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Articles 1  30 of 40
FullText Articles in Physical Sciences and Mathematics
Relativistic And Radiative Corrections To The Mollow Spectrum, Jorg Evers, Ulrich D. Jentschura, Christoph H. Keitel
Relativistic And Radiative Corrections To The Mollow Spectrum, Jorg Evers, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
The incoherent inelastic part of the resonance fluorescence spectrum of a laserdriven atom is known as the Mollow spectrum [B. R. Mollow, Phys. Rev. 188, 1969 (1969)]. Starting from this level of description, we discuss theoretical foundations of highprecision spectroscopy using the resonance fluorescence light of strongly laserdriven atoms. Specifically, we evaluate the leading relativistic and radiative corrections to the Mollow spectrum, up to the relative orders of ( Z α )^{2} and α ( Z α )^{2} , respectively, and BlochSiegert shifts as well as stimulated radiative corrections involving offresonant virtual states. Complete results are provided for the hydrogen 1 S  2 ...
Nucleation Rates Of Water And Heavy Water Using Equations Of State, Abdalla Obeidat, JinSong Li, Gerald Wilemski
Nucleation Rates Of Water And Heavy Water Using Equations Of State, Abdalla Obeidat, JinSong Li, Gerald Wilemski
Physics Faculty Research & Creative Works
The original formula of Gibbs for the reversible work of critical nucleus formation is evaluated in three approximate ways for ordinary and heavy water. The least approximate way employs an equation of state to evaluate the pressure difference between the new and old phases. This form of the theory yields a temperature dependence for the nucleation rate close to that observed experimentally. This is a substantial improvement over the most commonly used (and most approximate) form of classical theory.©2004 American Institute of Physics.
TwoLoop Bethe Logarithms For Higher Excited S Levels, Ulrich D. Jentschura
TwoLoop Bethe Logarithms For Higher Excited S Levels, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
Processes mediated by two virtual lowenergy photons contribute quite significantly to the energy of hydrogenic S states. The corresponding level shift is of the order of ( α / π )^{2} ( Z α )^{6} m_{e}c^{2} and may be ascribed to a twoloop generalization of the Bethe logarithm. For 1 S and 2 S states, the correction has recently been evaluated by Pachucki and Jentschura [Phys. Rev. Lett. 91, 113005 (2003)]. Here, we generalize the approach to higher excited S states, which in contrast to the 1 S and 2 S states can decay to P states via the electricdipole ...
Nucleation Near The Spinodal: Limitations Of Mean Field Density Functional Theory, Gerald Wilemski, JinSong Li
Nucleation Near The Spinodal: Limitations Of Mean Field Density Functional Theory, Gerald Wilemski, JinSong Li
Physics Faculty Research & Creative Works
We investigate the diverging size of the critical nucleus near the spinodal using the gradient theory ~GT! of van der Waals and Cahn and Hilliard and mean field density functional theory ~MFDFT!. As is well known, GT predicts that at the spinodal the free energy barrier to nucleation vanishes while the radius of the critical fluctuation diverges. We show numerically that the scaling behavior found by Cahn and Hilliard for these quantities holds quantitatively for both GT and MFDFT. We also show that the excess number of molecules Dg satisfies CahnHilliard scaling near the spinodal and is consistent with the ...
Fully Differential ThreeDimensional Angular Distributions Of Electrons Ionized In IonAtom Collisions, Michael Schulz, R. Moshammer, Daniel Fischer, Ahmad Hasan, N. V. Maydanyuk, J. D. Ullrich
Fully Differential ThreeDimensional Angular Distributions Of Electrons Ionized In IonAtom Collisions, Michael Schulz, R. Moshammer, Daniel Fischer, Ahmad Hasan, N. V. Maydanyuk, J. D. Ullrich
Physics Faculty Research & Creative Works
We compare experimental fully differential threedimensional angular distributions of electrons ionized from He in collision with ionic projectiles covering a broad range of perturbations (0.065 to 4.4). Even at very small perturbations clear signatures of higherorder contributions are observable. At large perturbations, such contributions become even dominant, especially those involving the postcollision interaction between the outgoing projectile and the ionized electron. Our results show that single ionization is not nearly as well understood as was assumed previously.
