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@PHDTHESIS{ElKhawaldeh:723332,
author = {El-Khawaldeh, Amir},
othercontributors = {Kull, Hans-Jörg and Bauer, Dieter},
title = {{Q}uantum {V}lasov theory of {M}ie oscillations in metal
clusters : a self-consistent approach to quantum surface
effects in nanoparticles},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2018-224139},
pages = {1 Online-Ressource (v, 144 Seiten) : Illustrationen},
year = {2018},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2018},
abstract = {The electron dynamics in metal clusters is studied in the
framework of the quantum Vlasov theory. The Vlasov theory
describes equilibria and excitations in ideal plasmas by a
self-consistent field approach. It is applied to the
spherical jellium model of atomic clusters with an emphasis
on quantum-size effects in nanometer sized clusters. A
proper understanding of the spill-out-induced surface
effects of the Mie plasmon is one of the major goals of this
work. For this purpose, the Vlasov model is treated by
theoretical and numerical methods both in the linear and
nonlinear regime of free and laser-driven cluster
excitations. Linear electrostatic cluster excitations are
treated in a multistream-Vlasov and in a reduced
single-state Vlasov model. In the framework of the
single-state model, the damping of the Mie plasmon can be
explained by a mode conversion process from surface to
volume plasmons due to surface scattering. Increasing the
number of representative states in the multistream approach,
it is shown that the residual volume plasmons are damped by
single-particle excitations (Landau damping).Reference
calculations are performed for specific Na clusters with the
multistream and the more common density-functional theory
approach. The plasmon damping rate in the multistream model
shows good quantitative agreement with the damping rate
obtained by the single-state model, which indicates the
importance of mode conversion for the plasmon decay. The
damping rate shows a characteristic scaling with the inverse
cluster radius. In addition, the resonance frequency is
redshifted with respect to the Mie frequency especially for
small clusters. By further including exchange-correlation
corrections, close agreement of the damping rate coefficient
with previous experimental and numerical results can be
achieved. Linear electromagnetic cluster excitations are
treated in the single-state model. Resonance absorption of
clusters is investigated at the critical density where the
light frequency equals the plasma frequency. In this
framework, the well-known theory of resonance absorption is
generalized from plane to spherical surfaces with variable
angles of incidence and light polarizations along the
surface. As a preparatory study for nonlinear electrostatic
cluster excitations, the non resonant collision less
absorption (Brunel mechanism) of thin foils is investigated.
Brunel’s scaling can be confirmed for thick foils in the
present quantum regime. However, the energy absorption shows
a clear signature of quantum-size effects for thin foils due
to the spill-out effect of the electron density. The main
result is an increase of Brunel’s scaling exponent for
thin foils. Nonlinear electrostatic cluster excitations are
investigated for spherical Na clusters. The nonlinear Mie
oscillation is studied based on an impulsive excitation of
the cluster. For moderate perturbations, the resonance
position of the Mieplasmon is blue shifted with respect to
the linear result. In addition, the plasmon line width
decreases. For sufficiently large perturbations, dynamical
deformation effects are observed, which lead to a splitting
of the Mie resonance. This splitting can be explained by a
coupling of the cluster dipole moment to the quadrupole
field induced by the electron cloud exterior to the cluster
region. The residual excitations in the interior region of
the cluster are characterized by local density fluctuations
on the timescale of the plasma period. The interaction of
clusters with femtosecond laser pulses is studied for peak
intensities up to 1014W/cm2.Nonlinear plasma-wave generation
at the cluster surface can be observed, which appears in the
presence of strong laser-induced polarization fields. The
acceleration of plasma waves through the cluster results in
enhanced outer ionization close to the cluster poles.
Recombinations of emitted electron wave packets result
infast density oscillations on the attosecond scale.},
cin = {135220 / 130000 / 100000},
ddc = {530},
cid = {$I:(DE-82)135220_20140620$ / $I:(DE-82)130000_20140620$ /
$I:(DE-82)100000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2018-224139},
url = {https://publications.rwth-aachen.de/record/723332},
}
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