An adaptive algorithm for n-body field expansions
Weinberg, Martin D.
1998-05-28
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Superconducting Tunnel Junctions (STJ's) are currently being developed as
photon detectors for a wide range of applications. Interest comes from their
ability to cumulate photon counting with chromaticity (i.e. energy resolution)
from the near infrared (2 $\mu$m) to the X-rays wavelengths and good quantum
efficiency up to 80%. Resolving power can exceed 10 in the visible wavelength
range. Our main goal is to use STJ's for astronomical observations at low light
level in the near infrared. This paper put the emphasis on two main points: the
improvement of the tantalum absorber epitaxy and the development of a new
version of the fabrication process for making Ta/Al-AlOx-Al/Ta photon counting
STJ's. The main features of this process are that pixels have aligned
electrodes and vias patterned through a protecting SiO2 layer. These vias are...
Theoretical optical and x-ray spectra of model structures of water and ice
are calculated using a many-body perturbation theory, Bethe-Salpeter equation
(BSE) approach implemented in the valence- and core-excitation codes AI2NBSE
and OCEAN. These codes use ab initio density functional theory wave functions
from a plane-wave, pseudopotential code, quasi-particle self energy
corrections, and a BSE treatment of particle-hole interactions. The approach
improves upon independent-particle methods through the inclusion of a complex,
energy-dependent self energy and screened particle-hole interactions to account
for inelastic losses and excitonic effects. These many-body effects are found
to be crucial for quantitative calculations of ice and water spectra.
Comment: 17 pages, 9 figures, 2 tables
Comment: 4 pages, 4 figures, submitted to Physical Review Letters
Comment: 25 pages includind 5 figures
Comment: 4 pages, 3 figures, submitted to Applied Physics Letters
Comment: 29 pages, 12 figures
Comment: 10 pages, 3 figures, submitted to Phys. Rev. B
For a single crystal of TmGa3, two-dimensional angular correlation of
positron annihilation radiation spectra were measured and subjected to a
deconvolution algorithm based on the Van Citter iterative method. The
three-dimensional electron-positron momentum density was reconstructed both via
the Cormack and a modified Fourier-transform-based method. After the 3D LCW
transformation, the resulting k-space density was in fair agreement with band
structure LMTO calculations. In particular, the use of deconvoluted data helped
to reveal small details of the Fermi surface in the 6th band.
