Tunable Fano resonances and plasmonic hybridization of gold triangle–rod dimer nanostructure

A gold dimer structure consisting of a notched triangle nanoslice and a rectangle nanorod is proposed to produce distinct Fano resonance. Owing to the coupling between the dipole plasmon mode of the nanorod and the dipole or quadrupole plasmon mode of the nanoslice, the extinction spectrum with a deep Fano dip is formed and can be well fitted by the Fano interference model for different geometry parameters. In addition, Fano resonance of the gold dimer nanostructure also intensely depends on the polarization direction of incident light. Moreover, Fano resonance of the triangle–rod trimer is also analyzed by adding another nanorod into the former dimer and exhibits the splitting of plasmonic resonant peak in high order coupling modes. The plasmonic hybridizations in these nanostructures have been analyzed for revealing the physical origin of the Fano resonance.     

Dual-band asymmetric transmission of linearly polarized wave using Π-shaped metamaterial

A bilayered chiral metamaterial with Π-shaped structure is proposed, which demonstrates to exhibit dual-band asymmetric transmission (AT) of linearly polarized electromagnetic (EM) waves in two opposite directions. Incident x-polarized wave is almost converted to y-polarized wave while incident y-polarized wave is locked through the Π-shaped slab at 10.82 GHz; incident y-polarized wave is almost converted to x-polarized wave while incident x-polarized wave cannot pass through the Π-shaped slab at 14.1 GHz. The property of the AT is similar to the diode-switching characteristics, and the EM wave can be switched on/off by changing the polarization state of the incident wave. The surface current distributions of the Π-shaped structure are discussed to look into the physical mechanism.     

Tunable Fano resonances in heterogenous Al–Ag nanorod dimers

We theoretically investigate the plasmonic coupling in heterogenous Al–Ag nanorod dimers. A pronounced Fano dip is found in the extinction spectrum produced by the destructive interference between the bright dipole mode from a short Al nanorod and the dark quadrupole mode from a long Ag nanorod nearby. This Fano resonance can be widely tuned in both wavelength and amplitude by varying the rod dimensions and end geometry, the separation distance and the local dielectric environment. The Al–Ag heterogeneous nanorod dimer shows a high sensitivity to the surrounding environment with a local surface plasmon resonance figure of merit of 7.0, which enables its promising applications in plasmonic sensing and detection.     

Tunable Fano resonances in silver–silica–silver multilayer nanoshells

We study the plasmonic properties of silver–silica–silver multilayer nanoshells using finite-difference time-domain methods. Silver is a weakly dissipating metal and is able to support higher order resonances compared to strongly dissipating metals like gold. We show that Fano resonances occur even in symmetric cases. Symmetry breaking via the introduction of core offset further enhances these Fano resonance peaks and leads to the appearance of higher order resonances. The optical properties of the multilayer nanoshells are explained using the plasmon hybridization theory and the results are compared to similar multilayer nanoshells with gold core and outer shell.     

Transmission gaps,trapped modes and Fano resonances in Aharonov–Bohm connected mesoscopic loops

A simple mesoscopic structure consisting of a double symmetric loops coupled by a segment of length $d_0$ in the presence of an Aharonov–Bohm flux is designed to obtain transmission band gaps and Fano resonances. A general analytical expression for the transmission coefficient and the density of states (DOS) are obtained for various systems of this kind within the framework of the Green's function method in the presence of the magnetic flux. In this work, the amplitude of the transmission and DOS are discussed as a function of the wave vector. We show that the transmission spectrum of the whole structure may exhibit a band gap and a resonance of Fano type without introducing any impurity in one arm of the loop. In particular, we show that for specific values of the magnetic flux and the lengths of the arms constituting the loops, the Fano resonance collapses giving rise to the so-called trapped states or bound in continuum (BIC) states. These states appear when the width of the Fano resonance vanishes in the transmission coefficient as well as in the density of states. Also, we show that the shape of the Fano resonances and the width of the band gaps are very sensitive to the value of the magnetic flux and the geometry of the structure. These results may have important applications for electronic transport in mesoscopic systems.     

