Showing papers on "Resonance published in 1999"
TL;DR: The plasmon resonance of metal nanoshells displays a geometric tunability controlled by the ratio of the core radius to the total radius for gold-coated Au2S as discussed by the authors.
Abstract: A metal nanoshell consists of a nanometer-scale dielectric core surrounded by a thin metallic shell. The plasmon resonance of metal nanoshells displays a geometric tunability controlled by the ratio of the core radius to the total radius. For gold-coated Au2S this ratio varies from 0.6 to 0.9, yielding a plasmon resonance tunable from 600 to greater than 1000 nm. Mie scattering theory for the nanoshell geometry quantitatively accounts for the observed plasmon resonance shifts and linewidths. In addition, the plasmon linewidth is shown to be dominated by electron surface scattering.
575 citations
TL;DR: In this paper, the authors review the nonlinear optical properties of semiconductor quantum wells that are grown inside high-Q Bragg-mirror microcavities and explain the Coulomb interacting electron-hole system in the quantum well.
Abstract: The authors review the nonlinear optical properties of semiconductor quantum wells that are grown inside high-Q Bragg-mirror microcavities. Light-matter coupling in this system is particularly pronounced, leading in the linear regime to a polaritonic mixing of the excitonic quantum well resonance and the single longitudinal cavity mode. The resulting normal-mode splitting of the optical resonance is observed in reflection, transmission, and luminescence experiments. In the nonlinear regime the strong light-matter coupling influences the excitation-dependent bleaching of the normal-mode resonances for nonresonant excitation, leads to transient saturation and normal-mode oscillations for resonant pulsed excitation and is responsible for the density-dependent signatures in the luminescence characteristics. These and many more experimental observations are summarized and explained in this review using a microscopic theory for the Coulomb interacting electron-hole system in the quantum well that is nonperturbatively coupled to the cavity light field.
492 citations
TL;DR: In this paper, the authors developed a theory of the extrinsic contributions to the ferromagnetic resonance linewidth and frequency shift of ultrathin films by two magnon scattering by defects at surfaces and interfaces.
Abstract: We develop a theory of the extrinsic contributions to the ferromagnetic resonance linewidth and frequency shift of ultrathin films. The basic mechanism is two magnon scattering by defects at surfaces and interfaces. In the presence of dipolar couplings between spins in the film, one realizes short wavelength spin waves degenerate with the ferromagnetic resonance (FMR) mode, provided the magnetization is parallel to the film surfaces. Defects on the surface or interface thus scatter the FMR mode into such short wavelength spin waves, producing a dephasing contribution to the linewidth, and a frequency shift of the resonance field. The mechanism described here is inoperative when the magnetization is perpendicular to the film.
478 citations
TL;DR: In this article, the first-order Raman bands are broadened, but not significantly shifted, and no additional bands are observed, indicating that the atomic structure is preserved, at least locally, in the nanoparticles.
Abstract: Raman and resonance Raman spectra of ${\mathrm{MoS}}_{2}$ nanoparticles, in the form of inorganic fullerenelike nanoparticles with diameters ranging from 200 to 2000 \AA{} in size, and platelets ranging from 50 to 5000 \AA{} in size, are presented. Off resonance, the first-order Raman bands are broadened, but not significantly shifted, and no additional bands are observed, indicating that the atomic structure is preserved, at least locally, in the nanoparticles. The broadening effect is assigned to phonon confinement by facet boundaries. In the resonance Raman spectra of the nanoparticles, several additional first-order peaks are observed. The electron-phonon coupling responsible for the strong-resonance conditions is identified through dynamic band calculations. Using temperature-dependent resonance Raman measurements, we assign these peaks to zone-boundary phonons activated by disorder and finite-size effects. By analyzing the position of the dispersive peak at 429 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ under resonance conditions, it was possible to probe the softening of modes propagating in the c-axis direction.
474 citations
TL;DR: In this article, the theory of binary collision Feshbach resonances and its effects on the many-body physics of the condensate is reviewed. But the authors focus on the effect of the number of atoms and molecules in the binary collisions.
448 citations
TL;DR: In this paper, a thin-film bulk acoustic resonator (TFBAR) with fundamental resonance at 3.6 GHz has been fabricated to assess resonator properties, and the material parameters derived from the thickness resonance were a coupling factor k=0.23 and a sound velocity vs.
