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2005

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Articles 31 - 60 of 626

Full-Text Articles in Physics

Inclusive Jet Cross Sections And Dijet Correlations In D*± Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini Nov 2005

Inclusive Jet Cross Sections And Dijet Correlations In D*± Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini

Faculty Publications

Inclusive jet cross sections in photoproduction for events containing a D* meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb-1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2, and a photon-proton centre-of-mass energy in the range 130 < Wγp < 280 GeV. The measurements are compared with next-to-leading-order (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) models which incorporate leading-order matrix elements followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where contributions from higher orders are expected to be significant. The MC models give a better description than the NLO predictions of the shape of the measured cross sections. © 2005 Elsevier B.V. All rights reserved.

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Search For BS0→Μ+Μ- And BD0→Μ+Μ- Decays In PΡ̅ Collisions With Cdf Ii, A. Abulencia, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2005

Search For BS0→Μ+Μ- And BD0→Μ+Μ- Decays In PΡ̅ Collisions With Cdf Ii, A. Abulencia, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on a search for Bs0→µ+µ- and Bd0→µ+µ- decays in pρ̅ collisions at √8=1.96 TeV using 364 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the Bs0 or Bd0 mass windows. The resulting upper limits on the branching fractions are Ɓ (Bs0→µ+µ-)<1.5×10-7 and Ɓ (Bd0→µ+µ-)<3.9×10-8 at 90% confidence level.

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Performance Of A C4f8o Gas Radiator Ring Imaging Cherenkov Detector Using Multi-Anode Photomultiplier Tubes, Raymond Mountain, Marina Artuso, Chaouki Boulahouache, S. Blusk Nov 2005

Performance Of A C4f8o Gas Radiator Ring Imaging Cherenkov Detector Using Multi-Anode Photomultiplier Tubes, Raymond Mountain, Marina Artuso, Chaouki Boulahouache, S. Blusk

Physics - All Scholarship

We report on test results of a novel ring imaging Cherenkov (RICH) detection system consisting of a 3 meter long gaseous C4F8O radiator, a focusing mirror, and a photon detector array based on Hamamatsu multi-anode photomultiplier tubes. This system was developed to identify charged particles in the momentum range from 3-70 GeV/c for the BTeV experiment.

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Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery Nov 2005

Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery

Dartmouth Scholarship

We present direct numerical simulations of dynamo action in a forced Roberts flow. The behavior of the dynamo is followed as the mechanical Reynolds number is increased, starting from the laminar case until a turbulent regime is reached. The critical magnetic Reynolds for dynamo action is found, and in the turbulent flow it is observed to be nearly independent on the magnetic Prandtl number in the range from ∼0.3 to ∼0.1. Also the dependence of this threshold with the amount of mechanical helicity in the flow is studied. For the different regimes found, the configuration of the magnetic and velocity …

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Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson Nov 2005

Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson

Physics Faculty Research

Progress is described in experiments to generate coherent terahertz acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation. Future experiments are proposed that would use the superlattice as a transducer in a terahertz cryogenic acoustic reflection microscope with sub-nanometer resolution.

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Nanomesa And Nanowell Formation In Langmuir–Blodgett Polyvinylidene Fluoride Trifluoroethylene Copolymer Films, Jiangyu Li, Yang Luo, Mengjun Bai, Stephen Ducharme Nov 2005

Nanomesa And Nanowell Formation In Langmuir–Blodgett Polyvinylidene Fluoride Trifluoroethylene Copolymer Films, Jiangyu Li, Yang Luo, Mengjun Bai, Stephen Ducharme

Department of Physics and Astronomy: Faculty Publications

In this letter, we report an energetics-based model to explain the self-organizing nanomesa and nanowell patterns recently observed in Langmuir-Blodgett (LB) films of polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] copolymers. The feature size of nanomesas and nanowells has been estimated using a linear stability analysis, and the morphology of the nanomesas and nanowells has been revealed by the numerical simulation, both in good agreement with experiments. A number of other model predictions regarding the nanomesa and nanowell formation also agree with experimental observations. The model can be used to guide the design and optimization of nanostructures in the P(VDF-TrFE) LB films and …

