共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Quinten 《Applied physics. B, Lasers and optics》1998,67(1):101-106
Received: 19 December 1997/Revised version: 24 March 1998 相似文献
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J.C. Pivin M. Sendova-Vassileva M. Nikolaeva D. Dimova-Malinovska A. Martucci 《Applied Physics A: Materials Science & Processing》2002,75(3):401-410
Three methods based on ion-beam irradiation were used to fabricate Ag and Au colloids in silica and alumina. Their surface-plasmon
resonance in the visible was characterised by transmittance measurements and interpreted on the basis of transmission electron
microscope observations. Despite their bimodal size distribution, particles formed by ion-beam mixing of sandwich layers exhibit
much narrower resonances than those obtained by ion implantation. This unusual effect of an inhomogeneity in cluster size
is ascribed to the spatial organisation of these clusters. Irradiation of supersaturated solid solutions at much lower ion
fluences produces colloids with more uniform size and spatial distributions, and equally strong resonances.
Received: 17 March 2001 / Accepted: 31 July 2001 / Published online: 11 February 2002 相似文献
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D. Basko G.C. La Rocca F. Bassani V.M. Agranovich 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):353-362
We predict an efficient electronic energy transfer from an excited semiconductor quantum well to optically active organic
molecules of the nearby medium (substrate and/or overlayer). The energy transfer mechanism is of the F?rster type and, at
semiconductor-organic distances of about 50 ?, can easily be as fast as 10-100 ps, which is about an order of magnitude shorter
than the effective exciton lifetime in an isolated quantum well. In such conditions, the Wannier-Mott exciton luminescence
is quenched and the organic luminescence is efficiently turned on. We consider both free as well as localized quantum well
excitons discussing the dependence of the energy transfer rate on temperature and localization length. A similar mechanism
for the non-radiative energy transfer to the organic overlayer molecules from unbound electron-hole pairs excited in the 2D
continuum is shown to be much less competitive with respect to other relaxation channels inside the inorganic quantum well
(in particular, 2D exciton formation).
Received 20 July 1998 相似文献
6.
R. Citro M. Marinaro 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):235-242
The spin magnetic susceptibility of the p-d model is calculated by means of a perturbation theory in the hybridization term V through a generalized cumulant expansion (GCE). The analysis is approached from the paramagnetic metallic phase. The results
qualitatively reproduce some unusual magnetic properties in the normal state of the hole-doped cuprates, supporting the scenario
of a Van Hove singularity near the Fermi level.
Received 15 October 1998 and Received in final form 24 March 1999 相似文献
7.
M.S. Mikhelashvili 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):187-192
A common theory of reversible charge transfer (RCT) kinetics for low and high excitation power with the use of the conditional
concentration of acceptors is presented. A comparison with recently published RCT theory is given. The results are similar
or identical only in restricted or fractal spaces of low dimension, and in the case of low concentration of acceptors, i.e. in all the cases when the conditions of the binary approximation are fulfilled. The deviation from the binary approximation
results in a physically incorrect picture, the cause being due to the different space averaging procedure. The probability
of the donor's cation state is an increasing function of the concentration of the acceptor and of the characteristic parameters
of the rate constants.
Received 26 May 1999 相似文献
8.
M. Valín-Rodríguez A. Puente Ll. Serra 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):493-498
We present calculations within density functional theory of the ground state and collective electronic oscillations in small
two-dimensional quantum rings. No spatial symmetries are imposed to the solutions and, as in a recent contribution, a transition
to a broken symmetry solution in the intrinsic reference frame for an increasingly narrow ring is found. The oscillations
are addressed by using real-time simulation. Conspicuous effects of the broken symmetry solution on the spectra are pointed
out.
Received 6 April 2000 and Received in final form 9 June 2000 相似文献
9.
S.A. Prosandeev V.S. Vikhnin S. Kapphan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):469-474
Experimental data on the temperature and electric field dependence of the Second Harmonic Generation Intensity in the solid
solution KTaO3:Li is analyzed in the framework of a new percolation-type approach which considers the history of cluster formation averaged
over a large number of samples. In order to take into account that two cluster dipole moments turn when joining clusters together,
a constraint is imposed on the cluster growth. This constraint leads to cluster-size saturation just after the percolation
threshold. Owing to this circumstance, the connected cluster coexists with free clusters in some range of the impurity concentration
and temperature. There is qualitative agreement between the computational results and experiments on Second Harmonic Generation
intensities. The algorithm was written in C++ which allowed realistic computations to be performed on a standard PC.
Received 26 August 1999 and Received in final form 27 December 1999 相似文献
10.