Nonrelativistic Qed Approach To The BoundElectron G Factor, Krzysztof Pachucki, Ulrich D. Jentschura, Vladimir A. Yerokhin
Nonrelativistic Qed Approach To The BoundElectron G Factor, Krzysztof Pachucki, Ulrich D. Jentschura, Vladimir A. Yerokhin
Physics Faculty Research & Creative Works
Within a systematic approach based on nonrelativistic quantum electrodynamics, we derive the oneloop selfenergy correction of order α ( Z α )^{4} to the boundelectron g factor. In combination with numerical data, this analytic result improves theoretical predictions for the selfenergy correction for carbon and oxygen by an order of magnitude. Basing on oneloop calculations, we obtain the logarithmic twoloop contribution of order α^{2} ( Z α )^{4} ln [ ( Z α )^{ 2} ] and the dominant part of the corresponding constant term. The results obtained improve the accuracy of the theoretical predictions for the 1 S boundelectron g factor and influence the ...
Electronic Structure Properties And Bcs Superconductivity In ßPyrochlore Oxides: Ko_{S}S₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman
Electronic Structure Properties And Bcs Superconductivity In ßPyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman
Physics Faculty Research & Creative Works
We report a firstprinciples densityfunctional calculation of the electronic structure and properties of the recently discovered superconducting βpyrochlore oxide KOs_{2}O_{6}. We find that the electronic structure near the Fermi energy E_{F} is dominated by strongly hybridized Os 5d and O 2p states. A van Hove singularity very close to E_{f} leads to a relatively large density of states at E_{F}, and the Fermi surface exhibits strong nesting along several directions. These features could provide the scattering processes leading to the observed anomalous temperature dependence of the resistivity and to the rather large specificheat mass ...
Electron Loss From 1.4Mev / U U^{4,6,10+} Ions Colliding With Ne, N₂, And Ar Targets, Robert D. Dubois, Antonio C. Santos, Th. Stohlker, F. Bosch, A. BrauningDemian, A. Gumberidze, S. Hagmann, C. Kozhuharov, R. Mann, A. Orsic Muthig, U. Spillman, S. Tachenov, W. Bart, L. Dahl, B. Franzke, J. Glatz, L. Groning, S. Richter, D. Wilms, K. Ullmann, O. Jagutzki
Electron Loss From 1.4Mev / U U4,6,10+ Ions Colliding With Ne, N₂, And Ar Targets, Robert D. Dubois, Antonio C. Santos, Th. Stohlker, F. Bosch, A. BrauningDemian, A. Gumberidze, S. Hagmann, C. Kozhuharov, R. Mann, A. Orsic Muthig, U. Spillman, S. Tachenov, W. Bart, L. Dahl, B. Franzke, J. Glatz, L. Groning, S. Richter, D. Wilms, K. Ullmann, O. Jagutzki
Physics Faculty Research & Creative Works
Absolute, total, single and multipleelectronloss cross sections are measured for 1.4MeV / u U^{4,6,10+} ions colliding with neon and argon atoms and nitrogen molecules. It is found that the cross sections all have the same dependence on the number of electrons lost and that multiplying the cross sections by the initial number of electrons in the 6s, 6p, and 5f shells yields good agreement between the different projectiles. By combining the present data with previous measurements made at the same velocity, it is shown that the scaled cross sections slowly decrease in magnitude for ...
Breakup Of H₂ In Singly Ionizing Collisions With Fast Protons: ChannelSelective LowEnergy Electron Spectra, Christina Dimopoulou, Robert Moshammer, Daniel Fischer, C. Hohr, Alexander Dorn, Pablo Daniel Fainstein, Jose R. Crespo LopezUrrutia, Claus Dieter Schroter, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich
Breakup Of H₂ In Singly Ionizing Collisions With Fast Protons: ChannelSelective LowEnergy Electron Spectra, Christina Dimopoulou, Robert Moshammer, Daniel Fischer, C. Hohr, Alexander Dorn, Pablo Daniel Fainstein, Jose R. Crespo LopezUrrutia, Claus Dieter Schroter, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
The dissociation of H_{2} in singly ionizing collisions with fast protons was analyzed using channelselective lowenergy electron spectra. Dissociative and nondissociative single ionization of H_{2} by 6MeV proton impact was described in a kinematically by determining momentum vectors of electron and H^{+} fragment of H_{2}^{+} target ion, respectively. The electron spectra exhibited role of autoionization of doubly and singly excited states of H_{2}. The doubly and singly excited states of H_{2} involve coupling between electronic and nuclear motion of molecule.