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Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi Nov 2005

Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

A scheme for the generation of a photocurrent in bent quantum wires is proposed. We calculate the current using a generalized Landauer-Büttiker approach that takes into account the electromagnetic radiation. For circularly polarized light, it is demonstrated that the curvature in the bent wire induces an asymmetry in the scattering coefficients for left and right moving electrons. This asymmetry results in a current at zero bias voltage. The effect is due to the geometry of the wire which transforms the photon angular momentum into translational motion for the electrons. Possible experimental realizations of this scheme are discussed.

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Combination Of Cdf And D0 Results On The W Boson Mass And Width, V. M. Abazov, Gregory Snow, D0 Collaboration Nov 2005

Combination Of Cdf And D0 Results On The W Boson Mass And Width, V. M. Abazov, Gregory Snow, D0 Collaboration

Gregory Snow Publications

The results based on 1992–95 data (Run 1) from the CDF and D0 experiments on the measurements of the W boson mass and width are presented, along with the combined results. We report a Tevatron collider average Mw = 80.456 ± 0.059 GeV. We also report the Tevatron collider average of the directly measured W boson width Γw = 2.115 ± 0.105 GeV. We describe a new joint analysis of the direct W mass and width measurements. Assuming the validity of the standard model, we combine the directly measured W boson width with the width extracted from the …

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Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev Nov 2005

Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev

Physics and Astronomy Faculty Patents

A system capable of pumping or mixing fluids using a rotating magnetic element or bearing levitated by a cold superconducting element is disclosed.

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Nonlinear All-Optical Gan/Algan Multi-Quantum-Well Devices For 100 Gb/S Applications At Λ = 1.55 Μm, Greg Sun, Jacob B. Khurgin, Richard A. Soref Nov 2005

Nonlinear All-Optical Gan/Algan Multi-Quantum-Well Devices For 100 Gb/S Applications At Λ = 1.55 Μm, Greg Sun, Jacob B. Khurgin, Richard A. Soref

Physics Faculty Publications

Using quantum-mechanical analysis, a strain-balanced stack of coupled GaN/AlGaNquantum wells has been engineered for bandwidth-optimized all-optical switching at low switching powers. Intersubband transitions between three conduction subbands provide the basis for the large, fast, nonlinear optical response. Optimized performance for a given symbol rate is obtained by engineering the response time and nonlinear phase shift.

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Parametrizations And Dynamical Analysis Of Angle-Integrated Cross Sections For Double Photoionization Including Nondipole Effects, Andrei Y. Istomin, Anthony F. Starace, N. L. Manakov, A. V. Meremianin, A. S. Kheifets, Igor Bray Nov 2005

Parametrizations And Dynamical Analysis Of Angle-Integrated Cross Sections For Double Photoionization Including Nondipole Effects, Andrei Y. Istomin, Anthony F. Starace, N. L. Manakov, A. V. Meremianin, A. S. Kheifets, Igor Bray

Department of Physics and Astronomy: Faculty Publications

Similarly to differential cross sections for one-electron photoionization, the doubly differential cross section for double photoionization (DPI) may be conveniently described by four parameters: the singly differential (with respect to energy sharing) cross section (sigma0), the dipole asymmetry parameter (beta), and two nondipole asymmetry parameters (gamma and delta). Here we derive two model-independent representations for these parameters for DPI from a 1S0 atomic bound state: (i) in terms of one-dimensional integrals of the polarization-invariant DPI amplitudes and (ii) in terms of the exact two-electron reduced matrix elements. For DPI of He at excess energies, Eexc, of 100 eV, 450 eV, …

