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1.
The dispersoon curves for surface plasma waves (SPW) in Ag have been determined from calculated reflectivity minima as exhibited by attenuated total reflection (ATR spectra) for the prism-metal-air (PMA) configuration and from the direct calculation of the dispersion relation for the same configuration. Comparison is made with published results. The dispersion curves for Au and Cu have been determined for the same configuration from calculated ATR spectra and verified experimentally. Comparison is made with the direct calculation of the dispersion relation. The direct calculation yields two types of modes; namely the surface or Brewster mode and the virtual mode. Both modes are discussed. The marked effect of small electronic damping as exhibited by Ag and moderate electronic damping as exhibited by Au and Cu upon the PMA dispersion curves from ATR spectra is examined. Finally the direct calculation of the dielectric shift (perturbing effect of the prism-metal surface upon the active metal-air surface dispersion curve) is presented for the three metals as a function of film thickness and photon energy. 相似文献
2.
S. Farjami Shayesteh K. Hidari 《International Journal of Infrared and Millimeter Waves》2002,23(10):1455-1464
Infrared Fourier transform spectroscopy has been used to investigate phonon, plasmon, surface polariton and plasma-longitudinal optical phonon coupling in highly donor doped multi quantum wells (GaAs/Al0.33Ga0.67As) and direct band gap n- type AlXGa1-XAs thin layer on GaAs substrate. Using different samples with different concentration of free carriers. The dispersion equation of coupling modes have been calculated by using the condition which the dielectric functions of samples are zero for longitudinal coupled modes and experimental papameters which have been obtained from the best fit p-polarized oblique incidence far infrared reflection spectra. In MQW samples, the free carriers confined to the well and carriers are quasi two dimensional. So, plasmon- LO phonon coupling occur in the well (GaAs). In n- type AlXGa1-XAs thin layer, the coupled modes consist of three branches of the high, intermediate and low frequency modes. Their frequencies depend on both concentration and alloy composition. To analyses the surface polariton modes we carry out attenuated total reflection (ATR) measurements. In order to support our assignment the magnetic field profiles and surface polariton dispersion curves have been calculated. 相似文献
3.
The dispersion relation of surface waves propagating on a homogeneous Maxwellian plasma column with sharp boundary and surrounded by dielectric and vacuum is investigated in the low-frequency domain. The thermal motion of ions is also taken into account. The spectra and damping rates both of short and longwavelength surface modes in thick and thin columns are obtained. 相似文献
4.
A theoretical approach for the calculation of the
bimetallic nanoparticles absorption spectra has been developed as an
extension of the Mie theory in which nanoparticle dielectric function is
found by the weighted linear combination of the dielectric functions for
particles made of the corresponding pure metals. In the frame work of the
theoretical model an expression for the resonance light absorption frequency
were derived taking into account the interband transitions in the dielectric
functions. We propose a simple method for the on-line monitoring of the
bimetallic nanoparticles composition based on the measurement of the
absorption peak position. Elaborated theoretical approach was used to
investigate the polymer embedded Ag/Au nanoparticles which were prepared by
reducing gold and silver salts (HAuCl4 and AgNO3, respectively) by ethylene
glycol in presence of poly(vinyl pyrrolidone) (PVP) at room temperature.
Calculated absorption spectra for the Ag/Au nanoscopic systems showed good
agreement with the experimental data. Temporal evolution of the Ag/Au
nanoparticles has also been investigated by this approach. 相似文献
5.
The dispersion of ordinary and extraordinary surface polaritons in uniaxial CdS has been measured using the ATR technique. The results have been compared with theoretical dispersion curves based on a classical oscillator model. The dielectric dispersion has also been generated. Comparison is made between the bulk phonons derived from Raman, infrared and from the surface mode data. Infrared measurements of small crystallites of CdS are in good agreement with the frequencies predicted for surface modes of small isolated spheres. 相似文献
6.
7.
We report a magnetoplasmon-polariton spectra in superlattices made up of two alternating media A and B, where one of the layers shows spatial dispersion in its frequency dependent dielectric function. We have used a theoretical approach based on the effective medium theory to determine the expression for the dielectric tensor of the superlattice in the presence of a magnetic field. It is applied to find out the bulk and surface polariton dispersion relation, as well as the Attenuated Total Reflection (ATR) spectra. Numerical results are presented and discussed to illustrate our theoretical predictions, with emphasis on a particular choice of the exciton’s additional boundary conditions (ABC). 相似文献
8.
