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University of Nebraska - Lincoln

2005

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Articles 1 - 30 of 143

Full-Text Articles in Physics

Magnetic And Spectroscopic Characteristics Of Znmno System, Aswini K. Pradhan, D. Hunter, Kai Zhang, J.B. Dadson, S. Mohanty, T.M. Williams, K. Lord, R.R. Rakimhov, U.N. Roy, Y. Cui, A. Burger, Jun Zhang, David J. Sellmyer Dec 2005

Magnetic And Spectroscopic Characteristics Of Znmno System, Aswini K. Pradhan, D. Hunter, Kai Zhang, J.B. Dadson, S. Mohanty, T.M. Williams, K. Lord, R.R. Rakimhov, U.N. Roy, Y. Cui, A. Burger, Jun Zhang, David J. Sellmyer

David Sellmyer Publications

We report on the observation of room-temperature ferromagnetism in epitaxial (Zn,Mn)O films grown by a pulsed-laser deposition technique using high-density targets. The X-ray, microscopic, spectroscopic and magnetic properties of target material containing 6 at.% of Mn and films were compared. The target shows the presence of large clusters exhibiting paramagnetic behavior. However, ferromagnetic properties were observed in (Zn,Mn)O films grown at a substrate temperature of 500 °C and with an oxygen partial pressure of 1 mTorr. Although, crystalline quality of the film improves with increasing substrate temperature, the ferromagnetism becomes weaker.


Rescattering Effects In The Multiphoton Regime, M. V. Frolov, A. V. Flegel, N. L. Manakov, Anthony F. Starace Dec 2005

Rescattering Effects In The Multiphoton Regime, M. V. Frolov, A. V. Flegel, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

LETTER TO THE EDITOR

The plateau features that characterize the low-frequency spectra of fundamental strong-field processes such as harmonic generation, above-threshold ionization and laser-assisted electron-atom scattering are shown to exist also for photon energies Eγ of the order of the energy |E0| of a bound electron. The existence of these rescattering effects in such a high-frequency (and thus nontunnelling) regime is supported by accurate quantum analyses of intense Ti-Sapphire laser interactions with halogen negative ions, for which Eγ ≈ 0.5|E0|.


Focused-Laser Interferometric Position Sensor, Stephen J. Friedman, Brett E. Barwick, Herman Batelaan Dec 2005

Focused-Laser Interferometric Position Sensor, Stephen J. Friedman, Brett E. Barwick, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

We describe a simple method to measure the position shifts of an object with a range of tens of micrometers using a focused-laser (FL) interferometric position sensor. In this article we examine the effects of mechanical vibration on FL and Michelson interferometers. We tested both interferometers using vibration amplitudes ranging from 0 to 20 μm. Our FL interferometer has a resolution much better than the diffraction grating periodicities of 10 and 14 μm used in our experiments. A FL interferometer provides improved mechanical stability at the expense of spatial resolution. Our experimental results show that Michelson interferometers cannot be used ...


Ferroelectric Polymer Langmuir–Blodgett Films For Nonvolatile Memory Applications, Stephen Ducharme, Timothy J. Reece, Christina M. Othon, R. K. Rannow Dec 2005

Ferroelectric Polymer Langmuir–Blodgett Films For Nonvolatile Memory Applications, Stephen Ducharme, Timothy J. Reece, Christina M. Othon, R. K. Rannow

Faculty Publications, Department of Physics and Astronomy

We review the potential for integrating ferroelectric polymer Langmuir–Blodgett (LB) films with semiconductor technology to produce nonvolatile ferroelectric random-access memory (NV-FRAM or NV-FeRAM) and data-storage devices. The prototype material is a copolymer consisting of 70% vinylidene fluoride (VDF) and 30% trifluoroethylene (TrFE), or P(VDF-TrFE 70:30). Recent work with LB films and more conventional solventformed films shows that the VDF copolymers are promising materials for nonvolatile memory applications. The prototype device is themetal–ferroelectric–insulator–semiconductor (MFIS) capacitance memory. Field-effect transistor (FET)-based devices are also discussed. The LB films afford devices with low-voltage operation, but there are ...


Reversible Hysteresis Loop Tuning, Andreas Berger, Christian Binek, D. T. Margulies, A. Moser, E. E. Fullerton Nov 2005

Reversible Hysteresis Loop Tuning, Andreas Berger, Christian Binek, D. T. Margulies, A. Moser, E. E. Fullerton

Christian Binek Publications

We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching fi eld distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The nonoverlapping switching fi eld distribution allows the measurement of magnetization reversal in the SL at low fi elds while keeping the magnetization state of the HL unperturbed. Applying an appropriate high fi eld or high fi eld sequence changes the ...