Exotic Versus Conventional Scaling And Universality In A Disordered Bilayer Quantum Heisenberg Antiferromagnet, Rastko Sknepnek, Thomas Vojta, Matthias Vojta
Exotic Versus Conventional Scaling And Universality In A Disordered Bilayer Quantum Heisenberg Antiferromagnet, Rastko Sknepnek, Thomas Vojta, Matthias Vojta
Physics Faculty Research & Creative Works
We present Monte Carlo simulations of a twodimensional bilayer quantum Heisenberg antiferromagnet with random dimer dilution. In contrast with exotic scaling scenarios found in other random quantum systems, the quantum phase transition in this system is characterized by a finitedisorder fixed point with powerlaw scaling. After accounting for corrections to scaling, with a leading irrelevant exponent of ω ≈ 0.48, we find universal critical exponents z = 1.310(6) and ν = 1.16(3). We discuss the consequences of these findings and suggest new experiments.
Broadening Of A Nonequilibrium Phase Transition By Extended Structural Defects, Thomas Vojta
Broadening Of A Nonequilibrium Phase Transition By Extended Structural Defects, Thomas Vojta
Physics Faculty Research & Creative Works
We study the effects of quenched extended impurities on nonequilibrium phase transitions in the directed percolation universality class. We show that these impurities have a dramatic effect: they completely destroy the sharp phase transition by smearing. This is caused by rare strongly coupled spatial regions which can undergo the phase transition independently from the bulk system. We use extremal statistics to determine the stationary state as well as the dynamics in the tail of the smeared transition, and we illustrate the results by computer simulations.
Approximately SelfSimilar Critical Collapse In 2+1 Dimensions, Marco Cavaglia, Gerard Clement, Alessandro Fabbri
Approximately SelfSimilar Critical Collapse In 2+1 Dimensions, Marco Cavaglia, Gerard Clement, Alessandro Fabbri
Physics Faculty Research & Creative Works
Critical collapse of a selfgravitating scalar field in a (2+1)dimensional spacetime with negative cosmological constant seems to be dominated by a continuously selfsimilar solution of the field equations without cosmological constant. However, previous studies of linear perturbations in this background were inconclusive. We extend the continuously selfsimilar solutions to solutions of the field equations with negative cosmological constant, and analyze their linear perturbations. The extended solutions are characterized by a continuous parameter. A suitable choice of this parameter seems to improve the agreement with the numerical results. We also study the dynamics of the apparent horizon in the ...
Hopping Versus Bulk Conductivity In Transparent Oxides: 12cao  7al₂O₃, Julia E. Medvedeva, Arthur J. Freeman
Hopping Versus Bulk Conductivity In Transparent Oxides: 12cao  7al₂O₃, Julia E. Medvedeva, Arthur J. Freeman
Physics Faculty Research & Creative Works
Firstprinciples calculations of the mayenitebased oxide, [Ca_{12}Al_{14}O_{32}]^{2+}(2e), reveal the mechanism responsible for its high conductivity. A detailed comparison of the electronic and optical properties of this material with those of the recently discovered transparent conducting oxide, Hdoped UVactivated Ca_{12}Al_{14}O_{33}, allowed us to conclude that the enhanced conductivity in [Ca_{12}Al_{14}O_{32}]^{2+}(2e) is achieved by elimination of the Coulomb blockade of the charge carriers. This results in a transition from variable rangehopping behavior with a Coulomb gap in Hdoped UVirradiated Ca_{12}Al_{14 ...}
Instantons In Quantum Mechanics And Resurgent Expansions, Ulrich D. Jentschura, Jean ZinnJustin
Instantons In Quantum Mechanics And Resurgent Expansions, Ulrich D. Jentschura, Jean ZinnJustin
Physics Faculty Research & Creative Works
Certain quantum mechanical potentials give rise to a vanishing perturbation series for at least one energy level (which as we here assume is the ground state), but the true groundstate energy is positive. We show here that in a typical case, the eigenvalue may be expressed in terms of a generalized perturbative expansion (resurgent expansion). Modified BohrSommerfeld quantization conditions lead to generalized perturbative expansions which may be expressed in terms of nonanalytic factors of the form exp(a/g), where a>0 is the instanton action, and power series in the coupling g, as well as logarithmic factors. The groundstate ...
Test Of The Pluvinage Wave Function For The Helium Ground State, S. Jones, Joseph H. Macek, Don H. Madison
Test Of The Pluvinage Wave Function For The Helium Ground State, S. Jones, Joseph H. Macek, Don H. Madison
Physics Faculty Research & Creative Works
The accuracy of the Pluvinage wave function for the ground state of helium is investigated by considering a number of different physical processes including double ionization by photoabsorption, Compton scattering, and electron impact. In the highenergy limit of these processes, the accuracy of the initial ground state can be ascertained without reference to the final doublecontinuum state. In this limit, we find that a Hylleraas description is superior to the Pluvinage one. For intermediate energies, finalstate correlation becomes important, so we employ a 3C description of the final state (the 3C wave function is the doublecontinuum analog of the Pluvinage ...
