Showing papers on "Resonance published in 2007"
TL;DR: It is reported that a resonance response with a very high quality factor can be achieved in a planar metamaterial by introducing symmetry breaking in the shape of its structural elements, which enables excitation of trapped modes, i.e., modes that are weakly coupled to free space.
Abstract: We report that a resonance response with a very high quality factor can be achieved in a planar metamaterial by introducing symmetry breaking in the shape of its structural elements, which enables excitation of trapped modes, i.e., modes that are weakly coupled to free space.
1,066 citations
TL;DR: This work has shown that distance measurements between spin labels if pulsed electron paramagnetic resonance techniques such as electron-electron double resonance (ELDOR) and double-quantum EPR are used are well suited to biomacromolecules with an intrinsic flexibility as distributions of distances can be measured.
Abstract: The biological function of protein, DNA, and RNA molecules often depends on relative movements of domains with dimensions of a few nanometers. This length scale can be accessed by distance measurements between spin labels if pulsed electron paramagnetic resonance (EPR) techniques such as electron-electron double resonance (ELDOR) and double-quantum EPR are used. The approach does not require crystalline samples and is well suited to biomacromolecules with an intrinsic flexibility as distributions of distances can be measured. Furthermore, oligomerization or complexation of biomacromolecules can also be studied, even if it is incomplete. The sensitivity of the technique and the reliability of the measured distance distribution depend on careful optimization of the experimental conditions and procedures for data analysis. Interpretation of spin-to-spin distance distributions in terms of the structure of the biomacromolecules furthermore requires a model for the conformational distribution of the spin labels.
560 citations
TL;DR: In this paper, an interpolation function that precisely represents e(ν,t) at standard atmospheric pressure was derived for frequencies and temperatures in the ranges 0⩽ν⩻25THz and 0 ⩽t⩾100°C.
Abstract: All the currently available experimental permittivity data for pure water are used to derive an interpolation function that precisely represents e(ν,t,) at standard atmospheric pressure, for frequencies and temperatures in the ranges 0⩽ν⩽25THz and 0⩽t⩽100°C. The permittivity data is represented in terms of relaxations and resonances processes. There are three relaxations in the microwave region and two resonances in the far infrared. The temperature dependence of the relaxation and resonance parameters are determined. For example, at 25°C the three relaxation frequencies are 18.56GHz, 167.83GHz, 1.944THz and the two resonance frequencies are 4.03 and 14.48THz.
557 citations
TL;DR: In this article, fast magnetosonic waves, detected by Cluster 3, can accelerate electrons between ∼10 keV and a few MeV inside the outer radiation belt, which is required to explain electron flux increases in the outer Van Allen radiation belt during magnetic storms.
Abstract: [1] Local acceleration is required to explain electron flux increases in the outer Van Allen radiation belt during magnetic storms. Here we show that fast magnetosonic waves, detected by Cluster 3, can accelerate electrons between ∼10 keV and a few MeV inside the outer radiation belt. Acceleration occurs via electron Landau resonance, and not Doppler shifted cyclotron resonance, due to wave propagation almost perpendicular to the ambient magnetic field. Using quasi-linear theory, pitch angle and energy diffusion rates are comparable to those for whistler mode chorus, suggesting that these waves are very important for local electron acceleration. Since pitch angle diffusion does not extend into the loss cone, these waves, on their own, are not important for loss to the atmosphere. We suggest that magnetosonic waves, which are generated by unstable proton ring distributions, are an important energy transfer process from the ring current to the Van Allen radiation belts.
354 citations
TL;DR: Experimental extinction spectra and Mie theory calculations of single microscale rod-shaped particles reveal three observable midinfrared resonant modes, allowing unexplored dielectric metamaterial designs.