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

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

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.


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

Faculty Publications, Department of Physics and Astronomy

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 ...


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 ...


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

Faculty Publications, Department of Physics and Astronomy

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 ...


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 ...


Magnetization Reversal Of Fe Films On Ag Submicrometer Pyramidal Islands, Chin-Chung Yu, Yeong-Der Yao, Sy_Hwang Liou Oct 2005

Magnetization Reversal Of Fe Films On Ag Submicrometer Pyramidal Islands, Chin-Chung Yu, Yeong-Der Yao, Sy_Hwang Liou

Si-Hwang Liou Publications

Ag submicrometer pyramidal islands with a (100) truncated top and four (111) sidewalls were successfully fabricated on Si(100) substrates at a deposition temperature of 500/spl deg/C. The magnetization reversal of 30 nm thick Fe films grown on Ag pyramidal islands was studied by magnetic force microscopy. The magnetization reversal of Fe films was first started at the sidewalls of pyramidal islands. Then, the formation and propagation of wall-like structures were observed under a higher external magnetic field, namely 95 Oe. The magnetic domain images indicated that the Fe films grown on the sidewalls of pyramidal islands and ...


Metal Hybridization And Electronic Structure Of Tris(8-Hydroxyquinolato)Aluminum (Alq3), Anthony N. Caruso, D. L. Schulz, Peter A. Dowben Sep 2005

Metal Hybridization And Electronic Structure Of Tris(8-Hydroxyquinolato)Aluminum (Alq3), Anthony N. Caruso, D. L. Schulz, Peter A. Dowben

Peter Dowben Publications

The metal-organic complex Tris(8-hydroxyquinolato)aluminum (Alq3) has been studied by energy and light polarization dependent photoemission. Resonant photoemission was used to identify the molecular orbitals involved in metal chelation. When adsorbed on cobalt and gold surfaces, marked differences in the Alq3 metal-to-ligand bonds were observed. The results indicate intramolecular aluminum-to-ligand bonding through the oxygen heteroatom when Alq3 is adsorbed on gold, but through the nitrogen heteroatom when on cobalt. These results indicate that substrate interfacial complex formation plays an important role in the Alq3 molecular configuration and intramolecular bonding.


Search For New Physics Using High-Mass Tau Pairs From 1.96 Tev Pp̅ Collisions, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Sep 2005

Search For New Physics Using High-Mass Tau Pairs From 1.96 Tev Pp̅ Collisions, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present the results of a search for anomalous resonant production of tau lepton pairs with large invariant mass, the first such search using the CDF II Detector in Run II of the Tevatron pp̅ collider. Such anomalous production could arise from various new physics processes. In a data sample corresponding to 195 pb-1 of integrated luminosity we predict 2.8±0.5 events from standard model background processes and observe 4. We use this result to set limits on the production of heavy scalar and vector particles decaying to tau lepton pairs.


Creation Of Optical Vortices In Femtosecond Pulses, I. G. Mariyenko, James Strohaber, Cornelis J. Uiterwaal Sep 2005

Creation Of Optical Vortices In Femtosecond Pulses, I. G. Mariyenko, James Strohaber, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We experimentally created a femtosecond optical vortex using a pair of computer-synthesized holographic gratings arranged in a 2f - 2f optical setup. We present measurements showing that the resulting donut mode is free of spatial chirp, and support this finding with an analysis of the optical wave propagation through our system based on the Kirchhoff- Fresnel diffraction integral. An interferogram confirms that our ultrashort vortex has topological charge 1, and a conservative experimental estimation of its duration is 280 fs. We used 25-fs radiation pulses (bandwidth approximately 40 nm) produced by a Ti:sapphire laser oscillator.


Circular Dichroism In Classical Coulomb Scattering Involving Bremsstrahlung, A. A. Krylovetsky, N. L. Manakov, S. I. Marmo, Anthony F. Starace Sep 2005

Circular Dichroism In Classical Coulomb Scattering Involving Bremsstrahlung, A. A. Krylovetsky, N. L. Manakov, S. I. Marmo, Anthony F. Starace

Faculty Publications, Department of Physics and Astronomy

Classical orbit derivations of the triply differential cross section for electron bremsstrahlung (BrS) in a Coulomb field are presented; the classical origin of the circular dichroism effect in the electron scattering angular distributions is established for both spontaneous and laser-stimulated BrS.


