Isotopic Analysis of 28Si-Enriched Silicon Using Laser Mass Spectrometry

A procedure for the isotopic analysis of ²⁸Si-enriched silicon by laser mass spectrometry is described. The procedure is based on the analysis of a dry concentrate or a film obtained by the pneumatic nebulization of an analyte and an internal standard solution or by the laser sputtering of a solid phase onto a support of a high-purity substance. The range of determinable isotope concentrations is (100–n× 10^–6) at %; the total error in determining the major isotope is n× 10^–2at % at an enrichment factor higher than 99%. The procedure provides the simultaneous control of 70 impurity elements in the sample.     

Force action of a shock wave on a sphere or a cylinder in numerical and physical experiments

The results of an investigation of the unsteady and steady stages of the action of a plane shock v/ave on a sphere or a cylinder are given. The volume compression force which determines the signal amplitude of a nondirectional spherical transducer [1] and the force acting on the body in the direction of the shock wave motion are analyzed. Good agreement of the results is obtained between the numerical and physical experiments and with the data of other authors.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 134–139, November–December, 1985.The authors are grateful to B. I. Zaslavskii for the discussion of the results and to O. V. Zonovaya for the formulation and presentation of the calculated material.     

Submillimeter-wave spectroscopy of the K = 2–1 subband of the Ne–CO complex

The pure rotational spectrum of the Ne–CO van der Waals complex has been measured in the frequency range of 208–230 GHz by using the Cologne supersonic jet spectrometer for terahertz applications (SuJeSTA). Eleven new transitions were assigned as belonging to two R- and two Q-branches of the K = 2–1 subband detected for the first time in the ground vibrational state of CO (ν_CO = 0). Improved molecular parameters of the Ne–CO complex were obtained which allowed for a sensitive test of the available intermolecular potential energy surfaces of the Ne–CO system.     

Gd<Superscript>3+</Superscript> EPR in solid solutions based on ferroelectric lead germanate

The splitting of the ERP spectrum of a single Gd³⁺ ion into four intense components has been observed in crystals of Pb₅(Ge_{1 − x} Si _x )₃O₁₁ solid solutions, which is caused by the appearance of silicon ions in three nearest germanium spheres. The atomic structure of the observed centers has been determined. The conclusion has been made that silicon mainly substitutes for germanium in oxygen tetrahedra and for one of germanuim atoms in oxygen bitetrahedra, which is based on comparison of the measured ratio of component intensities with the results of the calculation of the concentrations of Gd³⁺ associations with silicon ions.     

Formation of submicron partially ordered domain structures in ferroelectric and magnetic materials

Formation of domains and partially ordered periodic domain structures in ferroelectric and magnetic oxides of metals of transition groups has been investigated. Physical features of appearance of submicron periodic domain structures and possibilities of their use for the control over the parameters of high-frequency acoustic waves have been considered using the example of single crystals of lithium niobate and lanthanum-strontium manganites.     

Constructive observability inequalities for weak generalized solutions of the wave equation with elastic restraint

Problems with one-sided boundary controls and a homogeneous Robin boundary condition set on the uncontrolled end are considered in the class of strong generalized solutions of the variable coefficient wave equation. In the adjoint class of weak generalized solutions of the dual problems with one-sided observations, new constructive observability inequalities are obtained that differ from previously known ones by an optimal threshold time. It is shown that, in the considered functional classes, the estimated constants degenerate as the time interval length approaches the threshold. Numerical illustrations are given showing that the stability of approximate solutions to control problems can be substantially enhanced by taking into account a priori information contained in the resulting observability inequalities.     

Effect of impurity iron ions on the formation of photoinduced lattices and domain structures in lithium niobate

Processes and mechanisms of the formation of lattices and periodic domain structures in iron-doped lithium niobate monocrystals under the effect of laser beams are examined. The role of Jahn-Teller Fe²⁺ ions in the formation of photoinduced periodic structures is demonstrated.     

Reactions of selenium dichloride and dibromide with diallyl telluride

Russian Journal of General Chemistry -     

Mass transfer in non-steady-state hydride epitaxy of Si1−x Gex/Si structures

Numerical simulation of the non-steady-state kinetics for the solid solutions MBE-grown from silane and germane with vapor sources was carried out. The smearing of the germanium distribution at the interfaces in the Si_1?x Ge_x/Si structures was studied both in the absence of the atomic fluxes in the reactor and in their presence (the “hot-wire” method). It is shown that the use of an additional hot source enhances the growth. Moreover, at gas pressures exceeding 10^?3 torr (provided that the gas flow remains molecular) and at growth temperatures T _gr<600°C, such conditions can minimize the width of the transition regions at the interfaces.