33,467 research outputs found
Long-range repulsive interaction between TTF molecules on a metal surface induced by charge transfer
The low-coverage adsorption of a molecular electron donor,
tetrathiafulvalene, on Au(111) is characterized by the spontaneous formation of
superlattice of monomers, whose spacing exceeds the equilibrium distance of
non-covalent interactions and depends on coverage. The origin of this peculiar
growth mode is due to a long-range repulsive interaction between molecules. The
analysis of molecular-pair distributions obtained by scanning tunneling
microscopy measurements permits us to determine that the nature of TTF
intermolecular interactions on Au (111) is electrostatic. A repulsion between
molecules is caused by the accumulation of charge due to electron donation into
the metal surface, as pictured through density functional theory calculations
Tomography of high-redshift clusters with OSIRIS
High-redshift clusters of galaxies are amongst the largest cosmic structures.
Their properties and evolution are key ingredients to our understanding of
cosmology: to study the growth of structure from the inhomogeneities of the
cosmic microwave background; the processes of galaxy formation, evolution, and
differentiation; and to measure the cosmological parameters (through their
interaction with the geometry of the universe, the age estimates of their
component galaxies, or the measurement of the amount of matter locked in their
potential wells). However, not much is yet known about the properties of
clusters at redshifts of cosmological interest. We propose here a radically new
method to study large samples of cluster galaxies using microslits to perform
spectroscopy of huge numbers of objects in single fields in a narrow spectral
range-chosen to fit an emission line at the cluster redshift. Our objective is
to obtain spectroscopy in a very restricted wavelength range (~100 A in width)
of several thousands of objects for each single 8x8 square arcmin field.
Approximately 100 of them will be identified as cluster emission-line objects
and will yield basic measurements of the dynamics and the star formation in the
cluster (that figure applies to a cluster at z~0.50, and becomes ~40 and ~20
for clusters at z~0.75 and z~1.00 respectively). This is a pioneering approach
that, once proven, will be followed in combination with photometric redshift
techniques and applied to other astrophysical problems.Comment: 4 pages, 3 figures. Proceedings of "Science with the GTC", Granada
(Spain), February 2002, RMxAA in pres
Theory of extraordinary transmission of light through quasiperiodic arrays of subwavelength holes
By using a theoretical formalism able to work in both real and k-spaces, the
physical origin of the phenomenon of extraordinary transmission of light
through quasi-periodic arrays of holes is revealed. Long-range order present in
a quasiperiodic array selects the wavevector(s) of the surface electromagnetic
mode(s) that allows an efficient transmission of light through subwavelength
holes.Comment: 4 pages, 4 figure
Observation of VH and VVH cosmic rays with an ionization-Cerenkov detector system
Heavy and ultraheavy nuclei observations of cosmic rays using ionization chamber-Cerenkov counter syste
New nonlinear coherent states and some of their nonclassical properties
We construct a displacement operator type nonlinear coherent state and
examine some of its properties. In particular it is shown that this nonlinear
coherent state exhibits nonclassical properties like squeezing and
sub-Poissonian behaviour.Comment: 3 eps figures. to appear in J.Opt
Existence of Eigenvalues for Anisotropic and Fractional Anisotropic Problems via Ljusternik-Schnirelmann Theory
In this work, our interest lies in proving the existence of critical values
of the following Rayleigh-type quotients where , and is an anisotropic Sobolev norm,
is a fractional version of the same anisotropic
norm, and is an anisotropic Lebesgue norm.
Using the Ljusternik-Schnirelmann theory, we prove the existence of a
sequence of critical values and we also find an associated Euler-Lagrange
equation for critical points. Additionally, we analyze the connection between
the fractional critical values and its local counterparts.Comment: 18 pages, submitte
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