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961.
An expression for the linewidth of phonons associated to a disorder mechanism in crystals is deduced. The linewidth of these ‘noise’ phonons is a function of the correlation time describing the statistical behavior of the disorder mechanism. A new view point to the application of the fluctuation-dissipation theorem for order-disorder crystals is presented. The relationship between the behavior of the linewidth of these phonons and phase-transitions mechanisms is discussed. 相似文献
962.
963.
The electric field alignment of substitutional CN- molecules in KCl crystals was studied by measurements of the field-induced optical birefringence (Kerr-effect). The electric field, temperature, wavelength and concentration dependence of the Kerr-effect and its pronounced anisotropy is found in quantitative agreement with a paraelectric alignment model for 〈111〉 oriented CN- molecules, which have electronic absorption transitions hidden under the fundamental crystal absorption, and are characterized by an anisotropic polarizability of . 相似文献
964.
C.E.T. Gonçalves da Silva 《Solid State Communications》1979,30(5):283-287
The magnetic properties of an intermediate valence compound are discussed within a single-ion framework. The effects of configuration mixing, crystalline electric fields, and external magnetic fields are included in the hamiltonian. The method incorporates in one single consistent approach both coherent (quantum) and incoherent (thermal) fluctuations. Numerical evaluation of the susceptibility and field dependent magnetization with parameters appropriate for TmSe yields results in good agreement with experiment. 相似文献
965.
A static, plane-symmetric scalar field of long range is considered in general relativity, and a one-parameter class of exact solutions with cosmical time is studied in harmonic coordinates. The geodetic equations are solved. A velocity-dependent acceleration field is found, acting attractively on the component of the velocity normal to the plane of symmetry, and repulsively on the component parallel to that plane. The manifold is complete. Test particles at rest are insensitive to it. 相似文献
966.
Alessandro D'Aprano Dorina Ines Donato Antonio Carrubba 《Journal of solution chemistry》1982,11(4):271-281
Conductance measurements of lithium picrate in solutions of water in n-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol and 3-methyl-1-butanol have been carried out at 25°C. Ionic association and conductance were found to change with water content and with the molecular structure of the alcohols (i.e. position of the OH group and degree of branching of the alkyl chain). These results indicate that both conductance and ion pair formation are not the consequence of the simple motion of ions in the electrical field as required by the continuum model. A more realistic approach, involving the internal structure of the solvent mixtures, has been considered. 相似文献
967.
968.
The energy barriers for the addition to ethylene of a series of carbenes have been calculated at an ab initio level. using the STO-3G and 3-21G basis sets. It is shown that the usual extrapolation of experiment results, which predicts that the reactivity of carbenes decreases when increasing its nucleophilic character, is not valid. 相似文献
969.
Fructuoso Barba M. Desamparados Velasco Antonio Guirado 《Journal of heterocyclic chemistry》1982,19(3):669-669
From electrochemical reduction of phenacyl bromide, 3,5-diphenyl-2(3H)-furanone was obtained as a side-product and its structure was determined by chemical and spectral techniques. 相似文献
970.