UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 Vardeny, Zeev ValentineRecombination kinetics in ?-Si:HMort et al.1 reinterpreted our data on the relaxation of photoinduced absorption (PA) in a-Si:H. 2 We want to show that the proposed interpretation contradicts one basic feature of the data while our original interpretation is in good agreement with experiment.Hydrogenated amorphous silicon; a-Si:H; Recombination kinetics; Photoinduced absorption; Decay; Relaxation1981
2 Lupton, John MarkEfficient dipole-dipole coupling of Mott-Wannier and Frenkel excitons in (Ga,In)N quantum well/polyfluorene semiconductor heterostructuresWe investigate interactions between Mott-Wannier (MW) and Frenkel excitons in a family of hybrid structures consisting of thin organic (polyfluorene) films placed in close proximity (systematically adjusted by GaN cap layer thickness) to single inorganic [(Ga, In)N/GaN] quantum wells (QWs). Charac...Mott-Wannier; Frenkel; Excitons; Dipole-dipole coupling; Semiconductor heterostructures2007-07
3 Vardeny, Zeev ValentineUltrafast studies of laser-action in poly-(p-pherylene vinylene) filmsThe recent demonstration of emission spectral narrowing in ∏-conjugated polymer has stirred widespread interest to the phenomenon of laser-action in these materials. It is now generally believed that spectral narrowing in superior polymer films is caused by amplified spontaneous emission (i.e. si...Ultrafast studies; Poly-(p-pherylene vinylene); PPV; Laser-action1999
4 Vardeny, Zeev ValentinePhoto induced infrared active phonons in trans polyacetyleneWe measured photogenerated ir active phonons in trans-(CH) by the photoinduced absorption technique. A correlation was found to exist with a photoinduced absorption band in which electronic transitions are involved. Our results show photoproduction of free charged defects with long lifetimes.Photoinduced phonons; Trans polyacetylene1983-06
5 Vardeny, Zeev ValentineCoherent phonon generation and detection by picosecond light pulsesUsing the picosecond pump and probe technique we have detected oscillations of photoinduced transmission and reflection in thin films of α-As2Te3 and cis-polyacetylene. These oscillations are due to the generation and propagation of coherent acoustic phonons in the film. We discuss the generation ...a-As2Te3; Cis-polyacetylene; Pump and probe technique1984-09
6 Vardeny, Zeev ValentinePicosecond optical generation and detection of phonon waves in a-As2Te3Using the pump and probe technique we have observed oscillations of photoinduced transmission in thin films of a-As2Te3. The oscillations have periods of 70-240 ps, depending on sample thickness. We ascribe these to phonon propagation in the films. Thermal expansion and carrier deformation potenti...Picosecond optical generation; a-As2Te3; Pump and probe technique1984
7 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
8 Vardeny, Zeev ValentineCylindrical micolasers and light emitting devices from conducting polymersSubstantially improved, photopumped polymer lasers are demonstrated using microrings and microdisks of various diameters D ranging from 5 to 200 mm. Various cavity-dependent laser modes were observed, which for D,10 mm were dominated by a single longitudinal mode with linewidth of less than 1 Å. Th...Cylindrical micolasers; OLED; Photopumped polymer lasers; Microrings; Microdisks; Microlasers1998
9 Vardeny, Zeev ValentinePhotoinduced infrared activity in polyacetylenePhotoexcitation of trans - but not cis -polyacetylene, results in the appearance of strongly-ir-active local modes at 1370 and 1260 cm-1. This observation demonstrates that the photogeneration of self-localized charge carriers is unique to the trans isomer. In spite of their localization the kineti...Photoinduced infrared activity; Photoexcitation1983-06
10 Mishchenko, EugeneThermal conductivity of a two-dimensional electron gas with Coulomb interactionWe demonstrate that forward electron-electron scattering due to Coulomb interaction in a two-dimensional ballistic electron-gas leads to the (T ln T)21 temperature dependence of the thermal conductivity, which is logarithmically suppressed compared to the usual Fermi-liquid behavior.Coulomb drag; Coulomb interaction2003-01
11 Mishchenko, EugeneCoulomb drag by small momentum transfer between quantum wiresWe demonstrate that in a wide range of temperatures Coulomb drag between two weakly coupled quantum wires is dominated by processes with a small interwire momentum transfer. Such processes, not accounted for in the conventional Luttinger liquid theory, cause drag only because the electron dispersion...Coulomb drag; Quantum wires; Luttinger liquid2003-09
12 Vardeny, Zeev ValentineExcitons in poly(para-phenylenevinylene)We show that one-electron band theory fails to describe optical absorption in PPV and the absorption spectrum can be described only within a Coulomb-correlated model. The lowest optical state is an exciton, whose binding energy is estimated theoretically to be 0.90 ± 0 . 1 5 e V Measurements of the...Poly(para-phenylenevinylene); PPV1994-11
13 Vardeny, Zeev ValentineStimulated emission in high-gain organic mediaStimulated emission was studied in various scattering gain media, including thin p-conjugated polymer films, organic dyes-doped gel films, and opal crystals saturated with polymer and laser dye solutions. We found that at high excitation intensities a featureless amplified spontaneous emission ban...Stimulated emission; High-gain organic media; pi-conjugated polymers; Scattering gain media; Organic dyes-doped gel films; Opal crystals1999-02