Erratum: Test Of The Pluvinage Wave Function For The Helium Ground State (Physical Review A  Atomic, Molecular, And Optical Physics (2004) 70 (012712)), Darryl B. Jones, Joseph H. Macek, Don H. Madison
Erratum: Test Of The Pluvinage Wave Function For The Helium Ground State (Physical Review A  Atomic, Molecular, And Optical Physics (2004) 70 (012712)), Darryl B. Jones, Joseph H. Macek, Don H. Madison
Physics Faculty Research & Creative Works
No abstract provided.
Charge Transfer In Slow Collisions Of O⁸⁺ And Ar⁸⁺ Ions With H(1s) Below 2 Kev/Amu, TeckGhee Lee, M. Hesse, AnhThu Le, C. D. Lin
Charge Transfer In Slow Collisions Of O⁸⁺ And Ar⁸⁺ Ions With H(1s) Below 2 Kev/Amu, TeckGhee Lee, M. Hesse, AnhThu Le, C. D. Lin
Physics Faculty Research & Creative Works
We calculated the chargetransfer cross sections for O⁸⁺ + H collisions for energies from 1eV/amu to 2keV/amu, using the recently developed hyperspherical closecoupling method. In particular, the discrepancy for electron capture to the n = 6 states of O⁷⁺ from the previous theoretical calculations is further analyzed. Our results indicate that at low energies (below 100eV∕amu) electron capture to the n=6 manifold of O7+ becomes dominant. The present results are used to resolve the longstanding discrepancies from the different elaborate semiclassical calculations near 100eV/amu. We have also performed the semiclassical atomic orbital closecoupling calculations with straightline trajectories ...
Electronic Structure And LightInduced Conductivity Of A Transparent Refractory Oxide, Julia E. Medvedeva, Arthur J. Freeman, Mariana I. Bertoni, Thomas O. Mason
Electronic Structure And LightInduced Conductivity Of A Transparent Refractory Oxide, Julia E. Medvedeva, Arthur J. Freeman, Mariana I. Bertoni, Thomas O. Mason
Physics Faculty Research & Creative Works
Combined firstprinciples and experimental investigations reveal the underlying mechanism responsible for a drastic change of the conductivity (by 10 orders of magnitude) following hydrogen annealing and UV irradiation in a transparent oxide, 12CaO · 7Al_{2}O_{3}, found by Hayashi et al. [Nature (London) 419, 462 (2002).] The charge transport associated with photoexcitation of an electron from H^{} occurs by electron hopping.We identify the atoms participating in the hops, determine the exact paths for the carrier migration, estimate the temperature behavior of the hopping transport, and predict a way to enhance the conductivity by specific doping.
Comparison Of Hyperspherical Versus CommonReactionCoordinate CloseCoupling Methods For IonAtom Collisions At Low Energies, AnhThu Le, C. D. Lin, L. F. Errea, L. Mendez, A. Riera, B. Pons
Comparison Of Hyperspherical Versus CommonReactionCoordinate CloseCoupling Methods For IonAtom Collisions At Low Energies, AnhThu Le, C. D. Lin, L. F. Errea, L. Mendez, A. Riera, B. Pons
Physics Faculty Research & Creative Works
We present detailed comparisons between the two quantal approacheshyperspherical closecoupling and commonreactioncoordinate closecoupling methodson an exemplary case of He²⁺ + H(1s) collisions at centerofmass energy from 20eV up to 1.6keV. It is shown that the partialwave chargetransfer cross sections from the two approaches agree very well at low energy below 200eV down to 30eV. This good agreement is a strong indication of the validity of both methods. The small difference at very low energies and the convergence with respect to the number of channels in both approaches at higher energies are also discussed.
