The Comptoп effect in а two-dimeпsioпal approximation of quaпtum electrodyпamics
The Comptoп effect in а two-dimeпsioпal approximation of quaпtum electrodyпamics
Yu.М. Lоskutоv, V.V. SkоЬеlеv
In this paper we obtain the general form of the cross section for photon scattering by electrons in a strong magnetic field. We find the total scattering cross section in the nonrelativistic limit. It is shown that the scattered radiation is linearly polarized. Quantitative estimates are given, according to which it is hoped that the results can be checked experimentally.
Show AbstractSpecific heat of liquids from the correspoпdiпg states priпciple
Specific heat of liquids from the correspoпdiпg states priпciple
L.Р. Рhуliрроv
It is shown by analysis of data in the literature that the excess molar heat capacity of normal (nonassociated) liquids on the saturation curve is described by a single function of the reduced temperature and the defining criterion of thermodynamic similarity. Formulas approximating this function are given for the isobaric and isochoric specific heat. We examine the use of these principles for evaluating the specific heat of liquids.
Show AbstractSelf-focusing stability of a laser beam in the isotropic phase of a liquid crystal
Self-focusing stability of a laser beam in the isotropic phase of a liquid crystal
G.A. Lyakhov and V.A. Makarov
The conditions for self-focusing and stratification of a laser beam in liquid crystals at a temperature close to the phase-transition point from the isotropic to the liquid-crystal phase are found. It is shown that the spatial dispersion of the nonlinear susceptibility, due to a thermal or orientational mechanism, can ensure self-focusing of intense beams that is stable with respect to stratification. The analysis of the spatial dispersion mechanisms presented shows that liquid crystals are promising materials for forming continuous light beams of high intensity.
Show AbstractMicroscopic theory of the intermediate structure of gigantic resonances in nuclear reactions
Microscopic theory of the intermediate structure of gigantic resonances in nuclear reactions
F.A. Zhivopistsev and К.V. Shitikova
The microscopic theory of the coupling between a particle and a hole with more complex states is developed. Particular attention is given to considering coupling with two-particle - two-hole states. It is shown that particle-hole states plus the low-lying collective state play an important role. As regards the extent to which interaction between the particles is taken into account a comparison is made with the theory of finite Fermi systems. The results obtained using the microscopic theory are compared with the corresponding results obtained using the phenomenological theory. A correspondence is established between the parameters of the model considered. When an appropriate choice of the parameters is made and the formfactors are matched, the matrix elements of the interaction between the nucleon and the core calculated by the two models are practically identical.
Show AbstractLocal nets of the algebra of observables for a free scalar charge field
Local nets of the algebra of observables for a free scalar charge field
V.A. II'in
It is shown that algebras of observables in the case of a charge scalar free field (also defined as the gradient-invariant parts of the corresponding field algebras) can be obtained using a simple mathematical operation, namely, finding the second commutant of a denumerable set of generating operators corresponding to the specified region of spacetime.
Show AbstractThe effect of plasma oscillations on the inelastic scattering spectrum of a fast electron in metals
The effect of plasma oscillations on the inelastic scattering spectrum of a fast electron in metals
F.A. Zhivopistsev and F.E. Komas (Cuba)
Using the Nozieres-de Dominicis-Langreth theory the effect of plasmons on the structure and features of the dynamic formfactor describing the scattering of a fast electron with a transition of an internal electron from an atomic level onto the Permi surface is investigated. Neglecting dispersion of the plasmons an expression is obtained for the dynamic formfactor which explains the features of the spectrum due to plasmons. It is shown that the probability of an (e, e')-process W(q,ω)depends to a large extent on the sign of the exponent of the energy factor a(1). For a(l)< 0 the function W(q,ω) is a decreasing function of ω,which vanishes when ω = ω(n) = ω + а ω(p) + n ω(p), when а(l)> 0 the function W(q,ω) has a singularity of the type (ω—ω(n))^(-α(β)). These features are important when a fairly wide range of the transmitted energy spectrum is being investigated.