Abstract: Aluminum nitride thin films have been grown by reactive magnetron sputter technique using a pulsed power supply. The highly (002)-textured columnar films deposited on platinized silicon substrates exhibited quasi-single-crystal piezoelectric properties. The effective d33 was measured as 3.4 pm/V, the effective e31 as 1.0 C/m2. The pyroelectric coefficient turned out to be positive (4.8 μC m−2 K−1) due to a dominating piezoelectric contribution. Thin-film bulk acoustic resonators (TFBAR) with fundamental resonance at 3.6 GHz have been fabricated to assess resonator properties. The material parameters derived from the thickness resonance were a coupling factor k=0.23 and a sound velocity vs=11 400 m/s. With a quality factor Q of 300, the TFBARs proved to be apt for filter applications. The temperature coefficient of the frequency could be tuned to practically 0 ppm/K.
415 citations
TL;DR: In this paper, the authors measured angularly resolved and absolutely calibrated spectra of the multi-MeV electrons produced by relativistic self-channeling in a high-density gas jet.
Abstract: We have measured angularly resolved and absolutely calibrated spectra of the multi-MeV electrons produced by relativistic self-channeling in a high-density gas jet. Using 200 fs laser pulses with ${P}_{L}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.2\mathrm{TW}$, we have investigated the electron spectrum dependence on the plasma electron density in the range of $3\ifmmode\times\else\texttimes\fi{}{10}^{19}--4\ifmmode\times\else\texttimes\fi{}{10}^{20}{\mathrm{cm}}^{\ensuremath{-}3}$. The experimentally obtained results are closely reproduced by three-dimensional particle-in-cell simulations. A detailed analysis shows that the self-modulated laser wake field, although active, cannot explain the experimental energy spectrum. The bulk of the fast electrons are produced by direct laser acceleration at the channel betatron resonance.
359 citations
TL;DR: In this paper, the authors present data on nanofabricated suspended silicon wires driven at resonance, which are electrostatically driven and detected optically, and they have observed wires with widths as small as 45 nm and resonant frequencies as high as 380 MHz.
Abstract: We present data on nanofabricated suspended silicon wires driven at resonance. The wires are electrostatically driven and detected optically. We have observed wires with widths as small as 45 nm and resonant frequencies as high as 380 MHz. We see a strong dependence of the resonant quality factor on the surface to volume ratio.
322 citations
TL;DR: In this paper, the fast-response resonance fluorescence instrument for the airborne measurement of carbon monoxide described by Gerbig et al. was modified by implementing an improved optical filter with more efficient optics and an optimized resonance lamp.
Abstract: The fast-response resonance fluorescence instrument for the airborne measurement of carbon monoxide described by Gerbig et al. [1996] was modified by implementing an improved optical filter with more efficient optics and an optimized resonance lamp. Besides reductions in size and weight, the new instrument achieves a sensitivity 10 times higher, a lower background (65 ppb compared with 250 ppb), and a faster time response (<0.1 s) than the original instrument. The precision is ±1.5 ppb at an atmospheric mixing ratio of 100 ppb CO, and the detection limit is 3 ppb (2σ) for an integration time of 1 s. First results from the North Atlantic Regional Aerosol Characterization Experiment (ACE-2) campaign during July 1997, when the new instrument was deployed aboard the U.K. Meteorological Office C-130 aircraft, are used to demonstrate the performance of the new instrument.
306 citations
TL;DR: In this paper, a prism-coupled excitation of surface electromagnetic waves in one-dimensional photonic band-gap arrays is described. And the low loss of photonic bandsgap materials leads to narrow angular reflectivity resonances and high surface fields.
Abstract: Experiments are described on the prism-coupled excitation of surface electromagnetic waves in one-dimensional photonic band-gap arrays. The low loss of photonic band-gap materials leads to narrow angular reflectivity resonances and high surface fields. These attributes, coupled with the ability to engineer the optical properties of photonic band-gap arrays, suggest these materials as powerful replacements for metal films in many applications that make use of surface-plasmon resonance.
210 citations
TL;DR: In this article, a new continuum spectral model, called NPEX, was developed for the Ginga spectra of binary X-ray pulsars, which was tested against the classical cyclotron scattering line profile, and it was confirmed that 4U 1907+09 and Vela X-1 exhibit fundamental Cyclotron resonances at approximately 20 and 25 keV, respectively.
