Towards the design of tunable X-ray lasers by dressing the plasma with the elliptically polarized radiation of an optical laser

We present detailed results of calculating the modifications in X-ray lasing lines of a H-like ion under a strong elliptically-polarized electric field of an optical laser. We show that using an elliptically-polarized electric field of an optical laser, it is possible to control the amplification and polarization of the X-ray radiation, and to vary the frequency of the X-ray lasing line.     

Mössbauer and X-ray studies of Fe-powder mechanically alloyed with C using power ultrasonics

The M?ssbauer and X-rays analysis of as-received Fe-powder and Fe-powder mechanically alloyed with C using high power ultrasonics were carried out. The powder blend of Fe-powder and graphite was processed in He environment during 5 to 50 h. The dissolution of carbon in iron particles and inhomogeneous distribution of C atoms in crystallites was revealed. The ultrasonic milling of the f.c.c. Fe-Ni-powder with graphite was carried out. As established, the saturation of iron particles with carbon under ultrasonic milling occurs for much shorter time as compared to the high-energy ball milling.     

Form of the Frequency Spectrum of Fluctuating Radiation in the Case of Interferometric Reception During Experiments on Radio Sounding of the Solar Corona

We study theoretically the profile of a spectral line of radiation which is received by an interferometer after propagation through a medium with developed turbulent structure. We derive a formula describing the resulting frequency spectrum of an initially monochromatic radiation after its propagation through a multi-scale medium with strong large-scale and weak small-scale irregularities. It is shown that the frequency spectrum observed in this case should comprise the main spectral line with Gaussian profile and wings decreasing according to a power law with index dependent on the orientation of the interferometer baseline with respect to the direction of regular drift of frozen-in irregularities of the medium. We analyze distortions of the spectral response of a very-long-baseline interferometer due to the effect of large-scale irregularities of a medium with developed turbulent structure on wideband radiation from extraterrestrial discrete radio sources. It is shown that if the amplitude fluctuations of the received radiation are weak, then the measured frequency spectrum contains information on the drift velocity and the index of the spatial spectrum of interplanetary plasma irregularities with scales from hundreds to thousands of kilometers.     

Crystal structure of chabazite K

The crystal structure of the chabazite K with the formula (K_1.33Na_1.02Ca_0.84)[Al₄Si₈O₂₄] · 12.17H₂O from late hydrothermalites in the Khibiny alkaline massif (Kola Peninsula) is established by X-ray diffraction analysis (CAD4 four-circle diffractometer, λMoK_α radiation, graphite monochromator, T=193 K, 2θ_max = 70°, R₁ = 0.047 for 4745 reflections) on the basis of experimental data (6265 reflections) obtained from a twin (twinning parameter 0.535(1)): a = 13.831(3) Å, c = 15.023(5) Å, sp. gr. \(R\bar 3m\), Z = 3, ρ_calcd = 2.016 g/cm³. It is shown that cations occupy five independent positions in large cavities of the tetrahedral Al,Si,O anionic framework in potassium-rich chabazite. A comparative crystallochemical analysis of chabazites of different composition and origin is performed.     

Fano resonances in the impurity photoexcitation spectra of semiconductors doped with shallow donors

A theory describing the photoexcited current peaks in the spectral region corresponding to the energies of longitudinal optical phonons in semiconductors doped with shallow donors is developed. The experimental data available for n-GaAs are in good agreement with the results obtained using the proposed theory.     

Shallow acceptor levels in Ge/GeSi heterostructures with quantum wells in a magnetic field

Shallow acceptors in Ge/GeSi heterostructures with quantum wells are studied theoretically and experimentally in the presence of a magnetic field. It is shown that, in addition to the cyclotron resonance lines, magnetoabsorption spectra reveal transitions from the acceptor ground state to excited states related to Landau levels from the first and second confinement subbands, as well as the resonances caused by ionization of A⁺ centers.     

Optical second harmonic spectroscopy of boron-reconstructed Si(001)

Optical second harmonic generation (SHG) spectroscopy is used to probe Si(001) following thermal decomposition of diborane at the surface. Incorporation of boron (B) at second layer substitutional sites at H-free Si(001) intensifies and redshifts the E1 SHG spectral peak, while subsequent H termination further intensifies and blueshifts E1, in sharp contrast to the effect of bulk B doping or nonsubstitutional B. Ab initio pseudopotential and semiempirical tight binding calculations independently reproduce these unique trends, and attribute them to the surface electric field associated with charge transfer to electrically active B acceptors, and rehybridization of atomic bonds.     

Dialkylaluminum derivatives of saturated and unsaturated acids

Summary Some salts of dialkylaluminum with both saturated and unsaturated acids were obtained. The salts of dialkylaluminum with unsaturated acids are capable of being polymerized and copolymerized in the presence of azobisisobutyronitrile as initiator.