UScholar Works
 
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CreatorTitleDescriptionSubjectDate
51 Vardeny, Zeev ValentineTransient spectroscopy of excitons and polarons in C60 films from femtosecond to millisecondsWe have studied photoexcitations in C60 films using transient photomodulation and photoluminescence from 100 fs to 50 ms and absorption-detected magnetic resonance (ADMR). We show that singlet Frenkel excitons are the primary photoexcitations; their recombination kinetics in the picosecond time dom...Transient spectroscopy; C60 films; Femtoseconds; Milliseconds1994-11
52 DeTar, CarletonHeavy-light decay constants - MILC results with the Wilson actionWe present the current status of our ongoing calculations of pseudoscalar meson decay constants for mesons that contain one light and one heavy quark (fB, fBs , fD, fDs ). We are currently generating new gauge configurations that include dynamical quarks and calculating the decay constants. In add...Decay constants; Wilson action; Kogut-Susskind quarks; Staggered quarks; Chiral extrapolation1998-01
53 Wu, Yong-ShiQuantized spin Hall effect in 3He-A and other p-wave paired Fermi systemsIn this paper, we propose the quantized spin Hall effect (SHE) in the vortex state of a rotating p-wave paired Fermi system in an inhomogeneous magnetic field and in a weak periodic potential. It is the three-dimensional extension of the spin Hall effect for a 3He-A superfluid film previously stud...Fermi systems; Spin Hall conductance2008-04
54 Mattis, Daniel C.; Sutherland, BillStrange solutions to field theories in one spatial dimensionMany models of interacting particles rely heavily for their solution on restriction to one-dimensional motion and a linearized kinetic energy. We examine this in detail, and find that the linearization can lead to patently strange and possible spurious solutions in first quantization. The usual, co...Eigenstates; Field theories1981
55 Mattis, Daniel C.Multicomponent polaronBy a slight modification of the Fröhlich Hamiltonian (the introduction of an internal quantum number) we reduce the polaron problem to the solution of a continued fraction, even at finite temperature. We analyze both the stationary states and the resonances (in one- and three-dimensional versions o...Ground-state energy; Coupling constant; Fröhlich model; Finite temperature1991-10
56 DeTar, CarletonContinuum limit in the quenched approximationPrevious work at G/g2 = 5.7 with quenched staggered quarks is extended with new calculations at 5.85 and 6.15 on lattices up to 323 x 64. These calculations allow a more detailed study of extrapolation in quark mass, finite volume and lattice spacing than has heretofore been possible. We discuss h...Decay constants; Staggered quarks; Wilson quarks1996-03
57 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Phonon spectroscopy in π-conjugated polymers; the role of the excited electronic statesThe Raman active vibrational modes in 7r-conjugated polymers are known to have different frequencies in different types of experiments. The best known examples are the resonant Raman scattering (RRS) and doping or photoinduced absorption infrared active vibrations (IRAV) measurements, in which the s...pi-conjugated polymers; Phonon spectroscopy; Resonant Raman scattering; ir-active phonons1997
58 Wu, Yong-ShiQuantum dynamics and statistics of vortices in two-dimensional superfluidsThe phase change of the wave function of a superfluid film as a vortex moves around a closed path counts the number of superfluid particles enclosed by that path. This result is used to investigate whether such vortices obey "fractional statistics." We conclude that this is not the case in compress...Superfluid films; Vortices; Fractional statistics1985-12
59 Vardeny, Zeev Valentine; Raikh, Mikhail E.Universal properties of random lasersThe design and fabrication of laser resonators is often difficult. However, random lasers occur in gain media with numerous scatterers and produce coherent laser emission without any predesigned cavity. The generation of coherent emission from multiple scattering is quite general and its basic prin...Random lasers; Laser resonators; pi-conjugated polymers; Rhodamine-TiO2 suspensions; Random media; Random lasing2003-01
60 Wu, Yong-ShiScale and conformal invariance in Chern-Simons-matter field theoryWe study perturbative renormalization of Dsss3 Chern-Simons gauge theory coupled to scalar and fermionic matter. We show that in the non-Abelian case the coefficient of the Chern-Simons term has infinite renormalization and that both the matter and the non-Abelian gauge fields acquire nonvanishing ...Chern-Simons gauge theory; Renormalization1991-09
61 DeTar, CarletonQCD thermodynamics with an improved lattice actionWe have investigated QCD with two flavors of degenerate fermions using the Symanzik-improvement program for both the gauge and fermion actions. Our study focuses on the deconfinement transition on an Nt=4 lattice. Having located the thermal transition, we performed zero temperature simulations nea...Wilson fermions; Polyakov loop; Chiral symmetry; Phase transitions1997-11
62 Vardeny, Zeev ValentineBelow-gap excitation of ∏-conjugated polymer-fullerene blends: implications for bulk organic heterojunction solar cellsWe used a variety of optoelectronic techniques such as broadband fs transient and cw photomodulation spectroscopies, electroabsorption, and short-circuit photocurrent in bulk heterojunctions organic solar cells for studying the photophysics in ∏-conjugated polymer-fullerene blends with below-gap...pi-conjugated polymers; Fullerene blends; Below-gap excitations; Bulk heterojunctions; Bulk organic heterojunction solar cells; Photophysics2008-07