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Using Ultrasonic Atomization To Produce An Aerosol Of Micron-Scale Particles, Thomas D. Donnelly, J. Hogan '03, A. Mugler '04, M. Schubmehl '02, N. Schommer '04, Andrew J. Bernoff, S. Dasnurkar, T. Ditmire Nov 2005

Using Ultrasonic Atomization To Produce An Aerosol Of Micron-Scale Particles, Thomas D. Donnelly, J. Hogan '03, A. Mugler '04, M. Schubmehl '02, N. Schommer '04, Andrew J. Bernoff, S. Dasnurkar, T. Ditmire

All HMC Faculty Publications and Research

A device that uses ultrasonic atomization of a liquid to produce an aerosol of micron-scale droplets is described. This device represents a new approach to producing targets relevant to laser-driven fusion studies, and to rare studies of nonlinear optics in which wavelength-scale targets are irradiated. The device has also made possible tests of fluid dynamics models in a novel phase space. The distribution of droplet sizes produced by the device and the threshold power required for droplet production are shown to follow scaling laws predicted by fluid dynamics.

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Effects Of Disorder On Electron Transport In Arrays Of Quantum Dots, Alan Middleton, Shantenu Jha Nov 2005

Effects Of Disorder On Electron Transport In Arrays Of Quantum Dots, Alan Middleton, Shantenu Jha

Physics - All Scholarship

We investigate the zero-temperature transport of electrons in a model of quantum dot arrays with a disordered background potential. One effect of the disorder is that conduction through the array is possible only for voltages across the array that exceed a critical voltage $V_T$. We investigate the behavior of arrays in three voltage regimes: below, at and above the critical voltage. For voltages less than $V_T$, we find that the features of the invasion of charge onto the array depend on whether the dots have uniform or varying capacitances. We compute the first conduction path at voltages just above $V_T$ …

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Laser-Powered Thermoelectric Generators Operating At Cryogenic Temperatures, S. R. Harutyunyan, V. H. Vardanyan, A. S. Kuzanyan, V. R. Nikoghosyan, S. Kunii, K. Winzer, K. S. Wood, Armen Gulian Nov 2005

Laser-Powered Thermoelectric Generators Operating At Cryogenic Temperatures, S. R. Harutyunyan, V. H. Vardanyan, A. S. Kuzanyan, V. R. Nikoghosyan, S. Kunii, K. Winzer, K. S. Wood, Armen Gulian

Mathematics, Physics, and Computer Science Faculty Articles and Research

A thermoelectric generator, operating in a cryostat at liquid helium temperatures, is described. Energy to the generator is supplied via an external laser beam. For this prototype device the associated heat load at permanent operation is comparable with the heat load associated with power delivery via metallic wires. Estimates indicate that still better performance can be enabled with existing thermoelectric materials, thereby far exceeding efficiency of traditional cryostat wiring. We used a prototype generator to produce electric power for measuring critical currents in Nb3Sn-films at 4K.

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Observations And Analysis Of Uncorrelated Rain, Michael L. Larsen, Alexander Kostinski, Ali Tokay Nov 2005

Observations And Analysis Of Uncorrelated Rain, Michael L. Larsen, Alexander Kostinski, Ali Tokay

Department of Physics Publications

Most microphysical models in precipitation physics and radar meteorology assume (at least implicitly) that raindrops are completely uncorrelated in space and time. Yet, several recent studies have indicated that raindrop arrivals are often temporally and spatially correlated. Resolution of this conflict must begin with observations of perfectly uncorrelated rainfall, should such “perfectly steady rain” exist at all. Indeed, it does. Using data with high temporal precision from a two-dimensional video disdrometer and the pair-correlation function, a scale-localized statistical tool, several ∼10–20-min rain episodes have been uncovered where no clustering among droplet arrival times is found. This implies that (i) rain …

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Coherence And Polarization Properties Of Far Fields Generated By Quasi-Homogeneous Planar Electromagnetic Sources, Olga Korotkova, Brian G. Hoover, Victor L. Gamiz, Emil Wolf Nov 2005

