14,763 research outputs found
Noise-Activated Escape from a Sloshing Potential Well
We treat the noise-activated escape from a one-dimensional potential well of
an overdamped particle, to which a periodic force of fixed frequency is
applied. We determine the boundary layer behavior, and the physically relevant
length scales, near the oscillating well top. We show how stochastic behavior
near the well top generalizes the behavior first determined by Kramers, in the
case without forcing. Both the case when the forcing dies away in the weak
noise limit, and the case when it does not, are examined. We also discuss the
relevance of various scaling regimes to recent optical trap experiments.Comment: 9 pages, no figures, REVTeX, expanded versio
Theory of plasmon-enhanced high-harmonic generation in the vicinity of metal nanostructures in noble gases
We present a semiclassical model for plasmon-enhanced high-harmonic
generation (HHG) in the vicinity of metal nanostructures. We show that both the
inhomogeneity of the enhanced local fields and electron absorption by the metal
surface play an important role in the HHG process and lead to the generation of
even harmonics and to a significantly increased cutoff. For the examples of
silver-coated nanocones and bowtie antennas we predict that the required
intensity reduces by up to three orders of magnitudes and the HHG cutoff
increases by more than a factor of two. The study of the enhanced high-harmonic
generation is connected with a finite-element simulation of the electric field
enhancement due to the excitation of the plasmonic modes.Comment: 4 figure
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Integration with Ontologies
One of today’s hottest IT topics is integration, as bringing together information from different sources and structures is not completely solved. The approach outlined here wants to illustrate how ontologies [Gr93] could help to support the integration process
On surface plasmon polariton wavepacket dynamics in metal-dielectric heterostructures
The WKB equations for dynamics of the surface plasmon polariton (SPP)
wavepacket are studied. The dispersion law for the SPP in the metal-dielectric
heterostructure with varying thickness of a perforated dielectric layer is
rigorously calculated and investigated using the scattering matrix method. Two
channels of the SPP wavepacket optical losses related to the absorption in a
metal and to the SPP leakage are analyzed. It is shown that change of the
dielectric layer thickness acts on the SPP as an external force leading to
evolution of its quasimomentum and to the wavepacket reversal or even to the
optical Bloch oscillations (BO). Properties of these phenomena are investigated
and discussed. Typical values of the BO amplitude are about tens of microns and
the period is around tens or hundreds of femtoseconds.Comment: 12 pages, 5 figure
Phase behavior of the Confined Lebwohl-Lasher Model
The phase behavior of confined nematogens is studied using the Lebwohl-Lasher
model. For three dimensional systems the model is known to exhibit a
discontinuous nematic-isotropic phase transition, whereas the corresponding two
dimensional systems apparently show a continuous
Berezinskii-Kosterlitz-Thouless like transition. In this paper we study the
phase transitions of the Lebwohl-Lasher model when confined between planar
slits of different widths in order to establish the behavior of intermediate
situations between the pure planar model and the three-dimensional system, and
compare with previous estimates for the critical thickness, i.e. the slit width
at which the transition switches from continuous to discontinuous.Comment: Submitted to Physical Review
Off-resonance field enhancement by spherical nanoshells
We study light scattering by spherical nanoshells consistent of
metal/dielectric composites. We consider two geometries of metallic nanoshell
with dielectric core, and dielectric coated metallic nanoparticle. We
demonstrate that for both geometries the local field enhancement takes place
out of resonance regions ("dark states"), which, nevertheless, can be
understood in terms of the Fano resonance. At optimal conditions the light is
stronger enhanced inside the dielectric material. By using nonlinear dielectric
materials it will lead to a variety nonlinear phenomena applicable for
photonics applications
High-order localized spoof surface plasmon resonances and experimental verifications
We theoretically demonstrated and experimentally verified high-order radial
spoof localized surface plasmon resonances supported by textured metal
particles. Through an effective medium theory and exact numerical simulations,
we show the emergence of these geometrically-originated electromagnetic modes
at microwave frequencies. The occurrence of high-order radial spoof plasmon
resonances is experimentally verified in ultrathin disks. Their spectral and
near-field properties are characterized experimentally, showing an excellent
agreement with theoretical predictions. Our findings shed light into the nature
of spoof localized surface plasmons, and open the way to the design of
broadband plasmonic devices able to operate at very different frequency
regimes.Comment: 29 pages, 10 figure
Light scattering by a medium with a spatially modulated optical conductivity: the case of graphene
We describe light scattering from a graphene sheet having a modulated optical
conductivity. We show that such modulation enables the excitation of surface
plasmon-polaritons by an electromagnetic wave impinging at normal incidence.
The resulting surface plasmon-polaritons are responsible for a substantial
increase of electromagnetic radiation absorption by the graphene sheet. The
origin of the modulation can be due either to a periodic strain field or to
adatoms (or absorbed molecules) with a modulated adsorption profile.Comment: http://iopscience.iop.org/0953-8984/24/24/24530
Methyl iodide production in the open ocean
Production pathways of the prominent volatile organic halogen compound methyl iodide (CH3I) are not fully understood. Based on observations, production of CH3I via photochemical degradation of organic material or via phytoplankton production has been proposed. Additional insights could not be gained from correlations between observed biological and environmental variables or from biogeochemical modeling to identify unambiguously the source of methyl iodide. In this study, we aim to address this question of source mechanisms with a three-dimensional global ocean general circulation model including biogeochemistry (MPIOM-HAMOCC (MPIOM - Max Planck Institute Ocean Model HAMOCC - HAMburg Ocean Carbon Cycle model)) by carrying out a series of sensitivity experiments. The simulated fields are compared with a newly available global data set. Simulated distribution patterns and emissions of CH3I differ largely for the two different production pathways. The evaluation of our model results with observations shows that, on the global scale, observed surface concentrations of CH3I can be best explained by the photochemical production pathway. Our results further emphasize that correlations between CH3I and abiotic or biotic factors do not necessarily provide meaningful insights concerning the source of origin. Overall, we find a net global annual CH3I air-sea flux that ranges between 70 and 260 Gg yr(-1). On the global scale, the ocean acts as a net source of methyl iodide for the atmosphere, though in some regions in boreal winter, fluxes are of the opposite direction (from the atmosphere to the ocean)
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