Peculiarities of induced radiation and controlled dechanneling of relativistic particles in crystals under the Cherenkov—Vavilov extreme condition

Peculiarities of induced radiation and absorption of hard electromagnetic radiation are considered on the basis of the channeling of relativistic particles in crystals under the Vavilov—Cherenkov extreme condition. It is shown that the consistent inclusion of quantum recoil in the relativistic region makes it possible to produce a number of anomalous effects having no analogs in optics. In particular, it is predicted that it is possible to simultaneously cool the beam of fast particles during radiation and absorption and to create a tandem laser for which successive radiation of quasicharacteristic-radiation quanta at the normal and anomalous Doppler effect leads to the restoration of the initial state of the quantum system and to the multiple repetition of the radiation cycle. It is shown that the main difficulties preventing these effects from being produced directly in the X-and gamma-ray spectral regions are related to the necessity to use media with positive dispersion. It is considered that such dispersion can be produced by changing the effective susceptibility of the medium in the case of radiation diffraction.     

A Determination of the Relationship between Energies of Vavilov–Cherenkov Radiation and Cathodoluminescence Excited by an Electron Beam in Diamond

Optics and Spectroscopy - The ratio between energies of Vavilov–Cherenkov radiation and cathodoluminescence excited by an electron beam in diamond samples is determined taking into account...     

Origin of the E.S.R. hyperfine anisotropy and the cos2 θ rule of the β-fluorine couplings

The origin of the hyperfine couplings of β-fluorine nuclei in free radicals has been studied using the hyperfine tensors determined for and in single crystals. The direction of the maximum principal element of the β-fluorine coupling tensor in was found to be very close to the direction of the maximum overlap of the fluorine 2p π orbital with the half-filled carbon 2p π orbital. This means that the spin density in the fluorine 2p π orbital is mainly due to the direct overlap with the carbon 2p π orbital and the contributions from the hyperconjugation and the spin polarization mechanisms are less important. The cos²θ rule, B ₀ + B cos²θ, for the β-fluorine coupling tensor was also derived from the conformational dependence of the overlap integral. Using the ratio of B/B ₀ calculated from the overlap integral together with the observed hyperfine tensor for , the absolute values of B ₂ and B were determined and results were applied to the β-fluorine coupling tensor of the rotating CF₃ group in . The calculated tensor is in very good agreement with the one observed.     

From extensive air showers to the characteristics of primary cosmic rays. To the 120th Anniversary of the Birth of D. V. Skobel’tsyn

The works by D.V. Skobel’tsyn that laid the foundation of the contemporary physics of cosmic rays and the physics of high energies are considered. Skobel’tsyn demonstrated that cosmic rays contain particles whose energy substantially surpasses the energies that are typical of radioactive decay, discovered the existence of air showers, i.e., when several particles hit an array simultaneously, and performed a series of investigations into extensive air showers that resulted in the discovery of a nuclear-cascade process in the atmosphere. The results that Skobel’tsyn obtained were of primary importance for the further development of cosmic-ray physics.     

‘Factors of ignorance’ and the rationalized M.K.S.A. system of units

An attempt is made, by means of an allusive (rather than a systematic) historical account of the development of the subject, to exhibit the essentially unique character of the rationalized M.K.S.A. system of units. The establishment of this system involved one arbitrary decision—the determination to retain unaltered the size of the previously accepted unit of current. Thereafter, any choice of derived units, other than the choice actually made, would have destroyed the basic symmetry of the formulation.     

Reply to “on one of the ways of application of the lattice-gas model to describe the kinetics of desorption” by V.P. Zhdanov

Zhdanov's criticism on the applicability of our desorption rate which is proportional to the factor θ/(1−θ), where θ is the surface coverage, is shown to be irrelevant. To be precise, the difference between our and former conventional transition state theory is clarified. Also, the differences between our model and the precursor model are stressed, although these two models result in a similar desorption rate.     

N.M.R. spectra of the XnAA′ Xn′ type

The method described previously for the calculation of the X spectrum for spin systems of of the X_nAA′X_n′ type is extended by means of magnetic equivalence factoring to cases in which the long-range coupling constant J_x is non-zero. This coupling is treated as a first-order perturbation to the energy levels obtained when J_x =0, and it is found that J_x may be measured directly from the separations between easily identified lines in the spectrum. A detailed account of the X ₃ AA′X ₃′ system is given, and the N.M.R. spectrum of fluoro-N,N′-dimethyl-1,3,2,4-diazadiphosphetidine is analysed. The spectral parameters obtained are discussed. A computer programme which calculates the spectra of systems involving magnetic equivalence is used to examine the validity of the approximations in the method.     

E.S.R. spectra of the radicals produced in γ-irradiated diborane in the solid state

The hopping and Coulomb repulsion integrals of the Hubbard model, as applied to the NMP-TCNQ charge-transfer crystal, are found by an INDO calculation of the neutral and charged monomer and dimer of TCNQ. The ratio of these integrals is in satisfactory agreement with experiment, although the calculated integrals themselves are very different from the effective ones for electronic transport, due to renormalization, caused largely by counter-ion polarizability.     

Modeling Order–Disorder Phase Transitions. Inclusion of the Range of Action of the Interatomic Interaction Potential

Results of a computer experiment simulating the atomic ordering process in a model alloy of stoichiometric composition AB and accounting for the range of action of the interatomic-interaction potential are analyzed. The effect of the range of action of the interaction potential (influence of the number of coordination spheres included in the interatomic interaction) on the disordering kinetics and on the order–disorder phase transition in the material at temperatures T _c between 0 and 1.1 (T _c is the temperature at which the atomic long-range order vanishes) is studied. The structure and energy features of atomic ordering are discussed. The objective necessity of accounting for long-range contributions in modeling order–disorder phase transitions and for the kinetics of temperature–induced ordering and disordering processes is examined.     

