Nature of coherent enhancement of inelastic electron scattering from disordered media

The mechanism of weak localization of relatively fast electrons scattered with a fixed energy loss from disordered media is examined. The main focus of this paper is to put forward an explanation for why coherent enhancement of electron scattering in the inelastic-scattering channel takes place at angles which differ from π. A simplified kinematic model is proposed to determine the basic properties of the weak localization of electrons in the inelastic scattering channel. The model easily reproduces the range of scattering angles typical for the weak localization of electrons with fixed energy loss. The procedure does not require calculation of the contribution from the crossed diagrams. The results agree with those based on the dynamical theory associated with the calculation of the crossed and ladder diagrams. It is possible to follow the transition from the weak localization of the new type to the ordinary weak localization with decreasing energy loss. The weak localization of the new type is in accord with the weak localization of regular type if the energy loss is about the energy of an optical phonon.     

Mechanisms of EPR line broadening in Pb5Ge3O11 near a structural transition

The polar angular dependence of the anomalous linewidth of three EPR transitions in the Gd³⁺ trigonal center has been used to determine the broadening mechanism. It is shown that the dominant mechanism of Gd³⁺ EPR signal broadening in the vicinity of the ferroelectric transition is the critically growing spread of the b ₂₁ and c ₂₁ parameters accounting for the odd-order fields of remote charge-compensating defects. Fiz. Tverd. Tela (St. Petersburg) 40, 321–326 (February 1998)     

Generalized amplitude of an n-vertex one-loop process in a strong magnetic field

Physics of Atomic Nuclei - A general analysis of the amplitude for an n-vertex one-loop process in a strong magnetic field is performed by using the asymptotic form of the electron propagator in a...     

Carbon phase transformations under electrodynamic compression

The graphite-diamond phase transition under shock-wave-induced electrodynamic compression has been studied. A sample of a carbon-containing material was loaded by axisymmetric collapse of a copper liner. The liner was acted upon by ponderomotive forces generated by pulsed electric currents with amplitudes of 2–4 MA. The collapse of the cylindrical copper liner with a velocity of ∼1 km/s produced stepped loading of the carbon material in an ampoule from 5 to 40 GPa over 4 μs. Purification of the preserved material yielded agglomerates containing polycrystalline diamond. The average size of diamond polycrystals in the agglomerates is 1–2 μm, and the agglomerate yield is ∼3%. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 4, 2004, pp. 659–661. Original Russian Text Copyright ? 2004 by Makarevich, Rakhel, Rumyantsev, Fridman.     

Kinetics of Alkylated Biladiene-a,c Deprotonation

The kinetics of deprotonation of 1,3,7,13,17,19-hexamethyl-2,8,12,18-tetrabutylbiladiene-a,c dyhydrobromide on treatment with nucleophilic reagents (pyridine, dimethylformamide, dimethyl sulfoxide) in carbon tetrachloride was measured by electron absorption spectroscopy in the temperature range of 293.15–303.15 K. The effects of the reactant concentrations, the temperature, and the electron-donor properties of the nucleophilic reagent on the kinetics of deprotonation of biladiene-a,c as the salt with HBr are discussed.     

On the theory of quantum interference between inelastic and elastic electron scattering events

The mechanism of weak localization of relatively fast electrons scattered with a fixed energy loss from disordered media is examined. The main focus of this paper is to put forward an explanation why coherent enhancement of electron scattering in the inelastic-scattering channel takes place at angles which differ from π. A simplified kinematic model is proposed to determine the basic properties of the weak localization of electrons in the inelastic scattering channel. The model reproduces easily the range of scattering angles typical of the weak localization of electrons with a fixed energy loss. The procedure does not require calculation of the contribution from the crossed diagrams. The results agree with those based on the dynamical theory associated with the calculation of the crossed and ladder diagrams. It is possible to follow the transition from the new type of weak localization to the ordinary weak localization with decreasing energy loss. The new-type weak localization is in agreement with the regular weak localization if the energy loss is approximately equal to the energy of an optical phonon. Zh. éksp. Teor. Fiz. 111, 1001–1015 (March 1997) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Reaction of 1,2-diaminoimidazoles with isatins. Degree of orderliness of compounds in a liquid-crystal matrix as a criterion of their structure

The reaction of 1,2-diamino-4-arylimidazoles with isatin and N-methylisatin, as a result of which the corresponding imidazo[1,2:2,3]-1,2,4-triazino[6,5-b]indoles were obtained, was studied. The corresponding Schiff base was also isolated in the case of the reaction of 1,2-diamino-4-(p-tert-butylphenylene)imidazole with N-methylisatin. The electronic and IR spectra of the synthesized compounds were studied. The possibility of the use of the degree of orderliness of the synthesized compounds in a liquid-crystal matrix as an additional spectral method in proving the structures of the compounds is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 242–245, February, 1982.     

Propagation of light in a quasi-two-dimensional Si/SiO2 superlattice with variable strip thickness

Optics and Spectroscopy - The propagation of an electromagnetic excitation localized in a nonideal quasi-two-dimensional Si/SiO2 system that constitutes a topologically ordered set of strips with a...