The Coadsorption And Interaction Of Molecular Icosahedra With Mercury, C.C. Ilie, Snjezana Balaz, Luis G. Rosa, Jun Zhang, P. Lunca-Popa, C. Bianchetti, R. Tittsworth, Jennifer I. Brand, B. Doudon, Peter A. Dowben Sep 2005

The Coadsorption And Interaction Of Molecular Icosahedra With Mercury, C.C. Ilie, Snjezana Balaz, Luis G. Rosa, Jun Zhang, P. Lunca-Popa, C. Bianchetti, R. Tittsworth, Jennifer I. Brand, B. Doudon, Peter A. Dowben

Peter Dowben Publications

We have investigated the changes in the electronic structure of molecularly adsorbed orthocarborane films, as a function of Hg co-adsorption, using photo emission. The interaction between Hg and molecular orthocarborane is weak and results in the formation of some small aggregates of Hg. This behavior is very different from alkali metals interaction with molecular carborane films and the interaction of Hg with semiconducting boron carbide films. Hg doping of semiconducting boron carbide may decrease the activation barrier for intrinsic carrier mobility, but does not significantly increase the number of carriers.


Measurement Of Ɓ(T→Wb)/ Ɓ(T→Wb) At The Collider Detector At Fermilab, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Sep 2005

Measurement Of Ɓ(T→Wb)/ Ɓ(T→Wb) At The Collider Detector At Fermilab, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the ratio of top-quark branching fractions R=Ɓ (t→Wb)/ Ɓ(t→Wq), where q can be a b, s, or a d quark, using lepton-plus-jets and dilepton data sets with an integrated luminosity of ~162 pb-1 collected with the Collider Detector at Fermilab during Run II of the Tevatron. The measurement is derived from the relative numbers of t t̅ events with different multiplicity of identified secondary vertices. We set a lower limit of R>0.61 at 95% confidence level.


Simultaneous Elastic And Electromechanical Imaging By Scanning Probe Microscopy: Theory And Applications To Ferroelectric And Biological Materials, J. Shin, B. J. Rodriguez, Arthur P. Baddorf, T. Thundat, E. Karapetian, M. Kachanov, Alexei Gruverman, Sergei V. Kalinin Sep 2005

Simultaneous Elastic And Electromechanical Imaging By Scanning Probe Microscopy: Theory And Applications To Ferroelectric And Biological Materials, J. Shin, B. J. Rodriguez, Arthur P. Baddorf, T. Thundat, E. Karapetian, M. Kachanov, Alexei Gruverman, Sergei V. Kalinin

Alexei Gruverman Publications

An approach for combined imaging of elastic and electromechanical properties of materials, referred to as piezoacoustic scanning probe microscopy (PA-SPM), is presented. Applicability of this technique for elastic and electromechanical imaging with nanoscale resolution in such dissimilar materials as ferroelectrics and biological tissues is demonstrated. The PA-SPM signal formation is analyzed based on the theory of nanoelectromechanics of piezoelectric indentation and signal sensitivity to materials properties and imaging conditions. It is shown that simultaneous measurements of local indentation stiffness and indentation piezocoefficient provide the most complete description of the local electroelastic properties for transversally isotropic materials, thus making piezoacoustic SPM ...


Direct Studies Of Domain Switching Dynamics In Thin Film Ferroelectric Capacitors, Alexei Gruverman, B. J. Rodriguez, C. Dehoff, J. D. Waldrep, A. I. Kingon, R. J. Nemanich, J. S. Cross Aug 2005

Direct Studies Of Domain Switching Dynamics In Thin Film Ferroelectric Capacitors, Alexei Gruverman, B. J. Rodriguez, C. Dehoff, J. D. Waldrep, A. I. Kingon, R. J. Nemanich, J. S. Cross

Alexei Gruverman Publications

An experimental approach for direct studies of the polarization reversal mechanism in thin film ferroelectric capacitors based on piezoresponse force microscopy (PFM) in conjunction with pulse switching capabilities is presented. Instant domain configurations developing in a 3x3 μm2 capacitor at different stages of the polarization reversal process have been registered using step-by-step switching and subsequent PFM imaging. The developed approach allows direct comparison of experimentally measured microscopic switching behavior with parameters used by phenomenological switching models. It has been found that in the low field regime (just above the threshold value) used in the present study, the mechanism of ...


