276 - 300 of 924
Number of results to display per page
276 Saam, Brian; Laicher, GernotLiquid hyperpolarized 129Xe produced by phase exchange in a convection cellWe present a method for the production of liquid hyperpolarized 129Xe that employs spin-exchange optical pumping in the gas phase and subsequent phase exchange with a column of xenon liquid. A convection loop inside the sealed glass cell allows efficient transfer of magnetization between the gas an...Liquid hyperpolarized 129Xe; Phase exchange; Spin-exchange optical pumping; SEOP; NMR; Spin polarization2004
277 Mattis, Daniel C.Ground state of the Kondo modelThe single-impurity Kondo problem is investigated with the use of the nonperturbative Lanczos (tridiagonalization) method. We are able to obtain an explicit expression for the ground-state energy in terms of the Kondo coupling constant J. The method places no restrictions on the range of J.Kondo model; Ground-state energy; Coupling constant1985-06
278 Vardeny, Zeev ValentineResonant Raman-scattering spectroscopy of polydiacetylene films at high pressureWe studied the electronic energies and phonon frequencies of polydiacetylene 4-BCMU thin films at high pressures up to 50 kbar using Raman scattering under preresonant and resonant conditions. Pressure-induced changes in the resonant Raman scattering (RRS) include (1) hardening of the most strongly...Resonant raman scattering spectroscopy; Polydiacetylene films; Pi-conjugated polymers1993-02
279 Wu, Yong-ShiOvercoming the slowing down of flat-histogram Monte Carlo simulations: cluster updates and optimized broad-histogram ensemblesWe study the performance of Monte Carlo simulations that sample a broad histogram in energy by determining the mean first-passage time to span the entire energy space of d-dimensional ferromagnetic Ising/Potts models. We first show that flat-histogram Monte Carlo methods with single-spin flip upda...Energy space; Spin dynamics; Density of states; Cluster dynamics2005-10
280 Symko, Orest GeorgeSuperconducting microphone for photoacoustic spectroscopyA superconducting microphone has been developed for photoacoustic spectroscopy at low temperatures. The microphone consists of a thin mylar membrane coated with a film of lead whose motion is detected by SQUID magnetometer. For the simple set-up presented here, the limiting pressure sensitivity is ...Superconducting microphone; Photoacoustic spectroscopy; Low temperatures1982
281 Williams, Clayton C.Atomic force microscope-force mapping and profiling on a sub 100-Å scaleA modified version of the atomic force microscope is introduced that enables a precise measurement of the force between a tip and a sample over a tip-sample distance range of 30-150Å. As an application, the force signal is used to maintain the tip-sample spacing constant, so that profiling can be ...Attractive force; Silicon wafer1987
282 Mishchenko, EugeneElectronic Raman scattering in a magnetic fieldRaman scattering in a magnetic field is proposed as a possible method to solve the problem of whether the light scattering in high-Tc superconductors comes from conduction electrons or not. The electronic Raman light scattering in a magnetic field is studied theoretically. The semiclassical approa...Raman scattering1996-01
283 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
284 Vardeny, Zeev Valentine; Nahata, AjayMidinfrared optical response and thermal emission from plasmonic lattices on Al filmsWe studied the midinfrared optical transmission and thermal light emission spectra of subwavelength hole arrays in the form of square lattice with 4 µm periodicity (plasmonic lattice) in aluminum films deposited on silicon substrates. The optical transmission of these films showed temperature inde...Plasmonic lattices; Midinfrared optical response; Thermal emission; Surface plasmon polaritons; Anomalous transmission; Extraordinary optical transmission; EOT2007-11
285 Sokolsky, Pierre; Cassiday, George L.; Kieda, David B.Search for y rays above 10^14 eV from Cygnus X-3 during the June and July 1989 radio outburstsWe have looked for γ-ray emission above 100 TeV from the binary x-ray source Cygnus X-3 during a period of intense radio emission in the summer of 1989. We find no evidence for excess air showers from the direction of the source and the muon content of air showers from this direction is the same as...Cygnus X-3; Radio outbursts; Extensive air showers1989-11
286 Mishchenko, EugeneBreached superfluidity via p-wave couplingAnisotropic pairing between fermion species with different Fermi momenta opens two-dimensional areas of gapless excitations, thus producing a spatially homogeneous state with coexisting superfluid and normal fluids. This breached pairing state is stable and robust for arbitrarily small mismatch and ...Spin-orbit coupling; Gapless excitations; Cooper instability2005-03
287 DeTar, CarletonSemileptonic decays of D mesons in three-flavor lattice QCDWe present the first three-flavor lattice QCD calculations for D→ rrlv and D→ Klv semileptonic decays. Simulations are carried out using ensembles of unquenched gauge fields generated by the MILC Collaboration. With an improved staggered action for light quarks, we are able to simulate at light ...Semileptonic decay; Staggered quarks2005-01
288 Vardeny, Zeev ValentinePicosecond trapping of photocarriers in amorphous siliconTrapping of photoexcited carriers in the picosecond and subnanosecond time domains was studied by measuring the decay of photoinduced absorption (PA) in a-Si, a-Si:F, a-Si:H, and a-Si:H:F. We found that when the midgap density of states decreases, both the trapping time and its temperature dependenc...Photocarriers; Amorphous silicon; Picosecond trapping; Photoinduced absorption1983
