The dual photochemical reactivity of 1,2-dihydroquinolines

Conclusions The lack of electrocyclic ring opening in 1,2-dihydroquinolines not containing a substituent at the nitrogen atom is related to the possibility of efficient homolytic dissociation in the excited state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 768–772, April, 1985.     

Multifrequency EPR spectroscopy of Ho3+ ions in synthetic forsterite

Electron paramagnetic resonance (EPR) of Ho³⁺ single ions and Ho³⁺?Mg²⁺-vacancy-Ho³⁺ associates in holmium-doped forsterite single crystals are studied at 9.4, 37.3 and 65–250 GHz. Crystals were grown from melt by the Czochralski technique in slightly oxidizing atmosphere. For both centers, directions of the principal magnetic axes and parameters of the effective spin Hamiltonians describing dependences of electron-nuclear levels on applied magnetic field are obtained. For Ho³⁺ substituting Mg²⁺ in the M2 site as the single ion and for Ho³⁺ ions in dimer centers, values of crystal field parameters related to a real crystal lattice structure are estimated in the framework of the exchange charge model. The calculated crystal field energies, values of theg-factors of the ground Ho³⁺ quasi-doublet and the directions of the corresponding magnetic moments agree satisfactorily with the data obtained from measurements of EPR and optical absorption and site-selective luminescence spectra.     

Symplectic structures associated to Lie-Poisson groups

The Lie-Poisson analogues of the cotangent bundle and coadjoint orbits of a Lie group are considered. For the natural Poisson brackets the symplectic leaves in these manifolds are classified, and the corresponding symplectic forms are described. Thus the construction of the Kirillov symplectic form is generalized for Lie-Poisson groups.Supported in part by a Soros Foundation Grant awarded by the American Physical SocietyUnité Associée au C.N.R.S., URA 280     

Photodissociation of aromatic thiols and disulfides

For the first time, the quantum yields of cleavage of SS and SH bonds in a disulfide and a thiol and also the extinction coefficient of the photoinduced aminophenylthiyl radical were determined, on the basis of which the relation of the photodissociation quantum yield to the energy of an absorbed quantum was observed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 540–543, March, 1990.     

General characteristics of the visco-elastic properties of flexible-chain polymer solutions over a wide range of concentrations

Summary The paper summarizes the ideas and results of investigations of viscous and high-elastic properties of polymer solutions in the whole interval of concentrations, chemical structure of the polymers used and the goodness of the solvents tried being varied in wide ranges.

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Zusammenfassung In diesem Beitrag sind die Ideen und experimentellen Resultate der Forschung von viscosen und hochelastischen Eigenschaften polymerer Lösungen im gesamten. Konzentrationsbereich zusammengestellt. Dabei wurden die chemische Struktur und Lösungsmittelqualität in weiten Grenzen variiert.

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With 20 figures     

Temperature-frequency reduction of the dynamic functions of black-filled rubbers in the nonlinear region

The possibility of using temperature-frequency reduction of the dynamic functions of black-filled rubbers in the nonlinear region is demonstrated and an additional applicability criterion — similar slopes of the isotherms of the amplitude dependences of the dynamic functions — is formulated. In the case of heavily filled rubbers it may be necessary to determine the constants of the Williams-Landel-Ferry equation and the reference temperature T_S from the experimental data — they may not coincide with the universal values. Master curves of the dynamic functions are obtained for a series of shock-absorbing rubbers at a shear strain amplitude =0.01.A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 751–754, July–August, 1973.     

Ponderomotive effects in intense pumping wave action on electron and plasma bunches

Ponderomotive effects that arise when an intense plane pumping wave acts on low-concentration electron and plasma bunches are theoretically studied within the framework of a one-dimensional model. Using the Lagrange variables, an electron (plasma) bunch under the action of a pumping field can be represented as a gas comprising macroparticles with ponderomotive and Coulomb interactions. The ponderomotive force at small interparticle distances is attractive, that is, directed oppositely to the Coulomb force; it cannot, however, completely balance the latter. The constructed model is used to study superradiance, which arises when an intense pumping wave acts on an extended electron bunch. Radiation is then scattered in the form of narrow pulses whose amplitude is proportional to the total number of particles in the bunch. In addition, we describe acceleration of a neutral plasma layer, narrow on the wavelength scale, in the field of an intense wave and radiation field-induced partial contraction of an electron bunch with an incompletely compensated charge.     

Coherent states and asymptotic behavior of the symmetric top wave functions

Wave packets which may be considered as an analogue of the coherent states of the top are constructed. New integral representations are obtained for the D-function; making use of those, various types of the asymptotic behaviour of the D-function are obtained in the region of large quantum numbers.     

Viscoelastic properties and unstable flow of monodisperse polybutadiene solutions

The conditions governing the onset of unstable flow when concentrated solutions of monodisperse polybutadiene in -methylnaphthalene are extruded through a capillary have been investigated. The critical values of the parameters corresponding to these conditions have been found. It is shown that unstable flow of the "elastic turbulence" type is associated with transition of the system to the forced high-elastic state.Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 132–137, January–February, 1973.