UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
476 - 500 of 924
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CreatorTitleDescriptionSubjectDate
476 Mattis, Daniel C.New wave-operator identity applied to the study of persistent currents in 1DWe show that a large class of backward-scattering matrix elements involving Δk ~ + 2k F vanish for fermions interacting with two-body attractive forces in one dimension. (These same matrix elements are finite for noninteracting particles and infinite for particles interacting with two-body repulsiv...Persistent current; Supercurrents1974
477 Ailion, David CharlesNMR determination of structural domains in NaCNMeasurements of the first- and second-order quadrupole energy-level shifts are performed in a 23Na NMR experiment in a single crystal of NaCN. Twelve orthorhombic domains are found below the phase transition at 15°C. They consist of six pairs of domains with each one oriented by an angle 2/3 rel...NMR; Nuclear magnetic resonance; Crystals; Structural domains1980
478 Ailion, David CharlesNMR determination of the Edwards-Anderson order parameter in the deuterated pseudo-spin glass Rb1-x(ND4)xD2PO4: anisotropy and concentration dependence of the ND4 deuteron second momentWe measured the rotationally averaged N D 4 + deuteron second moment in deuterated mixed single crystals Rb1_x(ND4 ) xD2P04 with x = 0.22, 0.44, 0.78, and pure ND4D2P04 . We found that the linewidths of the mixed systems show a strong dependence on the crystal's orientation with respect to the exter...NMR; Crystals; Deuteron second moment; Anisotropy; Linewidth1990
479 Ailion, David CharlesNMR in lithium metal: thermal mixingWe present a calculation of the thermal mixing rate t~ 1 between nuclear Zeeman and dipolar reservoirs in the presence of large rf fields. We applied this calculation to slow-motion diffusion in lithium metal. In particular, we measured the rotating frame spin-lattice relaxation time Tl p as a funct...NMR; Nuclear magnetic resonance; Lattices; Relaxation time1977
480 Ailion, David CharlesNMR in substitutionally disordered incommensurate (Rb1-xKx)2ZnCl4The impurity-concentration dependence of the 8 7Rb NMR line shapes and phason-induced spin-lattice relaxation rates has been studied over a wide temperature range in substitutional^ disordered incommensurate (Rb1_xKJ C)2ZnCl4 for x =0.00, 0.02, and 0.06. The results yield information on the impurity...NMR; Line shapes; Phasons; Spin-lattice; Phase fluctuations1994
481 Ailion, David CharlesNMR lineshapes and order parameter determination in proton pseudo-spin glassesThe quadrupole-perturbed NMR line shape has been evaluated in the local approximation for an arbitrary static random-field distribution coexisting with Gaussian time-fluctuating random fields. The special case of a spin-glass-type static local random-field distribution is treated also. The results ...NMR; Nuclear magnetic resonance; Line shape; Random fields; Proton pseudo-spin-glasses1988
482 Ailion, David CharlesNMR methods for identifying and studying diffusion of different spin species in heteronuclear systemsWe introduce a new dipolar relaxation lime TU)' which characterizes the spin-lattice relaxation of secular dipolar interactions in the presence of a large rf field. Measurements of T]D' are particularly useful for studying slow atomic motions in muitispin systems, since such measurements enable us ...NMR; Nuclear magnetic resonance; Nuclear-spin species; Diffusion; Molecular rotations1978
483 Ailion, David CharlesNMR observations of molecular motions and Zeeman-quadrupole cross relaxation in 1,2- difluorotetrachloroethaneWe report measurements of "F NMR relaxation times Tu Tlf, TID, and T2 in the plastic crystal CFCL2-CFCL2 . From the data near the melting point, we obtain the jump time for translational selfdiffusion. At lower temperatures, we observe on the cold side of the T, and Tif minima an unusual field depe...NMR; Nuclear magnetic resonance; Order-disorder; Diffusion1979
484 Ailion, David CharlesNMR relaxation study of molecular motions between unequal potential wells in solid trans, trans- muconodinitrileWe report observations of extremely unusual proton NMR relaxation rates in solid trans, transmuconodinitrile (TMD, N=C-CH = CH-CH = CH-C = N). In particular we measured, over the temperature range 77-423 °K, proton dipolar relaxation times Tw and spin lattice relaxation times Tt (at 24 and 58 MH...NMR; Nuclear magnetic resonance; Lattices; Relaxation time1977
485 Ailion, David CharlesNMR spectra and relaxation in incommensurate systems in the presence of a devil's staircaseThe possibility of discriminating true incommensurate phases from long period commensurate phases via NMR lineshape and spin-lattice relaxation measurements is discussed. The theoretical results are compared with experimental data in Rb2ZnCl4, Rb2ZnBr4, and [N(CH3)4]2ZnCl4. Devil's staircase effects...Incommensurate phases; Commensurate phases; Phason gap; Spin-lattice relaxation1985
486 Symko, Orest GeorgeNoise characteristics and instabilities of long Josephson junctionsIn a magnetic field, current biased long Josephson junctions exhibit the dynamics of fluxon motion which are affected by fluctuations. These consist of telegraph noise at voltage steps and instabilities due to chaotic behavior. Results on long junctions with McCumber number fic ranging from 10 to 10...Fluxon motion; Current biased; Instabilities; Telegraph noise; Perturbed sine-Gordon equation1989-03
487 Williams, Clayton C.Noise reduction technique for scanning tunneling microscopyNoise stemming from mechanical vibration, electronic noise, or low frequency (l / f power spectrum) inherent in the tunneling process, often limits the resolution, speed, or range of application of scanning tunneling microscopy (STM). We demonstrate a technique for minimizing the effect of these noi...Noise reduction; Dithering; Graphite1988