Abstract: The Ginga X-ray spectra of the two binary X-ray pulsars, 4U 1907+09 and Vela X-1, were analyzed for effects due to electron cyclotron resonance. For this purpose, a new continuum spectral model, called NPEX, was developed. The NPEX model, combined with the classical cyclotron scattering line profile, was first tested against the Ginga spectra (typically in 2-50 keV) of Her X-1, 4U 0115+63, 4U 1538-52, X0331+53, and Cep X-4 and was confirmed to reproduce successfully their overall spectra including the previously known cyclotron resonance features. Through application of the same model to the pulse-phase-averaged and phase-resolved Ginga spectra, it was confirmed that 4U 1907+09 and Vela X-1 exhibit fundamental cyclotron resonances at ~20 and ~25 keV, respectively. The data for both objects are also consistent with the presence of the second-harmonic resonances, which were discovered with hard X-ray experiments. Including these two examples, the cyclotron resonance effects are now established in about a dozen binary X-ray pulsars. Their surface magnetic field strengths, implied by their resonance energies, apparently distribute over a narrow range of (1-4) × 1012 G. Although the fewer number of higher field objects may be an instrumental selection effect, the lack of objects with magnetic fields of (0.2-1) × 1012 G is concluded to be real. A limited number of ASCA data are utilized to reinforce this conclusion. These results suggest that the magnetic field of binary X-ray pulsars do not decay significantly at least in ~108 yr.
TL;DR: In this article, an experimental investigation of the far-infrared properties of several nonlinear crystals using terahertz time-domain spectroscopy (THz-TDS) was reported.
Abstract: In this article we report an experimental investigation of the far-infrared properties of several nonlinear crystals, LiNbO3, LiTaO3, ZnTe and CdTe Using Terahertz Time-Domain Spectroscopy (THz-TDS) we have measured the complex frequency response, ie both index of refraction and absorption up to 3 THz (100 cm−1) for the electro-optic crystals at room temperature The single Lorentzian oscillator model is used to describe the aquired data Additional resonance features are observed, especially in the II-VI compounds
TL;DR: Specific data collection strategies, coupled with these computer programs, allow automated analysis of extensive backbone and sidechain resonance assignments and three-dimensional structures for proteins of 50 to 200 amino acids.
TL;DR: In this paper, the connection between the asymptotic normalization coefficient (ANC) and the fitting parameters in K- and R-matrix theory methods for low energy experimental data was shown.
Abstract: We present here useful relations showing the connection between the asymptotic normalization coefficient (ANC) and the fitting parameters in K- and R-matrix theory methods which are often used when analyzing low energy experimental data. It is shown that the ANC of a subthreshold bound state defines the normalization of both direct radiative capture leading to this state and resonance capture in which the state behaves like a subthreshold resonance. A determination of the appropriate ANC(s) thus offers an alternative method for finding the strength of these types of capture reactions, both of which are important in nuclear astrophysics.
TL;DR: In this article, the utility of heteronuclear double-resonance NMR methods involving the quadrupolar nuclei 11B and 27Al is demonstrated for probing the intermediate-range order in aluminoborate glasses.
Abstract: The utility of heteronuclear double-resonance NMR methods involving the quadrupolar nuclei 11B and 27Al is demonstrated for probing the intermediate-range order in aluminoborate glasses. Results from both rotational echo double resonance (REDOR) and heteronuclear cross-polarization magic angle spinning (CPMAS) studies are presented and discussed. While both techniques are strongly affected by the presence of large quadrupolar splittings, a working strategy is developed on the basis of which reliable structural interpretations are possible. Using this strategy, the effects of the cation type M on the structures of two basic glass compositions, 25M(2)O-45B2O3-30Al2O3 and 40M(2)O-40B2O3-20Al2O3 (M = Na, Ca, Mg), are discussed. Within each series having the same basic network composition, replacement of the modifier cation Na by Ca or Mg produces a large change in the speciation of framework aluminum (“cation effect”): while in the sodium-containing glass the overwhelming fraction of Al is present as tetrahe...
TL;DR: A new variant of this technique, coupled plasmon-waveguide resonance (CPWR) spectroscopy, allows the characterization of anisotropic biological membranes.
TL;DR: In this paper, the curve-of-growth (COG) method was applied to a laser-induced plasma, which was produced by a Nd:YAG laser on the surface of steel samples containing 0.007-1.3% of Cr atoms.
TL;DR: Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques.
Abstract: Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques. With this active feedback, an 8.5-microm QC distributed-feedback laser is locked to the side of a rovibrational resonance of nitrous oxide (N(2) O) at 1176.61cm (-1) . A stabilized frequency-noise spectral density of 42Hz/ radicalHz has been measured at 100 kHz; the calculated laser linewidth is 12 kHz.
TL;DR: In this paper, the oscillations of atmospheric neutrinos in the earth in the three-neutrino scheme with a Δm2 hierarchy and a small admixture of the electron neutrino in the heavy mass eigenstate characterized by the mixing angle θ13.6 were investigated.
