Nutations of magnetizations of sublattices and their role in the formation of Mössbauer spectra of antiferromagnetic nanoparticles

A law determining the dispersion shift of the anti-Stokes band of the supercontinuum of a light bullet in a filament of a femtosecond laser pulse in transparent dielectrics has been established. The dispersion equation theoretically obtained for the anti-Stokes shift has been confirmed by spectroscopic studies of the filamentation of the near and middle infrared ranges in fused silica and fluorides.     

Phase problem in three-beam X-ray diffraction

It is shown that, apart from the purely elastic scattering of X-rays, their inelastic coherent scattering by phonons can play, in some cases, a significant part in the formation of reflection curves for multiple X-ray diffraction. This process may affect the interference pattern for weak reflection, and it must be taken into account when extracting the triplet phase, as was demonstrated by an analysis of the experimental rocking curves obtained for the coplanar three-beam diffraction by a KDP crystal.     

Electronic absorption spectra or carbonium and dicarbonium ions containing heterocyclic rings with a biphenylene base

An analysis has been made of -^* -electronic excitations of carbonium and dicarbonium ions obtained by the interaction of concentrated sulfuric or fluoboric acid with alcohols or glycols containing a heterocyclic bridge structure, i.e., nuclei of dibenzofuran, dibenzothiophene, carbazole, and N-methylcarbazole; this analysis has been aimed at establishing a correlation of their structure and spectral characteristics. From an analysis of experimental data, calculated results, and indexes quantitatively characterizing the structure of the -^* -electronic excitations, it has been established that there are four electronic transitions in the visible region of the electronic absorption spectrum of the carbonium ions. The long-wave, intense band of the spectrum is due to superposition of intense (p-type) and weak (-type) transitions proceeding from corresponding excitations of the heterocyclic fragment. In the electronic spectra of the dicarbonium ions, a doublet of p-transitions is clearly manifested. It has been shown that the interaction of chromophores through the bridge structure increases by a factor of approximately 1.8 when the change is made from dibenzofuran to dibenzothiophene, carbazole, and Nmethylcarbazole; in comparison with the corresponding dihydroxycarbonium ions, the degree of interaction of the chromophores is greater by a factor of approximately 1.5.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 284–291, May–June, 1990.     

Structural features of light-sensitive crystals of N′-[2-nitrofurfuryl-5-vinyl]benzhydrazide and [N′-furfurylidene)]benzhydrazide

An x-ray structural study found that N-[2-nitrofurfuryl-5-vinyl]benzhydrazide and [N-(furfurylidene)]benzhydrazide do not form crystal hydrates although they have polar syn-conformations. Molecules in the crystal are joined by linear chains of intermolecular H-bonds C=O...H-N. The light-sensitivity of the crystals increases with decreasing packing density.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1556–1562, July, 1990.     

Phase relations in analysis of glancing incidence X-ray rocking curves from superlattices

Nontrivial features of the formation of glancing incidence x-ray rocking curves from superlattices are revealed and analyzed for the magnetic digital alloy GaSb/15(Mn/GaSb)/GaAs. The qualitative analysis of the shape of the experimental curve in the framework of specific phase relations in the reflection amplitude makes it possible not only to describe these features, in particular, the two-humped profile of the first Bragg peak and to reconstruct the real structure of the alloys under investigation, but also to develop the general scheme for analyzing x-ray rocking curves from imperfect superlattices.     

Modified model of self-consistent field for an electron solvated in a polar liquid

The self-consistent field model is modified to take into account the effect of orientation correlations on the behavior of an electron solvated in a polar liquid. This model is used as the basis for calculating the maximum of the absorption spectrum as well as the temperature dependence of this maximum for an electron sol-vated in water and ammonium. The results are in accord with experimental data and with the results of calcu-lation by the quantum molecular dynamics method.     

Quantum model of the magnetic dynamics of single-domain particles for describing their magnetization curves and Mössbauer spectra in a weak magnetic field

A universal approach to describing the equilibrium magnetization curves and relaxation Mössbauer spectra of magnetic nanoparticles is proposed for consistent analysis of magnetometry and gamma-resonance experimental data, based solving a quantum-mechanical problem for a particle with spin S that has intrinsic magnetic anisotropy and is positioned in an external magnetic field.     

Photochemical properties and structures of substituted norbornadienes

The spectral and photochemical properties of 3-phenylnorbornadiene-2-(N-phenyl)aldimine and 3-phenyl-2-(2,2-dicyanovinyl)norbornadiene have been studied, and their structures have been established by X-ray analysis. It was found that the C(2)=C(3) bonds in these compounds are longer than those in unsubstituted norbornadienes. It was established that long-wave absorbtion boundaries and quantum yields of the photoisomerization of 2,3-disubstituted norbornadienes to give the corresponding quadricyclanes increase as the C(2)=C(3) bond length increases and as the bond order decreases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–508, March, 1995.This work was supported by the International Science Foundation (grant No. RNC 000).