201 - 225 of 924
Number of results to display per page
201 Vardeny, Zeev ValentinePhotogenerated gap states in polyacetyleneWe have measured the optical absorption spectrum of photogenerated gap states in polyacetylene, (CH)X . From a comparison with electroabsorption spectra the charge state of the excitations is determined. In both isomers of (CH)X locally neutral (exciton-like) states are observed. In addition a charg...Gap state; Photoexcitation1983-06
202 Wu, Yong-ShiOn the Kadomtsev-Petviashvili hierarchy, Ŵ∞ algebra, and conformal SL(2,R)/U(1) model. II. The quantum caseThis article is devoted to constructing a quantum version of the famous Kadomtsev-Petviashvili (KP) hierarchy by deforming its second Hamiltonian structure, namely, the nonlinear W, algebra. This is achieved bx quantizing the conformal noncompact SL(2,R) k/ U(1) coset model, in which W, appears as ...Kadomtsev-Petviashvili hierarchy; Quantum charges; W-algebras1993
203 Boehme, ChristophLight-intensity and temperature dependence of trap-dangling bond recombination in hydrogenated microcrystalline siliconA quantitative study of the trap-dangling bond tunneling recombination in hydrogenated microcrystalline silicon (μc-Si:H) is presented. The transition coefficients were measured at various light exposures and temperatures between T= 10 K and T= 140 K using time-domain measurements of spin-dependen...Hydrogenated microcrystalline silicon; Spin-dependent recombination2002
204 Boehme, ChristophSpin-dependent recombination - an electronic readout mechanism for solid state quantum computersIt is shown that coherent spin motion of electron-hole pairs localized in band gap states of silicon can influence charge carrier recombination. Based on this effect, a readout concept for silicon based solid-state spin-quantum computers as proposed by Kane is suggested. The 31P quantum bit (qbit) i...Spin readout; qbit; Spin-dependent recombination2002-10
205 Ailion, David CharlesDetection of slow modulation wave diffusion in incommensurate barium sodium niobate by 93Nb 2D exchange NMR93Nb two-dimensional (2D) exchange NMR was used to study ultraslow motions in incommensurate barium sodium niobate (BSN) in the temperature range 500 - 560 K. These 2D exchange data provide strong evidence for diffusionlike motion of the modulation wave in BSN. Such motions in BSN had been previousl...NMR; Hahn spin-echo decay; Incommensurate systems.2001
206 Vardeny, Zeev ValentinePicosecond photoinduced dichroism in trans-(CH)x: direct measurement of soliton diffusionPhotoinduced dichroism caused by bleaching of the interband transition in tran s-(CH)x was observed in the picosecond time domain,, The bleaching is induced instantaneously and decays with time as £~1 / / 2 , changing to a lower power after ~50 psec. Although the photoinduced bleaching persists to...Photoinduced dichroism; Trans-(CH)x1982-11
207 Lupton, John MarkHyperfine-field-mediated spin beating in electrostatically bound charge carrier pairsOrganic semiconductors offer a unique environment to probe the hyperfine coupling of electronic spins to a nuclear spin bath. We explore the interaction of spins in electron-hole pairs in the presence of inhomogeneous hyperfine fields by monitoring the modulation of the current through an organic li...Spin beating; Electrostatically-bound; Charge carrier pairs; Electronic spins; Nuclear spin bath; Organic light-emitting diodes2010-01
208 Gondolo, PaoloSection on prospects for dark matter detection of the white paper on the Status and future of ground-based TeV gamma-ray astronomyThis is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed sec...Annihilations; Dwarf spheroidal2008
209 Boehme, ChristophTransport and recombination through weakly coupled localized spin pairs in semiconductors during coherent spin excitationSemianalytical predictions for the transients of spin-dependent transport and recombination rates through localized states in semiconductors during coherent electron-spin excitation are made for the case of weakly spin-coupled charge-carrier ensembles. The results show that the on-resonant Rabi freq...Larmor frequency; Larmor separations2006-12