Coherence And Polarization Properties Of Far Fields Generated By Quasi-Homogeneous Planar Electromagnetic Sources, Olga Korotkova, Brian G. Hoover, Victor L. Gamiz, Emil Wolf

Physics Articles and Papers

In studies of radiation from partially coherent sources the so-called quasi-homogeneous (QH) model sources have been very useful, for instance in elucidating the behavior of fields produced by thermal sources. The analysis of the fields generated by such sources has, however, been largely carried out in the framework of scalar wave theory. In this paper we generalize the concept of the QH source to the domain of the electromagnetic theory, and we derive expressions for the elements of the cross-spectral density matrix, for the spectral density, the spectral degree of coherence, the degree of polarization, and the Stokes parameters of …

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Towards A Precision Measurement Of The Casimir Force In A Cylinder-Plane Geometry, M. Brown-Hayes, D. A.R. Dalvit, F. D. Mazzitelli, W. J. Kim, R. Onofrio Nov 2005

Towards A Precision Measurement Of The Casimir Force In A Cylinder-Plane Geometry, M. Brown-Hayes, D. A.R. Dalvit, F. D. Mazzitelli, W. J. Kim, R. Onofrio

Dartmouth Scholarship

We report on a proposal aimed at measuring the Casimir force in the cylinder-plane configuration. The Casimir force is evaluated including corrections due to finite parallelism, conductivity, and temperature. The range of validity of the proximity force approximation is also discussed. An apparatus to test the feasibility of a precision measurement in this configuration has been developed, and we describe both a procedure to control the parallelism and the results of the electrostatic calibration. Finally we discuss the possibility of measuring the thermal contribution to the Casimir force and deviations from the proximity force approximation, both of which are expected …

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Functional Characterization Of Core Promoter Elements: The Downstream Core Element Is Recognized By Taf1, Dong-Hoon Lee, Naum I. Gershenzon, Malavika Gupta, Ilya P. Ioshikhes, Danny Reinberg, Brian A. Lewis Nov 2005

Functional Characterization Of Core Promoter Elements: The Downstream Core Element Is Recognized By Taf1, Dong-Hoon Lee, Naum I. Gershenzon, Malavika Gupta, Ilya P. Ioshikhes, Danny Reinberg, Brian A. Lewis

Physics Faculty Publications

Downstream elements are a newly appreciated class of core promoter elements of RNA polymerase II-transcribed genes. The downstream core element (DCE) was discovered in the human β-globin promoter, and its sequence composition is distinct from that of the downstream promoter element (DPE). We show here that the DCE is a bona fide core promoter element present in a large number of promoters and with high incidence in promoters containing a TATA motif. Database analysis indicates that the DCE is found in diverse promoters, supporting its functional relevance in a variety of promoter contexts. The DCE consists of …

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Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund Nov 2005

Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund

Physics Faculty Publications

Recent theory has found that native defects such as the O vacancy VO and Zn interstitial ZnI have high formation energies in n-type ZnO and, thus, are not important donors, especially in comparison to impurities such as H. In contrast, we use both theory and experiment to show that, under N ambient, the complex ZnI-NO is a stronger candidate than H or any other known impurity for a 30 meV donor commonly found in bulk ZnO grown from the vapor phase. Since the Zn vacancy is also the dominant acceptor in such material, we must …

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Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof P. Bzymek, Sabina I. Swierczek, Brian Bennett, Richard C. Holz Nov 2005

Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof P. Bzymek, Sabina I. Swierczek, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

Previous kinetic characterization of the glutamate 151 (E151)-substituted forms of the leucine aminopeptidase from Aeromonas proteolytica (Vibrio proteolyticus; AAP) has provided critical evidence that this residue functions as the general acid/base. The close proximity of similar glutamate residues to the bridging water/hydroxide of the dinuclear active sites of metalloenzymes (2.80 and 3.94 Å in carboxypeptidase G2 and 3.30 and 3.63 Å in AAP), suggests it may also be involved in stabilizing the active-site metal ions. Therefore, the structural perturbations of the dinuclear active site of AAP were examined for two E151-substituted forms, namely E151D-AAP and E151A-AAP, by …