Corresponding member of the Russian Academy of Sciences M.G. Meshcheryakov (1910–1994) on the centennial of his birth

Chronicles

Corresponding member of the Russian Academy of Sciences M.G. Meshcheryakov (1910–1994) on the centennial of his birth     

Structurally asymmetric d.c. SQUID’s in the presence of coupling energy inhomogeneity of the junctions studied by means of the reduced two-junction interferometer model

The effects of structural asymmetries and of inhomogeneities in the junction parameters on the electrodynamic response of conventional d.c. SQUIDs are studied both analytically and numerically. By a first-order perturbative expansion with respect to the parameter and to the deviation parameters describing structural asymmetry and inhomogeneity, we write the reduced dynamical equation for the average superconducting phase difference of a conventional d.c. SQUID. As in homogeneous and symmetric SQUIDs, the resulting dynamical equation is seen to be similar to that of a single junction with an unconventional current-phase relation characterized by a second harmonic contribution; in addition, a cosine term appears as a consequence of superconducting coupling inhomogeneity. By means of the reduced dynamical equation, the I-V characteristics in the presence of an external rf field and the critical current of the device are studied in the absence of noise.     

Direct gauging of the Poincaré group. II

This paper continues the study of direct gauge theory of the Poincaré groupP ₁₀. The meanings and implications of transformations induced by the local action ofP ₁₀ are studied, and transformation rules for all field quantities are derived for the local action ofP ₁₀ in a sufficiently small neighborhood of the identity. These results lead directly to a system of fundamental partial differential equations that are both necessary and sufficient for invariance of the free field Lagrangian density. Homogeneity arguments and the classical theory of invariants are used to obtain the most general free field Lagrangian density. Gauge conditions are shown to imply coordinate conditions, and an algebraic system of antiexact gauge conditions is implemented. The underlying Minkowski space,M ₄, and the resulting Riemann-Cartan space,U ₄, become attached at their centers, as do their respective frame and coframe bundles. Weak constraints of vanishing torsion are studied. All field quantities are shown to be determined in terms of the compensating l-forms for the Lorentz sector alone provided an explicit system of integrability conditions is satisfied. Field equations of the Einstein type are shown to result.     

Large field renormalization. I. The basic step of the ℝ operation

We construct the renormalization operation of the expressions connected with the large field regions. This operation, denoted by , removes the main obstacle to prove the ultraviolet stability of four-dimensional gauge field theories. The proof will be completed in the second part of this paper.Research supported in part by the National Science Foundation under Grant DMS-86 02207     

Yu. N. Denisyuk’s ideas in the development of holographic methods of obtaining and projection of images

The main investigations carried out by Yuri Nikolaevich Denisyuk at the Ioffe Institute of the Russian Academy of Sciences have been presented. His investigations were aimed at developing methods of recording and projecting three-dimensional images in order to reduce the volume of information contained in the images for use in optical computers, optical interconnections, and displays.     

Can one hear the shape of an electrode? II. Theoretical study of the Laplacian transfer

The flux across resistive irregular interfaces driven by a force deriving from a Laplacian potential is computed on a rigorous basis. The theory permits one to relate the size of the active zone to the derivative of the spectroscopic impedance with respect to the surface resistivity r through: . It is shown that the macroscopic transfer properties through a system of arbitrary shape are determined by the characteristics of a first-passage interface-interface random walk operator . More precisely, it is the distribution of the harmonic measure (or normalized primary current) on the eigenmodes of this linear operator that controls the transfer. In addition, it is also shown that, whatever the dimension, the impedance of a weakly polarizable electrode for any irregular geometry scales under a homothety transformation as L^d-1, L being the size of the system and d its topological dimension. In this new formalism, the question addressed in the title is transformed in a open mathematical question: “Knowing the distribution of the harmonic measure on the eigenmodes of the self-transport operator, can one retrieve the shape of the interface?” Received 3 November 1998     

Direct gauging of the poincaré group. III. Interactions with internal symmetries

The problem of gauging matter fields with a Poincaré invariant action functional that admits anr parameter, semisimple groupG(r) of internal symmetries is considered. A minimal replacement operator for the total groupP ₁₀×G(r) is obtained, together with the requisite compensating 1-forms for both the Poincaré and theG(r) sectors. A basis forP ₁₀×G(r)-invariant Lagrangian densities for the free fields is obtained. Restriction to Lagrangian densities that are at most quadratic in the associated curvature and torsion fields eliminates active coupling between theP ₁₀ free field Lagrangian and theG(r) free field Lagrangian, although there is passive coupling that arises through the requirement of tensorial covariance under general coordinate transformations generated by the local action of the translation group. A superposition principle, modulo passive coupling, thus holds for quadratic free field Lagrangian for the total group:L _TOT=L _P +L _G(r) . Field equations for the matter fields and the compensating fields of theG(r) sector are obtained. Both share the passive coupling toP ₁₀ that is required in order to achieve tensorial covariance, but only the matter fields couple directly to the Poincaré fields and only to the Lorentz sector. For weak Poincaré fields, the field equations for the matter fields and the compensating fields of the internal symmetries go over into the standard field equations of gauge theory for an internal symmetry group.     

Anomalies of the electrical properties and the stability of the double layer at a metal-electrolyte boundary. Characteristics of the capacitance of a double layer with relaxing “plates∝

An electromechanical model of the electric double layer, whose plates are displaced on charging, is proposed; it is shown for the example of this model that the differential capacitance can diverge and become negative. The reasons why these anomalies were not predicted in the well-known models of the double layer are examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 9–15, November 1987.