30,291 research outputs found
Effect of dipolar interactions on optical nonlinearity of two-dimensional nanocomposites
In this work, we calculate the contribution of dipole-dipole interactions to
the optical nonlinearity of the two-dimensional random ensemble of
nanoparticles that possess a set of exciton levels, for example, quantum dots.
The analytical expressions for the contributions in the cases of TM and
TE-polarized light waves propagating along the plane are obtained. It is shown
that the optical nonlinearity, caused by the dipole-dipole interactions in the
planar ensemble of the nanoparticles, is several times smaller than the similar
nonlinearity of the bulk nanocomposite. This type of optical nonlinearity is
expected to be observed at timescales much larger than the quantum dot exciton
rise time. The proposed method may be applied to various types of the
nanocomposite shapes.Comment: 8 page
Enhancement of field generation via maximal atomic coherence prepared by fast adiabatic passage in Rb vapor
We have experimentally demonstrated the enhancement of coherent Raman
scattering in Rb atomic vapor by exciting atomic coherence with fractional
stimulated Raman adiabatic passage. Experimental results are in good agreement
with numerical simulations. The results support the possibility of increasing
the sensitivity of CARS by preparing atomic or molecular coherence using short
pulses
Strong and Electromagnetic Decays of X(1835) as a Baryonium State
With the assumption that the recently observed X(1835) is a baryonium state
we have studied the strong decays of and the electromagnetic decay of in the framework of effective Lagrangian formalism. In the present
investigation we have included the contributions from the iso-singlet light
scalar resonances but we have not included the isospin violating effect. Our
result for the strong decay of is
smaller than the observed data. The decay width for the radiative decay of
is consistent with the assumption that it decays through
the glueball. In addition, the width for the strong decay of is larger than that of the strong decay of due to the large phase space and coupling constant
. From our investigation, it is not possible to interpret
X(1835) as a baryonium.Comment: Corrected typo
Photoluminescence and spectral switching of single CdSe/ZnS colloidal nanocrystals in poly(methyl methacrylate)
Emission from single CdSe nanocrystals in PMMA was investigated. A fraction
of the nanocrystals exhibiting switching between two energy states, which have
similar total intensities, but distinctly different spectra were observed. We
found that the spectral shift characteristic frequency increases with the pump
power. By using the dynamic shift in the spectral position of emission peaks,
we were able to correlate peaks from the same nanocrystal. The measured
correlation is consistent with assignment of low energy lines to phonon
replicas.Comment: 5 pages, 4 figure
Independent ferroelectric contributions and rare-earth-induced polarization reversal in multiferroic TbMn2O5
Three independent contributions to the magnetically induced spontaneous
polarization of multiferroic TbMn2O5 are uniquely separated by optical second
harmonic generation and an analysis in terms of Landau theory. Two of them are
related to the magnetic Mn3+/4+ order and are independent of applied fields of
up to 7 T. The third contribution is related to the long-range
antiferromagnetic Tb3+ order. It shows a drastic decrease upon the application
of a magnetic field and mediates the change of sign of the spontaneous electric
polarization in TbMn2O5. The close relationship between the rare-earth
long-range order and the non-linear optical properties points to isotropic
Tb-Tb exchange and oxygen spin polarization as mechanism for this rare-earth
induced ferroelectricity.Comment: 8 pages, 5 figure
Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs
In a composite system of gravitationally coupled stellar and gaseous discs,
we perform linear stability analysis for axisymmetric coplanar perturbations
using the two-fluid formalism. The background stellar and gaseous discs are
taken to be scale-free with all physical variables varying as powers of
cylindrical radius with compatible exponents. The unstable modes set in as
neutral modes or stationary perturbation configurations with angular frequency
.Comment: 7 pages using AAS styl
What has Been Learned About Storm Surge Dynamics from Hurricane Isabel Model Simulation?
An unstructured grid hydrodynamic model was used to study storm surge in the Chesapeake Bay during Hurricane Isabel. The model-simulated, storm-induced water level compared reasonably well with the measured data collected around the Bay. Calibrated water level was extracted from the model to further analyze the dynamics of the surge as it formed and propagated along the mainstem Chesapeake. Based on time-series analysis, formation of the surge due to the pumping of coastal waters (hereafter called the primary surge) into the Chesapeake was first identified at the Bay mouth with a peak height of 1.5 m above mean sea level (MSL). Once formed, it propagated northward with gradually diminishing amplitude at a speed of about 5 m⋅sec-1 until reaching Windmill Point, near the mouth of the Rappahannock River in Virginia. Beyond Windmill Point, the surge height increased monotonically toward the northern part of the Chesapeake Bay. Spatial analysis of surge height revealed that a second-stage surge was induced directly by the southerly wind following Hurricane Isabel’s passage inland. The persistent southerly wind induced a setup and a set-down in the upper and lower Chesapeake respectively, with the dividing line near Windmill Point where the water level stayed at approximately 0.5 m above MSL during the event. Space-time analysis provided further evidence that the abnormally high water in the upper Chesapeake Bay was the result of the primary surge wave as well as the second-stage surge caused by the southerly wind-induced setup.https://scholarworks.wm.edu/vimsbooks/1007/thumbnail.jp
Coherence Length of Excitons in a Semiconductor Quantum Well
We report on the first experimental determination of the coherence length of
excitons in semiconductors using the combination of spatially resolved
photoluminescence with phonon sideband spectroscopy. The coherence length of
excitons in ZnSe quantum wells is determined to be 300 ~ 400 nm, about 25 ~ 30
times the exciton de Broglie wavelength. With increasing exciton kinetic
energy, the coherence length decreases slowly. The discrepancy between the
coherence lengths measured and calculated by only considering the acoustic
phonon scattering suggests an important influence of static disorder.Comment: 4 Pages, 4 figure
Giant Enhancement of Surface Second Harmonic Generation in BaTiO_3 due to Photorefractive Surface Wave Excitation
We report observation of strongly enhanced surface SHG in BaTiO_3 due to
excitation of a photorefractive surface electromagnetic wave. Surface SH
intensity may reach 10^{-2} of the incident fundamental light intensity.
Angular, crystal orientation and polarization dependencies of this SHG are
presented. Possible applications of this effect in nonlinear surface
spectroscopy are discussed.Comment: 5 pages, 6 figures, submitted to Physical Review Letters on the
3/29/199
Critical factors affecting the quality of industrialized building system projects in China
2016-2017 > Academic research: refereed > Publication in refereed journal201804_a bcmaVersion of RecordPublishe
- …