Abstract: Silicon carbide particles exhibit both electric and magnetic optical resonances, allowing unexplored dielectric metamaterial designs. Experimental extinction spectra and Mie theory calculations of single microscale rod-shaped particles reveal three observable midinfrared resonant modes. Two of the modes are degenerate, with a frequency that can be tuned according to a resonance condition derived within the Letter. The existence of both electric and magnetic resonances may enable a novel negative refractive index metamaterial design.
323 citations
TL;DR: It is measured that 6.3 dB of relative intensity squeezing is generated by stimulated, nondegenerate four-wave mixing in a hot rubidium vapor, which is of interest for experiments involving cold atoms or atomic ensembles.
Abstract: We have measured −3.5 dB (−8.1 dB corrected for losses) relative intensity squeezing between probe and conjugate beams generated by stimulated, nondegenerate four-wave mixing in hot rubidium vapor. Unlike early observations of squeezing in atomic vapors based on saturation of a two-level system, our scheme uses a resonant nonlinearity based on ground-state coherences in a three-level system. Since this scheme produces narrowband, squeezed light near an atomic resonance, it is of interest for experiments involving cold atoms or atomic ensembles.
299 citations
TL;DR: In this article, a software package for solving partial-differential-equations (PDEs), as based on the finite-element method, can be configured to efficiently calculate the frequencies and fields of the whispering-gallery (WG) modes of axisymmetric dielectric resonators.
Abstract: This paper explains how a popular commercially available software package for solving partial-differential-equations (PDEs), as based on the finite-element method, can be configured to efficiently calculate the frequencies and fields of the whispering-gallery (WG) modes of axisymmetric dielectric resonators. The approach is traceable; it exploits the PDE-solver's ability to accept the definition of solutions to Maxwell's equations in so-called weak form. Associated expressions and methods for estimating a WG mode's volume, filling factor(s), and in the case of closed (open) resonators, its wall (radiation) loss, are provided. As no transverse approximation is imposed, the approach remains accurate even for quasi-transverse-magnetic/electric modes of low finite azimuthal mode order. The approach's generality and utility are demonstrated by modeling several nontrivial structures, i.e., 1) two different optical microcavities (one toroidal made of silica, the other an AlGaAs microdisk), 2) a third-order sapphire:air Bragg cavity, and 3) two different cryogenic sapphire WG-mode resonators; both 2) and 3) operate in the microwave X-band. By fitting one of 3) to a set of measured resonance frequencies, the dielectric constants of sapphire at liquid-helium temperature have been estimated.
286 citations
TL;DR: The design of a BRET-based QD biosensor for detection of the activity of matrix metalloproteinases (MMPs), a family of zinc-dependent secreted endopeptidases that are crucial for the regulated degradation and processing of extracellular matrices, is reported.
Abstract: Semiconductor quantum dots (QDs) are bright fluorescence emitters with high quantum yields, high molar extinction coefficients, size-dependent tunable emission, and high photostability. These attractive fluorescence properties prompt a wide interest in developing QD-based sensors for biological detection and imaging. One often-used strategy towards the development of QD nanosensors is based on fluorescence resonance energy transfer (FRET) with the QDs as the FRET donor. There are numerous examples of FRETbased QD biosensors that include self-assembled nanocomplexes for detecting maltose, pH, 2,4,6-trinitrotoluene, thrombin, and enzyme activity. In these FRET-based QD nanosensors, multiple copies of the FRET acceptor were often present on one QD, which may result in self-quenching and lead to low emission from the FRET acceptor. We have recently demonstrated that QDs can also serve as an energy acceptor for a light-emitting protein (for example, the bioluminescent protein Renilla luciferase) in bioluminescence resonance energy transfer (BRET). When the QD conjugates are exposed to the luciferase substrate, the energy released in the oxidation of the substrate is transferred to the QDs through BRET, thus generating light emission from the QDs. The QD BRET has been shown to have high sensitivity for in vivo imaging and detection. Herein, we report the design of a BRET-based QD biosensor for detection of the activity of matrix metalloproteinases (MMPs). MMPs are a family of zinc-dependent secreted endopeptidases that are crucial for the regulated degradation and processing of extracellular matrices, and are upregulated in almost every type of human cancer. The significant role of MMPs in promoting cancer progression makes them important targets for drug development and in vivo tumor detection. Fluorescenceand magnetic-resonance-based approaches have been used to detect the activity of MMPs. Here, we describe a BRET-based QD nanosensor for detecting the activity of gelatinase MMP-2 with high sensitivity.
