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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: 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
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.
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