488 Wu, Yong-ShiNoncommutative gauge theories in matrix theoryWe present a general framework for matrix theory compactified on a quotient space Rn/G, with G a discrete group of Euclidean motions in R". The general solution to the quotient conditions gives a gauge theory on a noncommutative space. We characterize the resulting noncommutative gauge theory in t...Matrix theory; Noncommutative space1998-09
489 Wu, Yong-ShiNoncommutative geometry and D-branesWe apply noncommutative geometry to a system of N parallel D-branes, which is interpreted as a quantum space. The Dirac operator defining the quantum differential calculus is identified to be the zero-momentum mode of the supercharge for strings connecting D-branes. As a result of the calculus, Con...1997-04
490 Lupton, John MarkNonequilibrium polariton dynamics in organic microcavitiesMicrocavities containing a J-aggregate forming organic dye were prepared in the strong-coupling regime. Changing the position of the neat organic films within the microcavity allows a tuning of the giant Rabi splitting observed. We set the Rabi splitting to 25 meV and study the thermal activation o...Nonequilibrium polariton dynamics; Organic microcavities; Optical microcavities; Rabi splitting; Light-matter interactions; Arrhenius activation2002-08
491 Mattis, Daniel C.Nonlinear lattice dynamics in two dimensionsIn general, dynamical and quantum-mechanical properties of anharmonic lattices are best expressed in terms of bond variables. A transformation from atomic (site) to bond coordinates is generated in two dimensions, with the help of a number of subsidiary conditions expressed on plaquettes. It is sho...Phonons; Plaquettes; Harmonic oscillators; Ferromagnets1983-04
492 Wu, Yong-ShiNonlinear optical properties of an electromagnetically-induced-transparency medium interacting with two quantized fieldsWe study linear and nonlinear optical properties of electromagnetically induced transparency (EIT) medium interacting with two quantized laser fields for adiabatic EIT case. We show that EIT medium exhibits normal dispersion. Kerr and higher order nonlinear refractive-index coefficients are also cal...2003-08-01
493 Vardeny, Zeev ValentineNonlinear optical spectroscopy of excited states in disubstituted polyacetyleneWe used a variety of nonlinear optical (NLO) spectroscopies for studying the excited states order and primary photoexcitations in disubstituted polyacetylene (DPA). The NLO spectroscopies include ultrafast pump-probe photomodulation in a broad spectral range of 0.2-2.5 eV, two-photon absorption in...2010-05
494 Vardeny, Zeev ValentineNonlinear optical spectroscopy of excited states in polyfluoreneWe used a variety of nonlinear optical (NLO) spectroscopies to study the singlet excited-state order and primary photoexcitations in polyfluorene, an important blue-emitting ∏-conjugated polymer. The polarized NLO spectroscopies include ultrafast pump-probe photomodulation in a broad spectral rang...pi-conjugated polymers; Polyfluorene; Photoexcitations2007-03
495 Mishchenko, EugeneNonlinear voltage dependence of the shot noise in mesoscopic degenerate conductors with strong electron-electron scatteringIt is shown that measurements of zero-frequency shot noise can provide information on electron-electron interaction, because the strong interaction results in the nonlinear voltage dependence of the shot noise in metallic wires. This is due to the fact that the Wiedemann-Franz law is no longer vali...Shot noise; Degenerate conductors2000-11
496 Wu, Yong-ShiNonlinear Ŵ∞ current algebra in the SL(2,R)/U(1) coset modelWe show that in the world-sheet SL(2,R)/U(l) coset model there exists a hidden nonlinear W∞ current algebra, which incorporates all higher-spin (s≥ 2) currents including the energy-momentum tensor. Our proof is based on a free-field realization of Woo in terms of two scalars, as well as an ele...W-algebras; Coset model; World-sheet; String theory; Spacetime; Quantum currents1992-05
497 Bernstein, Paul S.; Gellermann, WernerNonmydriatic fluorescence-based quantitative imaging of human macular pigment distributions.We have developed a CCD-camera-based nonmydriatic instrument that detects fluorescence from retinal lipofuscin chromophores ("autofluorescence") as a means to indirectly quantify and spatially image the distribution of macular pigment (MP). The lipofuscin fluorescence intensity is reduced at all ret...Cytology; Sensitivity and Specificity2006-10
498 DeTar, CarletonNt = 6 equation of state for two flavor QCDWe improve the calculation of the equation of state for two flavor QCD by simulating on Nt = 6 lattices at appropriate values of the couplings for the deconfinement/chiral symmetry restoration crossover. For amq = 0.0125 the energy density rises rapidly to approximately 1 GeV/fm3 just after the cro...Kogut-Susskind fermions; Quark-gluon plasma1996-03
499 Ailion, David CharlesNuclear double resonance: cross relaxation rates between two spin speciesA rotating-frame nuclear-double-resonance experiment is reported in which the cross-relaxation rates between 7Li and 6Li in powdered lithium metal were measured. The theory developed my McArthur, Hahn, and Walstedt (MHW) is applied to these data and good agreement is obtained. We also apply this t...Nuclear-double-resonance; Lithium; MHW; Cross-relaxation1977
500 Ailion, David CharlesNuclear magnetic resonance in LiF: a single nuclear-dipolar-spin temperature in crystals with more than one spin speciesIn a crystal containing more than one species of nuclear spin in a large dc magnetic field, the secular dipolar interactions between all spins, unlike as well as like, form a single reservoir described by a single spin temperature. We demonstrated this concept with experiments on LiF. In particula...Spin species; Spin-lattice relaxation; NMR; Nuclear magnetic resonance1977
476 - 500 of 924