281 citations
TL;DR: In this paper, an electrically tunable negative permeability metamaterial consisting of a periodic array of split ring resonators infiltrated with nematic liquid crystals is demonstrated, which can be continuously and reversibly adjusted by an applied electric field, and the maximum shift is about 210MHz with respect to the resonance frequency around 11.08GHz.
Abstract: An electrically tunable negative permeability metamaterial consisting of a periodic array of split ring resonators infiltrated with nematic liquid crystals is demonstrated. It shows that the transmitted resonance dip of the metamaterial can be continuously and reversibly adjusted by an applied electric field, and the maximum shift is about 210MHz with respect to the resonance frequency around 11.08GHz. Numerical simulation shows that the permeability is negative near the resonance frequency, and the frequency range with negative permeability can be dynamically adjusted and widened by about 200MHz by the electric field. It provides a convenient means to design adaptive metamaterials.
271 citations
TL;DR: In this article, a process for tuning the magnetic resonance frequency of a fixed split-ring resonator array, by adding material near the split ring elements, was demonstrated. But this fine tuning is done post fabrication and is demonstrated to be reversible.
Abstract: A process is demonstrated for tuning the magnetic resonance frequency of a fixed split-ring resonator array, by way of adding material near the split-ring elements. Applying drops of a silicon-nanospheres/ethanol solution to the surface of the sample decreases the magnetic resonance frequency of the split-ring array in incremental steps of 0.03THz. This fine tuning is done post fabrication and is demonstrated to be reversible. The exhibited sensitivity of the split-ring resonance frequency to the presence of silicon nanospheres also suggests further application possibilities as a sensor device.
269 citations
TL;DR: It is shown that, in the limit of extremely thin strips and narrow gaps, both structures exhibit the same Q factor of the resonance which is primarily determined by the complex dielectric function of metal.
Abstract: General properties of retardation-based resonances involving slow surface plasmon-polariton (SPP) modes supported by metal nanostructures are considered. Explicit relations for the dispersion of SPP modes propagating along thin metal strips embedded in dielectric and in narrow gaps between metal surfaces are obtained. Strip and gap subwavelength resonant structures are compared with respect to the achievable scattering and local-field enhancements lending thereby their distinction as nano-antennas and nano-resonators, respectively. It is shown that, in the limit of extremely thin strips and narrow gaps, both structures exhibit the same Q factor of the resonance which is primarily determined by the complex dielectric function of metal.
TL;DR: In this paper, the authors examined the current status of theoretical and experimental research on nonlinear phenomena arising when a powerful radio wave propagates in the ionosphere, where the focus is on the modification of ionosphere under the resonance excitation of natural plasma oscillations by radio waves.
Abstract: The review is based in a report presented by the author at the RAS Physical Sciences Division's session in honor of Vitaly L Ginzburg's 90th birthday. It examines the current status of theoretical and experimental research on nonlinear phenomena arising when a powerful radio wave propagates in the ionosphere. The focus is on the modification of the ionosphere under the resonance excitation of natural plasma oscillations by radio waves. The upper-hybrid resonance gives rise to strong upper- and lower-hybrid plasma waves; excites strongly elongated ionospheric irregularities, and induces artificial ionospheric radio emission. Nonlinear processes are found to undergo complete transformation near double resonances, when the upper-hybrid frequency is close to a multiple of the electron gyromagnetic frequency. In the neighborhood of the Langmuir resonance, intense plasma waves and ion-sound waves are excited, electrons are effectively accelerated, and an artificial glow of the ionosphere appears.
