UScholar Works
 
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CreatorTitleDescriptionSubjectDate
1Ailion, David Charles14N study of the role of N-D---O bonds in the deuteron glass transition14N spin-lattice relaxation-time measurements in Rb0.28(ND4)0.72D2PO4 provide direct evidence for the fast exchange averaging of the "long" and "short" N-D---O hydrogen bonds between the ND4 group and the four surrounding PO4 groups. This exchange and the associated distortion of the ND4 tetrahedron...NMR; Hydrogen bonds; Spin-lattice; Relaxation-time; Deuteron glass1999
2Williams, Clayton C.Advances in experimental technique for quantitative two dimensional dopant profiling by scanning capacitance microscopySeveral advances have been made toward the achievement of quantitative two-dimensional dopant and carrier profiling. To improve the dielectric and charge properties of the oxide-silicon interface, a method of low temperature heat treatment has been developed which produces an insulating layer with c...Doping; Scanning capacitance microscope; SCM1999
3Gondolo, PaoloAGAPEROS: searching for microlensing in the LMC with the pixel method. I. Data treatment and pixel light curves productionRecent surveys monitoring millions of light curves of resolved stars in the LMC have discovered several microlensing events. Unresolved stars could however signi _x000C_cantly contribute to the microlensing rate towards the LMC. Monitoring pixels, as opposed to individual stars, should be able to ...Data analysis techniques; Halo; Galaxies; Gravitational lensing; Pixel method; Large Magellanic Cloud; LMC1999
4Gondolo, PaoloAgapeZ1: a large amplification microlensing event or an odd variable star towards the inner bulge of M31AgapeZ1 is the brightest and the shortest duration microlensing candidate event found to date in the Agape experiment. It occurred only 4200 from the centre of M31 at RA = 0h42m41:47s and Dec = 41°16'39.1" (J2000). Our photometry shows that the half intensity duration of the event is 5.3 days and ...AgapeZ1; Galaxy; Halo; Cosmology; Gravitational lensing; M31; Pixel method1999
5Vardeny, Zeev ValentineAmplified spontaneous emission and lasing in conducting polymers and fluorescent dyes in opals as photonic crystalsSpectral narrowing of photoluminescence (PL) and evolution of sharp emission lines upon optical excitation have been observed in opals made of SiO2 spheres infiltrated with conducting polymers such as OOPPV and MDDOPPV and also fluorescent dyes such as rhodamine 6G, NK-3483, and coumarin 120. Their ...Amplified spontaneous emission; Lasing; Fluorescent dyes1999
6Sokolsky, PierreAn analog light scattering experiment of hexagonal icelike particles. part I: experimental apparatus and test measurementsAn experimental apparatus to measure the scattering properties of hexagonal icelike particles in the analog manner at the helium neon laser wavelength of 0.633 mm has been designed and built. The instrument consists of an array of 36 highly sensitive and linear photodiode detectors that are positi...1999
7Sokolsky, PierreAn analog light scattering experiment of hexagonal icelike particles. part II: experimental and theoretical resultsThe scattering properties of hexagonal icelike crystals as measured in the analog manner by the experimental apparatus described in Part I are presented. The crystals are made out of sodium fluoride (NaF), which has an index of refraction similar to that of water ice. The experimentally determined...1999
8Lupton, John MarkDevice model for polymer light emitting diodes: effect of temperature and oxidationWe present a temperature-dependent single carrier device model for polymer light-emitting diodes. The model includes both the injection of charge carriers over a barrier and the transport of charges across the device. To test the model, the temperature dependence of an LED based on the conjugated po...Single carrier; Temperature dependent; Poly(phenylene vinylene); Transport measurements; ITO; Disorder1999
9Symko, Orest GeorgeEnergy conversion using thermoacoustic devicesThermoacoustic engines offer the possibility for simple and efficient energy convmiondevices. They can be prime movers where heat produces sound or heat pumps and refrigerators where sound pump heat. An important element in such engines is the secondary thermodynamic medium, the stack which provides...Thermoacoustic devices; Thermoacoustics1999
10Gondolo, PaoloIndirect detection of dark matter in km-size neutrino telescopesNeutrino telescopes of kilometer size are currently being planned. They will be two or three orders of magnitude larger than presently operating detectors, but they will have a much higher muon energy threshold. We discuss the trade-off between area and energy threshold for indirect detection of ne...Neutrino telescopes; Energy threshold; Neutralino annihilations; Supersymmetric models1999
11Vardeny, Zeev ValentineLaser action in polydialkylfluorene films: influence of low-temperature thermal treatmentWe have used a variety of optical probes to investigate the changes occurring upon low-temperature thermal treatment to the emissive properties of dialkyl substituted polyfluorene thin films. We found that the low-temperature-driven morphological changes involving aggregates formation, which are ob...Laser action; Polydialkylfluorene films; pi-conjugated polymers; Thermal treatment1999
12Williams, Clayton C.Scanning capacitance microscope methodology for quantitative analysis of P-N junctionsQuantification of dopant profiles in two dimensions (2D) for p-n junctions has proven to be a challenging problem. The scanning capacitance microscope (SCM) capability for p-n junction imaging has only been qualitatively demonstrated. No well-established physical model exists yet for the SCM data in...p-n junctions; Scanning capacitance microscope; SCM1999
