New method for the restoration of the continuous distribution function of hyperfine fields andits possibilities

A mathematical approach for the evaluation of hyperfine field distribution functions based on an analytical approximation of Mössbauer spectra was developed. The calculations were performed for different model spectra andfor the experimental spectra of crystalline andamorphous alloys. It was possible to obtain an adequate interpretation of complicated Mössbauer spectra of multicomponent heterophase amorpho-crystalline alloys of the Nd-Fe-B-type.     

Laser treatment of Si-Al2O3 two-layer target

The laser treatment of two-layer Si-Al₂O₃ target at λ=1064 nm and P=170 W in a N₂+O₂ atmosphere by electron microscopy, atomic force microscopy, X-ray microanalysis, and IR-spectroscopy was investigated. It is established that in the stage of fracture of a silicon plate, the ablation products were silicon clusters into which, when passing over, oxygen and nitrogen diffused. On collective plate, a SiO_xN composite film formed. In the stage of fracture of an alumina plate, the oxidation of silicon in the channel zone and the interaction of Al and Si oxides, accompanied by their nitration, occurred. In this stage, evolved oxide vapors and ejected mullite drops deposit on the SiO_xN film. On collective plate, mullite nanowhiskers grew from mullite drops by the vapor-liquid-solid body mechanism.     

Features of formation of channels during laser treatment of AlN ceramics

Using electron microscopy and X-ray microanalysis, the formation of tracks by laser processing of AlN:Y₂O₃ ceramic surfaces was investigated. The main process of channel formation is the decomposition of aluminum nitride (AlN). Due to aluminothermic reduction of Y₂O₃, the metallization of channel surfaces occurs. The main products of ablation are Al₂O₃, AlN, and AlON.     

Nitrone cycloadditions to 1,2-diphenylcyclopropenes and subsequent transformations of the isoxazolidine cycloadducts

1,3-Dipolar cycloaddition of C-aryl,N-aryl (or N-methyl) nitrones with a number of 1,2-diphenylcyclopropenes substituted at the C(3) position occurs with the formation of expected "normal" cycloadducts (with N-methylnitrones) and products of their subsequent transformations. Among them are corresponding alpha-acetophenyl aziridines and tetra (or penta) -arylpyrroles. Aziridines and the normal cycloadducts can be also thermally converted to such arylpyrroles with moderate to good yields. Substitution at the C(3( position of cyclopropenes by an electron acceptor group decreases the reactivity of cyclopropenes.     

Spectroscopic and quantum chemical studies of isocytosine

The methods of electronic and vibrational (IR) spectroscopy were used to study the spectral properties of isocytosine in H₂O, D₂O, chloroform, and hexane in a wide concentration interval. Quantum chemical calculations of tautomeric forms and dimers of isocytosine were carried out. The bands of the calculated and experimental spectra were assigned. The results of the quantum calculations were compared with the experimental data. The spectral bands were classified according to the type of tautomer or dimer to which they belong.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 29–36, January–February, 1988.The authors are grateful to I. M. Ginzberg and L. F. Strelkova for their participation in the discussion of the infrared spectroscopy results.