210 Boehme, ChristophLong-lived spin coherence in silicon with an electrical spin trap readoutPulsed electrically detected magnetic resonance of phosphorous (31P) in bulk crystalline silicon at very high magnetic fields (B0 > 8:5 T) and low temperatures (T = 2:8 K) is presented. We find that the spin-dependent capture and reemission of highly polarized (>95%) conduction electrons by equall...Spin coherence2008-11
211 Mattis, Daniel C.Effect of exciton hopping upon the mass of an excitonA plausible formula derived in a previous paper for the mass Mn* of an exciton in an nth bound state of the electron-hole binding potential is extended so as to include the effect of an exciton-hopping (or Heller-Marcus) mechanism upon Mn*.Frenkel excitons; Exciton-hopping; Heller-Marcus energy; Binding potential1985-10
212 Symko, 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
213 Mishchenko, EugeneEffect of electron-electron interactions on the conductivity of clean grapheneMinimal conductivity of a single undoped graphene layer is known to be of the order of the conductance quantum, independent of the electron velocity. We show that this universality does not survive electron-electron interaction, which results in nontrivial frequency dependence. We begin with analyzi...Optical conductivity; Perturbation theory2007-05
214 Mattis, Daniel C.Three-body bound states on a latticeThe theory of three-body bound states for particles moving on a lattice and interacting with attractive two-body pointlike potentials is presented. The applications are to bosons, fermions (no three-body bound states are found), and magnons. When a three-body bound state forms in three dimensions, i...Particle; Fermions; Ferromagnet1984
215 Mishchenko, EugeneFluctuations of radiation from a chaotic laser below thresholdRadiation from a chaotic cavity filled with gain medium is considered. A set of coupled equations describing the photon density and the population of gain medium is proposed and solved. The spectral distribution and fluctuations of the radiation are found. The full noise is a result of a competitio...Chaotic laser2004-03
216 DeTar, CarletonCritical behavior at the chiral phase transitionIt is generally expected that two-flavor QCD undergoes a high temperature chiral symmetry restoring phase transition at zero quark mass, with O(4) critical behavior[1]. Verifying this expectation is important for understanding the phenomenology of the transition and for facilitating an extrapolation...Phase transitions; Staggered fermions1998-04
217 Gondolo, PaoloDark Stars: Död och ÅteruppståndelseThe first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the univers...Dark stars; WIMP; Weakly interacting massive particles2009
218 Vardeny, Zeev ValentinePhotophysics of excitons in quasi-one-dimensional organic semiconductors: single-walled carbon nanotubes and ∏-conjugated polymersThe nature of the primary photoexcitations in semiconducting single-walled carbon nanotubes (S-SWCNTs) is of strong current interest. We have studied the emission spectra of S-SWCNTs and two different rr-conjugated polymers in solutions and films, and have also performed ultrafast pump-probe spectro...Photophysics; Excitons; Quasi-one-dimensional; Single-walled carbon nanotubes; pi-conjugated polymers2006-02
219 Vardeny, Zeev ValentineInterchain photogeneration of charged solitons in trans-(CH)xIn a recent Letter1 Rothberg, Jedju, Etemad, and Baker (RJEB) used a novel photoinduced-absorption (PA) technique to study charged-soliton (S ?) dynamics in trans-(CH)X with picosecond resolution by measuring transient PA at 0.45 eV. Both intrachain and interchain photogeneration of S ? are rep...Interchain photogeneration; Charged solitons; Trans-(CH)x1987
220 Ailion, David CharlesFrequency modulation method for performing adiabatic demagnetization in the rotating reference frameA new method for preforming adiabatic demagnetization in the rotating reference frame in NMR experiments is presented in this paper. In this new method the frequency of a crystal oscillator rather than the actual magnetic field is pulsed off resonance. Using simple circuits which are described in th...Demagnetization; Physics experiments; NMR1970
221 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
222 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
223 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
224 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
225 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
201 - 225 of 924