TL;DR: In this article, the optical properties of a structure called a nanosheet plasmon cavity were analyzed using the boundary element method, which can be seen as a Fabry-Perot-like resonance caused by reflection of the guided mode at the entrance and the exit surfaces.
Abstract: We present detailed analysis of the optical properties of a structure called a nanosheet plasmon cavity. It is a metal-insulator-metal (MIM) waveguide with a finite length. First, propagation of the lowest-energy surface-plasmon mode of a MIM waveguide, which is the fundamental structure of our cavity, is analytically investigated. In addition to the dispersion relation, localization and dissipation of the electromagnetic energy are discussed. Next, the optical properties of the nanosheet plasmon cavity are numerically examined with the boundary element method. The nanosheet plasmon cavity is found to inherit various natures of the original MIM waveguide. The resonance in this cavity can be understood as a Fabry-Perot-like resonance caused by the reflection of the guided mode at the entrance and the exit surfaces. This enables easy design of a cavity on the basis of the analytical dispersion relation of a MIM waveguide. The fields in a MIM waveguide are localized around the dielectric core, and the wavelength of the surface plasmon becomes shorter with decreasing the thickness of the core. Therefore the electromagnetic energy can be confined in a volume as small as $0.001\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{3}$ in a nanosheet plasmon cavity. Another feature of this cavity is that the electric field is maximized at the core entrance. By only letting molecules be adsorbed on the surface of the core, the molecules are exposed to the maximum field. This exhibits great potential of the nanosheet plasmon cavity for enhanced Raman spectroscopy.
TL;DR: Bending-mode vibrations of carbon nanotube resonators were mechanically detected in air at atmospheric pressure by means of a novel scanning force microscopy method and the resonance frequency and the eigenmode shape of multiwall nanotubes are consistent with the elastic beam theory for a doubly clamped beam.
Abstract: Bending-mode vibrations of carbon nanotube resonators were mechanically detected in air at atmospheric pressure by means of a novel scanning force microscopy method The fundamental and higher order bending eigenmodes were imaged at up to 31 GHz with subnanometer resolution in vibration amplitude The resonance frequency and the eigenmode shape of multiwall nanotubes are consistent with the elastic beam theory for a doubly clamped beam For single-wall nanotubes, however, resonance frequencies are significantly shifted, which is attributed to fabrication generating, for example, slack The effect of slack is studied by pulling down the tube with the tip, which drastically reduces the resonance frequency
TL;DR: The present approach provides a technologically feasible way for single spin manipulation by precise thickness control of thin films by placing magnetic molecules on silicon-supported nanostructures.
Abstract: Manipulating the Kondo effect by quantum confinement has been achieved by placing magnetic molecules on silicon-supported nanostructures. The Kondo resonance of individual manganese phthalocyanine (MnPc) molecules adsorbed on the top of Pb islands was studied by scanning tunneling spectroscopy. Oscillating Kondo temperatures as a function of film thickness were observed and attributed to the formation of the thickness-dependent quantum-well states in the host Pb islands. The present approach provides a technologically feasible way for single spin manipulation by precise thickness control of thin films.
TL;DR: In this article, the relative frequency stability of a millimeter scale resonator was shown to be at most one part per 10−12 per 1 s integration time, where s is the number of s.
Abstract: We discuss thermodynamic as well as quantum limitations of the stability of resonance frequencies of solid-state whispering-gallery-mode resonators. We show that the relative frequency stability of a millimeter scale resonator can reach one part per 10−12 per 1 s integration time.
01 Jan 2007
TL;DR: In this article, the authors investigate slow light via stimulated Brillouin scattering (SBS) in a room temperature optical fiber that is pumped by a spectrally broadened laser and find that partial overlap of the Stokes and anti-Stokes resonances can actually lead to an enhancement of the slow light delay-bandwidth product when Deltaomegapsime 1.3OmegaB.
