1,255 research outputs found
Experimental verification of a fully inseparable tripartite continuous-variable state
A continuous-variable tripartite entangled state is experimentally generated
by combining three independent squeezed vacuum states and the variances of its
relative positions and total momentum are measured. We show that the measured
values violate the separability criteria based on the sum of these quantities
and prove the full inseparability of the generated state.Comment: 5 pages, 4 figure
Criteria for the experimental observation of multi-dimensional optical solitons in saturable media
Criteria for experimental observation of multi-dimensional optical solitons
in media with saturable refractive nonlinearities are developed. The criteria
are applied to actual material parameters (characterizing the cubic
self-focusing and quintic self-defocusing nonlinearities, two-photon loss, and
optical-damage threshold) for various glasses. This way, we identify operation
windows for soliton formation in these glasses. It is found that two-photon
absorption sets stringent limits on the windows. We conclude that, while a
well-defined window of parameters exists for two-dimensional solitons (spatial
or spatiotemporal), for their three-dimensional spatiotemporal counterparts
such a window \emph{does not} exist, due to the nonlinear loss in glasses.Comment: 8 pages, to appear in Phys. Rev.
High pressure evolution of FeO electronic structure revealed by X-ray absorption
We report the first high pressure measurement of the Fe K-edge in hematite
(FeO) by X-ray absorption spectroscopy in partial fluorescence yield
geometry. The pressure-induced evolution of the electronic structure as
FeO transforms from a high-spin insulator to a low-spin metal is
reflected in the x-ray absorption pre-edge. The crystal field splitting energy
was found to increase monotonically with pressure up to 48 GPa, above which a
series of phase transitions occur. Atomic multiplet, cluster diagonalization,
and density-functional calculations were performed to simulate the pre-edge
absorption spectra, showing good qualitative agreement with the measurements.
The mechanism for the pressure-induced phase transitions of FeO is
discussed and it is shown that ligand hybridization significantly reduces the
critical high-spin/low-spin pressure.Comment: 5 pages, 4 figures and 1 tabl
Detection of abundant solid methanol toward young low mass stars
We present detections of the absorption band at 3.53 micron due to solid
methanol toward three low-mass young stellar objects located in the Serpens and
Chameleon molecular cloud complexes. The sources were observed as part of a
large spectroscopic survey of ~40 protostars. This is the first detection of
solid methanol in the vicinity of low mass (M <1 Msol) young stars and shows
that the formation of methanol does not depend on the proximity of massive
young stars. The abundances of solid methanol compared to water ice for the
three sources are in the range 15-25% which is comparable to those for the most
methanol-rich massive sources known. The presence of abundant methanol in the
circumstellar environment of some low mass young stars has important
consequences for the formation scenarios of methanol and more complex organic
species near young solar-type stars.Comment: Accepted for publication in A&A letter
Inelastic X-Ray Scattering Study of Exciton Properties in an Organic Molecular crystal
Excitons in a complex organic molecular crystal were studied by inelastic
x-ray scattering (IXS) for the first time. The dynamic dielectric response
function is measured over a large momentum transfer region, from which an
exciton dispersion of 130 meV is observed. Semiempirical quantum chemical
calculations reproduce well the momentum dependence of the measured dynamic
dielectric responses, and thus unambiguously indicate that the lowest Frenkel
exciton is confined within a fraction of the complex molecule. Our results
demonstrate that IXS is a powerful tool for studying excitons in complex
organic molecular systems. Besides the energy position, the IXS spectra provide
a stringent test on the validity of the theoretically calculated exciton wave
functions.Comment: 4 pages, 4 figure
Temporal and spatial coordination of chromosome movement, spindle formation, and nuclear envelope breakdown during prometaphase in Drosophila melanogaster embryos.
The chaperone FACT and histone H2B ubiquitination maintain S. pombe genome architecture through genic and subtelomeric functions
Determining the in-plane orientation of the ground-state orbital of CeCu2Si2
We have successfully determined the hitherto unknown sign of the B44 Stevens
crystal-field parameter of the tetragonal heavy-fermion compound CeCu2Si2 using
vector q dependent non-resonant inelastic x-ray scattering (NIXS) experiments
at the cerium N4,5 edge. The observed difference between the two different
directions q||[100] and q||[110] is due to the anisotropy of the crystal-field
ground state in the (001) plane and is observable only because of the
utilization of higher than dipole transitions possible in NIXS. This approach
allows us to go beyond the specific limitations of dc magnetic susceptibility,
inelastic neutron scattering, and soft x-ray spectroscopy, and provides us with
a reliable information about the orbital state of the 4f electrons relevant for
the quantitative modeling of the quasi-particles and their interactions in
heavy-fermion systems
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