UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 Lupton, John MarkAir-induced fluorescence bursts from single semiconductor nanocrystalsWe observe a dramatic enhancement of the fluorescence intensity from single core/shell CdSe/ZnS nanocrystals upon sudden exposure to air from an evacuated surrounding. Both the number of particles contributing to emission increases as well as the average emission intensity from a single particle, le...CdSe; ZnS; Air-induced; Fluorescence bursts2004
2 Vardeny, Zeev Valentine; Raikh, Mikhail E.Coherent random lasing: trapping of light by the disorderRecent discovery of the coherent lasing from various disordered materials adds a new dimension to the conventional physics of light propagation in multiply scattering media. It suggests that in the situation, when the propagation of light is diffusive on average, the coherent feedback can be provid...Coherent random lasing; Coherent lasing; Disorder; Disordered materials; Random lasers; Random resonators; Power Fourier transform; Light propagation2004
3 Vardeny, Zeev ValentineDirectional emission from asymmetric microlaser resonators of ∏-conjugated polymersA ∏-conjugated polymer film was fabricated into an asymmetric microlaser resonator having a quadrapole deformation with irregular boundaries and a Q factor of 600. At high excitation intensities above the threshold for lasing, we observed multimode laser emission spectra and directional emission a...Directional emission; Asymmetric microlaser resonators; pi-conjugated polymers; DOO-PPV; poly(dioctyloxy) phenylene vinylene2004
4 Ailion, David CharlesGallium and thallium NMR study of phase transitions and incomemensurability in the layered semiconductor TlGaSe2We report on the first NMR study of phase transitions and incommensurability in the layered semiconductor TlGaSe2. 69,71Ga and 205Tl NMR data from a powder sample show phase transitions at 118, 108 and around 69 K. The 69Ga and 71Ga spin-lattice relaxation times T1 are short and nearly temperature i...NMR; Atomic motion; Phase transitions; Spin-lattice; Relaxation-time2004
5 Williams, Clayton C.Instability induced tunneling and repeatable charge injection to SiO2 surfaces by electrostatic force microscopyThe dynamic response and stability of a voltage biased oscillating cantilever in the proximity of an insulating sample surface is investigated. As the tip approaches the sample surface, the cantilever can jump between two different oscillation modes. The jump is detected as an abrupt increase in t...Electrostatic force microscopy; EFM; Dielectric films2004
6 DeTar, CarletonLattice quantum chromodynamics comes of ageThe strength of the electron-photon interaction is characterized by the fine-structure constant α ≈ 1/137.036. Because α is small, quantum electrodynamics (QED), the theory of interacting electrons and photons, can be solved to very good approximation with the traditional technology of pencil an...Quarks; Gluons; Mesons; CKM matrix2004
7 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
8 Lupton, John MarkLow-threshold polymeric distributed feedback lasers with metallic contactsOptical losses in waveguides comprising metallic contacts are thought to be a major hurdle to the realization of organic laser diodes. We demonstrate here that careful tuning of the waveguide mode in flexible distributed feedback lasers can allow lasing action to occur in organic thin films in the p...Metallic contacts; Organic laser diodes; Waveguides; Feedback lasers2004
9 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
10 Williams, Clayton C.Modeling and experimental investigation of cantilever dynamics in force detected single electron tunnelingThe dynamic response of a voltage biased oscillating cantilever probe is investigated through experimental and theoretical analysis as it approaches a dielectric surface. When the tip reaches the appropriate gap single electron tunneling events are detected between the metallic tip and the surface. ...Oscillating cantilever probe; Electron tunneling2004
11 Vardeny, Zeev ValentineOptical and magneto-optical studies of two-dimensional metallodielectric photonic crystals on cobalt filmsWe studied the optical transmission and magneto-optical effect through a subwavelength hole array fabricated on a ferromagnetic cobalt (Co) thin film in comparison to a control unperforated Co film having the same thickness. We found that the perforated film sustains extraordinary transmission bands...Metallodielectric photonic crystals; Cobalt films2004
12 Vardeny, Zeev ValentineOptical studies of metallodielectric photonic crystals: bismuth and gallium infiltrated opalsWe have fabricated three-dimensional metallodielectric photonic crystals that consist of bismuth and gallium metals infiltrated into porous synthetic opals that have 300 nm diam silica balls. The specular reflectivity was measured in a broad spectral range from 0.3 to 25 mm using a variety of light ...Metallodielectric photonic crystals; Bismuth infiltrated opals; Gallium infiltrated opals; Bragg; Porous synthetic opals2004
13 Bromley, Benjamin C.Periodic standing-wave approximation: overview and three dimensional scalar modelsThe periodic standing-wave method for binary inspiral computes the exact numerical solution for periodic binary motion with standing gravitational waves, and uses it as an approximation to slow binary inspiral with outgoing waves. Important features of this method presented here are: (i) the mathe...Periodic standing wave method; Black holes; Neutron stars2004