TL;DR: In this paper, the authors used cross-phase and related methods to determine the field line resonance frequency across 2.4 and 2.8 days in the Southern Hemisphere at 226° magnetic longitude, for several days in October and November 1990.
Abstract: It is well known that the resonant frequency of geomagnetic field lines is determined by the magnetic field and plasma density. We used cross-phase and related methods to determine the field line resonance frequency across 2.4≤
TL;DR: In this paper, the lowest energy dipole-allowed absorption band of [Au2(dcpm)2]-ClO4)2 (dcpm = bis(dicyclohexylphosphine)methane) was investigated.
Abstract: We present a resonance Raman investigation of the lowest energy dipole-allowed absorption band of [Au2(dcpm)2](ClO4)2 (dcpm = bis(dicyclohexylphosphine)methane). The resonance Raman spectra provide...
TL;DR: In this article, the authors used scanning tunneling spectroscopy and atomic manipulation to study the interaction between a single pair of magnetic atoms at the surface of a nonmagnetic metal.
Abstract: We have used scanning tunneling spectroscopy and atomic manipulation to study the interaction between a single pair of magnetic atoms at the surface of a nonmagnetic metal. The local electronic structure of cobalt adatoms on Au(111) was measured for different cobalt-cobalt interatomic spacings at $T=6$ K. Artificially fabricated cobalt dimers are found to show an abrupt disappearance of the Kondo resonance for cobalt-cobalt separations less than 6 \AA{}. This behavior is explained as the result of reduced exchange coupling between gold conduction electrons and ferromagnetic cobalt dimers.
TL;DR: In this article, a noncontacting resonant-ultrasound-spectroscopy (RUS) method for measuring elastic constants and internal friction of conducting materials is described, and applied to monocrystalline copper.
Abstract: A noncontacting resonant-ultrasound-spectroscopy (RUS) method for measuring elastic constants and internal friction of conducting materials is described, and applied to monocrystalline copper. This method is called electromagnetic acoustic resonance (EMAR). Contactless acoustic coupling is achieved by energy transduction between the electromagnetic field and the ultrasonic vibrations. A solenoidal coil and static magnetic field induce Lorentz forces on specimen surfaces without using a coupling agent. By changing the field direction, a particular set of vibration modes can be selectively excited and detected, an advantage in identifying the vibration modes of the observed resonance peaks. Contactless coupling allows the measure of intrinsic internal friction free from energy loss associated with contact coupling. The elastic constants and internal friction measured by EMAR are compared with those by the usual RUS method for a rectangular-parallelepiped copper monocrystal. Both methods yielded the same ela...
TL;DR: Theoretical results demonstrate that distilled water can sustain dielectric resonances in head-sized spheres near 200 and 360 MHz, but the presence of significant conductivity suppresses these resonances.
Abstract: Purpose: Dielectric resonances have previously been advanced as a significant cause of image degradation at higher fields. In this work, a study of dielectric resonances in ultra high field MRI is presented to explore the real importance of dielectric resonances in the human brain in this setting. Method: Gradient-recalled echo images were acquired using a transverse electromagnetic resonator at 1.5, 4.7, and 8 T. Images were obtained from the human head and from phantoms filled with pure water, saline, and mineral oil. In addition, an exact theoretical analysis of dielectric resonances is presented for a spherical phantom and for a model of the human head. Results: Theoretical results demonstrate that distilled water can sustain dielectric resonances in head-sized spheres near 200 and 360 MHz, but the presence of significant conductivity suppresses these resonances. These findings are confirmed experimentally with proton images of water and saline (0.05 and 0.125 M NaCl). For lossy phantoms, coupling between the source and phantom overwhelms the dielectric resonance. Because of their low relative permittivity, mineral oil phantoms with 20 cm diameter do not exhibit dielectric resonances below -900 MHz. Significant dielectric resonances were not observed in human head images obtained at 1.5, 4.7, and 8 T. Conclusion: It appears that dielectric resonances do not have any real importance in determining image quality for MR studies of the human head. It is advanced that RF coils are much more likely to be the source of any inhomogeneity. Index Terms: Magnetic resonance imaging, artifacts-Magnetic resonance imaging, ultra high frequency-Dielectric resonance-Image quality.
TL;DR: In this paper, electrical and infrared optical properties of polycrystalline ZnO:Al films grown at varying oxygen flow rates were studied on samples prepared in the same deposition run, which suggests that the low carrier mobility in these films is mainly caused by scattering processes taking place within the film grains and that grain boundary scattering plays a minor role.