New Limits On The Drift Of Fundamental Constants From Laboratory Measurements, Marc P. Fischer, Nikolai N. Kolachevsky, Marcus Zimmermann, Ronald Holzwarth, Th H. Udem, Theodor Wolfgang Hansch, Michel Abgrall, Jan Grunert, Ivan Maksimovic, Sebastien Bize, Harold Marion, Franck Pereira M Dos Santos, Pierre Lemonde, Giorgio Santarelli, Ph Laurent, Andre Clairon, Christophe Salomon, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel
New Limits On The Drift Of Fundamental Constants From Laboratory Measurements, Marc P. Fischer, Nikolai N. Kolachevsky, Marcus Zimmermann, Ronald Holzwarth, Th H. Udem, Theodor Wolfgang Hansch, Michel Abgrall, Jan Grunert, Ivan Maksimovic, Sebastien Bize, Harold Marion, Franck Pereira M Dos Santos, Pierre Lemonde, Giorgio Santarelli, Ph Laurent, Andre Clairon, Christophe Salomon, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
We have remeasured the absolute 1S2S transition frequency ν_{H} in atomic hydrogen. A comparison with the result of the previous measurement performed in 1999 sets a limit of (29 ± 57) Hz for the drift of ν_{H} with respect to the ground state hyperfine splitting ν_{Cs} in ^{133}Cs. Combining this result with the recently published optical transition frequency in ^{199}Hg^{+} against ν_{Cs} and a microwave ^{87}Rb and ^{133}Cs clock comparison, we deduce separate limits on α˙ / α = (0.9 &plusm; 2.9) x 10^{15} yr^{1} and the fractional time variation of the ...
Electron SelfEnergy For Higher Excited S Levels, Ulrich D. Jentschura, Peter J. Mohr
Electron SelfEnergy For Higher Excited S Levels, Ulrich D. Jentschura, Peter J. Mohr
Physics Faculty Research & Creative Works
A nonperturbative numerical evaluation of the onephoton electron selfenergy for the 3S and 4S states with charge numbers Z=1 to 5 is described. The numerical results are in agreement with known terms in the expansion of the selfenergy in powers of Zα.
CloseCoupling And DistortedWave Calculations For ElectronImpact Excitation Of The (5p⁵6p) States Of Xenon, K. Bartschat, Anand Dasgupta, Don H. Madison
CloseCoupling And DistortedWave Calculations For ElectronImpact Excitation Of The (5p⁵6p) States Of Xenon, K. Bartschat, Anand Dasgupta, Don H. Madison
Physics Faculty Research & Creative Works
We report on a series of calculations for electronimpact excitation of the (5p56p) states in xenon from the ground state (5p6)1S0 . As in previous calculations for other noblegas targets, we find strong evidence of channel coupling for all incident energies considered (between threshold and 200 eV ). Although qualitative agreement with the experimental results of Fons and Lin [Phys. Rev. A 58, 4603 (1998)] is achieved, severe quantitative discrepancies of sometimes more than a factor of 2 remain.
Gravitational Energy Loss In High Energy Particle Collisions: Ultrarelativistic Plunge Into A Multidimensional Black Hole, Emanuele Berti, Marco Cavaglia, Leonardo Gualtieri
Gravitational Energy Loss In High Energy Particle Collisions: Ultrarelativistic Plunge Into A Multidimensional Black Hole, Emanuele Berti, Marco Cavaglia, Leonardo Gualtieri
Physics Faculty Research & Creative Works
We investigate the gravitational energy emission of an ultrarelativistic particle radially falling into a Ddimensional black hole. We numerically integrate the equations describing black hole gravitational perturbations and obtain the energy spectra, total energy, and angular distribution of the emitted gravitational radiation. The black hole quasinormal modes for scalar, vector, and tensor perturbations are computed in the WKB approximation. We discuss our results in the context of black hole production at the TeV scale.
SelfEnergy Correction To The TwoPhoton Decay Width In Hydrogenlike Atoms, Ulrich D. Jentschura
SelfEnergy Correction To The TwoPhoton Decay Width In Hydrogenlike Atoms, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We investigate the guage invariance of the leading logarithmic radiative correction to the twophoton decay width in hydrogenlike atoms, was investigated. The effective treatment of the correction using a Lambshift led to the equivalent results in both the length and velocity gages. The relevant radiative corrections were found to be related to the energies that entered into the propagator denominators, to the Hamiltonian, to the wave functions, and to the energy conservation condition, that holds between two photons. The results show that the dominant radiative correction to the 2S twophoton decay width is about 2.020 536(α/π)(Zα ...
