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Abstract This study presents data on concentrations of n -alkylbenzenes, n -alkylnaphthalenes, phytanylnaphthalene, and methylphytanylnaphthalene in representative crude oils of Tatarstan. The results of the study reveal the elevated concentrations of C 19 , C 21 , and C 23 homologues of n -alkylbenzenes and n -alkylnaphthalenes, which can be considered as biomarkers. The proposed procedure for comprehensive quantification of this group of biomarkers can be used as an efficient tool to study oils from the major petroleum basins of Russia. Based on the results of the study, four genetic groups of oils in Tatarstan have been distinguished: (1) oils from the north and northwest (Bir saddle, Lower Kama system of linear faults, and Saraily saddle), (2) oils from Devonian terrigenous reservoirs within the South Tatar arch and Melekes depression, (3) oils from Carboniferous reservoirs, and (4) oils from Devonian carbonate reservoirs. All these oils belong to the same genetic macrotype. Based on the results of this study, the sedimentary sections of the Melekes depression cannot be regarded as potential source rocks. It is assumed that oil has migrated to the northern part of the region from the north or east. Some of the possible migration routes for oils from the remaining part of Tatarstan are from the southeast and/or south. [ABSTRACT FROM AUTHOR]

Interaction between high-power ultrashort laser pulse and giant clusters (microdroplets) consisting of 109 to 1010 atoms is considered. The microdroplet size is comparable to the laser wavelength. A model of the evolution of a microdroplet plasma induced by a high-power laser pulse is developed, and the processes taking place after interaction with the pulse are analyzed. It is shown theoretically that the plasma is superheated: its temperature is approximately equal to the ionization potential of an ion having a typical charge. The microdroplet plasma parameters are independent of the pulse shape and duration. The theoretical conclusions are supported by experimental studies of x-ray spectra conducted at JAERI, where a 100-terawatt Ti–sapphire laser system was used to irradiate krypton and xenon microdroplets by laser pulses with pulse widths of 30 to 500 fs and intensities of 6×1016 to 2×1019W/cm2. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Studies the first- and second-order Raman scattering and infrared reflection for hexagonal InN layers grown on (0001) and (1102) sapphire substrates. Raman-active optical phonons observed; Ratio between the InN static dielectric constants for the ordinary and extraordinary directions.

The electronic structure of the promising Li-ion battery anode material Li 7 MnN 4 synthesized by a solid-state reaction is studied using ab initio calculations completed by Raman spectroscopy experiments. The structural optimization reliably reproduces the experimental one, hence validating the accuracy of the chosen Density Functional Theory method. The theoretical analysis of the electronic structure reveals the nature of the valence band as composed from band filled by electrons with spin-up states only, which allows refuting literature data about the claimed electronic character of Li 7 MnN 4. Actually, the calculated electronic band gap E g = 0.95 eV is found to be in good agreement with available experimental data. A careful experimental approach provides the first experimental Raman spectra of hygroscopic Li 7 MnN 4 at 293 K and 130 K. The analysis of the phonon states in the Γ-point of the Brillouin zone, completed by the computation of the Raman scattering intensities of the vibrational modes of the Li 7 MnN 4 structure give a remarkable agreement between simulated and experimental Raman spectra. With such a good matching, a reliable assignment of all the observed Raman peaks to the vibrations of specific structural units in the Li 7 MnN 4 lattices is proposed. In particular, the most intense band in the Raman spectrum is ascribed to a totally symmetric MnN 4 breathing mode. We also show that, using different wavelengths of exciting radiation, the transition from off-resonance to resonance Raman scattering process can be observed. Furthermore, Raman spectroscopy is revealed as an efficient in situ diagnostic tool to control the degradation of the Li 7 MnN 4 powder in open air through the observation of extra bands in the Raman spectra. Results of this study shed a light on the understanding of the fundamental properties of Li 7 MnN 4 and pave a way for the upcoming operando Raman spectroscopy investigation of the atomic-scale induced structural changes of this negative electrode material for Li-ion battery. • Raman spectra of hygroscopic Li 7 MnN 4 (LMN) in 293 K and 130 K are reported for the first time. • DFT calculations well reproduce LMN experimental structure and Raman spectra. • Calculated electronic structure characterizes LMN as indirect band gap semiconductor with a narrow gap. • The calculations provide a complete explanation of the vibrational dynamics of the compound. • The oxidation state of Mn in LMN and the reactivity of LMN in air can be monitored by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Minor role of the electron lone pairs of Te atom on non-linear optic properties. [•] TeIVO4 →TeVIO6 evolution induces an augmentation of the χ 3 susceptibility. [•] The Te-O-Te chain -length influences on the lattice χ 3 susceptibility. [ABSTRACT FROM AUTHOR]

Highlights: [•] The detailed P–T phase diagram of BiMnO3 was established. [•] We found three monoclinic modifications of BiMnO3 at pressure and temperature. [•] A suppression of monoclinic C2/c phase have been observed under pressure. [•] We found a new orthorhombic Imma phase of BiMnO3 at P >20GPa. [Copyright &y& Elsevier]

Abstract: The dielectric properties of the glassy telluria have been modeled and studied via the ab initio calculations of the linear- and hyper-polarizabilities of chain-like (TeO2) n clusters. By using the localized molecular orbitals approximation (GAMESS program), it is shown that their linear polarizability is mainly associated with the tellurium atom lone pairs and with the Te–O–Te bridges, whose contributions are comparable. On contrary, the bridge contributions unequivocally dominate the hyperpolarizability value (providing 75% of this) whereas the role of the lone pair on tellurium atoms is minimal (5%). The same estimations can be obtained for the relevant characteristics of TeO2 glass. [Copyright &y& Elsevier]