UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 Gondolo, PaoloAGAPE, a microlensing search in the direction of M31: status reportThe M31 galaxy in Andromeda is the nearest large galaxy after the Small and Large Magellanic Clouds. It is a giant galaxy, roughly 2 times as large as our Milky Way, and has its own halo. As pointed by some of us [1, 2] and independantly by A. Crotts [3], M31 provides a rich field of stars to searc...AGAPE; Andromeda Gravitational Amplification Pixel Experiment; Microlensing; MACHO; Massive compact halo objects1995
2 Ailion, David CharlesHigh sensitivity nuclear quadrupole resonance approach for detection of modulation wave motion in incommensurate systemsIn contrast to conventional NMR techniques that use magnetic field gradients (MFCs) to detect the diffusion of moving atoms, we have developed a highly sensitive approach for detecting electric field gradient (EFG) fluctuations seen by stationary atoms. These EFG fluctuations were observed in the ...NMR; MFG; Magnetic field gradients; Diffusion constants; Atoms; Nuclei1995
3 Mattis, Daniel C.Limit model of CuO2 planes: exact resultsWe solve the simplest tight-binding model of electrons in a CuO2 plane with Coulomb repulsion only on the copper ions, by a limiting procedure which retains all contributions 0(t2/U) while projecting out the higher order terms. In addition to the ground state energy we identify a variety of quasipar...Electrons; Particle-hole1995
4 Williams, Clayton C.Micromachined submicrometer photodiode for scanning probe microscopyA submicrometer photodiode probe with a sub-50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al-Si...Submicrometer; Photodiode; Scanning probe microscopy; Nanoprobe1995
5 Williams, Clayton C.Micromachined submicrometer photodiode for scanning probe microscopyA submicrometer photodiode probe with a sub-50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al-Si Sc...Submicrometer photodiode; Scanning probe microscopy; Nanobrobes1995
6 Vardeny, Zeev ValentineOptical probes of photoexcitations in fullerene thin films from femtoseconds to millisecondsWe have studied photoexcitations in various fiillerene thin films using transient photomodulation and photoluminescence from 100 fs to 50 ms and absorption-detected magnetic resonance (ADMR). We show that singlet Frenkel type excitons are the primary photoexcitations; their recombination kinetics in...Photoexcitations; Femtosecond; Transient photomodulation; Transient photoluminescence; Frenkel type excitons; Triplet excitons1995
7 Vardeny, Zeev ValentinePhotoresponse and electroresponse of polymers light emitting diodesWe have studied the photoresponse and electroresponse of light emitting diodes (LEDs ) made from a variety of soluble conducting polymers sandwiched between indium tin oxide (ITO) and metals including calcium, aluminum and copper. Under illumination all freshly prepared LEDs exhibit relatively large...Photoresponse; Electroresponse; Photovoltage; I-V curves1995
8 Williams, Clayton C.; Huang, YufengQuantitative two-dimensional dopant profile measurement and inverse modeling by scanning capacitance microscopyQuantitative dopant profile measurements are performed on a nanometer scale by scanning capacitance microscopy (SCM). An atomic force microscope is used to position a nanometer scale tip at a semiconductor surface, and local capacitance change is measured as a function of sample bias. A new feedback...Dopant profile; Capacitance change; Scanning capacitance microscopy; Feedback control1995
9 Efros, Alexei L.Sensor-based distributed control scheme for mobile robotsIn this paper we present a sensor-based distributed control scheme for mobile robots. This scheme combines centralized and decentralized control strategies. A server-client model is used to implement this scheme where the server is a process that caries out the commands to be executed, and each clie...Sensor-based; Distributed control scheme1995
10 Williams, Clayton C.Shear force microscopy with capacitance detection for near-field scanning optical microscopyShear force microscopy is very useful for distance regulation in near-field scanning optical microscopy (NSOM). However, the optical method used to detect the shear force can cause problems when imaging photosensitive materials, i.e., the shear force detection beam can optically pump the sample. We ...Shear force microscopy; Atom force microscope; AFM; Capacitance sensing1995
11 Vardeny, Zeev ValentineSymmetric light emitting divices from poly(p-di ethynylene phenylene) (p-di phenylene vinylene) derivativesLight emitting devices were fabricated from 2,5-dialkoxy derivatives of poly(p-di ethynylene phenylene-p-di phenylene vinylene) (PDEPDPV) sandwiched between indium tin oxide (ITO) and Al. The current-voltage (Iel-V) curve, electroluminescence (EL) intensity-voltage (IEL-V) curve, and the EL spectra ...Poly(p-di ethynylene phenylene); PPV; Pi-conjugated polymers1995
