751 research outputs found
Unmixing AVIRIS data to provide a method for vegetation fraction subtraction
Five flight lines of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were acquired over the Dolly Varden Mountains in northeastern Nevada on 2 June 1989. Signal-to-noise ratio values are given. The empirical line method was used to convert AVIRIS radiance values to reflectance. This method involves calculating gain and offset values for each band. These values are based upon a comparison of the imaging spectrometer data and field reflectance measurements, both taken over the same ground targets. The targets used were a dark andesite flow and a bright playa
Electronic ground states of Fe and Co as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy
The electronic ground state of the Co diatomic molecular cation
has been assigned experimentally by x-ray absorption and x-ray magnetic
circular dichroism spectroscopy in a cryogenic ion trap. Three candidates,
, , and , for the electronic ground state of Fe
have been identified. These states carry sizable orbital angular momenta that
disagree with theoretical predictions from multireference configuration
interaction and density functional theory. Our results show that the ground
states of neutral and cationic diatomic molecules of transition elements
cannot generally be assumed to be connected by a one-electron process
Coordination-driven magnetic-to-nonmagnetic transition in manganese doped silicon clusters
The interaction of a single manganese impurity with silicon is analyzed in a
combined experimental and theoretical study of the electronic, magnetic, and
structural properties of manganese-doped silicon clusters. The structural
transition from exohedral to endohedral doping coincides with a quenching of
high-spin states. For all geometric structures investigated, we find a similar
dependence of the magnetic moment on the manganese coordination number and
nearest neighbor distance. This observation can be generalized to manganese
point defects in bulk silicon, whose magnetic moments fall within the observed
magnetic-to-nonmagnetic transition, and which therefore react very sensitively
to changes in the local geometry. The results indicate that high spin states in
manganese-doped silicon could be stabilized by an appropriate lattice
expansion
The census of interstellar complex organic molecules in the Class I hot corino of SVS13-A
We present the first census of the interstellar Complex Organic Molecules
(iCOMs) in the low-mass Class I protostar SVS13-A, obtained by analysing data
from the IRAM-30m Large Project ASAI (Astrochemical Surveys At IRAM). They
consist of an high-sensitivity unbiased spectral survey at the 1mm, 2mm and 3mm
IRAM bands. We detected five iCOMs: acetaldehyde (CHCHO), methyl formate
(HCOOCH), dimethyl ether (CHOCH), ethanol (CHCHOH) and
formamide (NHCHO). In addition we searched for other iCOMs and ketene
(HCCO), formic acid (HCOOH) and methoxy (CHO), whose only ketene was
detected. The numerous detected lines, from 5 to 37 depending on the species,
cover a large upper level energy range, between 15 and 254 K. This allowed us
to carry out a rotational diagram analysis and derive rotational temperatures
between 35 and 110 K, and column densities between and
cm on the 0."3 size previously determined by
interferometric observations of glycolaldehyde. These new observations clearly
demonstrate the presence of a rich chemistry in the hot corino towards SVS13-A.
The measured iCOMs abundances were compared to other Class 0 and I hot corinos,
as well as comets, previously published in the literature. We find evidence
that (i) SVS13-A is as chemically rich as younger Class 0 protostars, and (ii)
the iCOMs relative abundances do not substantially evolve during the
protostellar phase.Comment: 24 pages, MNRAS in pres
BDS tuning and Luminosity Monitoring in CLIC
The emittance preservation in the Beam Delivery System (BDS) is one of the
major challenges in CLIC. The fast detuning of the final focus optics requires
an on-line tuning procedure in order to keep luminosity close to the maximum.
Different tuning techniques have been applied to the CLIC BDS and in particular
to the Final Focus System (FFS) in order to mitigate static and dynamic
imperfections. Some of them require a fast luminosity measurement. Here we
study the possibility to use beam-beam backgrounds processes at CLIC 3 TeV CM
energy as fast luminosity signal. In particular the hadrons multiplicity in the
detector region is investigated.Comment: Proceedings of LCWS1
Spin and orbital magnetic moments of size-selected iron, cobalt, and nickel clusters and their link to the bulk phase diagrams
Spin and orbital magnetic moments of cationic iron, cobalt, and nickel
clusters have been determined from x-ray magnetic circular dichroism
spectroscopy. In the size regime of atoms, these clusters show
strong ferromagnetism with maximized spin magnetic moments of 1~ per
empty state because of completely filled majority spin bands. The
only exception is where an unusually low average spin
magnetic moment of ~ per unoccupied state is
detected; an effect, which is neither observed for nor
.\@ This distinct behavior can be linked to the existence
and accessibility of antiferromagnetic, paramagnetic, or nonmagnetic phases in
the respective bulk phase diagrams of iron, cobalt, and nickel. Compared to the
experimental data, available density functional theory calculations generally
seem to underestimate the spin magnetic moments significantly. In all clusters
investigated, the orbital magnetic moment is quenched to \,\% of the
atomic value by the reduced symmetry of the crystal field. The magnetic
anisotropy energy is well below 65 eV per atom
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