63 Lupton, John MarkMonitoring surface charge movement in single elongated semiconductor nanocrystalsWe demonstrate a universal correlation between the spectral linewidth and position of the excitonic transition in the spectral jitter observed from single elongated colloidal quantum dots. Breaking the symmetry of electron and hole confinement as well as of the spatial directions for surface charge ...Surface charge movement; Spectral linewidth; Excitonic transition; Spectral jitter; Colloidal nanocrystals2004-10
64 Vardeny, Zeev ValentineUltrafast electronic and acoustic effects in conducting polymersThe polarized picosecond pump and probe technique with 50 fsec resolution has been used to generate and detect electronic excitations and propagation of ultrasonic phonons in thin films of oriented and unoriented polyacetylene and polythiophene. We found that the photoexcitations are instantaneou...Ultrafast electronic effects; Ultrafast acoustic effects; Polarized picosecond pump; Pump and probe technique; Ultrasonic phonons1990
65 Lupton, John MarkTime-gated electroluminescence spectroscopy of polymer light-emitting diodes as a probe of carrier dynamics and trappingWe present time-gated electroluminescence (EL) spectroscopy of a polyfluorene-based conjugated polymer. The technique is shown to be sensitive enough to pick out impurity emission orders of magnitude weaker than the cw emission. By considering the temperature dependence of the delayed emission spect...Time-gated electroluminescence spectroscopy; Carrier dynamics; Trapping; Delayed emission2002-04
66 Gondolo, PaoloFluid interpretation of Cardassian expansionA fluid interpretation of Cardassian expansion is developed. Here, the Friedmann equation takes the form H2=g(ρM) where ρM contains only matter and radiation ~no vacuum!. The function g(ρM) returns to the usual 8πM /(3mpl 2 ) during the early history of the Universe, but takes a different form...Cardassian expansion; Friedmann equation2003-09
67 Vardeny, Zeev ValentineSpin-dependent delayed luminescence from nongeminate pairs of polarons in ∏-conjugated polymersWe measured cw photoinduced absorption (PA) and spin- 1 2 PA- and photoluminescence detected magnetic resonance (PADMR and PLDMR, respectively) in films of two representative p-conjugated polymers; poly(phenylene-vinylene) and polythiophene. From the dependences of the polaron PA and PLDMR on the ...pi-conjugated polymers; Nongeminate pairs; Spin-dependent delayed luminescence; Photoinduced absorption; Poly(phenylene-vinylene)2002-12
68 Williams, Clayton C.; Stringfellow, Gerald B.Effect of substrate misorientation on ordering in Ga0.5In0.5POrdering produced in Gao.5Ino.5P epitaxial layers grown by OMVPE can be controlled by variations in the substrate misorientation as well as the growth temperature and the growth rate. The ordering produced at a growth temperature of 620°C and a relatively low growth rate of 0.5 /μm/hr is found to ...Ga0.5In0.5P; Epitaxial layers; Epitaxial growth; OMVPE1994
69 Symko, Orest GeorgeSpin freezing below the nearest-neighbor percolation concentration in Cd1-xMnxTe and Cd1-xMnxSeThe very-low-temperature magnetization of Cdi_xMnxTe and Cdj-xMnxSe alloys shows spinglass behavior for concentrations below the nearest-neighbor percolation limit. This is attributed to short-range exchange and dipolar interactions. New magnetic phase diagrams for both systems are presented.Spin freezing; Cd1-xMnxTe; Cd1-xMnxSe; Very-low-temperature magnetization; Spin-glass behavior1986-05
70 Gerton, JordanOptimizing contrast of tip-enhanced fluorescence microscopy for imaging high-density samplesQuantum dots are imaged using tip-enhanced fluorescence microscopy. Optimization of the operation parameters leads to high-contrast images of high-density samples and a novel photon analysis improves contrast further.2007-05
71 Williams, Clayton C.High resolution photothermal laser probeAt frequencies near 1 GHz, the acoustic wavelength in argon gas becomes half that of visible light, making possible collinear Bragg scattering of laser light by the sound. This acousto-optic interaction has been used to detect photothermally generated acoustic power at the surface of solids. This ne...Photothermal laser probe; Silicon wafer1984
72 DeTar, CarletonUpdate on fBWe describe the current status of the MILC collaboration computation of fB, fBs , fD, fDs and their ratios. Progress over the past year includes: better statistics and plateaus at _x000C_β = 6.52 (quenched), β_x000C_ = 5.6 (NF = 2) and β_x000C_ = 5.445 (NF = 2), new runs with a wide range of dyn...Decay constants; Wilson quarks1997-02
73 Kieda, David B.Toward a revival of stellar intensity interferometryBuilding on technological developments over the last 35 years, intensity interferometry now appears a feasible option by which to achieve diffraction-limited imaging over a square-kilometer synthetic aperture. Upcoming Atmospheric Cherenkov Telescope projects will consist of up to 100 telescopes, ...Intensity interferometry; Air Cherenkov Telescope2008
74 Symko, Orest GeorgeScattering times and mean free path in AlCuFe quasicrystalline thin filmsWe present magnetoresistivity measurements on AlCuFe quasicrystalline thin films from which the temperature dependence of the inelastic scattering time (ri e) has been deduced down to 200 mK in the low field limit. We show that ri e presents a weak temperature dependence below 4 K (1/ гie ~ T°-87)...AlCuFe; Quasicrystalline thin films; Scattering times; Free path1995-05
75 Vardeny, Zeev ValentinePhotoexcitations in polythiophene at high pressureWe report optical-absorption, photoluminescence (PL), and picosecond photoinduced absorption (PA) decay in films of poly-3-hexyl-thiophene at pressures up to 80 kbar. The spectral bands redshift nonlinearly with pressure and the PL intensity decreases markedly. Thermochromic transitions are complete...Photoexcitations1993-01
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