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Kinetic Evaluation Of Human Cloned Coproporphyrinogen Oxidase Using A Ring Isomer Of The Natural Substrate, Marjorie A. Jones, Christopher L. Cooper, Timothy D. Lash Nov 2005

Kinetic Evaluation Of Human Cloned Coproporphyrinogen Oxidase Using A Ring Isomer Of The Natural Substrate, Marjorie A. Jones, Christopher L. Cooper, Timothy D. Lash

Faculty Publications – Chemistry

Background: The enzyme coproporphyrinogen oxidase (copro'gen oxidase) converts coproporphyrinogen-Ill (GIII) to protoporphyrinogen-IX via an intermediary monovinyl porphyrinogen. The A ring isomer coproporphyrinogen-IV (C-IV) has previously been shown to be a substrate for copro'gen oxidase derived from avian erythrocytes. In contrast to the authentic substrate (GIII) where only a small amount of the monovinyl intermediate is detected, C-IV gives rise to a monovinyl intermediate that accumulates before being converted to an isomer of protoporphyrinogen-IX. No kinetic studies have been carried out using the purified human copro'gen oxidase to evaluate its ability to process both the authentic substrate as well as analogs. …

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W Production At Large Transverse Momentum At The Large Hadron Collider, Richard J. Gonsalves, Nikolaos Kidonakis, Agustín Sabio Vera Nov 2005

W Production At Large Transverse Momentum At The Large Hadron Collider, Richard J. Gonsalves, Nikolaos Kidonakis, Agustín Sabio Vera

Faculty and Research Publications

We study the production of W bosons at large transverse momentum in pp collisions at the Large Hadron Collider (LHC). We calculate the complete next-to-leading order (NLO) corrections to the differential cross section. We find that the NLO corrections provide a large increase to the cross section but, surprisingly, do not reduce the scale dependence relative to leading order (LO). We also calculate next-to-next-to-leading-order (NNLO) soft-gluon corrections and find that, although they are small, they significantly reduce the scale dependence thus providing a more stable theoretical prediction.

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Intra-Atomic Aspects Of Magnon-Plasmon Interactions, Ralph Skomski, Peter A. Dowben Nov 2005

Intra-Atomic Aspects Of Magnon-Plasmon Interactions, Ralph Skomski, Peter A. Dowben

Peter Dowben Publications

Magnon-plasmon interactions are modeled by considering the spin-dependent dielectric response of atoms placed in crystalline environment. Hund's exchange rules favor parallel spin alignment, but the strength of the exchange depends on the displacement of the centers of gravity of the atomic spin-up and spin-down electron charge clouds. The intra-atomic exchange is modeled by considering a Hubbard-type interaction, and interatomic interaction then yields a k-space dispersion. The eigenmodes of the plasma are a mixture of spin-up and spin-down degrees of freedom, described by a 2×2 interaction matrix. Minority and majority bands yield different plasmon frequencies. However, these modes are not orthogonal …

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Entropic Characterization Of Mixing In Microchannels, Marco Camesasca, Ica Manas Zloczower, Miron Kaufman Nov 2005

Entropic Characterization Of Mixing In Microchannels, Marco Camesasca, Ica Manas Zloczower, Miron Kaufman

Physics Faculty Publications

A methodology for rigorous mixing assessment in microchannels is presented. The analysis is based on numerical simulations of flow in different geometries coupled with mixing assessment using entropic measures. The results show enhanced mixing efficiency for the staggered herringbone micromixer by comparison with a mixer with straight diagonal ridges and a lack of mixing in a non-patterned channel. These results are in agreement with published experimental data.