Protonium Formation In The P̅H Collision At Low Energies By A Diabatic Approach, M. Hesse, AnhThu Le, C. D. Lin
Protonium Formation In The P̅H Collision At Low Energies By A Diabatic Approach, M. Hesse, AnhThu Le, C. D. Lin
Physics Faculty Research & Creative Works
We present a diabatization technique in combination with the recently developed hyperspherical close coupling (HSCC) method. In contrast to the strict diabatization, our simple diabatization procedure transforms only sharp avoided crossings in the adiabatic hyperspherical potential curves into real crossings. With this approach, the weak collision channels can be removed from the closecoupling calculations. This method is used to study the antiprotonhydrogen collision at low energies. In the case of a scaled down (anti)proton mass, we show that a 10channel calculation is enough to obtain converged cross sections at low energies. The results also indicate that protonium formation occurs ...
Comment On "Role Of The Ground State In ElectronAtom Double Ionization" [1] (Multiple Letters), Jamal Berakdar, Stephenie J. Jones, Don H. Madison
Comment On "Role Of The Ground State In ElectronAtom Double Ionization" [1] (Multiple Letters), Jamal Berakdar, Stephenie J. Jones, Don H. Madison
Physics Faculty Research & Creative Works
No abstract provided.
Scaling Laws For Single And Multiple Electron Loss From Projectiles In Collisions With A ManyElectron Target, Antonio C. Santos, Robert D. Dubois
Scaling Laws For Single And Multiple Electron Loss From Projectiles In Collisions With A ManyElectron Target, Antonio C. Santos, Robert D. Dubois
Physics Faculty Research & Creative Works
Using measured cross sections, empirical scaling laws are extracted for projectile stripping induced by collisions with a manyelectron target. by scaling both the cross sections and the impact velocities, it is shown that a single universal curve can be used to fit data for single and multiple electron loss from negative ions, neutral particles, and singly or multiply charged positive ions. The scaling applies to projectiles ranging from hydrogen to uranium and collision energies ranging from below keV∕u to hundreds of MeV∕u . At high energies, existing data are consistent with a v−1 impact velocity dependence for scaled ...
Doubly Differential Multiple Ionization Of Krypton By Positron And Electron Impact, Kay Dubois, Antonio C. Santos, Ahmad Hasan
Doubly Differential Multiple Ionization Of Krypton By Positron And Electron Impact, Kay Dubois, Antonio C. Santos, Ahmad Hasan
Physics Faculty Research & Creative Works
Measurements of doubly differential single and multiple ionization of krypton atoms have been performed for 750 eV positron and electron impact. Data were measured as a function of projectile energyloss and scattering angle. For electrons, the energyloss range was 085% of the initial projectile energy and scattering angles were between ±22°. Following the procedure adopted previously for argon, the electron impact data were placed on an absolute scale by normalizing to total ionization cross sections available in the literature. The present results for krypton show differences between positron and electron impact that are less pronounced than was found for argon ...
OrderParameter Symmetry And ModeCoupling Effects At Dirty Superconducting Quantum Phase Transitions, Rastko Sknepnek, Thomas Vojta, Rajesh Narayanan
OrderParameter Symmetry And ModeCoupling Effects At Dirty Superconducting Quantum Phase Transitions, Rastko Sknepnek, Thomas Vojta, Rajesh Narayanan
Physics Faculty Research & Creative Works
We derive an orderparameter field theory for a quantum phase transition between a disordered metal and an exotic (non s wave) superconductor. Mode coupling effects between the order parameter and other fermionic soft modes lead to an effective longrange interaction between the anomalous density fluctuations which is reflected in singularities in the free energy functional. However, this longrange interaction is not strong enough to suppress disorder fluctuations. The asymptotic critical region is characterized by runaway flow to large disorder. For weak coupling, this asymptotic region is very narrow. It is preempted by a wide crossover regime with meanfield critical behavior ...
Ultraviolet Photonic Crystal Laser, Alexey Yamilov, Hui Cao, Robert P. H. Chang, Xiaohua Wu, Xang Liu, Shuyou Li, Vinayak P. Dravid
Ultraviolet Photonic Crystal Laser, Alexey Yamilov, Hui Cao, Robert P. H. Chang, Xiaohua Wu, Xang Liu, Shuyou Li, Vinayak P. Dravid
Physics Faculty Research & Creative Works
We fabricated twodimensional photonic crystal structures in zinc oxide films with focusedionbeam etching. Lasing is realized in the nearultraviolet frequency at room temperature under optical pumping. From the measurement of lasing frequency and spatial profile of the lasing modes, as well as the photonic band structure calculation, we conclude that lasing occurs in the strongly localized defect modes near the edges of photonic band gap. These defect modes originate from the structure disorder unintentionally introduced during the fabrication process. ©2004 American Institute of Physics