In this paper we investigate the band structure of guided modes in a segmented planar waveguide for the terahertz range. The dispersion curves are obtained using two different methods. The first approach is based on a close relationship between the band structure and narrow resonances in transmission spectra: transmission spectra are therefore calculated using a transfer matrix method and compared to the experimental ones. The second technique involves a modal analysis approach of diffraction gratings and it is used for direct calculation of the band structure. Propagation of THz guided waves along the grating considered as a segmented dielectric waveguide is also investigated using a bi-directional mode expansion and propagation method. All approaches are compared to each other and discussed. 相似文献
9.
10.
We calculate the plasmon frequency and damping rate in a 3-layer graphene system made of parallel monolayer and bilayer graphene sheets using the random-phase-approximation dielectric function and taking into account the inhomogeneity of the dielectric background of the system. Numerical results show that two out-of-phase acoustic and one in-phase optical plasmon modes can be found from the zeroes of dynamical dielectric function of the structure. Plasmon frequencies and damping rate of plasma oscillations depend significantly on the inhomogeneity of environment, so plasmon curves become more distinctive from each other in single-particle excitation region, compared to the case of homogeneous medium. Finally, Plasmon dispersion patterns depend remarkably on the number (but not order) of bilayer graphene sheet constructing to the system. 相似文献
11.
The interaction system of a semi-infinite diatomic dielectric and the electromagnetic field propagating parallelly to the surface is studied. The long-wave optical phonon modes of the semi-infinite dielectric are calculated including the electronic polarizability by a quantum-mechanical theory. Retardation effects are neglected. A quantum field theory method of surface polaritons is developed to calculate the operator describing the interaction between a photon and the phonon polarization fields of the semi-infinite crystal, with explicit inclusion of surface effects. The dispersion relations of the surface phonon-polaritons are derived and discussed. The results are in good agreement with those obtained by the conventional, macroscopic dielectric theory of surface polaritons and experimental ATR (attenuated total reflection) spectra. The dispersion cuwes of polariton leaking modes caused by the interaction between bulk TO mode with surface effect and photons are presented in a graphical form. The k||-dependence of the electric field strength in each polariton branch is calculated and presented also in a graphical form. We also research the spatial dependence of the field strength in each polariton branch. It is found that these properties are influenced and modulated by the surface phonons because of the interaction between photons and the surface phonon modes of the semi-infinite dielectric system. Hence the divergent nature (diffraction effect) of light propagating along the fib& and waveguides is restrained. We present a method how to use the boundary conditions in the quantum theory, which will be discussed in detail. 相似文献
12.
The dispersion relations of normal modes in the layered constructions are studied. In the frequency region with negative permittivity, we investigate the normal modes near the air--metal and the air--matematerial interfaces and compare them. An extra bulk mode appearing in a pass band of two media is found near the air--matematerial interface, which is different from the air--metal case. Moreover, the bulk mode will be further proved by the attenuated total reflection (ATR) technique, in which the coupling between the incident electromagnetic waves and the normal modes is studied. For p-polarized incident waves, the ATR spectra based on the Otto and the Kretschmann configurations are obtained numerically, where the dips present the excitations of the surface and bulk modes. Furthermore, we also discuss the influences of the middle layer thickness, the incident angle and the damping term on the reflection in detail. It is found that the coupling frequencies and the maximum strength are strongly dependent on the above media parameters. 相似文献
13.
Electromagnetic oscillations in a rectangular waveguide with a transversely magnetized ferrite plate
The complex propagation constant in a rectangular waveguide with a transversely magnetized ferrite plate has been found by a numerical calculation. The magnetic properties of the ferrite medium are described by the standard permeability tensor for a polycrystalline ferrite, having real and imaginary parts. The solutions are given as curves on the complex propagation-constant plane. The parameter is the relative magnetizing field, which varies over a wide range including a ferromagnetic resonance. From the family of curves obtained for various relative magnetizations and damping parameters, one can quantitatively evaluate the relation between the types of oscillations. This relation depends on the position of the ferrite plate in the waveguide and on the dielectric constant of the ferrite as well as on the magnetization and damping constant.Translated from Izvestiya VUZ. Fizika, No. 4, pp. 74–81, April, 1970. 相似文献
14.
The results of the theoretical study of optical properties of composite nanoparticles consisting of a metal core (Ag, Au,
Cu, Al, Ni, Cr) and a J-aggregate shell of organic dye are presented. Light extinction, absorption, and scattering coefficients
in colloidal solutions were calculated within the model based on the Mie theory modified taking into account dimensional phenomena
and complemented by calculations of complex dielectric functions of the metal core and J-aggregate shell. The model adequately
explains the features observed in light absorption and scattering spectra by hybrid nanoparticles, associated with the plasmon
resonance in the metal core and with electronic excitation of the J-aggregate. The strong dependence of the results on geometrical
parameters of nanoparticles and dielectric constants of core and shell materials was demonstrated. Methods for controlling
the effects of the plasmon-exciton interaction in the system and optical properties of composite materials developed based
on nanoparticles under study are discussed. 相似文献
15.