Optical response of thin plasma-polymer films with non-spherical silver nanoparticles 总被引:1,自引:0,他引:1
A. Heilmann M. Quinten J. Werner 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(4):455-461
The size and shape of silver nanoparticles which are embedded in a plasma-polymer matrix were obtained by transmission electron
microscopy and analyzed with optical image processing. We used a sample in which silver particles were present before and
after reshaping caused by thermal annealing in adjacent regions. As most of the particles appeared as elongated rotational
ellipsoids, the major and minor half axis were determined for each particle. We adopted the model of Gans in the Rayleigh
approximation to calculate for each investigated particle the extinction spectra from to using the data from the image processing. The various spectra for 368 silver particles were added to get total extinction
spectra for the sample as deposited and after reshaping, respectively. We found good agreement with the experimental spectra.
The blue shift of the plasma-resonance absorption, which occurs due to the reshaping of the silver particles during thermal
annealing, was also confirmed by using only changes in the particle sizes and shapes.
Received: 23 July 1997 / Revised: 27 October 1997 / Accepted: 3 December 1997 相似文献
11.
M. Valın-Rodrıguez A. Puente Ll. Serra 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):387-390
We report an analysis of the dipole response of a symmetric quantum-dot molecule as a function of the dot-dot separation and
intensity of a perpendicular magnetic field. The potential barrier is assumed proportional to the interdot distance using
a two-center oscillator potential. The results are obtained within the symmetry-unrestricted TDLSDA. It is shown that the
FIR details, specially the fragmentation of the low-energy brach, are quite sensitive to the interdot separation and that
in both the small and large separation limits the results converge towards the analytic Kohn's magnetoplasmon energies. The
validity of the LSDA is checked by comparison with the Hartree-Fock dipole spectrum in one case.
Received 29 November 2000 相似文献
12.
A. -B.M.A. Ibrahim J. Osman 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):193-198
In this paper we investigate the intrinsic optical bistability (IOB) in a
ferroelectric (FE) single layer using an alternative analysis. The FE
material is considered to have an intensity-dependent refractive index where
the third order nonlinear susceptibility χ(3) acts like Kerr
coefficient. The nonlinear response of the FE medium is modeled using the
Landau-Khalatnikov (LK) dynamical equation with the nonlinear anharmonic
potential obtained from the Landau-Devonshire free energy expressed in terms
of polarization. Within a single frequency approximation, the
electromagnetic wave equation is written in terms of the polarization P
rather than the electric field E as the dependent variable. With the
application of the nonlinear boundary conditions we have derived expressions
for both reflectance and transmittance as a function of the electric field
incident amplitude, polarization and other material parameters. The
formalism proves to be more suitable for FE materials since most of these
materials have highly linear and nonlinear coefficients especially when the
operating frequency is in the resonance region. The effects of thickness,
operating frequency and temperature on BaTiO3 single film are
investigated theoretically. The results presented here agree in principle
with the recent experimental observations of intrinsic OB in BaTiO3
monocrystal and other FE photorefractive materials. 相似文献
13.
M. Gorkunov M. Lapine E. Shamonina K.H. Ringhofer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):263-269
Effective magnetic properties of a composite meta-material consisting of periodically arranged circular conductive elements
are studied theoretically. A general expression for the effective bulk permeability is obtained with mutual effects and lattice
ordering being taken into account. The resonance frequency of the permeability is found to be strongly dependent on the size
and shape of the unit cell. Frequency dispersion of the permeability is studied with special attention paid to the frequency
range, where negative values of the permeability are possible. Corresponding recommendations for optimisation of the meta-materials
with negative permeability are made. The results are confirmed by numerical simulations of the finite structure behaviour
in an external magnetic field.
Received 19 April 2002 Published online 31 July 2002 相似文献
14.
O. Filippov K.H. Ringhofer B.I. Sturman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):285-290
Analytically and numerically we investigate the dependence of the first Fourier harmonics of the space-charge field, induced
in an AC-biased sillenite crystal by a light-interference pattern, on the light contrast m. It is shown that within the whole contrast range, 0 < m < 1, these dependences are controlled by the only scalar parameter - the space-charge wave quality factor Q. In the low-contrast limit, m Q
-2, this factor defines the degree of enhancement of the nonlinear response while for larger contrasts it characterizes strong
saturation effects. The data obtained are compared with the results of the previous studies of the AC-response. The possibilities
of experimental detection of predicted dependences and their possible implications are discussed.
Received 13 September 2002 / Received in final form 27 December 2002 Published online 11 February 2003 相似文献
15.
The optical properties of the quarter-filled single-band CDW systems
have been reexamined in the model with the electron-phonon coupling
related to the variations of electron site energies.