Fano Resonance in Landau Fermi and Luttinger Liquids

With a two-channel model, we study the influence of temperature, external voltage and magnetic flux on the line shape of the Fano resonance, and show that in the Luttinger liquid case, the background transmittance and the asymmetric parameter depend strongly on the temperature and external voltage, while for the Landau Fermi liquid case they are nearly independent of these parameters in the low energy region. Moreover, we demonstrate that the asymmetric parameter changes periodically with an external magnetic flux, which is consistent with the recent experimental data.     

Confinement resonances in photoionization of Xe@C₆₀+

Experimental evidence is presented for confinement resonances associated with photoabsorption by a Xe atom in a C60 cage. The giant 4d resonance in photoionization of Xe is predicted to be redistributed into four components due to multipath interference of photoelectron waves reflected by the cage. The measurements were made in the photon energy range 60-150 eV by merging a beam of synchrotron radiation with a mass/charge selected Xe@C??+ ion beam. The phenomenon was observed in the Xe@C(58)(3+) product ion channel. [corrected]     

Charge-exchange resonances and restoration of Wigner’s supersymmetry in heavy and superheavy nuclei

Various facets of the question of whether Wigner’s supersymmetry [SU(4) symmetry] may be restored in heavy and superheavy nuclei are analyzed on the basis of a comparison of the results of calculations with experimental data. The energy difference between the giant Gamow–Teller resonance and the analog resonance (the difference of E _G and E _A) according to calculations based on the theory of finite Fermi systems is presented for the case of 33 nuclei for which experimental data are available. The calculated difference ΔE _G–A of E _G and E _A tends to zero in heavier nuclei, showing evidence of the restoration of Wigner’s SU(4) symmetry. Also, the isotopic dependence of the Coulomb energy difference between neighboring isobaric nuclei is analyzed within the SU(4) approach for more than 400 nuclei in the mass-number range of A = 5–244. The restoration of Wigner’s SU(4) symmetry in heavy nuclei is confirmed. It is shown that the restoration of SU(4) symmetry is compatible with the possible existence of the stability island in the region of superheavy nuclei.     

Decay of amplitude-modulation property of song and an analysis of sounding mechanism in mottled cicade (Gaeana maculata Drury)

I-IntroductionTheamp1itudc-modulationpropcrtyexistsgcnerallyinthesongsofarthropods.Insingingorthoptcraninsccts,suchasmo1c-cricket,1ocust,cricketandkatydid,thesongsproduccdbystridulationsarctypica1andcachwave(thetoothstrike)incarrierwavesisisproducedbythatthescrapcrstrikesateachtoothofthedenticulatedvein(fi1e)t'J.IncicadasoftheHomoptera,thesongsareproduccdbycontractionmovcmentsofthesoundingmusc1etodrivethesoundingmembranewithribstructurestovibrations,andaregeneral1yamplitude-modu1ationpu1sesou…     

Hadronic decays of N and Δ resonances in a chiral quark model

π and η decay modes of light baryon resonances are investigated within a chiral quark model whose hyperfine interaction is based on Goldstone-boson exchange. For the decay mechanism a modified version of the ³ P ₀ model is employed. Our primary aim is to provide a further test of the recently proposed Goldstone-boson exchange constituent quark model. We compare the predictions for π and η decay widths with experiment and also with results from a traditional one-gluon exchange constituent quark model. The differences between nonrelativistic and semirelativistic versions of the constituent quark models are outlined. We also discuss the sensitivity of the results on the parameterization of the meson wave function entering the ³ P ₀ model. Received: 11 May 2001 / Accepted: 17 September 2001     

Numerical analysis of the mechanism of carrier transport in organic light—emitting devces

The mechanism of carrier transport in organic light-emitting devices is numerically studied,on the basis of trappedcharge-limited conduction with an exponential trap distribution.The spatial distributions of the electrical potential,field and carrier density in the organic layer are calculated and analysed.Most carriers are distributed near the two electrodes,only a few of them are distributed over the remaining part of the orgaic layer,The carriers are accumulated near the electrodes,and the remaining region is almost exhausted of carriers.When the characteristic energy of trap distribution is greater than 0.3eV.it leads to a reduction of current density.In order to improve the device efficiency,organic materials with minor traps and low characteristic energy should be chosen.The diffusion current is the dominant component near the injection electrode.whereas the drift current dominates the remaining region of the organic layer.     

