Magnetism of Co layers in a Co/Si multilayer film

The magnetic properties of Co/Si multilayer films produced through rf ion sputtering were studied in the temperature range 4.2–300 K. The dependences of the spontaneous magnetization and hysteresis characteristics of the films on the thicknesses of the magnetic layers and nonmagnetic spacers are established. It is shown that these dependences are determined to a large extent by interlayer interfaces, in which the effective magnetic moment of the Co atoms and the exchange interaction decrease and magnetic-anisotropy dispersion arises. A probable cause of the interface formation is interlayer mixing (which is estimated to penetrate to a depth of 15 Å) and the strong effect of Si on the Co electronic structure.     

High-temperature ceramic composites stable during long-term use at temperatures up to 2000°C with a multilevel complex protection system

The development of new promising heat-resistant materials capable of functioning at high temperatures under oxidation conditions is considered. The results of the development of a technology for producing high-temperature ceramic composites with a multilevel complex protection system are presented.     

Simulation of the Kinetics of Cyclohexane Oxidation in a Barrier Discharge Reactor

The kinetics of cyclohexane oxidation in a barrier discharge reactor was simulated for a single voltage pulse. A significant difference between the yields of O₃ obtained experimentally (not detected) and theoretically (15.5 wt %) suggests that O₃ was absent from the reaction mixture because of a fast reaction between O(³ P) and an excited cyclohexane molecule. This hypothesis was indirectly supported by experimental data on the oxidation of a mixture of n-hexane and cyclohexene (50 : 50 wt %). The integrated rate constant of the reaction of O(³ P) with n-hexane was 1.4 × 10^–12 cm³/s, which is an order of magnitude higher than the published value 1.2 × 10^–13 cm³/s.     

Oxidation of propylene and isobutylene in a reactor with barrier discharge

The oxidation of propylene and isobutylene in barrier-discharge plasma in the presence of octane was studied. The possible reaction mechanism was considered.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1922–1924.Original Russian Text Copyright © 2004 by Kudryashov, Ryabov, Sirotkina, Shchegoleva.     

ESR Spectra and structure of radical-anions of fluorinated benzonitrile derivatives

Isotropic ESR spectra have been taken from radical-anions of fluorinated benzonitrile derivatives. Quantum-chemical analysis of the hfi constants has demonstrated that 3-fluoro- and 3,5-difluoro-benzonitrile radical-anions are planar π radical,s while the radical-anions with fluorine atoms in the positions 2 and/or 4 relative to the nitrile group are characterized by non-planar deformation resulting from the interaction between the ground π and the lower excited σ states within the pseudo-Jahn-Teller effect.     

Reactions of triethylborate with amines

Russian Chemical Bulletin -     

Inadequacy of one-electron approach for investigating antiaromatic molecules and their isomerization reactions

Institute of Catalysis, Siberian Branch, Academy of Sciences of the USSR. Institute of Organic Chemistry, Siberian Branch, Academy of the Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 30–41, September–October, 1991.     

Formation of o-H-perfluoroalkylbenzenes from polyfluorobenzocyclobutenes in the HF-SbF5 system

HF adds to perfluorinated benzocyclobutene, 1-methyl-, and 1-ethylbenzocyclobutenes in the presence of SbF₅ to give o-H-perfluoroethyl, o-H-perfluoroisopropyl-, and o-H-perfluoro-sec-butylbenzenes, respectively. The ease of this reaction decreases in the same order. Perfluoro-1,1- and perfluoro-1,2-diethylbenzocyclobutenes, perfluoroindane, and perfluorotetralin are virtually unaltered under analogous conditions. The difference in the behavior of benzocyclobutenes may be related to the stability of the carbocations, which are intermediates or models of the transition state. This is in accord with the results of MNDO calculations with complete geometrical optimization for the relative energies of the starting compounds and intermediate ions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2618–2622, November, 1991.     

Indo study of the angular dependences of isotropic hyperfese interaction constants in the model conformations of the nitrobenzene radical anion

The UHF/INDO calculations of the model conformations of the nitrobenzene radical onion show that rotation of the nitro group relative to the plane of the benzene ring is accompanied by a pyramidal distortion of the group caused by the pseudo-Jahn-Teller effect (vibronic interaction between the ground n and totally symmetric lowest excited σ states). The angular dependences of the¹⁴N,¹³C,¹H, and¹⁷O Isotropic hyperfine interaction constants are analyzed. Experimental ESR data are interpreted for the radical anions of nitrobenzene derivatives with ortho-alkyl groups. Translated fromZhumal Strukturnoi Khimii, Vol. 41, No. 3, pp. 457-467, May-June, 2000.