968 research outputs found
Energy Dependence of Cu L2,3 Satellites using Synchrotron Excited X-ray Emission Spectroscopy
The L2,3 X-ray emission of Cu metal has been measured using monochromatic
synchrotron radiation. The self-absorption effect in the spectra is shown to be
very small in our experimental geometry. From the quantitative analysis of
spectra recorded at different excitation energies, the L3/L2 emission intensity
ratio and the partial Auger-width are extracted. High-energy satellite features
on the L3 emission line are separated by a subtraction procedure. The satellite
intensity is found to be slowly increasing for excitation energies between the
L3, L2 and L1 core-level thresholds due to shake-up and shake-off transitions.
As the excitation energy passes the L2 threshold, a step of rapidly increasing
satellite intensity of the L3 emission is found due to additional Coster-Kronig
processes.Comment: 8 pages, 3 figures, http://link.aps.org/doi/10.1103/PhysRevB.56.1223
Calibrating the Cepheid Period-Luminosity relation with the VLTI
The VLTI is the ideal instrument for measuring the distances of nearby
Cepheids with the Baade-Wesselink method, allowing an accurate recalibration of
the Cepheid Period-Luminosity relation. The high accuracy required by such
measurement, however, can only be reached taking into account the effects of
limb darkening, and its dependence on the Cepheid pulsations. We present here
our new method to compute phase- and wavelength-dependent limb darkening
profiles, based on hydrodynamic simulation of Classical Cepheid atmospheres.Comment: 3 pages, 2 postscript figures, uses eas.cls LaTeX class file, to
appear in the proc. Eurowinter School "Observing with the VLTI", Feb 3-8
2002, Les Houches (France
Magnetic circular dichroism in X-ray fluorescence of Heusler alloys at threshold excitation
The results of fluorescence measurements of magnetic circular dichroism (MCD)
in Mn L_2,L_3 X-ray emission and absorption for Heusler alloys NiMnSb and
Co2MnSb are presented. Very intense resonance Mn L_3 emission is found at the
Mn 2p_3/2 threshold and is attributed to a peculiarity of the threshold
excitation in materials with the half-metallic character of the electronic
structure. A theoretical model for the description of resonance scattering of
polarized x-rays is suggested.Comment: 3 pages, 2 figures. Discussed at conferences, submitting process in
progres
Topographical Choroidal Thickness Change Following PDT for CSC: An OCT Case Report
Purpose. To describe topographical changes in choroidal thickness as measured by optical coherence tomography following photodynamic therapy (PDT) for central serous chorioretinopathy (CSC). Methods. Case report. Results. By 1 month following PDT, mean (SD) choroidal thickness decreased from 562 microns (24) to 424 microns (27) (P < 0.01) at 3âmm temporal to fovea, 483 microns (9) to 341 microns (21) (P < 0.01) at 1.5âmm temporal to fovea, 576 microns (52) to 370 microns (81) (P < 0.01) under the fovea, 442 microns (30) to 331 microns (54) (P < 0.04) at 1.5âmm nasal to fovea, and 274 microns (39) to 171 microns (17) (P < 0.01) at 3âmm nasal to fovea. The Location of greatest choroidal thickness (648 microns) prior to treatment was at point of leakage on fluorescein angiogram (FA). This region decreased to 504 microns following treatment. Conclusion. A decrease in choroidal thickness can be seen following PDT for CSC as far as 3âmm temporal and 3âmm nasal to fovea. The Location of greatest choroidal thickness may be at point of leakage on FA
Improved Baade-Wesselink surface-brightness relations
Recent, and older accurate, data on (limb-darkened) angular diameters is
compiled for 221 stars, as well as BVRIJK[12][25] magnitudes for those objects,
when available. Nine stars (all M-giants or supergiants) showing excess in the
[12-25] colour are excluded in the analysis as this may indicate the present of
dust influencing the optical and near-infrared colours as well. Based on this
large sample, Baade-Wesselink surface-brightness (SB) relations are presented
for dwarfs, giants, supergiants and dwarfs in the optical and near-infrared.
M-giants are found to follow different SB-relations from non-M giants, in
particular in V-(V-R). The preferred relation for non-M giants are compared to
earlier relation by Fouque & Gieren (1997, based on 10 stars) and Nordgren et
al. (2002, based on 57 stars). Increasing the sample size does not lead to a
lower rms value. It is shown that the residuals do not correlate with
metallicity at a significant level. The finally adopted observed angular
diameters are compared to those predicted by Cohen et al. (1999) for 45 stars
in common, and there is reasonable overall, to good agreement when \theta <6
mas. Finally, I comment on the common practice in the literature to average,
and then fix, the zero point of the V-(V-K), V-(V-R) and K-(J-K) relations, and
then re-derive the slopes. Such a common zero point at zero colour is not
expected from model atmospheres for the (V-R) colour and depends on gravity.
Relations derived in this way may be biased.Comment: accepted for publication in the MNRA
Electronic structure investigation of CoO by means of soft X-ray scattering
The electronic structure of CoO is studied by resonant inelastic soft X-ray
scattering spectroscopy using photon energies across the Co 2p absorption
edges. The different spectral contributions from the energy-loss structures are
identified as Raman scattering due to d-d and charge-transfer excitations. For
excitation energies close to the L3 resonance, the spectral features are
dominated by quartet-quartet and quartet-doublet transitions of the 3d7
configuration. At excitation energies corresponding to the satellites in the Co
2p X-ray absorption spectrum of CoO, the emission features are instead
dominated by charge-transfer transitions to the 3d8L-1 final state. The spectra
are interpreted and discussed with the support of simulations within the single
impurity Anderson model with full multiplet effects which are found to yield
consistent spectral functions to the experimental data.Comment: 8 pages, 2 figures, 2 tables,
http://link.aps.org/doi/10.1103/PhysRevB.65.20510
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