Pyroelectric Study Of Polarization Switching In Langmuir-Blodgett Films Of Poly(Vinylidene Fluoride Trifluoroethylene), A.V. Sorokin, V.M. Fridkin, Stephen Ducharme Aug 2005

Pyroelectric Study Of Polarization Switching In Langmuir-Blodgett Films Of Poly(Vinylidene Fluoride Trifluoroethylene), A.V. Sorokin, V.M. Fridkin, Stephen Ducharme

Stephen Ducharme Publications

The ferroelectric switching in Langmuir-Blodgett films of poly (vinylidene fluoride trifluoroethylene) is studied. The films have a distribution of switching times several decades wide. Nearly a half of the film volume may be switched faster than 1 ms, though complete switching of a whole sample may require 100 s or more. The switching occurs through a domain nucleation and growth mechanism. The decay of polarization at zero bias is logarithmic in time, with a constant rate below 5% per decade at room temperatures. The coercive voltage may be as low as 5 V, which makes the films promising for use ...


Search For Long-Lived Doubly Charged Higgs Bosons In Pp̅ Collisions At √2=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Aug 2005

Search For Long-Lived Doubly Charged Higgs Bosons In Pp̅ Collisions At √2=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a search for long-lived doubly charged Higgs bosons (H±±), with signatures of high ionization energy loss and muonlike penetration. We use 292 pb-1 of data collected in pp̅ collisions at √2=1.96 TeV by the CDF II detector at the Fermilab Tevatron. Observing no evidence of long-lived doubly charged particle production, we exclude HL±± and HR±± bosons with masses below 133 GeV/c2 and 109 GeV/c2, respectively. In the degenerate case we exclude H±± mass below 146 GeV/c2. All limits are quoted at the 95% confidence level.


Measurement Of The T T̅ Production Cross Section In P P̅ Collisions At Sqrt(S)=1.96 Tev Using Lepton Plus Jets Events With Semileptonic B Decays To Muons, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Aug 2005

Measurement Of The T T̅ Production Cross Section In P P̅ Collisions At Sqrt(S)=1.96 Tev Using Lepton Plus Jets Events With Semileptonic B Decays To Muons, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the t[overline t] production cross section using 194 pb-1 of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% t→Wb branching fraction. Events consistent with tt̅ decay are found by identifying jets containing heavy-flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of 9.5±1.1 events, we measure a production cross section of 5.3±3.3-1.0+1 ...


Temperature Dependence Of The Training Effect In A Co/Coo Exchange-Bias Layer, Christian Binek, Xi He, Srinivas Polisetty Aug 2005

Temperature Dependence Of The Training Effect In A Co/Coo Exchange-Bias Layer, Christian Binek, Xi He, Srinivas Polisetty

Faculty Publications, Department of Physics and Astronomy

The temperature dependence of the training effect is studied in a Co/CoO exchange-bias bilayer and a phenomenological theory is presented. After field cooling the sample to below its blocking temperature, the absolute value of the exchange-bias field decreases when cycling the heterostructure through consecutive hysteresis loops. This decrease is known as the training effect and is studied in the temperature range 5 < =T < =120 K. An implicit sequence, which has been recently derived using the Landau-Khalatnikov approach of relaxation, fits the respective data set for each individual temperature. The underlying discretized dynamic equation involves an expansion of the free energy in powers of the interface magnetization of the antiferromagnetic pinning layer. The particular structure of the free energy with a leading fourth-order term is derived in a mean-field approach. The explicit temperature dependence of the leading expansion coefficient explains the temperature dependence of the training effect. The analytic approach is confirmed by the result of a best fit, which condenses the data from more than 50 measured hysteresis loops.


Thomson Scattering And Ponderomotive Intermodulation Within Standing Laser Beat Waves In Plasma, Scott Sepke, Y.Y. Lau, James Paul Holloway, Donald P. Umstadter Aug 2005

Thomson Scattering And Ponderomotive Intermodulation Within Standing Laser Beat Waves In Plasma, Scott Sepke, Y.Y. Lau, James Paul Holloway, Donald P. Umstadter

Donald Umstadter Publications

Electrons in a standing electromagnetic wave—an optical lattice—tend to oscillate due to the quiver and ponderomotive potentials. For sufficiently intense laser fields (lλ2≤5×1017 W cm-2 µm2) and in plasmas with sufficiently low electron densities (n≤1018 cm-3), these oscillations can occur faster than the plasma can respond. This paper shows that these oscillations result in Thomson scattering of light at both the laser and ponderomotive bounce frequencies and their harmonics as well as at mixtures of these frequencies. We term this mixing ponderomotive intermodulation. Here, the case of counterpropagating ...


