Electronic States of Cobalt Ions in EuBaCo2O5 + δ Layered Cobaltites

JETP Letters - The oxygen K-edge X-ray absorption spectra in EuBaCo2O5.52 ± 0.02 and EuBaCo2O5.24 ± 0.02 cobaltites are measured at temperatures of 300 and 440 K, which are below and...     

Thermoelectric properties of hydrogen ion-irradiated silicon crystals under ultrahigh pressures of up to 20 GPa

The thermopower S of p-Si samples containing a thin hydrogenated layer was studied at high pressures P of up to 20 GPa. Near the phase transition to a white-tin lattice (P ≤ 10 GPa), the thermopower of samples with a hydrogenated layer was found to decrease as compared to that in the starting p-Si samples. However, the values of S of high-pressure metallic phases with a β-Sn structure and orthorhombic (above 12 GPa) and simple hexagonal (above 16 GPa) structures are approximately the same for different sample groups. The variation in crystal structure induced by pressure treatment was studied by ultrasoft x-ray spectroscopy. The observed decrease in S induced by the pressure treatment is tentatively assigned to the formation of an amorphous phase in addition to the Si-III metastable phase.     

Local structure of porous silicon studied by means of X-ray emission spectroscopy

2,3 X-ray emission spectra of porous silicon (P-Si) and of spark-processed silicon (sp-Si). Both types of Si-structure display strong photoluminescence in the visible range of the spectrum. Porous samples were prepared by anodization of n^-- and p⁺-Si-wafers. Whereas for the P-Si processed from p⁺-Si the presence of some amorphous silicon is detected, the X-ray emission spectra of porous Si prepared from n^--Si display a higher content of SiO₂. For spark-processed Si the Si L_2,3 X-ray emission spectra reveal a much stronger degree of oxidation which extends to depths larger than 10000 Å. Furthermore, the chemical state of silicon atoms of sp-Si measured at the center of the processed area is close to that of silicon dioxide, and it has an influence on the photoluminescence energy. Specifically, green photoluminescent sp-Si shows a higher degree of oxidation than the blue luminescent specimen. However, the depth of oxidation consistently decreases in areas with weak or no PL. Possible origins of the observed photoluminescence are discussed. Accepted: 6 March 1997     

X-ray emission and Raman spectroscopy of CN<Subscript>0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.5</Subscript> nanocondensates prepared by pulsed arc sputtering of graphite in the presence of nitrogen

The nanocomposite structure of the DLC-C₂N condensate is confirmed by analyzing the x-ray emission spectra of the CN_{0 ≤ x ≤ 0.5} films prepared by pulsed arc sputtering of graphite in the presence of nitrogen.     

Dynamics of an ideal liquid with a free surface in conformal variables

Problems of mathematical hydrodynamics with a free surface in conformal variables are studied. Analytical solvability in Hilbert space scale and numerical techniques of finding approximate solutions are considered. The lifetime for solutions, a constructive evaluation, and application of mathematical statistics to the solvability of nonlinear equations are studied. Multiple numerical experiments of the methods considered are shown. A lot of these methods can be applied not only to problems of mathematical hydrodynamics with a free surface but to abstract Cauchy–Kovalevskaya problems in Banach spaces scale as well. Translated from Sovremennaya Matematika. Fundamental’nye Napravleniya (Contemporary Mathematics. Fundamental Directions), Vol. 28, Hydrodynamics, 2008.     

Erratum to: Several Articles in JETP Letters Published Online First

JETP Letters - An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022330013     

X-ray spectra and valence states of cations in nanostructured half-doped $$\hbox {La}_{0.5}\hbox {Ca}_{0.5}\hbox {MnO}_{3}$$ manganite

Soft X-ray absorption (XAS) and emission (XES) spectroscopies were applied to determine valence states of manganese ions in nanostructured powder of half-doped \(\hbox {La}_{0.5}\hbox {Ca}_{0.5}\hbox {MnO}_{3}\) manganite obtained by milling in a ball mill. XAS spectra were measured both in surface-sensitivity total electron-yield and in bulk-sensitivity total fluorescence-yield modes. O K\(_{\upalpha }\) XES and O 1s XAS spectra characterized the occupied and unoccupied partial O 2p densities of states are compared with band-structure calculations made using the TB-LMTO-ASA codes. Experimental Mn 2p, Ca 2p, and La 3\(d\) XAS spectra are compared with results of crystal field atomic multiplet calculations. For the nanostructured system of \(\hbox {La}_{0.5}\hbox {Ca}_{0.5}\hbox {MnO}_{3}\), concentrations of Mn\(^{4+}\) ions are found to be increased with increasing the time of milling.     

Alkylpyrazines from hymenoptera: Isolation,identification and synthesis of 5-methyl-3- n-propyl-2-(1-butenyl)pyrazine from Aphaenogaster ants (formicidae)

Mandibular glands of Aphaenogaster rudis workers contain 5 - methyl - 3-n - propyl - 2 -(1 -butenyl)pyrazine, a new natural product. This pyrazine and several of its isomers have been synthesized from the corresponding 2,3-, 2,5- or 2,6-dimethylpyrazines. Marked differences in the mass spectra of these multialkylated pyrazines are discussed. In addition, dimethylalkylpyrazines are reported from a variety of aculeate wasps.     

State and tendency of developing physical-chemical methods for making actinide microspherical particles

To obtain actinides oxides as microspheres, the internal gelation method is suggested. As a dispersive medium, we propose to use hydrocarbons containing fluorine and having a density of 2000 kg/m³. These substances are chemically inert, fire-proof, non-toxic and resistant to -radiolysis. Using a fluorohydrocarbon-containing liquid creates in the gelation column a vertical temperature gradient with minimal temperature in the zone of working solution dispersion and maximal one in the upper part of the column. This article treats the mechanism and model of a drop-forming process to control the process of microspheres formation, in which a working solution is dispersed in a dispersive medium.     

Study of Aluminum–Oxygen Binary Systems: Determination of Partial Interatomic Distances

This paper reports on an Auger-electron study of the oxidation of the perfect surface of polycrystalline Al in residual gas atmosphere at a partial pressure of oxygen of 10 ^-10 torr. Under supervacuum conditions, layer-by-layer oxidation of the aluminum surface takes place along with stabilization of the chemical composition of the oxide film. Oxygen can penetrate into the oxidation region not only by deposition from the residual atmosphere but also by other mechanisms. After the chemical composition of the oxide film was stabilized, its local atomic structure was studied by Al and O K-edge extended electron energy loss fine structure (EELFS) spectroscopy. The estimated partial interatomic distances for Al–Al, Al–O, O–Al, and O–O atomic pairs permitted us to conclude that an oxide-like phase is formed in the subsurface layers of aluminum oxidized under supervacuum conditions and to construct a model of the local atomic structure of this oxide-like phase.