14 Vardeny, Zeev ValentineUltrafast spectroscopy of even-parity states in ∏-conjugated polymersRelaxation dynamics of even parity (Ag) states in poly(p-phenylene vinylene) derivatives are studied using a novel fsec transient spectroscopy, in which two different excitation pulses successively generate odd parity (1 1Bµ) excitons at 2.2 eV and then reexcite them to higher Ag states. For reexci...pi-conjugated polymers; Ultrafast spectroscopy; PPV; Relaxation dynamics2000-09
15 Mishchenko, EugeneFull counting statistics of a charge pump in the Coulomb blockade regimeWe study full charge counting statistics (FCCS) of a charge pump based on a nearly open single electron transistor. The problem is mapped onto an exactly soluble problem of a nonequilibrium g=1/2 Luttinger liquid with an impurity. We obtain an analytic expression for the generating function of the...Counting statistics; Luttinger liquid2001-11
16 Lupton, John MarkRoom-temperature exciton storage in elongated semiconductor nanocrystalsThe excited state of colloidal nanoheterostructures consisting of a spherical CdSe nanocrystal with an epitaxially attached CdS rod can be perturbed effectively by electric fields. Field-induced fluorescence quenching coincides with a conversion of the excited state species from the bright exciton ...Exciton storage; Colloidal nanoheterostructures; CdSe nanocrystal2007-01
17 Mishchenko, EugeneZero-bias anomaly in disordered wiresWe calculate the low-energy tunneling density of states v(ε, T) of an N-channel disordered wire, taking into account the electron-electron interaction nonperturbatively. The finite scattering rate 1/r results in a crossover from the Luttinger liquid behavior at higher energies, v ∞ εa, to the ...Disordered wires; Luttinger liquid; Coulomb interaction2001-11
18 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
19 Ailion, David Charles79Br nuclear-quadrupole-resonance lineshape and Raman-induced spin-lattice relaxation in the incommensurate phase of β- ThBr4We performed 7 9Br nuclear-quadrupole-resonance (NQR) line-shape and spin-lattice relaxation time measurements in the incommensurate (D system j8-ThBr4 over the temperature range 293-2.5 K. In addition, we extended the theory of the effects of Raman processes on amplitudon and phason spin-lattice re...Spin-lattice; NQR; Raman process; Line shape; Phason gap; Incommensurate systems1989
20 Vardeny, Zeev Valentine; Nahata, AjayThermal emission from metallic films perforated with subwavelength hole arraysThis report presents an overview of our study on the optical transmission and thermal light emission properties of subwavelength hole arrays fabricated in a square lattice with 4 um periodicity. The structures were fabricated in thin aluminum (Al) films on silicon (Si) substrates using conventional ...2008
21 Vardeny, Zeev ValentineMechanism for photogeneration of charge carriers in polyacetyleneIn light of new experimental observations, a mechanism for the photogeneration of charge carriers in trans-polyacetylene is presented. By way of introduction, we discuss the qualitative changes in the picture of charged-soliton photogeneration that are expected due to the inclusion of electron corre...Photogeneration; Charge carriers; Photocarriers1984-07
22 Vardeny, Zeev ValentineLasing and stimulated emission in ∏-conjugated polymersRecent studies of lasing and stimulated emission in luminescent -conjugated polymers performed by our group are presented. Optical properties of cylindrical high- polymer microcavities are discussed. The emission spectra of plastic microring and microdisk lasers are measured and analyzed. Light-emi...Lasing; Stimulated emission; pi-conjugated polymers; Microcavities; Polymer lasers2000-01
23 Mishchenko, EugeneZero-bias anomaly in two-dimensional electron layers and multiwall nanotubesThe zero-bias anomaly in the dependence of the tunneling density of states n (e) on the energy e of the tunneling particle for two- and one-dimensional multilayered structures is studied. We show that for a ballistic two-dimensional (2D) system the first-order interaction correction to density of s...Spin-orbit coupling; Coulomb interaction2002-05
24 Vardeny, Zeev ValentineExcited-state relaxation in ∏-conjugated polymersWe study ultrafast relaxation processes of odd- (Bu) and even-parity (Ag) exciton states in poly(p-phenylene vinylene) derivatives. The Bu states are studied using a regular two-beam pump-and-probe spectroscopy, which can monitor vibronic relaxation and exciton diffusion. In order to observe the A...Ultrafast relaxation; Excited-state relaxation; pi-conjugated polymers; PPV2002-05
25 Bernstein, Paul S.; Gellermann, WernerMacular pigment Raman detector for clinical applicationsClinical studies of carotenoid macular pigments (MP) have been limited by the lack of noninvasive, objective instruments. We introduce a novel noninvasive optical instrument, an MP Raman detector, for assessment of the carotenoid status of the human retina in vivo. The instrument uses resonant excit...Diagnosis, Computer-Assisted; Equipment Failure Analysis; Sensitivity and Specificity2004
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