Manifestation Of A Ferroelectric Phase Transition, A. R. Geivandov, S.G. Yudin, V.M. Fridkin, Stephen Ducharme Aug 2005

Manifestation Of A Ferroelectric Phase Transition, A. R. Geivandov, S.G. Yudin, V.M. Fridkin, Stephen Ducharme

Stephen Ducharme Publications

Temperature dependences of the dielectric properties of ultrathin polyvinylidene fluoride films prepared using the Langmuir-Blodgett method were studied by linear and nonlinear dielectric spectroscopy. It is shown that ultrathin Langmuir films of polyvinylidene fluoride exhibit a manifestation of a first-order ferroelectric phase transition, which can be assigned to the interaction between the spontaneous polarization and the surfaces bounding the film. As the film thickness increases, the effect of the surfaces decreases and the ferroelectric phase transition shifts to high temperatures to vanish altogether when the temperature region of the transition rises above the melting point.


Photometry Of Type Ii Cepheids. Iii. The Intermediate-Period Stars, Edward G. Schmidt, Dale Johnston, Shawn Langan, Kevin M. Lee Aug 2005

Photometry Of Type Ii Cepheids. Iii. The Intermediate-Period Stars, Edward G. Schmidt, Dale Johnston, Shawn Langan, Kevin M. Lee

Faculty Publications, Department of Physics and Astronomy

We present 741 new photometric observations for 22 Cepheids with periods between 3 and 8 days. Many of the stars are probable type II Cepheids, but we have included some type I Cepheids for comparison. The shapes and stability of the shapes of the light curves, the stability of the periods, and the scatter of individual data points are discussed. Although none of these proves to be a reliable discriminator between type I and type II Cepheids, they do permit the identification of several unusual stars.


Geometry And Magnetism Of L10 Nanostructures, Kory D. Sorge, Ralph Skomski, Maria Daniil, Steven A. Michalski, L. Gao, Jian Zhou, M. Yan, Yucheng Sui, Roger D. Kirby, Sy_Hwang Liou, David J. Sellmyer Aug 2005

Geometry And Magnetism Of L10 Nanostructures, Kory D. Sorge, Ralph Skomski, Maria Daniil, Steven A. Michalski, L. Gao, Jian Zhou, M. Yan, Yucheng Sui, Roger D. Kirby, Sy_Hwang Liou, David J. Sellmyer

Roger Kirby Publications

The fabrication and magnetism of L10 nanostructures with different shapes (such as nanoparticles and nanotubes) is investigated. These nanostructures are produced by hydrogen processing and focused ion beam milling. The structures exhibit interesting reversal modes and are of present or potential interest for sensors and imaging, as well as magnetic recording.


Dissociative Electron Attachment To Uracil Deuterated At The N1 And N3 Positions, A. M. Scheer, C. Silvernail, John A. Belot Jr., Gordon A. Gallup, Paul Burrow Aug 2005

Dissociative Electron Attachment To Uracil Deuterated At The N1 And N3 Positions, A. M. Scheer, C. Silvernail, John A. Belot Jr., Gordon A. Gallup, Paul Burrow

Paul Burrow Publications

Deuteration at the nitrogen sites of uracil produces a striking change in the dissociative attachment cross-section at electron energies below 3 eV. In particular, sharp structures observed in uracil are absent or too small to observe. This result, as well as theoretical modeling, supports the earlier assignment of the sharp structure to vibrational Feshbach resonances that decay by tunneling of the N1 hydrogen atom through the barrier created by the avoided crossing of the dipole bound anion potential surface by that of the lowest 2Σ valence anion state.


Self-Organization Of Spatial Solitons, Martin Centurion, Ye Pu, Demetri Psaltis Aug 2005

Self-Organization Of Spatial Solitons, Martin Centurion, Ye Pu, Demetri Psaltis

Martin Centurion Publications

We present experimental results on the transverse modulation instability of an elliptical beam propagating in a bulk nonlinear Kerr medium, and the formation and self-organization of spatial solitons. We have observed the emergence of order, self organization and a transition to an unstable state. Order emerges through the formation of spatial solitons in a periodic array. If the initial period of the array is unstable the solitons will tend to self-organize into a larger (more stable) period. Finally the system transitions to a disordered state where most of the solitons disappear and the beam profile becomes unstable to small changes ...


Search For Higgs Bosons Decaying Into B B̅ And Produced In Association With A Vector Boson In P P̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Jul 2005

Search For Higgs Bosons Decaying Into B B̅ And Produced In Association With A Vector Boson In P P̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a new search for H0V production, where H0 is a scalar Higgs boson decaying into b b̅ with branching ratio β, and V is a Z0 boson decaying into e+e-, µ+µ-, or νν̅. This search is then combined with previous searches for H0V where V is a W± boson or a hadronically decaying Z0. The data sample consists of 106±4 pb-1 of p p̅ collisions at √s=1.8 TeV accumulated by the Collider Detector at Fermilab. Observing no evidence of a signal, we set 95% Bayesian ...