Show AbstractGrowth layers in the ferroelectric Ba$_{2}$NaNb$_{5}$O$_{15}$
Growth layers in the ferroelectric Ba$_{2}$NaNb$_{5}$O$_{15}$
I.I. Naumova, A.L. A1eksandrovskii and I.N. Leont'eva
For crystals grown under large temperature gradients from melts with seven different compositions, we study the effect of the conditions of crystallization on the formation of growth layers. We investigate the diffraction of light by the growth layers. It is observed that the variations of the refractive index (the optically observable growth layers) have a complicated nature due to the ferroelectric properties of the material. These cause two anomalies to arise in the temperature dependence of the intensities of the diffraction maxima. The lowtemperature anomaly (at T < 100°C) is explained by the pyroelectric charges on the domain boundaries. The high-temperature anomaly (at temperature close to the Curie point) is explained by the existence of variations in the Curie temperature with amplitudes of up to 1°C, which are synchronous with the variations in the composition of the crystal in the growth layers. As the content of sodium oxides in the melt is decreased, the Curie point of the crystals grown from it decreases from 575 to 542°C. The crystals with zero and 90-degree orientations were grown under conditions which were as similar as possible, but the Curie point for the latter orientation was lower by 10-20°C.
Show AbstractPhotomagnetic effect anomalies and the state of the surface layer in high-resistance crystals of gallium arsenide
Photomagnetic effect anomalies and the state of the surface layer in high-resistance crystals of gallium arsenide
V.V. Ostroborodova and M.S. Al Kuveiti (Iraq)
The field dependences of the short-circuited photomagnetic current when crystals of GaAs with oxygen, chromium, and iron impurity are illuminated with light of different wavelengths are investigated. In GaAs(O) with bipolar Hall mobility 0 « μ*(n)< μ(n) for i$_{pm}$(B) in addition to the usual diffusion component n = i(+), which is linear with respect to the magnetic field B, reverse components n = i(-) are found, the contribution of which increases as the depth of penetration of the light decreases. In the region 50-77°K a maximum of these currents is also observed and a sharp increase in the effective rate of surface recombination. In GaAs(Fe)μ$^*_{n}$= μ$_{n}$ is monopolar for T < 110°K; i$_{pm}$(B) in the temperature range 8-100°K contain explicitly nonlinear n-i(-) (B) and linear p-i(+)(B). A maximum of n-i(-) is also observed at 50-77°K. In GaAs(Cr) μ*(n)= μ(n) is monopolar at room temperature, and in P - i$_{pm}$(B) a contribution that is nonlinear in В n-i(-) is also observed. The results obtained indicate the presence of a layer of p-conductivity ≥ 10$^{-5}$ thick, common for all the crystals, situated under the spacecharge layer. The presence of a layer leads to strong compensation of the photomagnetic current in the case of n-type volume photoconductivity, and can produce an antigate system with a considerable reduction in the effective rate of surface recombination for volume p conductivity.
Show AbstractApplication of raman scattering of light for determining the vibrational-level populations of nitrogen in a nonequilibrium gas-dynamic current
Application of raman scattering of light for determining the vibrational-level populations of nitrogen in a nonequilibrium gas-dynamic current
D.G. Bakanov, A.I. Odintsov, A.I. Fedoseev and V.F. Sharkov
We describe an experimental apparatus and method for measuring the vibrational temperature of nitrogen and the density of particles in a gas-dynamic current of a С02—N2—Не mixture through the use of Raman scattering of light. Raman scattering is excited by the second harmonic of an yttrium aluminum garnet-neodymium laser (λ$_{L}$ = 532 nm) inside a multipass cuvette with the number of light passes ~50. The useful signals of the Stokes and anti-Stokes components of the scattering are discriminated with the aid of narrow-band contrast interference color filters. The degree of suppression of the parasitic signal in the optical system is not less than 10. The apparatus permits determination of the nitrogen density all the way up to applied pressures of about 1000 Pa. The measured values of the vibrational temperature of nitrogen are in the 850-1000°K range.
Show AbstractDynamical properties of a stanley model with long-range interaction
Dynamical properties of a stanley model with long-range interaction
A.G. Shumovskaya and A.S. Shumovskii
For a Stanley model with long-range interactions, we find exact equations for the time dependence of the order parameter within the framework of a unification of the Bogolyubov (Jr.) method of approximate Hamiltonians and the stochastic approach of Glauber.
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