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Erratum: Publisher's Note: Calculation Of The One- And Two-Loop Lamb Shift For Arbitrary Excited Hydrogenic States (Physical Review Letters (2005) 95 (180404)), Andrzej Czarnecki, Ulrich D. Jentschura, Krzysztof Pachucki Nov 2005

Erratum: Publisher's Note: Calculation Of The One- And Two-Loop Lamb Shift For Arbitrary Excited Hydrogenic States (Physical Review Letters (2005) 95 (180404)), Andrzej Czarnecki, Ulrich D. Jentschura, Krzysztof Pachucki

Physics Faculty Research & Creative Works

No abstract provided.

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Laser-Dressed Vacuum Polarization In A Coulomb Field, A. I. Milstein, Ivan S. Terekhov, Ulrich D. Jentschura, Christoph H. Keitel Nov 2005

Laser-Dressed Vacuum Polarization In A Coulomb Field, A. I. Milstein, Ivan S. Terekhov, Ulrich D. Jentschura, Christoph H. Keitel

Physics Faculty Research & Creative Works

We investigate quantum electrodynamic effects under the influence of an external, time-dependent electromagnetic field, which mediates dynamic modifications of the radiative corrections. Specifically, we consider the quantum electrodynamic vacuum-polarization tensor under the influence of two external background fields: a strong laser field and a nuclear Coulomb field. We calculate the charge and current densities induced by a nuclear Coulomb field in the presence of a laser field. We find the corresponding induced scalar and vector potentials. The induced potential, in first-order perturbation theory, leads to a correction to atomic energy levels. The external laser field breaks the rotational symmetry of …

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Alignment Dynamics Of Slow Light Diffusion In Ultracold Atomic 85Rb, S. Balik, R. G. Olave, C. I. Sukenik, M. D. Havey, V. M. Datsyuk, I. M. Sokolov, D. V. Kupriyanov Nov 2005

Alignment Dynamics Of Slow Light Diffusion In Ultracold Atomic 85Rb, S. Balik, R. G. Olave, C. I. Sukenik, M. D. Havey, V. M. Datsyuk, I. M. Sokolov, D. V. Kupriyanov

Physics Faculty Publications

A combined experimental and theoretical investigation of time- and alignment-dependent propagation of light in an ultracold atomic gas of atomic 85Rb is reported. Coherences among the scattering amplitudes for light scattering off excited hyperfine levels produce strong variations of the light polarization in the vicinity of atomic resonance. Measurements are in excellent agreement with Monte Carlo simulations of the multiple scattering process.

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The Photoelectric Effect In External Eields, Christian Bracher, John B. Delos, Vassiliki Kanellopoulos, Manfred Kleber, Tobias Kramer Nov 2005

The Photoelectric Effect In External Eields, Christian Bracher, John B. Delos, Vassiliki Kanellopoulos, Manfred Kleber, Tobias Kramer

Arts & Sciences Articles

Atoms and negative ions interacting with laser photons yield a coherent source of photoelectrons. Applying external fields to photoelectrons gives rise to interesting and valuable interference phenomena. We analyze the spatial distribution of the photocurrent using elementary quantum methods. The photoelectric effect is shown to be an interesting example for the use of coherent particle sources in quantum mechanics.

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The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof Nov 2005

The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof

Physics and Astronomy Faculty Publications

We have performed a series of calculations designed to reproduce infrared diagnostics used to determine physical conditions in star-forming regions. We self-consistently calculate the thermal and chemical structure of an H II region and photodissociation region (PDR) that are in pressure equilibrium. This differs from previous work, which used separate calculations for each gas phase. Our calculations span a wide range of stellar temperatures, gas densities, and ionization parameters. We describe improvements made to the spectral synthesis code Cloudy that made these calculations possible. These include the addition of a molecular network with ~1000 reactions involving 68 molecular species and …

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Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal Oct 2005

Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal

Faculty Publications

No abstract provided.

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