Channeling problem for charged particles produced by confining environment

Channeling problem produced by confining environment that leads to resonance scattering of charged particles via quasistationary states imbedded in the continuum is examined. Nonmonotonic dependence of physical parameters on collision energy and/or confining environment due to resonance transmission and total reflection effects is confirmed that can increase the rate of recombination processes. The reduction of the model for two identical charged ions to a boundary problem is considered together with the asymptotic behavior of the solution in the vicinity of pair-collision point and the results of R-matrix calculations. Tentative estimations of the enhancement factor and the total reflection effect are discussed. The text was submitted by the authors in English.     

Channeling of fast charged and neutral particles in nanotubes

We present a theory to describe the propagation of relativistic charged particles, X-rays and thermal neutrons through straight or slightly bent nanotubes and calculated the spectra of electromagnetic radiation accompanying the channeling of charged particles.     

Electron localization during an electronic-topological transition in Mo-Re alloys

Oscillations in the superconducting transition temperature ΔT _c (P), in the critical magnetic field ΔH _c (P), in the thermopower α / T (T ²), and in electrical resistivity ρ(T) (P is pressure) of Mo_1?x -Re _x alloys are observed at low temperatures against the background of specific features related to an electronic-topological transition (ETT) in these alloys. The oscillations are sensitive to the impurity concentration: they increase when the Re impurity concentration is close to the critical concentration C _c at which the ETT occurs. Oscillations are also detected in the concentration dependences of the temperature coefficient of resistivity (?ρ / ?T (C)) and the thermopower derivative (?(α/T) / ?T ² (C)) of Mo_1?x -Re _x alloys at low temperatures. The former and latter oscillations are shown to correlate with each other. These specific features are assumed to result from the ETT and to be related to the localization of the part of the electrons that fill a new cavity in the Fermi surface during this transition.     

Electron tomography as a tool for studying the structures of amorphous alloys

Structural defects in amorphous and nanocrystalline alloys of the CoP–CoNiP–NiP and CoW?CoNiW–NiW systems are studied by means of electron tomography. An algorithm and software are developed to optimize the level of binarization of tomographic models used to select objects. Computer simulations show that the distribution of the volume of material density fluctuations is a Pareto distribution. It is established that a modified Pareto distribution describes the experimental distribution of volumes with a smaller error.     

Channeling and electromagnetic radiation of relativistic charged particles in metal-organic frameworks

We have developed the theory of electromagnetic interaction of relativistic charged particles with metal-organic frameworks (MOFs). The electrostatic potential and electron number density distribution in MOFs were calculated using the most accurate data for the atomic form factors. Peculiarities of axial channeling of fast charged particles and various types of electromagnetic radiation from relativistic particles has been discussed.     

掺杂超晶格量子阱的沟道效应与沟道辐射

分析了超晶格量子阱的沟道效应和沟道辐射,利用正弦平方势描述了掺杂超晶格量子阱沟道粒子的运动行为,并在经典力学框架内,把粒子的运动方程化为摆方程。用Jacobian椭圆函数和椭圆积分解析地给出了系统的解和粒子运动周期,导出了量子阱沟道辐射的辐射强度和辐射能量。结果表明,对于能量为100 MeV左右的电子,辐射能量可达keV量级（X能区）。指出了用量子阱沟道辐射作为X激光或γ激光的可能性。     

Defect structures in nematic liquid crystals around charged particles

We numerically study the orientation deformations in nematic liquid crystals around charged particles. We set up a Ginzburg-Landau theory with inhomogeneous electric field. If the dielectric anisotropy e₁ \varepsilon_{1}^{} is positive, Saturn-ring defects are formed around the particles. For e₁ \varepsilon_{1}^{} < 0 , novel “ansa” defects appear, which are disclination lines with their ends on the particle surface. We find unique defect structures around two charged particles. To lower the free energy, oppositely charged particle pairs tend to be aligned in the parallel direction for e₁ \varepsilon_{1}^{} > 0 and in the perpendicular plane for e₁ \varepsilon_{1}^{} < 0 with respect to the background director. For identically charged pairs the preferred directions for e₁ \varepsilon_{1}^{} > 0 and e₁ \varepsilon_{1}^{} < 0 are exchanged. We also examine competition between the charge-induced anchoring and the short-range anchoring. If the short-range anchoring is sufficiently strong, it can be effective in the vicinity of the surface, while the director orientation is governed by the long-range electrostatic interaction far from the surface.     

Intensity of radiation of charged particles passing through crystals

We have calculated the intensity of radiation of a relativistic charged particle moving in a crystalline medium, taking into account the interaction of the charge with the crystal as well as with the radiation. Various modifications to the usual Cerenkov radiation are discussed and under certain conditions enhancement occurs.     

Dewetting as an investigative tool for studying properties of thin polymer films

Employing mass conservation, time-resolved dewetting experiments of thin polymer films allow to determine in real time the dynamic contact angle and the slippage length. Moreover, based on a systematic variation of interfacial properties of a polymer brush, dewetting makes it possible to calculate the force it needs to extract a single polymer chain from its own melt. In the visco-elastic regime close to the glass transition, the temperature and molecular weight dependence of the relaxation time of residual stresses resulting from film preparation by spin-coating can be obtained from the evolution of the shape of the dewetting rim. The presented examples demonstrate that dewetting represents a powerful approach for a sensitive characterization of rheological, frictional and interfacial properties of thin polymer films.     