12 Ailion, David Charles; Blinc, Robert35Cl spin-lattice relaxation in incommensurate bis(4-chlorophenyl)sulfoneThe 35C1 nuclear-quadrupole-resonance (NQR) spin-lattice relaxation rate in incommensurate bis(4- chlorophenyl)sulfone (BCPS) is determined by Raman processes below 60 K and by direct one-phonon processes above 60 K. The variation of the 35C1 spin-lattice relaxation rate over the incommensurate NQR...35Cl; Incommensurate bis(4-chlorophenyl)sulfone; Raman processes; NQR; Incommensurate systems1995-01
13 Wu, Yong-ShiBosonization of one-dimensional exclusons and characterization of Luttinger liquidsWe achieve a bosonization of one-dimensional ideal gas of particles obeying exclusion statistics A (so called A exclusons) at low temperatures, resulting in a new variant of c = 1 conformal field theory with compactified radius R = √1/λ. These ideal excluson gases exactly reproduce the low-7 crit...Bosonization; Exclusons; Ideal gas; Luttinger liquids1995-07
14 Vardeny, Zeev ValentineDetection of electronic excited states in conjugated polymers by picosecond transient strain spectroscopyWe describe a new type of spectroscopy based on picosecond transient strain in absorption photomodulation that can be used to detect and identify both allowed and forbidden optical transitions in solid thin films. We have applied the new spectroscopy to a variety of conducting polymer films such as ...Picosecond transient strain spectroscopy1995-02
15 DeTar, CarletonFinite temperature QCD: progress and outstanding problemsI review recent progress in numerical simulations of finite temperature quantum chromodynamics and discuss the status of some outstanding problems. Included is (1) a discussion of recent results determining the temperature of the "phase transition" in full QCD, (2) a scaling analysis of the Polyakov...Phase transitions; Staggered fermions; Wilson fermions; Polyakov loop; Deconfinement; Instanton1995-04
16 Symko, Orest GeorgeObservation of a narrow pseudogap near the Fermi level of AlCuFe quasicrystalline thin filmsWe present the first experimental determination by tunneling spectroscopy of the density of states (DOS) close to the Fermi energy of AlCuFe quasicrystalline thin film samples. The measurements show that the Fermi level in a quasicrystal lies in a deep narrow pseudogap 60 m e V wide. Above an applie...AlCuFe; Quasicrystalline thin films; Pseudogap; Fermi level; Density of states; DOS1995-05
17 DeTar, CarletonPreliminary heavy-light decay constants from the MILC collaborationPreliminary results from the MILC collaboration for fβ, / fβs, /fD, /fD„ and their ratios are presented. We compute in the quenched approximation at β = 6.3, 6.0 and 5.7 with Wilson light quarks and static and Wilson heavy quarks. We attempt to quantify all systematic errors other than quenchin...Decay constants; Wilson quarks1995-04
18 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
19 Vardeny, Zeev ValentineSpin dynamics of triplet photoexcitations in C60: evidence for a dynamic Jahn-Teller effectWe have used the absorption-detected magnetic-resonance (ADMR) technique to study the spin dynamics of triplet photoexcitations in C60 molecules dispersed in polystyrene glasses. We found that the ADMR spectra contain two triplet powder patterns A and B with substantial spin reorientation dynamics,...Spin dynamics; Triplet photoexcitations; C601995-07
20 DeTar, CarletonSU(3) lattice gauge theory with adjoint action at nonzero temperatureWe study the thermal phase diagram of pure SU(3) gauge theory with fundamental and adjoint couplings. We improve previous estimates of the position of the bulk transition line and determine the thermal deconfinement transition lines for Nt = 2,4,6, and 8. For Nt > 4 the deconfinement transition li...Phase transitions; Deconfinement1995-04
21 Mishchenko, EugeneSurface excitations in metals: Brillouin and Raman light scatteringThe theory of inelastic light scattering in anisotropic metals by conduction electrons interacting with acoustic and optical phonons and impurities is developed. The effects of a surface are studied in detail. The Coulomb interaction of carriers is included in a self-consistent way. The scattering c...Raman scattering1995-03
22 Mattis, Daniel C.Theory of superexchange in CuO2The limit method allows exact analysis of low-lying electronic states in a strong-coupling model Cu02 plane. We extend it to nonorthogonal orbitals and fit to a t-t'-J model. The superexchange parameter is J = g32t*, with the unit of energy and g3 a lumped parameter.Copper oxides; Superexchange1995-12
23 DeTar, CarletonThermal phase transition in mixed action SU(3) lattice gauge theory and Wilson fermion thermodynamicsWe study the thermal phase diagram of pure SU(3) lattice gauge theory with fundamental and adjoint couplings. We improve previous estimates of the position of the bulk transition line and determine the thermal deconfinement transition lines for Nt = 2, 4, 6, and 8. The endpoint of the bulk transitio...Wilson fermions; Wilson quarks; Phase transitions; Demon algorithms1995-05
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