14 Vardeny, Zeev ValentineRandom lasing in human tissuesA random collection of scatterers in a gain medium can produce coherent laser emission lines dubbed "random lasing." We show that biological tissues, including human tissues, can support coherent random lasing when infiltrated with a concentrated laser dye solution. To extract a typical random reson...Random lasing; Gain medium; Human tissues; Malignant tissues2004
15 Williams, Clayton C.Single electron tunneling to insulator surfaces measured by frequency detection electrostatic force microscopySingle-electron tunneling events between a metal probe and an insulator surface are measured by frequency detection electrostatic force microscopy. Single-electron tunneling events typically cause 1-10 Hz shifts in the 300 kHz resonance frequency of the oscillating force probe. The frequency shift...Electrons; Tunneling events; Electrostatic force microscopy2004
16 Williams, Clayton C.Sub-10 nm lateral spatial resolution in scanning capacitance microscopy achieved with solid platinum probesSub-10 nm resolution can be obtained in scanning capacitance microscopy (SCM) if the probe tip is approximately of the same size. Such resolution is observed, although infrequently, with present commercially available probes. To acquire routine sub-10 nm resolution, a solid Pt metal probe has bee...2004
17 Lupton, John MarkUltrafast intramolecular energy transfer in single conjugated polymer chains probed by polarized single chromophore spectroscopySingle molecule spectroscopy of rigid-rod ladder-type conjugated polymers reveals individual chromophore units on a polymer chain, exhibiting fluorescence linewidths of less than 1 nm. Whereas the fluorescence from a single chromophore is fully linearly polarized at low temperatures, a number of exc...Single molecule spectroscopy; Intramolecular energy transfer; Chromophore spectroscopy; Chromophores; Rigid-rod; Ladder-type2004
18 Gondolo, PaoloCan WIMP spin dependent couplings explain DAMA data, in light of null results from other experiments?We examine whether the annual modulation found by the DAMA dark matter experiment can be explained by Weakly Interacting Massive Particles (WIMPs), in light of new null results from other experiments. CDMS II has already ruled out most WIMP-nucleus spin-independent couplings as an explanation for DA...WIMP; Weakly interacting massive particles; DAMA; CDMS II; Parameter space2004-12
19 Vardeny, Zeev ValentineConfined and delocalized polarons in ∏-conjugated oligomers and polymers: a study of the effective conjugation lengthWe studied optical absorption of polarons in ∏-conjugated oligomers and polymers using the photoinduced absorption technique as well as chemical doping spectra from the literature. We find that the photon energy of the polaron low-energy transition obeys a relationship that depends only on the oli...Confined polarons; Delocalized polarons; pi-conjugated oligomers; pi-conjugated polymers; Effective conjugation length2004-06
20 Gondolo, PaoloDetectability of the Sgr dwarf leading tidal stream with Auger, EUSO, or OWLWe point out that if heavy metastable particles composing the dark matter of our galaxy are responsible for the ultrahigh energy cosmic rays (UHECR) then the leading tidal stream of the Sagittarius dwarf galaxy could be detected through UHECR. The signal would be an anisotropy in the UHECR flux sma...Sagittarius dwarf galaxy; Sgr stream; anisotropy2004-07
21 Sokolsky, PierreEffect of clouds on apertures of space-based air fluorescence detectorsSpace-based ultra-high-energy cosmic ray detectors observe fluorescence light from extensive air showers produced by these particles in the troposphere. Clouds can scatter and absorb this light and produce systematic errors in energy determination and spectrum normalization. We study the possibilit...Fluorescence; Cloud detection; Extensive air showers2004-01
22 Rogachev, AndreyEffect of morphology on the superconductor-insulator transition in one-dimensional nanowiresWe study the effect of morphology on the low-temperature behavior of superconducting nanowires which vary in length from 86 nm to 188 nm. A well-defined superconductor-insulator transition is observed only in the family of homogeneous wires, in which case the transition occurs when the normal resist...One-dimensional wires; Superconductor-insulator transition; Homogeneous wires; Inhomogeneous wires; Morphology; Low-temperature behavior2004-05
23 Gondolo, PaoloEffects of the Sagittarius dwarf tidal stream on dark matter detectorsThe Sagittarius dwarf tidal stream may be showering dark matter onto the solar neighborhood, which can change the results and interpretation of direct detection searches for weakly interacting massive particles (WIMPs). Stars in the stream may already have been detected in the solar neighborhood, an...Sagittarius dwarf galaxy; Sgr stream; WIMP; Weakly interacting massive particles2004-03
24 DeTar, CarletonExcited states in staggered meson propagatorsWe report on preliminary results from multi-particle fits to meson propagators with three flavors of light dynamical quarks. We are able to measure excited states in propagators with pion quantum numbers, which we interpret as the pion 2S state, and argue is evidence of locality of the action. In t...Excited states; Meson propagators2004-03
25 Lupton, John MarkExperimental evidence for exciton scaling effects in self-assembled molecular wiresResonant Rayleigh scattering from self-assembled one-dimensional molecular J-aggregate wires reveals a distinct dependence of the exciton energy on the width of lateral extension. For the J aggregates used in this study, strong in-line dipole coupling leads to a delocalization of the exciton wave fu...Exciton scaling effects; Molecular wires; J-aggregate wires; Quantum wires2004-12
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