Dynamical chaos in the motion of fast charged particles in crystals

It is demonstrated that the dynamical chaos effect can occur both for channeling and above-barrier motion of relativistic electrons and positrons in a crystal. Distinguishing features of the dynamical chaos in the physical processes that accompany the passage of relativistic particles through crystals are discussed.     

Channeling of fast particles in fullerites

A theory of channeling of relativistic electrons and positrons as well as positively and negatively charged ions in molecular crystals of fullerenes (fullerites) is developed. The crystal potentials are calculated, and the spatial and angular distributions of beams of particles propagating along principal crystallographic directions are determined. A method is developed for taking into account the effect of incoherent scattering on the channeling process.     

Effect of atomic arrangement on penetration of charged particles into crystals

The angular and spectral distributions of protons having initial energies of 4–7 MeV have been studied in simple cubic ionic crystals and in germanium and silicon crystals with and without the channeling effect. The average energy losses of the channeled and unchanneled protons in the crystals were measured. The concentration of structural defects in the crystals is shown to affect the proton energy spectra measured when channeling occurs. A procedure involving photographic plates was used to study the angular distributions of the channeled protons. The possible use of proton diffraction to study the structure and other characteristics of crystals is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 8, pp. 86–91, August, 1969.     

Ultrasound irradiation as an effective tool in synthesis of the slag-based catalysts for carboxymethylation

Waste minimization strategy was applied in the current work for synthesis of the catalysts from industrial solid waste, namely desulfurization slag. The starting slag material comprising CaCO₃, Ca(OH)₂, SiO₂, Al₂O₃, Fe₂O₃, and TiO₂ was processed by various treating agents systematically varying the synthesis parameters. A novel efficient technique – ultrasound irradiation, was applied as an additional synthesis step for intensification of the slag dissolution and crystallization of the new phases. Physico-chemical properties of the starting materials and synthesized catalysts were evaluated by several analytical techniques. Treatment of the industrial slag possessing initially poor crystal morphology and a low surface area (6 m²/g) resulted in formation of highly-crystalline catalysts with well-developed structural properties. Surface area was increased up to 49 m²/g. High basicity of the neat slag as well as materials synthesized on its basis makes possible application of these materials in the reactions requiring basic active sites. Catalytic performance of the synthesized catalysts was elucidated in the synthesis of carbonate esters by carboxymethylation of cinnamyl alcohol with dimethyl carbonate carried out at 150 °C in a batch mode. Ultrasonication of the slag had a positive effect on the catalytic activity. Synthesized catalysts while exhibiting similar selectivity to the desired product (ca. 84%), demonstrated a trend of activity increase for materials prepared using ultrasonication pretreatment. The choice of the treating agent also played an important role in the catalytic performance. The highest selectivity to the desired cinnamyl methyl carbonate (88%) together with the highest activity (TOF₃₅ = 3.89*10⁻⁷ (mol/g*s)) was achieved over the material synthesized using 0.6 M NaOH solution as the treating agent with the ultrasound pre-treatment at 80 W for 4 h.     

Ion implantation as a tool for studying the Kondo-systemZnMn

In the case ofZnMn alloys it is shown how low temperature ion implantation can be used for the production of dilute magnetic alloys. The Kondo effect in the resistivity (T) was studied between 1.1K and 20 K. The phonon part of the resistivity was subtracted using (T)-curves from Zn-Films with similar disorder produced by self-ion implantation. A logT-dependence with a slope proportional to the Mn-concentration was found below 200 ppm. The influence of disorder on the specific Kondo slope is discussed.Dedicated to Prof. Dr. W. Buckel on the occasion of his 60th birthday.     

Scintillation as a tool for studying the interstellar plasma

The interstellar plasma is characterized by variations of electron density having a wide range of physical scales. Radiation propagating through this inhomogeneous plasma is scattered, causing the received intensity to scintillate on a variety of time scales. Observations of the radio frequency spectrum and temporal variation of scintillation give information on the turbulence spectrum of the plasma and the distribution of density irregularities throughout the galaxy. Some uses of scintillation as a means of probing the interstellar plasma will be described.Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 6, pp. 685–692, June, 1994.     

二元体系胶体晶体性质的实验研究

利用Kossel衍射技术和反射光谱对由总体积分数为0.02的二元聚苯乙烯胶体体系(94nm+141nm)形成的胶体晶体的性质进行了研究,实验结果显示胶体晶体的形成时间,平均粒子间距,晶体结构都与二元胶体体系中两种粒子的数密度比相关,当94nm聚苯乙烯粒子相对于141nm聚苯乙烯粒子的数密度比趋向1∶1时,胶体晶体的形成时间延长,当94nm聚苯乙烯粒子相对于141nm聚苯乙烯粒子的数密度比由1∶0向0∶1变化时,胶体晶体的平均粒子间距变大,另外实验中发现在两种粒子的数密度比为5∶1时,胶体晶体出现了超晶格结 关键词： 胶体晶体 聚苯乙烯 Kossel衍射 反射光谱