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101.
G N Andreev B Schrader R Boese P Rademacher L von Cranach 《Fresenius' Journal of Analytical Chemistry》2001,371(7):1018-1022
Using an improved sampling arrangement we observed the FT Raman spectra of the different phases of a 'jumping crystal', an inositol derivative. The phase transition produced--as consequences of large changes of the unit cell constants--changes in frequency and intensity mainly of CH deformation vibrations. Photochemical reactions, usually produced with light quanta in the visible range, are not activated with the quanta from the Nd:YAG laser at 1064 nm. The Raman spectra of the 'dark' form of a dinitrobenzyl pyridine and afterwards the 'light' form, the product of its illumination in the visible range, were recorded. We could not observe changes of most bands, especially not of the NO2-vibrations; however, a new strong band appeared at 1253 cm(-1), which may be due to the expected NH-photo-isomer. Genuine gemstones and fakes can be unambiguously identified by FT Raman spectroscopy. This is especially useful for the stones whose physical properties are quite similar to those of diamonds--moissanite and zirconia. The quality of diamonds can be estimated from relative band intensities; however, this is not in complete agreement with the internationally accepted visual qualification. Synthetic diamonds produced by CVD (chemical vapor deposition) show remarkable differences from natural ones in their FT-Raman spectra. 相似文献
102.
We describe the logic approach to pattern recognition; its key notion is a test. Analyzing the tests allows us to construct
functionals characterizing the pattern, as well as procedures to compute them. We present qualitative and quantitative properties
of tests, functionals, and recognition procedures. Solutions of a series of known problems are also given. 相似文献
103.
104.
A.G. Andreev M. Georgiev M.S. Mladenova V. Krastev 《International journal of quantum chemistry》2002,89(4):371-376
Off‐center impurity ions in solids often perform rotations around their regular lattice sites. Unlike quasifree rotors with rotational line spectra subject to textbook attention in quantum mechanics, the off‐center species are hindered rotors with spectra quantized in rotational bands. These bands occur because of tunneling through barriers arising along the orbital path. For an off‐center ion rotating along a planar orbit, such as the Li+ impurity nearest‐neighboring an F center in alkali halide, the hindered rotation will give rise to specific magnetic moments that couple to and quantize external magnetic fields normal to the orbital plane. We present a simple theory and estimates of Li+ magnetic dipoles and rotational bands to find conditions for an experimental verification. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
105.
One new topological classification of the phase-matching direction loci for sum/difference frequency generation in biaxial acentric crystals is presented. Based on nine fundamental axial wave constant mismatches, 12 locus indices are used to distinguish permissible direction loci. Totally 66 kinds of combined loci belonging to 30 main classes are found and categorized by a set of ternary-digit class symbols or equivalently by sequence numbers. They are well illustrated in a classification diagram, indicative of 170 possible transitions among the loci. By an analysis of the dispersion of refractive indices, the historic “optically well-behaved crystals” are redefined and improved with simplified classification diagrams and corresponding schematic stereographic projections. 相似文献
106.
A. F. Andreev L. A. Melnikovsky 《Journal of Experimental and Theoretical Physics》2001,93(6):1261-1269
We explain the linear growth of smooth solid helium facets by the presence of lattice point defects. To implement this task, the framework of very general two-velocity elasticity theory equations is developed. Boundary conditions for these equations for various surface types are derived. We also suggest additional experiments the concept to justify. 相似文献
107.
108.
N.S. Andreev 《Journal of Non》1978,30(2):99-126
A kinematic theory of light scattering and modern concepts of phase-separation theory were used to examine the most typical experimental results obtained from the study of light scattering by glasses. The examination was made by taking into account the positions of figurative points in the immiscibility diagram. It has been shown that the anomalous phenomena (the predominant light scattering into the backward semi-sphere and the spectral dependence of intensity of type λ?p, where p > 4) arise in four cases: at the stage of decomposition when the figurative point lies in both the binodal and spinodal regions; after the completion of the decomposition stage when interparticle interference is essential; and in the one-phase region when the concentration fluctuations tend to a higher equilibrium level of development. In each case these phenomena are due to the sign-changed behavior of the dielectric constant and to the existence of a range of negative values in the correlation function. The processes of complete or partial homogenization of the glass are characterized by either the gradual disappearance of anomalous phenomena or the appearance of normal scattering due to the increase in space extension of the inhomogeneity regions at their dissolution. 相似文献
109.
A. Kokh E. Simonova A. Maillard R. Maillard V. Svetlichnyi Yu. Andreev A. Kragzhda A. Kuznetsov K. Kokh 《Crystal Research and Technology》2016,51(9):530-533
The bulk crystals of LiBa12(BO3)7F4 were obtained from two flux compositions by the top seeded solution growth method. Crystals grown from BaCO3:BaF2:H3BO3:Li2CO3 = 3:3:3:1 charge were found to have a distinct linear dichroism effect at 0.35–0.65 and around 0.73 μm. This suggests application of the material in the production of polarizing filters and attenuators for visible range lasers. 相似文献
110.
A. V. Ruseikina S. I. Kol’tsov O. V. Andreev L. A. Pimneva 《Russian Journal of Inorganic Chemistry》2017,62(12):1632-1637
The crystal structures of the first prepared EuLnAgS3 (Ln = Gd and Ho) compounds, which have two polymorphs, were determined by X-ray powder diffraction. α-EuLnAgS3 phases are isostructural to BaErAgS3 (monoclinic crystal system, space group C2/m): a = 17.3168(10) Å, b = 3.9683(2) Å, c = 8.3174(4) Å, β = 103.94° (EuGdCuS3); a = 17.1729(12) Å, b = 3.9367(3) Å, c = 8.2905(6) Å, β = 103.9° (EuHoCuS3). β-EuLnAgS3 phases belong to the AgBiS2 structure type (cubic crystal system, space group Fm-3m): a = 5.739(2) Å (EuGdCuS3) and a = 5.678 Å (EuHoCuS3). In the α-EuLnAgS3 crystal structure, LnS6 octahedra and AgS5 trigonal bipyramids share edges to form a three-dimensional (3D) structure with channels accommodating Eu2+ ions. A decrease in Ln3+ ionic radius gives rise to the crystal-chemical contraction of the 3D structure. 相似文献