Abstract: In this paper, we investigate slow light via stimulated Brillouin scattering (SBS) in a room temperature optical fiber that is pumped by a spectrally broadened laser. Broadening the spectrum of the pump field increases the linewidth Deltaomegap of the Stokes amplifying resonance, thereby increasing the slow-light bandwidth. One physical bandwidth limitation occurs when the linewidth becomes several times larger than the Brillouin frequency shift OmegaB so that the anti-Stokes absorbing resonance substantially cancels out the Stokes amplifying resonance and, hence, the slow-light effect. We find that partial overlap of the Stokes and anti-Stokes resonances can actually lead to an enhancement of the slow-light delay-bandwidth product when Deltaomegapsime1.3OmegaB. Using this general approach, we increase the Brillouin slow-light bandwidth to over 12 GHz from its nominal linewidth of ~30 MHz obtained for monochromatic pumping. We controllably delay 75-ps-long pulses by up to 47 ps and study the data-pattern dependence of the broadband SBS slow-light system
TL;DR: In this paper, the extinction, absorption, and scattering spectra for random and fixed orientations of the particle axis with respect to the incident transverse magnetic (TM) and transverse electric (TE) polarized light were calculated using extended precision T-matrix codes.
Abstract: T-matrix formalism was used to study the multipole resonances excited by electromagnetic plane waves in gold and silver nanorods whose shape was modeled by prolate spheroids and cylinders with flat or semispherical ends (s-cylinders). The particle diameters and aspect ratio were varied from 20 to 80 nm and from 2 to 20, respectively. By using extended precision T-matrix codes, we calculated the extinction, absorption, and scattering spectra for random and fixed orientations of the particle axis with respect to the incident transverse magnetic (TM) and transverse electric (TE) polarized light, where the reference plane is defined by the particle axis and the incident wave vector. We found that the parity of a given spectral resonance number n coincides with the parity of their multipole contributions l, where I is equal to or greater than n, and the total resonance magnitude is determined by the lowest multipole contribution. The random-orientation resonances are excited most effectively by the TM scattering configurations, except for the short-wavelength resonance, which equals the sum of the dominant dipole TE resonance and the other multipole contributions. The even multipole resonances are maximal at intermediate orientations, whereas the odd multipoles can effectively be excited at both perpendicular and intermediate orientations of the rod axis with respect to the TM incident wave. In particular, the quadrupole resonance can be excited only by the TM incident wave, and the resonance magnitude is maximal for orientation of the particle symmetry axis near 54° with respect to the incident light. Finally, we found that the multipole resonance wavelengths obey a universal linear scaling when plotted versus the particle aspect ratio divided by the resonance number. This remarkable property of multipole resonances can be understood in terms of a simple concept based on plasmon standing waves excited in metal nanowires by an electric field of incident light (Schider et al. Phys. Rev. B 2003, 68, 155427). The refractive index sensitivity of the multipole resonance wavelength to a dielectric environment also exhibits linear scaling properties. Specifically, the relative shift of the resonance wavelength is proportional to the relative refractive index increment with a universal angular slope coefficient.
TL;DR: In this article, the propagation of Lamb waves in two-dimensional locally resonant phononic-crystal plates, composed of periodic soft rubber fillers in epoxy host with a finite thickness, was studied.
Abstract: The authors study the propagation of Lamb waves in two-dimensional locally resonant phononic-crystal plates, composed of periodic soft rubber fillers in epoxy host with a finite thickness. Our calculations are based on the efficient plane wave expansion formulation which utilized Mindlin’s plate theory. Calculated results show that the low-frequency gaps of Lamb waves are opened up by the localized resonance mechanism. The resonant frequencies of flexure-dominated plate modes are significantly dependent not only on the radius of circular rubber fillers but also on the plate thickness. The properties of localized resonance are qualitatively analogous to the vibration of a circular thin plate.