TL;DR: In this article, it was shown that f-mode resonant effects can be included in constructing the templates of waveforms used in searching for gravitational wave signals from a coalescing binary neutron star.
Abstract: In a coalescing neutron star–neutron star or neutron star–black hole binary, oscillation modes of the neutron star can be resonantly excited by the companion during the final minutes of the binary inspiral, when the orbital frequency sweeps up from a few Hz to a few thousand Hz. The resulting resonant energy transfer between the orbit and the neutron star speeds up or slows down the inspiral, depending on whether the resonant mode has positive or negative energy, and induces a phase change in the emitted gravitational waves from the binary. While only g-modes can be excited for a non-rotating neutron star, f-modes and r-modes can also be excited when the neutron star is spinning. A tidal resonance, designated by the index ( jk, m) ({ jk} specifies the angular order of the mode, as in the spherical harmonic Yjk), occurs when the mode frequency equals m times the orbital frequency. For the f-mode resonance to occur before coalescence, the neutron star must have rapid rotation, with spin frequency νs≳710 Hz for the (22,2)-resonance and νs≳570 Hz for the (33,3)-resonance (assuming canonical neutron star mass, M=1.4 M⊙, and radius, R=10 km; however, for R=15 km, these critical spin frequencies become 330 and 260 Hz, respectively). Although current observations suggest that such high rotation rates may be unlikely for coalescing binary neutron stars, these rates are physically allowed. Because of their strong tidal coupling, the f-mode resonances induce a large change in the number of orbital cycles of coalescence, ΔNorb, with the maximum ΔNorb∼10–1000 for the (22,2)-resonance and ΔNorb∼1 for the (33,3)-resonance. Such f-mode resonant effects, if present, must be included in constructing the templates of waveforms used in searching for gravitational wave signals. Higher order f-mode resonances can occur at slower rotation rates, but the induced orbital change is much smaller (ΔNorb≲0.1). For the dominant g-mode (22,2)-resonance, even modest rotation (νs≲100 Hz) can enhance the resonant effect on the orbit by shifting the resonance to a smaller orbital frequency. However, because of the weak coupling between the g-mode and the tidal potential, ΔNorb lies in the range 10−3–10−2 (depending strongly on the neutron star equation of state) and is probably negligible for the purpose of detecting gravitational waves. Resonant excitations of r-modes require misaligned spin–orbit inclinations, and the dominant resonances correspond to octopolar excitations of the jk=2 mode, with (jk, m)=(22,3) and (22,1). Since the tidal coupling of the r-mode depends strongly on rotation rate, ΔNorb≲10−2(R/10 km)10(M/1.4 M⊙)−20/3 is negligible for canonical neutron star parameters, but can be appreciable if the neutron star radius is larger.
TL;DR: In this article, the authors obtained the Mn $3d$ partial density of states in GaAs using the resonance photoemission technique as well as by means of the difference between GaAs and GaAs.
Abstract: We have obtained the Mn $3d$ partial density of states in ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ using the resonance photoemission technique as well as by means of the difference between ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ and GaAs We have observed a strong satellite structure on the higher binding energy side of the main peak, as in Mn-doped II-VI compounds such as ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ Based on analysis using configuration-interaction calculation for a ${\mathrm{MnAs}}_{4}$ cluster, we could ascribe the spectral features to strong Mn $3d\ensuremath{-}\mathrm{As}$ $4p$ hybridization and Mn $3d\ensuremath{-}3d$ Coulomb interaction
TL;DR: In this article, the intensity distribution in the resonance Raman (RR) spectrum of the 11-cis protonated Schiff base of retinal (PSB11) is modeled for the first time on the basis of ab initio quantum chemical calculations.
Abstract: The intensity distribution in the resonance Raman (RR) spectrum of the 11-cis protonated Schiff base of retinal (PSB11) is modeled for the first time on the basis of ab initio quantum chemical calculations. To adequately represent the structure of PSB11, 4-cis-γ,η-dimethyl-C9H9 NH2+ is chosen as a model. The RR spectra of the model PSB11 and of several isotopomers are compared with the experimental spectra of PSB11 in solution. An excellent agreement is obtained in the structurally sensitive fingerprint region of the spectra (1100−1300 cm-1), where most of the observed details are quantitatively reproduced by the simulations. The 900−1100-cm-1 region of the RR spectrum of PSB11, which contains the signatures of the S0,S1 potential energy changes due to the protein environment, is also well reproduced. On the basis of the simulations, it is concluded that the activity observed at ca. 970 cm-1 in the spectrum of PSB11 in solution is due to in-plane modes, while a superposition of in-plane and out-of-plane m...