292 research outputs found
Classical Theory of Optical Nonlinearity in Conducting Nanoparticles
We develop a classical theory of electron confinement in conducting
nanoparticles. The theory is used to compute the nonlinear optical response of
the nanoparticle to a harmonic external field.Comment: Page margins have been adjusted; otherwise, identical to the previous
versio
Cubic optical nonlinearity of free electrons in bulk gold
A fast (τresponse <90 fs) free-electron spin-flipping frequency-degenerate nonlinearity with a significant value of |χ(3)xxyy(ω,ω,ω,-ω) χ(3)xyyx(ω,ω,ω,-ω)| ~ 10-8 esu has been observed in bulk gold at 1260 nm by use of a new pump-probe polarization-sensitive technique. <br/
Landau damping in thin films irradiated by a strong laser field
The rate of linear collisionless damping (Landau damping) in a classical
electron gas confined to a heated ionized thin film is calculated. The general
expression for the imaginary part of the dielectric tensor in terms of the
parameters of the single-particle self-consistent electron potential is
obtained. For the case of a deep rectangular well, it is explicitly calculated
as a function of the electron temperature in the two limiting cases of specular
and diffuse reflection of the electrons from the boundary of the
self-consistent potential. For realistic experimental parameters, the
contribution of Landau damping to the heating of the electron subsystem is
estimated. It is shown that for films with a thickness below about 100 nm and
for moderate laser intensities it may be comparable with or even dominate over
electron-ion collisions and inner ionization.Comment: 15 pages, 2 figure
Spectral classification of emission-line galaxies from the Sloan Digital Sky Survey. II. A supplementary diagnostic for AGNs using the Dn(4000) index
In this paper we present a classification of emission-line galaxies at
intermediate and high redshifts (0.52.5 for near-infrared spectra), using the
Dn(4000) index as a supplementary diagnostic. Our goal is to complement the
diagnostic based only on emission-line ratios from the blue part of the
spectra, which suffer from some limitations for the classification of Seyfert 2
and composite galaxies. We used a sample of 89 379 galaxies with a good
signal-to-noise ratio from the Sloan Digital Sky Survey (data release 7). Using
the classification scheme presented in Paper I, we classified these galaxies
with a diagnostic diagram involving the [Oiii]5007 /Hbeta and [Oii]3726+3729
/Hbeta emission-line ratios. Then we derived a supplementary diagnostic
involving Dn(4000) to improve this classification, in the regions where objects
of different types are mixed. To show the validity of our spectral
classification we established success-rate and contamination charts, then we
compared our results to those obtained with the reference classification that
was scheme obtained also using Halpha, [Nii]6584, and [Sii]6717+6731 emission
lines. We show that our supplementary classification based on the Dn(4000)
index allows to separate unambiguously star-forming galaxies from Seyfert 2 in
the region where they were mixed in Paper I. It also significantly reduces the
region where star-forming galaxies are mixed with composites.Comment: accepted for publication in A\&A, 10 pages corrected bug in LateX
file for equations 7 and
Size-Dependent Surface Plasmon Dynamics in Metal Nanoparticles
We study the effect of Coulomb correlations on the ultrafast optical dynamics
of small metal particles. We demonstrate that a surface-induced dynamical
screening of the electron-electron interactions leads to quasiparticle
scattering with collective surface excitations. In noble-metal nanoparticles,
it results in an interband resonant scattering of d-holes with surface
plasmons. We show that this size-dependent many-body effect manifests itself in
the differential absorption dynamics for frequencies close to the surface
plasmon resonance. In particular, our self-consistent calculations reveal a
strong frequency dependence of the relaxation, in agreement with recent
femtosecond pump-probe experiments.Comment: 8 pages + 4 figures, final version accepted to PR
Size-dependent Correlation Effects in Ultrafast Optical Dynamics of Metal Nanoparticles
We study the role of collective surface excitations in the electron
relaxation in small metal particles. We show that the dynamically screened
electron-electron interaction in a nanoparticle contains a size-dependent
correction induced by the surface. This leads to new channels of quasiparticle
scattering accompanied by the emission of surface collective excitations. We
calculate the energy and temperature dependence of the corresponding rates,
which depend strongly on the nanoparticle size. We show that the
surface-plasmon-mediated scattering rate of a conduction electron increases
with energy, in contrast to that mediated by a bulk plasmon. In noble-metal
particles, we find that the dipole collective excitations (surface plasmons)
mediate a resonant scattering of d-holes to the conduction band. We study the
role of the latter effect in the ultrafast optical dynamics of small
nanoparticles and show that, with decreasing nanoparticle size, it leads to a
drastic change in the differential absorption lineshape and a strong frequency
dependence of the relaxation near the surface plasmon resonance. The
experimental implications of our results in ultrafast pump-probe spectroscopy
are also discussed.Comment: 29 pages including 6 figure
The Global Energy Transition: A Review of the Existing Literature
This chapter presents an overview of the existing literature on the geopolitics of the global energy transition. Notwithstanding its potentially re-defining role for international relations, this issue has, so far, not been analysed in a comprehensive manner but in a rather fragmented way. This chapter represents a useful summary to the state-of-the-art of knowledge in the field, and therefore a useful starting point for the book
An HDG Method for Dirichlet Boundary Control of Convection Dominated Diffusion PDE
We first propose a hybridizable discontinuous Galerkin (HDG) method to
approximate the solution of a \emph{convection dominated} Dirichlet boundary
control problem. Dirichlet boundary control problems and convection dominated
problems are each very challenging numerically due to solutions with low
regularity and sharp layers, respectively. Although there are some numerical
analysis works in the literature on \emph{diffusion dominated} convection
diffusion Dirichlet boundary control problems, we are not aware of any existing
numerical analysis works for convection dominated boundary control problems.
Moreover, the existing numerical analysis techniques for convection dominated
PDEs are not directly applicable for the Dirichlet boundary control problem
because of the low regularity solutions. In this work, we obtain an optimal a
priori error estimate for the control under some conditions on the domain and
the desired state. We also present some numerical experiments to illustrate the
performance of the HDG method for convection dominated Dirichlet boundary
control problems
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