Soft-x-ray laser interferometry of a pinch discharge using a tabletop laser

Includes bibliographical references (page 917).We have used a tabletop soft-x-ray laser and a wave-front division interferometer to probe the plasma of a pinch discharge. A very compact capillary discharge-pumped Ne-like Ar laser emitting at 46.9 nm was combined with a wave division interferometer based on Lloyd's mirror and Sc-Si multilayer-coated optics to map the electron density in the cathode region of the discharge. This demonstration of the use of tabletop soft-x-ray laser in plasma interferometry could lead to the widespread use of these lasers in the diagnostics of dense plasmas

Applications of high repetition rate tabletop soft X-ray lasers become a reality in several fields

Includes bibliographical references (page 468).For many years researchers have envisioned the development of compact high repetition rate tabletop soft x-ray laser, that could be routinely used in application in numerous disciplines. With demonstrated average powers of several mW and millijoule-level pulse energy at 46.9nm, the Ne-like Ar capillary discharge-pumped laser is the first compact laser to reach this goal. In this paper we summarize the development status of high repetition rate tabletop soft x-ray lasers based on capillary discharge excitation, and give examples of their successful use in several applications. Results of the use of a caprllary discharge pumped 46.9nm laser m dense plasma interferometry, soft x-ray reflectometry for the determination of optical constants, characterization of diffraction gratings, laser ablation of materials, and plasma generation are described. The observation of lasing at 52.9nm line in Ne-like Cl with output pulse energy up to 10 μJ is also reported

Effects of Crystal Structure and the On-Site Coulomb Interactions on the Electronic and Magnetic Structure of Pyrochlores A2A_2Mo2_2O7_7 (A= Y, Gd, and Nd)

Being motivated by recent experimental studies, we investigate magnetic structures of the Mo pyrochlores $A_2$Mo$_2$O$_7$ ($A$= Y, Nd, and Gd) and their impact on the electronic properties. The latter are closely related with the behavior of twelve Mo($t_{2g}$) bands, located near the Fermi level and well separated from the rest of the spectrum. We use a mean-field Hartree-Fock approach, which combines fine details of the electronic structure for these bands, extracted from the conventional calculations in the local-density approximation, the spin-orbit interaction, and the on-site Coulomb interactions amongst the Mo(4d) electrons, treated in the most general rotationally invariant form. The Coulomb repulsion U plays a very important role in the problem, and the semi-empirical value U$\sim$1.5-2.5 eV accounts simultaneously for the metal-insulator (M-I) transition, the ferromagnetic (FM) - spin-glass (SG) transition, and for the observed enhancement of the anomalous Hall effect (AHE). The M-I transition is mainly controlled by $U$. The magnetic structure at the metallic side is nearly collinear FM, due to the double exchange mechanism. The transition into the insulating state is accompanied by the large canting of spin and orbital magnetic moments. The sign of exchange interactions in the insulating state is controlled by the Mo-Mo distances. Smaller distances favor the antiferromagnetic coupling, which preludes the SG behavior in the frustrated pyrochlore lattice. Large AHE is expected in the nearly collinear FM state, near the point of M-I transition, and is related with the unquenched orbital magnetization at the Mo sites. We also predict large magneto-optical effect in the same FM compounds.Comment: 26 pages, 17 figures (low resolution is used for Figs. 6, 8, and 9, please contact directly if you need the originals), 1 tabl

First-principles study of the new compounds CrGa

We present the density-functional calculations of the compounds CrGa2Sb2 and CrGaSb synthesized recently under high pressure. Calculation reproduces well all details of the crystal structure of these compounds, their spin ordering, and a larger metallicity of CrGaSb comparing to CrGa2Sb2. Particular attention is given to the room temperature ferromagnetic compound CrGa2Sb2, where the huge resistivity hinting at the possible semiconducting properties was measured. To understand the mechanism of its anisotropic conductivity, we analyze the band structure, calculated kinetic and optical characteristics of this compound. It is found that the density of states of CrGa2Sb2 has a pseudogap near the Fermi level, where the Cr atoms do not dominate, but contribute even less than the atoms of Ga and Sb. This explains a very high calculated resistivity of CrGa2Sb2, which can be characterized as a ferromagnetic compound with a low metallic conductivity. This type of conductivity remains unchanged, when a possible Cr-deficiency of CrGa2Sb2 is taken into account or the MBJ-LDA exchange-correlation potential is used instead of the GGA-LDA one in calculation. The potential of this compound for the development of spintronic materials is discussed

Electronic, optical spectra and the distribution of Mn impurities in GaN and group-IV semiconductors

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