Celtic gold coins in the light of Mössbauer spectroscopy, electron microprobe analysis and X-ray diffraction

Celtic gold coins found in Southern Germany were studied by Mössbauer spectroscopy, electron microprobe analysis and X-ray diffraction with special attention to coins rich in silver and copper. In such coins the electron microprobe analyses reveal a gold enrichment in a surface layer of more than 100 μm thickness. ¹⁹⁷Au conversion electron Mössbauer spectroscopy also shows that the surface of the coins consists of two phases, one of which is strongly enriched in gold compared to the bulk composition. In comparison with laboratory experiments the observed phenomena suggest that coin production in Celtic times may have involved deliberate heating and etching steps to enrich the surface layer in gold by depleting it of silver and copper.     

K-shell photoionization of boron-like carbon ions： analysis of ls-2p resonances

Close-coupling calculations based on an R-matrix formalism are performed for the 1s--2p resonance photoionizations from the low-lying states of boron-like carbon ions. The resonance energies, widths and oscillator strengths of 1s-2p core excitations are determined by analysing the calculated photoionization cross sections. Our calculations are in reasonable agreement with the experimental and theoretical results presented by other authors. The present numerical values may help to analyse the astrophysical and laboratory plasmas.     

A study in the coupled πNN-NN system and the question of dinucleon resonances

Conclusions We have presented soms of our preliminary results on the coupled NN-NN problem. The overall result obtained so far is rather encouraging and we are currently making the model more sophisticated in order to be able to make more quantitative arguments which may hopefully serve somehow to clarify the dibaryon resonance problems. To end we would like to emphasize that since all the channels (viz.d d, d NN, NN NN, etc.) are unitarily coupled, one cannot arbitrarily change some input parameters to attain a better fit in one of the channels alone: all the channels are closely linked, which serves as a very strong constraint to the input. In near future we wish to extend our model to calculate processes with three-body final statesWork supported in part by Bundesministerium für Forschung und Technologie.Invited talk at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.I am grateful to my collaborators, Y. Avishai, C. Fayard, G. -H. Lamot and S. Nahabetian for numerous discussions.     

The mechanism and rate of dtμ formation in solid hydrogen

The partial spectral distribution function for muonic molecule formation turns out to play an important role in understanding the effect of interactions with surrounding spectator molecules. We formulate and numerically calculate it for a solid hydrogen. First of all, in addition to a conventional Lorentzian peak centered at a resonance energy , there appears another very broad peak in the spectral distribution, which extends from the resonance energy to energies higher by the Debye energy _D of the solid. It is shown that the latter corresponds to the spectral distribution of phonon excitations caused by a sudden dt formation. Secondly, a strong intensity borrowing from the Lorentzian peak to the broad one occurs. Thanks to this fact, a large formation rate is yielded for subthreshold transitions. The comparison with Vesman's spectral distribution function, namely, of a dt formation for an isolated D₂, is made.     

Evaluation and analysis of the radiation force in laser trap

Forces exerted on a small transparent dielectric sphere in a Gaussian beam is an-alyzed.The stable position of the sphere in the Gaussian beam was calculated.The effects ofthe sphere size,the beam radius etc.on the exerted forces,on the equilibrium positions aswell as on other parameters of the sphere are discussed.     

High resolution FTIR study of the ν5 and ν6 bands of CH2D35Cl: analysis of resonances and determination of ground and upper state constants

The isotopically pure form of methyl chloride, CH₂D³⁵Cl, was synthesized and investigated by Fourier transform infrared spectroscopy with an unapodized resolution of 0.004?cm^?1 in the range 650–900?cm^?1, the region of the lowest fundamentals ν₅ (827?cm^?1) and ν₆ (714?cm^?1). These distinct bands have been analysed in detail in the P-, Q- and R-branches. In spite of their expected a/b-hybrid nature, both envelopes show the peculiar characteristic of only a-type bands of near prolate asymmetric top molecules. Ground state parameters have been determined for the first time through ground state combination differences from both bands. Parameters of the excited vibrational states and coupling constants have been obtained using a model which accounts for c-type Coriolis interaction and ΔK_a?=?±?2 anharmonic resonance.