13Mattis, Daniel C.; Paul, PrabasajStatistical transfer matrix of a spin-glass ladderThis work concerns the Edwards-Anderson Ising model of a spin ladder, in which random bonds +_J connect nearest-neighbor Ising spins. We calculate the exact free energy of the quenched, frustrated, spin-glass-like ladder as an integral over a probability distribution P(x), the eigenfunction of a s...Thermodynamics; Ising1999
14Vardeny, Zeev ValentineUltrafast studies of laser-action in poly-(p-pherylene vinylene) filmsThe recent demonstration of emission spectral narrowing in ∏-conjugated polymer has stirred widespread interest to the phenomenon of laser-action in these materials. It is now generally believed that spectral narrowing in superior polymer films is caused by amplified spontaneous emission (i.e. si...Ultrafast studies; Poly-(p-pherylene vinylene); PPV; Laser-action1999
15Gondolo, PaoloClumpy neutralino dark matterWe investigate the possibility to detect neutralino dark matter in a scenario in which the galactic dark halo is clumpy. We find that under customary assumptions on various astrophysical parameters, the antiproton and continuum γ-ray signals from neutralino annihilation in the halo put the strong...Neutralinos; Clumpiness1999-01
16Gondolo, PaoloDark matter annihilation at the galactic centerCold dark matter near the galactic center is accreted by the central black hole into a dense spike. Particle dark matter annihilation makes the spike a compact source of photons, electrons, positrons, protons, antiprotons, and neutrinos. The spike luminosity depends on the halo density profile: halo...Neutralinos; Neutrino flux1999-08
17Gerton, JordanDipolar relaxation collisions in magnetically trapped 7LiWe report the measurement of the rate constant for dipolar relaxation from the (F=2, mF=2) hyperfine state of 7Li. The atoms are confined in a permanent magnet trap at a field of 10^3 G. The measured value of (1.05±0.10)X10^-14 cm3/s agrees well with theory. Additionally, we determine an upper bo...1999-02
18Vardeny, Zeev ValentineElectromodulation of charge-transfer photoexcitations in pristine and C60-doped conjugated polymersWe study the effect of an electric field of up to 100 kV/cm on photoexcitations in pristine and C60-doped p-conjugated polymers by electromodulated photoinduced absorption (EPA). In EPA, we measure changes in the photoinduced absorption of a polymer film induced by an electric field. The dominant ...Electromodulation; Charge-transfer photoexcitations; Photoinduced absorption; pi-conjugated polymers; Electromodulation spectroscopy1999-04
19Mishchenko, EugeneElectron-lattice kinetics of metals heated by ultrashort laser pulsesWe propose a kinetic model of transient nonequilibrium phenomena in metals exposed to ultrashort laser pulses when heated electrons affect the lattice through direct electron-phonon interaction. This model describes the destruction of a metal under intense laser pumping. We derive the system of equa...Electron-lattice kinetics; Thermoconductivity; electron temperature; Lattice deformation1999-01
20Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Excitation dynamics in disubstituted polyacetyleneWe studied the excitation dynamics in films of disubstituted polyacetylene, a degenerate ground-state conjugated polymer, using psec transient and steady-state spectroscopies. The polymer is found to support charged and neutral topological soliton excitations concurrent with a strong intrinsic p...Excitation dynamics; Disubstituted polyacetylene; Laser action1999-05
21DeTar, CarletonExotic meson spectroscopy from the clover action at β = 5.85 and 6.15*We repeat our original simulations of the hybrid meson spectrum using the clover action, as a check on lattice artifacts. Our results for the 1−+ masses do not substantially change. We present preliminary results for the wave function of the 1−+ state in Coulomb gauge.Clover action; Quark spectroscopy1999-03
22DeTar, CarletonHeavy-light decay constants: conclusions from the Wilson actionWe report on the results of a MILC collaboration calculation of fB, fBs , fD, fDs and their ratios. We discuss the most important errors in more detail than we have elsewhere.Decay constants; Wilson action; Staggered quarks1999-03
23Mishchenko, EugeneKinetic theory of shot noise in nondegenerate diffusive conductorsWe investigate current fluctuations in nondegenerate semiconductors, on length scales intermediate between the elastic and inelastic mean free paths. We present an exact solution of the nonlinear kinetic equations in the regime of space-charge limited conduction, without resorting to the drift app...Shot noise; Conductors; Boltzmann equation1999-08
24Gerton, JordanLaser-free slow atom sourceA slow atom source, which does not rely on lasers, has been developed and characterized. The device, acting as an atomic low-pass velocity filter, utilizes permanent magnets to passively select the slow atoms present in a thermal atomic beam. Slow atoms are guided along a curved, conduction-limite...1999-11
25Wu, Yong-ShiMatrix compactification on orientifoldsGeneralizing previous results for orbifolds, in this paper we describe the compactification of the matrix model on an orientifold which is a quotient space Rd/G as a Yang-Mills theory residing on a quantum space. The information of the compactification is encoded in the action of the discrete symmet...Spacetime; Orientifolds; Compactification; Quantum space1999-06
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