TL;DR: The lifetime of bound p-wave molecules is measured to be 1.0+/-0.1 ms and 2.3+/- 0.2 ms for the ml=+/-1 and ml=0 angular momentum projections, respectively as discussed by the authors.
Abstract: We have produced and detected molecules using a p-wave Feshbach resonance between 40K atoms. We have measured the binding energy and lifetime for these molecules and we find that the binding energy scales approximately linearly with the magnetic field near the resonance. The lifetime of bound p-wave molecules is measured to be 1.0+/-0.1 ms and 2.3+/-0.2 ms for the ml=+/-1 and ml=0 angular momentum projections, respectively. At magnetic fields above the resonance, we detect quasibound molecules whose lifetime is set by the tunneling rate through the centrifugal barrier.
TL;DR: In this paper, the dispersion of the phonons involved in the double resonance Raman process in monolayer graphene has been analyzed using Raman spectroscopy, showing that the velocities of these phonons are 7.70 and 5.47, respectively.
Abstract: Raman spectroscopy was used to determine the dispersion of the longitudinal acoustic (LA) and in-plane transverse optic phonon branches near the Dirac $K$ point of monolayer graphene from the analysis of the dispersion of two second-order Raman peaks involving the LA and TO phonons. We show that the velocities of the phonons involved in the double resonance Raman process are given by ${v}_{\mathit{LA}}=7.70\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{v}_{F}$ and ${v}_{\mathit{TO}}=5.47\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{v}_{F}$, where ${v}_{F}$ is the Fermi velocity of the associated electrons. The experimental results for the phonon dispersion in monolayer graphene are compared with those for turbostratic graphite and also with different theoretical models.
TL;DR: The magnetic coupling between single Co atoms adsorbed on a copper surface is determined by probing the Kondo resonance using low-temperature scanning tunneling spectroscopy and adding a third atom to the antiferromagnetically coupled dimer results in the formation of a collective correlated state.
Abstract: The magnetic coupling between single Co atoms adsorbed on a copper surface is determined by probing the Kondo resonance using low-temperature scanning tunneling spectroscopy. The Kondo resonance, which is due to magnetic correlation effects between the spin of a magnetic adatom and the conduction electrons of the substrate, is modified in a characteristic way by the coupling of the neighboring adatom spins. Increasing the interatomic distance of a Cobalt dimer from 2.56 to 8.1 \AA{} we follow the oscillatory transition from ferromagnetic to antiferromagnetic coupling. Adding a third atom to the antiferromagnetically coupled dimer results in the formation of a collective correlated state.
TL;DR: The existence and nature of end and central plasmon resonances in a linear atomic chain, the 1D analog to surface and bulk plasmons in 2D metals, has been predicted by ab initio time-dependent density functional theory and is outlined.
Abstract: The existence and nature of end and central plasmon resonances in a linear atomic chain, the 1D analog to surface and bulk plasmons in 2D metals, has been predicted by ab initio time-dependent density functional theory. Length dependence of the absorption spectra shows the emergence and development of collectivity of these resonances. It converges to a single resonance in the longitudinal mode, and two transverse resonances, which are localized at the ends and center of the atom chains. These collective modes bridge the gaps, in concept and scale, between the collective excitation of atomic physics and nanoplasmonics. It also outlines a route to atomic-scale engineering of collective excitations.
TL;DR: In this paper, the fusion reactions 12C(12C,alpha)20Ne and 12C (12C p)23Na were studied from E=2.10 to 4.75 MeV by gamma-ray spectroscopy using a C target with ultralow hydrogen contamination.
Abstract: The fusion reactions 12C(12C,alpha)20Ne and 12C(12C,p)23Na have been studied from E=2.10 to 4.75 MeV by gamma-ray spectroscopy using a C target with ultralow hydrogen contamination. The deduced astrophysical S(E)* factor exhibits new resonances at E< or =3.0 MeV, in particular, a strong resonance at E=2.14 MeV, which lies at the high-energy tail of the Gamow peak. The resonance increases the present nonresonant reaction rate of the alpha channel by a factor of 5 near T=8x10(8) K. Because of the resonance structure, extrapolation to the Gamow energy EG=1.5 MeV is quite uncertain. An experimental approach based on an underground accelerator placed in a salt mine in combination with a high efficiency detection setup could provide data over the full EG energy range.
