron Capture Into High- Z Few-Electron Ions: Alignment Of The Excited Ionic States, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker, Stephan Fritzsche
Radiative Electron Capture Into High- Z Few-Electron Ions: Alignment Of The Excited Ionic States, Andrey S. Surzhykov, Ulrich D. Jentschura, Th H. Stohlker, Stephan Fritzsche
Physics Faculty Research & Creative Works
We lay out a unified formalism for the description of radiative electron capture into excited states of heavy, few-electron ions and their subsequent decay, including a full account of many-electron effects and higher-order multipoles of the radiation field. In particular, the density-matrix theory is applied to explore the magnetic sublevel population of the residual ions, as described in terms of alignment parameters. For the electron capture into the initially hydrogenlike U91+ and lithiumlike U89+ uranium projectiles, the alignment parameters are calculated, within the multiconfiguration Dirac-Fock approach, as a function of the collision energy and for different ionic states. …
Modeling Study Of The Dip-Hump Feature In Bi₂ Sr₂ Cacu₂ O8+Δ Tunneling Spectroscopy, Pierom Romano, Lutfi Ozyuzer, Zikri M. Yusof, Cihan Kurter, John F. Zasadzinski
Modeling Study Of The Dip-Hump Feature In Bi₂ Sr₂ Cacu₂ O8+Δ Tunneling Spectroscopy, Pierom Romano, Lutfi Ozyuzer, Zikri M. Yusof, Cihan Kurter, John F. Zasadzinski
Physics Faculty Research & Creative Works
The tunneling spectra of high-temperature superconductors on Bi2 Sr2 CaCu2 O8+δ (Bi-2212) reproducibly show a high-bias structure in the form of a dip-hump at voltages higher than the gap voltage. Of central concern is whether this feature originates from the normal state background or is intrinsic to the superconducting mechanism. We address this issue by generating a set of model conductance curves-a "normal state" conductance that takes into account effects such as the band structure and a possible pseudogap, and a pure superconducting state conductance. When combined, the result shows that the dip-hump feature present in …
Ƒ-Electron Correlations In Nonmagnetic Ce Studied By Means Of Spin-Resolved Resonant Photoemission, S. W. Yu, Takashi Komesu, B. W. Chung, Simon A. Morton, James G. Tobin, George Daniel Waddill
Ƒ-Electron Correlations In Nonmagnetic Ce Studied By Means Of Spin-Resolved Resonant Photoemission, S. W. Yu, Takashi Komesu, B. W. Chung, Simon A. Morton, James G. Tobin, George Daniel Waddill
Physics Faculty Research & Creative Works
We have studied the spin-spin coupling between two f electrons of nonmagnetic Ce by means of spin-resolved resonant photoemission using circularly polarized synchrotron radiation. The two f electrons participating in the 3d5/2-->4f resonance process are coupled in a singlet while the coupling is veiled in the 3d3/2-->4f process due to an additional Coster-Kronig decay channel. The identical singlet coupling is observed in the 4d-->4f resonance process. Based on the Ce measurements, it is argued that spin-resolved resonant photoemission is one approach to study the correlation effects, particularly in the form of spin, in the rare earths.
Erratum: Black Hole Particle Emission In Higher-Dimensional Spacetimes (Physical Review Letters (2006) 96 (071301)), Vitor Cardoso, Marco Cavaglia, Leonardo Gualtieri
Erratum: Black Hole Particle Emission In Higher-Dimensional Spacetimes (Physical Review Letters (2006) 96 (071301)), Vitor Cardoso, Marco Cavaglia, Leonardo Gualtieri
Physics Faculty Research & Creative Works
No abstract provided.
X-Ray Emission Cross Sections Following Charge Exchange By Multiply Charged Ions Of Astrophysical Interest, Sebastian Otranto, Ronald E. Olson, P. Beiersdorfer
X-Ray Emission Cross Sections Following Charge Exchange By Multiply Charged Ions Of Astrophysical Interest, Sebastian Otranto, Ronald E. Olson, P. Beiersdorfer
Physics Faculty Research & Creative Works
State selective nl-electron capture cross sections are presented for highly charged ions with Z=6-10 colliding with atoms and molecules. The energy range investigated was from 1 eV/amu(v=0.006 a.u.)to 100 keV/amu(v=2.0 a.u.). The energy dependence of the l-level populations is investigated. The K shell x-ray emission cross sections are determined by using the calculated state-selective electron capture results as input and then applying hydrogenic branching and cascading values for the photon emission. A major shift in the line emission from being almost solely Lyman-alpha transitions at the highest collisions energies to strong high-n to 1s transitions at the lowest energies is …
Black Hole Particle Emission In Higher-Dimensional Spacetimes, Vitor Cardoso, Marco Cavaglia, Leonardo Gualtieri
Black Hole Particle Emission In Higher-Dimensional Spacetimes, Vitor Cardoso, Marco Cavaglia, Leonardo Gualtieri
Physics Faculty Research & Creative Works
In models with extra dimensions, a black hole evaporates both in the bulk and on the visible brane, where standard model fields live. The exact emissivities of each particle species are needed to determine how the black hole decay proceeds. We compute and discuss the absorption cross sections, the relative emissivities, and the total power output of all known fields in the evaporation phase. Graviton emissivity is highly enhanced as the spacetime dimensionality increases. Therefore, a black hole loses a significant fraction of its mass in the bulk. This result has important consequences for the phenomenology of black holes in …
Simulations Of Black Hole Air Showers In Cosmic Ray Detectors, Eun-Joo Ahn, Marco Cavaglia
Simulations Of Black Hole Air Showers In Cosmic Ray Detectors, Eun-Joo Ahn, Marco Cavaglia