289 Vardeny, Zeev Valentine; Raikh, Mikhail E.Cooperative emission from a disordered system: a classical modelThe effect of disorder on the collective emission from a system of classical oscillators is studied theoretically. Three types of disorder are considered: random orientation of dipole moments, finite spread in frequencies of the individual oscillators (diagonal disorder), and dipole-dipole interacti...Cooperative emission; Disordered system; Dipole-dipole interaction; Oscillators1997
290 Lupton, John MarkUnraveling the inhomogeneously broadened absorption spectrum of conjugated polymers by single-molecule light-harvesting action spectroscopyThe distribution of chromophores in single polymer chains is revealed by photoluminescence excitation spectroscopy under excitation of the backbone and detection of emission from an end cap. Spectral broadening in excitation exceeds that in emission. An increase in vibronic coupling for shorter (h...Spectral broadening; Chromophores2009-10
291 Kieda, David B.; Sokolsky, PierreSearch for > 200 TeV photons from Cygnus X-3 in 1988 and 1989Over a period of 16 months from April 1988 to August 1989, we have monitored the flux of cosmic-ray showers with energies above 2X 101 4 eV. We used a two-level array of scintillators covering an area of 3 X 104 m2. Counters on the surface measure the size and direction of each shower while counters...TeV photons; Cosmic ray showers1990-07
292 Vardeny, Zeev ValentineRaman-scattering study of pressure-induced phase transitions in CuIThe pressure-induced phase transitions: zinc-blende (ZB) --* rhombohedral -> tetragonal in Cul were studied by Raman scattering. The rhombohedral primitive cell is presented as a slightly distorted ZB unit cell that is twice as long as the primitive cell in the [111] direction. By folding back the Z...Raman-scattering; Pressure cell; Phase transitions1977-01
293 Gondolo, PaoloRecoil momentum spectrum in directional dark matter detectorsDirectional dark matter detectors will be able to record the recoil momentum spectrum of nuclei hit by dark matter WIMPs. We show that the recoil momentum spectrum is the Radon transform of the WIMP velocity distribution. This allows us to obtain analytic expressions for the recoil spectra of a va...Recoil momentum spectrum; Radon transform; WIMP; Weakly interacting massive particles; Velocity distribution2002-11
294 Wu, Yong-ShiDeformed Hubbard operator, bosonization, and phase diagram of the one-dimensional t-J modelWe present an analytic study of the phase diagram of the one-dimensional t-J model and a couple of its cousins. To deal with the interactions induced by the no double occupancy constraints, we introduce a deformation of the Hubbard operators. When the deformation parameter ∆ is small, the induced...Hubbard operator; Bosonization; Deformation; t-J model2002-10
295 Mishchenko, Eugene; Raikh, Mikhail E.Planar array of semiconducting nanotubes in an external electric field: collective screening and polarizabilityWe study theoretically the charge separation in a planar array of semiconducting nanotubes (NTs) of length, 2h, placed in an external electric field, F, parallel to their axes. By employing the conformal mapping, we find analytically the exact distribution of the induced charge density for the arb...Planar array2006-12
296 Vardeny, Zeev ValentineFabrication and properties of gallium metallic photonic crystalsGallium metallic photonic crystals with 100% filling factor have been fabricated via infiltration of liquid gallium into opals of 300-nm silica spheres using a novel high pressure-high temperature technique. The electrical resistance of the Ga-opal crystals was measured at temperatures from 10 to 2...2003-10
297 Mattis, Daniel C.; Sutherland, BillAmbiguities with the relativistic δ-function potentialIn many cases of physical interest, the 6-function potential is a very convenient approximation to more structured, and more difficult, short-ranged potentials. In relativistic theories, its use is often mandated because only a mathematical point has a relativistically invariant shape. Neverthele...Delta function; Energy states1981-09
298 Gondolo, PaoloGroups of galaxies in the local supercluster: some hypotheses on the evolutionary stageWe present a method capable of determining the evolutionary stage of bound, isolated systems of galaxies. In particular, we apply it to a sample of groups, belonging to the Local Supercluster, taken from the Geller and Huchra's (1983) catalogue. We find that most of them are still in the phase of c...Evolution of galaxy clusters1988
299 Gondolo, PaoloDirect detection of neutralino dark matter in nonstandard cosmologiesWe compute the neutralino direct detection rate in nonstandard cosmological scenarios where neutralinos account for the dark matter of the Universe. Significant differences are found when such rates are compared with those predicted by the standard cosmological model. For b-ino-like neutralinos, the...Neutralinos2008-02
300 Williams, Clayton C.Depth dependent carrier density profile by scanning capacitance microscopyThe depth dependent carrier density was measured on an arsenic implanted silicon sample using scanning capacitance microscopy (SCM). The capacitance versus voltage scan was performed by applying dc biases with a dither ac signal. A strong dc bias dependence was observed at the interface of an abru...Carrier density; Silicon submicrometer technology; Scanning capacitance microscopy1997
276 - 300 of 924