Calculation of exclusive processes with baryons

Using the nucleon andΔ ₃₃-resonance wave functions found out in previous papers [14, 15] we calculate the electromagnetic and weak nucleon formfactors, the transition formfactorγ \(\bar N\) Δ and the decay widths of charmonium levels³ S ₁,³ P ₂ and³ P ₁ into \(\bar N\) N and \(\bar \Delta \) Δ.     

C-odd exchange in high energypp andp \bar p elastic diffraction

Following the arguments of QCD, a proposed model takes into account the significant difference ofpp andp \(\bar p\) elasticd σ/dt discovered at the ISR. An expression forC-odd exchange is discussed and comparison with data is made. Starting from the ISR energies, the model is shown to describe well the data in a wide range of transverse momenta 0≦?t≦10 (GeV/c)² (including the Coulomb-nuclear interference region). Several peculiar predictions of the model will be testable in the TeV energy range and beyond.     

Relativistic correction to the triton binding energy in the framework of relativistic Hamiltonian dynamics

The relativistic correction to the triton binding energy approximated to the order (v/c)² is calculated in the framework of relativistic Hamiltonian dynamics. We discuss the generator representation of the Poincaré group for three relativistic particles and its connection with the Feynman diagrams in the infinite-momentum frame (the light-front dynamics). The relativistic correction enhances the attraction in the three-nucleon system. The five-channel calculation with the Reid soft-core potential yeilds the result =–0.54 MeV, which is governed mainly by theD-wave contribution. TheS-wave contributions to are only –0.10 MeV.     

Laser-pulse fluctuations due to thermal self-action in a turbulent atmosphere

Conclusions Refractive-index fluctuations caused by heating alter the intensity and phase fluctuation spectra arising from the turbulence. The large-scale part of the spectra is weakened, whereas the small-scale part is strengthened, and the spatial-frequency range in which the fluctuations are attenuated becomes narrower as the beam energy increases. Correspondingly, the fluctuation structure functions alter. For values of the arguments in those functions less than the radius of the first Fresnel zone , the thermal nonlinearity causes increases in the structural functions D_, with the energy. For , the dependence of D_, on energy is nonmonotone, with the fluctuations at first weakened but then strengthened. The reduction in fluctuation variance and the improvement in coherence is less pronounced over long lines than on short ones. The range in which geometrical optics can be used to derive the fluctuations is independent of the nonlinearity and is defined by k₂z/2k /4. The trend to the diffraction asymptote becomes slower as the nonlinearity increases.Atmospheric Physics Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 9, pp. 1063–1071, September, 1989.     

The absorption of pulsed CO2-laser radiation by ethylene at total pressures from 25 to 3000 Torr

The absorption of pulsed CO₂-laser radiation by ethylene has been measured at total pressures from 25 to 3000 Torr, using the P(12) and P(14) lines in the 10.6 m band, with incident fluences from 0.1 to 0.7 J/cm². Marked deviations from the Beer-Lambert absorption law were observed, with the effective absorption coefficient varying with pressure, fluence, absorption path-length and the addition of non-absorbing gas. Pressure broadening of the rotational lines of the ethylene absorption spectrum was shown to be the major cause of these deviations, together with lesser effects which can be attributed to the rise in temperature of the absorbing gas during the laser pulse.     

Dynamical scattering of X-rays by dislocations in the Bragg and Laue case

The interbranch scattering of X-rays at dislocations is studied experimentally and with the aid of numerical simulations. Narrow beam of a small divergence is used for the study which is made both in the Laue and Bragg case of diffraction. The role of interbranch scattering in the formation of defect contrast in X-ray topography is discussed.     

Textural analysis of extruded materials with rhombohedral structure

A textural analysis of extruded rods of material with tetradymite (Bi₂Te₃) structure is conducted by constructing the distribution of the pole density of the (0001) and (1120) planes. The distribution of the poles of the planes is represented by a solid of revolution, and the pole density, which is a function of the angle () of the deviation of the normals to h_i from the extrusion axis, is determined by the diffraction method of specimen inclination using the diffracted ray intensity. It proves possible to identify textural components, and to determine how many there are and the degree of perfection of this method. A technique is worked out for the quantitative estimate of the average values of the components of the conductivity tensor in the grains, and the contribution of the texture to the macroscopic properties of the material is analyzed. To investigate the thin layers (for example, the layerwise distribution of texture in rods of rectangular cross section) we used the method of inverse pole diagrams, where the probability of coincidence of the h_i plane with the working surface of the specimen is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 33–39, December, 1989.     

Martensitic transformations in Ti (Ni,Fe) alloys

In this work we used x-ray structural analysis to investigate the martensitic transformations (MTs)B2R andRB19 in Ti(Ni, Fe) alloys containing 1, 2.5, 4, 5 at. % Fe, and the effect of heat treatment on the MT temperatures and sequence. In the majority of cases, it was found that the MTB2R proceeds through a two-phase region (+R). Heat treatment leads to a narrowing of the temperature interval of the existence of the two-phase region, weakly affects the onset temperatures of the MTsB2R T_R andRB19 M_s, and sharply increases the temperature-of the end of the MT M_e. The existence of the two-phase region is related to the two MT channelsB2R andB2B19 initially intrinsic to the allovs of the given compositions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 19–22, December, 1989.     

Structural investigation of phase transformations in an MnAl alloy

A comprehensive x-ray diffraction study is made of an MnAl alloy, including a phase analysis of the alloy. Changes in the lattice parameters of the phases during phase transformations are examined and an analysis is made of the dispersion of the metastable ferromagnetic -phase. The structural characteristics are studied with different annealing temperatures ranging from 450 to 900°C. The temperature sequence of the phase transformations of the alloy is determined, along with the optimum conditions for the formation of the magnetic phase in the alloy. The structural characteristics of the phases that are obtained provide evidence of a difference in the processes responsible for ordering of the - and -phases. It is shown that it is possible to use the lattice-parameter ratioc/a to study the directionality of phase transformations in the alloy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 34–38, August, 1989.     

Investigation of the character of the exchange interaction in the system Hg1−xMnxSe

A new method is proposed for determining the magnetic characteristics (magnitude and sign of the exchange interaction energy and the average size of clusters of magnetic ions) of dilute solid solutions of semimagnetic semiconductors at low temperatures based on oscillation measurements. The method makes it possible to find the magnetic characteristics of the indicated systems at temperatures between the point of the transition into the spin glass state and the temperature corresponding to the characteristic binding energy of magnetic atoms in clusters, for which standard methods based on the measurement of the magnetic susceptibility are not effective. The method is used to study the character of the exchange interaction in the system of solid solutions Hg_1–xMn_xSe as a function of their composition as well as under conditions of hydrostatic compression. To this end the oscillations of the magnetoresistance (Shubnikov-de Haas (SH) effect) in single-crystalline samples of Hg_1–xMn_xSe in the region of compositions 0.001 x 0.23 in magnetic fields H up to 65 kOe at temperatures T = (0.4–20) K and pressures up to 16 kbar were studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 29–39, November, 1989.