TL;DR: In this article, the optical properties of single nanoholes in optically thin (t = 20 nm) gold films on glass have been studied experimentally and theoretically, and the measured elastic scattering spectra from the nanosoles exhibit a broad resonance in the red part of the visible spectrum, which is qualitatively similar to localized surface plasmon (LSP) resonances in gold nanodisks.
Abstract: The optical properties of single nanoholes in optically thin (t = 20 nm) gold films on glass have been studied experimentally and theoretically The measured elastic scattering spectra from the nanoholes exhibit a broad resonance in the red part of the visible spectrum, which is qualitatively similar to localized surface plasmon (LSP) resonances in gold nanodisks The hole resonance red-shifts with increasing hole diameter (D = 60−107 nm), similar to particle LSP resonances These features could be well reproduced by electrodynamic simulations based on the boundary element method (BEM) Further, the electric field distribution around the resonant nanoholes, obtained from the BEM simulations, exhibits a clear electric dipole pattern This confirms the assignment of the hole resonance to a dipolar LSP resonance mode However, in comparison with Au nanodisks of similar size, the hole LSP resonance exhibits a shorter dephasing time (τ) This observation can be understood in terms of an additional decay channe
TL;DR: In this paper, the 6Li magic angle spinning (MAS) NMR spectra of compounds with low Ni/Mn contents (x ≤ 0.10) show several well-resolved resonances, which start to merge when the amount of Ni and Mn increases, finally forming a broad resonance at high Ni/mn contents.
Abstract: Several members of the compositional series Li[NixMnxCo(1–2x)]O2 (0.01 ≤ x ≤ 1/3) were synthesized and characterized. X-ray diffraction results confirm the presence of the layered α-NaFeO2-type structure, while X-ray absorption near-edge spectroscopy experiments verify the presence of Ni2+, Mn4+, and Co3+. Their local environment and short-range ordering were investigated by using a combination of 6Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and neutron pair distribution function (PDF) analysis, associated with reverse Monte Carlo (RMC) calculations. The 6Li MAS NMR spectra of compounds with low Ni/Mn contents (x ≤ 0.10) show several well-resolved resonances, which start to merge when the amount of Ni and Mn increases, finally forming a broad resonance at high Ni/Mn contents. Analysis of the 6Li MAS NMR 6Li[Ni0.02Mn0.02Co0.96]O2 spectrum, is consistent with the formation of Ni2+ and Mn4+ clusters within the transition-metal layers, even at these low-doping levels. The oxida...
TL;DR: The results support the idea that cis-azobenzene isomerizes rapidly via rotation about the NN bond, while isomerization proceeds via inversion for trans-azabenzene.
Abstract: Resonance Raman intensity analysis was used to investigate the initial excited-state nuclear dynamics of cis- and trans-azobenzene following S1 (npi*) excitation, and fluorescence quantum yield measurements were used to estimate the excited-state lifetimes. trans-Azobenzene exhibits the strongest Raman intensities in its skeletal stretching and bending modes, while torsional motions dominate the nuclear relaxation of cis-azobenzene as indicated by intense Raman lines at 275, 542, 594, and 778 cm(-1). The very weak fluorescence quantum yield for cis-azobenzene is consistent with its approximately 100 fs electronic lifetime while trans-azobenzene, with a fluorescence quantum yield of 1.1 x 10(-5), has an estimated S1 lifetime of approximately 3 ps. The absorption and Raman cross-sections of both isomers were modeled to produce a harmonic displaced excited-state potential energy surface model revealing the initial nuclear motions on the reactive surface, as well as values for the homogeneous and inhomogeneous linewidths. For cis-azobenzene, this modeling predicts slopes on the S1 potential energy surface that when extrapolated to the position of the harmonic minimum give excited-state changes of approximately 6-20 degrees in the CNNC torsion angle and a < or =3 degrees change in the CNN bending angle. The relatively large excited-state displacements along these torsional degrees of freedom provide the driving force for ultrafast isomerization. In contrast, the excited-state geometry changes of trans-azobenzene are primarily focused on the CNN bend and CN and NN stretches. These results support the idea that cis-azobenzene isomerizes rapidly via rotation about the NN bond, while isomerization proceeds via inversion for trans-azobenzene.