Physics Faculty Research & Creative Works
We present a comprehensive study of TeV black hole events in Earth's atmosphere originated by cosmic rays of very high energy. An advanced fortran Monte Carlo code is developed and used to simulate black hole extensive air showers from ultrahigh-energy neutrino-nucleon interactions. We investigate the characteristics of these events, compare the black hole air showers to standard model air showers, and test different theoretical and phenomenological models of black hole formation and evolution. The main features of black hole air showers are found to be independent of the model considered. No significant differences between models are likely to be observed …
Comparison Of Classical And Second Quantized Description Of The Dynamic Stark Shift, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel
Comparison Of Classical And Second Quantized Description Of The Dynamic Stark Shift, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
We compare the derivation of the dynamic Stark shift of hydrogenic energy levels in a classical framework with an adiabatically damped laser-atom interaction, which is equivalent to the Gell-Mann-Low-Sucher formula, and a treatment based on time-independent perturbation theory, with a second-quantized laser-atom dipole interaction Hamiltonian. Our analysis applies to a laser that excites a two-photon transition in atomic hydrogen or in a hydrogenlike ion with low nuclear charge number. Our comparisons serve to demonstrate why the dynamic Stark shift may be interpreted as a stimulated radiative correction and illustrates connections between the two derivations. The simplest of the derivations is …
Random Lasing In Weakly Scattering Systems, X. Wu, W. Fang, Alexey Yamilov, A. A. Asatryan, L. C. Botten, Andrey A. Chabanov, Hui Cao
Random Lasing In Weakly Scattering Systems, X. Wu, W. Fang, Alexey Yamilov, A. A. Asatryan, L. C. Botten, Andrey A. Chabanov, Hui Cao
Physics Faculty Research & Creative Works
We present detailed experimental and numerical studies of random lasing in weakly scattering systems. The interference of scattered light, which is weak in the passive systems, is greatly enhanced in the presence of high gain, providing coherent and resonant feedback for lasing. The lasing modes are confined in the vicinity of the pumped volume due to absorption of emitted light outside it. In the ballistic regime where the size of the gain volume is less than the scattering mean free path, lasing oscillation occurs along the direction in which the gain volume is most extended, producing directional laser output. The …
Adiabatic-Nonadiabatic Transition In The Diffusive Hamiltonian Dynamics Of A Classical Holstein Polaron, Alex A. Silvius, Paul Ernest Parris, Stephan De Bièvre
Adiabatic-Nonadiabatic Transition In The Diffusive Hamiltonian Dynamics Of A Classical Holstein Polaron, Alex A. Silvius, Paul Ernest Parris, Stephan De Bièvre
Physics Faculty Research & Creative Works
We study the Hamiltonian dynamics of a free particle injected onto a chain containing a periodic array of harmonic oscillators in thermal equilibrium. The particle interacts locally with each oscillator, with an interaction that is linear in the oscillator coordinate and independent of the particle's position when it is within a finite interaction range. At long times the particle exhibits diffusive motion, with an ensemble averaged mean-squared displacement that is linear in time. The diffusion constant at high temperatures follows a power law D~T 5/2 for all parameter values studied. At low temperatures particle transport changes to a hopping process …
Unexpected Higher-Order Effects In Charged Particle Impact Ionization At High Energies, M. Foster, Jerry Peacher, Michael Schulz, Don H. Madison, Zhangjin Chen, H. R. J. Walters
Unexpected Higher-Order Effects In Charged Particle Impact Ionization At High Energies, M. Foster, Jerry Peacher, Michael Schulz, Don H. Madison, Zhangjin Chen, H. R. J. Walters
Physics Faculty Research & Creative Works
Most of the experimental and theoretical studies of electron-impact ionization of atoms, referred to as (e, 2e), have concentrated on the scattering plane. The assumption has been that all the important physical effects will be observable in the scattering plane. However, very recently it has been shown that, for C6+-helium ionization, experiment and theory are in nice agreement in the scattering plane and in very bad agreement out of the scattering plane. This lack of agreement between experiment and theory has been explained in terms of higher-order scattering effects between the projectile and target ion. We have examined electron-impact ionization …
Magnetically Mediated Transparent Conductors: In₂O₃ Doped With Mo, Julia E. Medvedeva
Magnetically Mediated Transparent Conductors: In₂O₃ Doped With Mo, Julia E. Medvedeva
Physics Faculty Research & Creative Works
First-principles band structure investigations of the electronic, optical, and magnetic properties of Mo-doped In2O3 reveal the vital role of magnetic interactions in determining both the electrical conductivity and the Burstein-Moss shift which governs optical absorption. We demonstrate the advantages of the transition metal doping which results in smaller effective mass, larger fundamental band gap, and better overall optical transmission in the visible as compared to commercial Sn-doped In2O3. Similar behavior is expected upon doping with other transition metals opening up an avenue for the family of efficient transparent conductors mediated by magnetic interactions.