It appears that the indirect, electron-mediated coupling
between phase phonons and external electromagnetic fields
vanishes for symmetry reasons, at variance with the infrared selection
rules used in the generally accepted microscopic theory.
It is shown that the phase phonon modes and the electric fields
couple directly, with the coupling constant proportional to the
magnitude of the charge-density wave.
The single-particle contributions to the optical
conductivity tensor are determined for the ordered CDW state
and the related weakly doped metallic state by means of the Bethe-Salpeter
equations for elementary electron-hole excitations.
It turns out that this gauge-invariant approach establishes
a clear connection between the effective numbers of residual,
thermally activated and bound charge carriers.
Finally, the relation between these numbers and the activation energy of dc
conductivity and the optical CDW gap scale is explained in the way consistent
with the conductivity sum rules. 相似文献
16.
R. Lazzari I. Simonsen D. Bedeaux J. Vlieger J. Jupille 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):267-284
The light scattering by three-dimensional clusters supported by a substrate is modelled by representing clusters by truncated
spheroids whose polarizability is calculated via a multipolar development of the potential in the quasi-static limit. The determination of the mean island radius, density
and aspect ratio from the optical response is examined. The strong influence of both the particle-substrate interaction and
the particle shape on the optical behaviour is demonstrated, showing the limits of effective medium and dipolar theories.
The Surface Differential Reflectance spectra of silver on MgO(100) and titanium or aluminium on α-Al2O3(0001) surfaces have then been modelled by using the above model, illustrating the capability of optical means to deal with
various metals, including those belonging to transition series. In all cases, it is highlighted that the aspect ratio is central
in modelling the optical response of supported particles.
Received 5 June 2000 and Received in final form 31 July 2001 相似文献
17.
Ll. Serra A. Puente 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):77-81
The magnetic extension of the Thomas-Fermi-Weizs?cker kinetic energy is used within density-functional-theory to numerically
obtain the ground state densities and energies of two-dimensional quantum dots. The results are thoroughly compared with the
microscopic Kohn-Sham ones in order to assess the validity of the semiclassical method. Circular as well as deformed systems
are considered.
Received 26 October 2000 and Received in final form 14 December 2000 相似文献
18.
M. G. Brik K. Ogasawara H. Ikeno I. Tanaka 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(3):345-355
Fully relativistic multielectron method based on the numerical solution of
the Dirac equation was used to calculate the L2,3-edge X-ray absorption
near edge structure (XANES) spectra of VO2, V2O3, and
V2O5 crystals. The key-points of the method are: i) usage of the
molecular orbitals (MO); ii) absence of any fitting parameters; iii) wide
area of application: to any ion in any symmetry; iv) possibility of
numerical analysis of the MO composition. The calculated spectra are in a
satisfactory agreement with experimental data available in the literature,
including the absolute values of the transitions energy, the shape of the
absorption bands, and polarization dependence. The assignment of the
absorption bands in terms of the electronic configurations was done. The
structure of the absorption bands is attributed to the splitting of the
vanadium p- and d-orbitals; the magnitude of this splitting is estimated from
the spectra. Covalency effects were considered for all hosts; it was shown
that the contribution of the oxygen wave functions increases with increasing
the vanadium oxidation state. Dependence of the relative positions of the
vanadium 3d and oxygen 2p levels and energies of the “ligand–metal” charge
transfer transitions on the vanadium oxidation state was analysed. 相似文献
19.
N. Baer C. Gies J. Wiersig F. Jahnke 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):411-418
A microscopic theory is used to study photoluminescence of
semiconductor quantum dots under the influence of Coulomb and carrier-photon correlation effects
beyond the Hartree-Fock level. We investigate the emission spectrum and the decay properties of the time-resolved luminescence
from initially excited quantum dots. The influence of
the correlations is included within a cluster expansion scheme up to the singlet-doublet level. 相似文献
20.
M. Cheng R. Chen S. Feng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(1):81-85
The lateral shift of a light beam at the surface of an anisotropic
metamaterial slab is investigated. Analytical expressions of the lateral
shifts are derived using the stationary-phase method, in the case that total
reflection does and does not occur at the first interface. The sign of the
lateral shift in two situations is discussed, and the necessary conditions
for the lateral shift to be positive or negative are given. It is shown that
the thickness and physical parameters of the anisotropic metamaterial slab,
as well as the incident angle of the light beam, strongly affect the
properties of the lateral shift, and numerical results validate these
conclusions. The effect of a lossy metamaterial on the lateral shift is also
investigated. A restriction on the thickness of the slab is obtained, which
is necessary for the stationary-phase method to remain valid. 相似文献