TL;DR: In this paper, the Fabry-Perot (FP) resonance condition can be tuned via both the periodicity and area fraction of holes, and it is shown that the FP resonance is smoothly linked to the surface wave-like mode induced by the periodic structure factor.
Abstract: By studying acoustic and electromagnetic wave transmission through a periodic array of subwavelength holes or slits with various channel lengths, we demonstrate both experimentally and theoretically that diffraction evanescent waves can play an important role in tuning the Fabry-Perot (FP) resonances. In particular, there can be total transmission peaks at wavelengths much below that of the Rayleigh-Wood limit, and FP resonances can occur for channel length $\ensuremath{\sim}16%$ thinner than the half wavelength. In addition, the FP resonance condition can be tuned via both the periodicity and area fraction of holes. As a function of the ratio between the periodicity and plate thickness, the FP resonance is smoothly linked to the surface-wave-like mode induced by the periodic structure factor.
TL;DR: In this article, a long range surface plasmon (LRSP) is excited on a layer structure consisting of a fluoropolymer buffer layer, a thin gold film, and an aqueous sample.
Abstract: A long range surface plasmon (LRSP) is an electromagnetic wave propagating along a thin metal film with an order of magnitude lower damping than conventional surface plasmon (SP) waves. Thus, the excitation of LRSP is associated with a narrower resonance and it provides larger enhancement of intensity of the electromagnetic field. In surface plasmon resonance (SPR) biosensors, these features allow a more precise observation of the binding of biomolecules in the proximity to the metal surface by using the (label-free) measurement of refractive index (RI) variations and by SP-enhanced fluorescence spectroscopy. In this contribution, we investigate LRSPs excited on a layer structure consisting of a fluoropolymer buffer layer, a thin gold film, and an aqueous sample. By implementing such structure in an SPR sensor, we achieved a 2.4- and 4.4-fold improvement of the resolution in the label-free and fluorescence-based detection, respectively, of the binding of biomolecules in the close proximity to the surface. Moreover, we demonstrate that the sensor resolution can be improved by a factor of 14 and 12 for the label-free and fluorescence-based detection, respectively, if the biomolecular binding events occur within the whole evanescent field of LRSP.
TL;DR: In this paper, the authors carried out two-port network analyzer ferromagnetic resonance measurements on a coplanar waveguide and presented a detailed description on how to calculate from the raw measurement data a value proportional to the complex susceptibility and permittivity of the material.
Abstract: We have carried out two-port network analyzer ferromagnetic resonance measurements on a coplanar waveguide. We present a detailed description on how to calculate from the raw measurement data a value proportional to the complex susceptibility and permittivity of the ferromagnetic material. Necessary corrections for errors due to imprecise sample placement on the waveguide and the sample dimensions are presented. Evaluated data up to 15 GHz are provided for two model samples: a 40 nm Co80Fe20 layer showing a large linewidth (≈900 MHz) and a 40 nm Co72Fe18B10 layer yielding a small linewidth (≈360 MHz). Using these experimental data the presented evaluation scheme based on all four scattering parameters is then compared to commonly used approximate evaluation schemes relying on only one S parameter. These approximate methods show close agreement for the ferromagnetic resonance frequencies (the relative error is below 1%). However, the resonance linewidths show a relative error that can reach 10% in comparis...