An analysis of LEED data from the Ag(111) surface at room temperature and 5° ? Θ ? 16°, φ = 12° has been carried out in order to test three different model potentials for the exchange and correlation part of the one-electron LEED potential. Clean Au(111) surfaces have been grown on Ag(111) at room temperature at a deposition rate of 0.15 Å s?1. Similar method of calculation and potentials have been employed for the Au overlay er on Ag(111). After the deposition of ? 2.5 monolayers of Au/Ag(111) the growth of Au can proceed in two different ways. One of them matches satisfactorily with the theoretical calculation for the Au(111) overlayer on Ag(111) following the fcc sequence. The other seems to be concerned with the diffusion of Ag during the Au growth. Similar curves have been obtained during the diffusion of Ag through 350 Å of Au(111). 相似文献
16.
We have derived a simple formula for the dispersion relation of surface plasmons on metals in the extreme anomalous skin effect region. Comparisons of this theory with the usual local dielectric theory is made for Cu, Ag, Au, Sn, and Pb. The two theories can be more than two orders of magnitude different in their predictions of propagation lengths, depending on the temperature. 相似文献
17.
Pampuch C Rader O Kachel T Gudat W Carbone C Klasges R Bihlmayer G Blugel S Eberhardt W 《Physical review letters》2000,85(12):2561-2564
Au chain structures have been prepared on Ni(110). Au6 s,p-derived features in photoemission spectra are identified as quantum-wire states due to their strong dispersion along the chains and absence of dispersion perpendicular to the chains in agreement with our ab initio calculation of the electronic structure. Spin analysis reveals that the states have minority-spin character showing that the confinement of electrons in the chain structure depends on the electron spin. 相似文献
18.
A. Khelif B. Djafari-Rouhani Ph. Lambin 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(3):437-445
The vibrational and electronic spectra of a semi-infinite crystal with a planar surface are modified by the presence of surface
inhomogeneities or roughness such as ridges or grooves, quantum wires or tips. We develop a Green's function formalism to
investigate the localized and resonant acoustic modes of shear horizontal polarization associated with the surface of a substrate
supporting a single and a periodic array of wires. Each material is assumed to be an isotropic elastic medium. The calculation
can be applied to an arbitrary choice of the shape and elastic parameters of the wires. The surface modes are obtained as
well-defined peaks of the densities of states (DOS). In this paper, we calculate the variation of the density of states associated
with the adsorption of a single wire, and the dispersion curves of the surface modes for a periodic array of wires on the
flat surface of a substrate. We discuss their behaviors as a function of the elastic parameters and the relationship between
resonant modes of the single wire and dispersion curves of the surface modes for a periodic structure.
Received 6 December 2000 相似文献
19.
A. V. Vdovin V. N. Moiseenko V. S. Gorelik Ya. V. Burak 《Physics of the Solid State》2001,43(9):1648-1654
The polarized infrared reflection spectra of Li2B4O7 were studied in the spectral range 80–1600 cm?1 and compared with Raman spectra. From the spectrum dispersion analysis, the frequencies, damping, and dielectric oscillator strengths were determined for all vibrational modes observed. A calculation of the effective charges and an analysis of the chemical-bond types of the Li2B4O7 crystal structural units were carried out on the basis of the obtained data. 相似文献
20.
We study guided modes propagating along a dielectric slab waveguide with a left handed material (LHM) cover or substrate. The dispersion relation is derived by using normalized waveguide parameters. An analytical method is then proposed to calculate the universal dispersion curves. Different from a slab waveguide with a LHM core, we find that guidance properties are strongly dependent on dielectric permittivity ε and magnetic permeability μ of the substrate and cover layers. For oscillating guided modes, fundamental zero order mode is not always absence, sometimes it exists in a restricted range of normalized propagation constant. First order mode behaves as other higher order modes and exists up to infinite high frequency. Higher order modes have no double degeneracy in the case of LHM cover layer. For surface guided modes, the existence and the type of the mode solutions with respect to different parameters are classified systematically and discussed in detail. Unlike a slab waveguide with a LHM core where the dispersion curve of TE1 surface mode continues with that of oscillating TE1 mode, the dispersion curve of TE1 surface mode continues with that of oscillating TE0 mode. It seems that the two different kinds of modes compensate each other to form one whole mode. Both TE and TM guided modes are discussed. 相似文献