On the possibility of phase transitions in dusty plasma structures in a glow discharge under the action of a magnetic field

The melting of a dusty plasma structure formed in a stratum of a glow discharge caused by application of a magnetic field and its subsequent increase is studied. The images of two-dimensional cross sections of dusty plasma structures previously obtained by the authors are considered. To identify the phase, the correlation functions are calculated and visual comparison with the space lattices of ideal crystals is performed. It is found that, under the conditions of the previous study of the authors, as the magnetic field increases, the phase state of the dusty structure changes from an anisotropic liquidlike (liquid-ice) state to a disordered one. There is a tendency to a change in the type of the space lattice of the structure.     

Comparison of the dynamics of grid structures under thermal and radiation actions on amorphous Co-Ni-P alloys

The dynamics of the grid structures of Co-Ni-P alloys is investigated via transmission electron microscopy under thermal action and irradiation by γ quanta. Statistical processing of the electron-microscopic images of grid structures makes it possible to construct the empirical functions of size distribution of grid cells in the presence of different types of actions. Analysis of empirical distribution functions and their moments has been performed to study the statistics of distribution functions corresponding to different stages of structural relaxation during thermal and radiation actions and to classify structural relaxation processes. The presence of correlative interaction between structure components has been found in the initial state of an amorphous alloy; the type of correlation has been determined. The correlation behavior is analyzed under irradiation by γ quanta and thermal action. It has been revealed that grid cells exhibit different correlative interactions determined by the type of action.     

Three-particle correlations in nonideal dusty plasma

Results are given of experimental investigation of three-particle correlations for liquid plasma-dust structures formed in the electrode layer of a high-frequency capacitive discharge. The obtained three-particle correlation functions for experimental and numerical data are analyzed and compared with the superposition approximation. The forming of clusters of macroparticles in plasma-dust systems being analyzed is revealed.     

Quasi-2D Monte Carlo simulations of phase transitions and internal aggregate structures in a highly dense suspension composed of magnetic plate-like particles

The phase transitions and the internal aggregate structures of a highly dense suspension composed of magnetic plate-like particles with a magnetic moment normal to the particle axis have been investigated by means of the Monte Carlo method. The present study considered a quasi-2D system in order to clarify the influences of the volumetric fraction of particles and the magnetic field strength on particle aggregations and phase transitions. The internal structures of particle aggregates have been discussed quantitatively in terms of pair correlation functions, orientational pair correlation functions, nematic and polar order parameters. The main results obtained here are summarized as follows. When the influence of the magnetic interaction between particles is of the same order of that of the perpendicular magnetic field strength, the particles form column-like clusters, and the internal structure of the suspension shows solid-like structures. For the case of a strong applied magnetic field, the internal structure is transformed from solid-like structures into isotropic ones. However, as the volumetric fraction increases, the particles form brick wall-like structures under the situation of a strong applied magnetic field, and the internal structure exhibits solid-like ones. The brick wall-like structures also appear for a relatively weak magnetic field applied along the in-plane direction despite a slightly smaller volumetric fraction compared with the case of the perpendicular applied magnetic field.     

高压下液态硝基甲烷的分子动力学模拟

 对高压下液态硝基甲烷的性质进行经典和基于第一性原理计算的Car-Parrinello分子动力学（CPMD）模拟。利用经典势的分子动力学（MD）模拟研究了高压压缩状态下液态硝基甲烷的结构和热力学性质,得到了高达14.2 GPa压力下的理论Hugoniot数据。对于一些热力学函数,如总能和粒子速度,经典势模拟给出了很好的总趋势,基本特征和实验观测一致。但是在给定的密度下,经典模拟预言的Hugoniot压力偏高。在几个选定的密度下,进行了CPMD模拟,得到了二体相关函数、速度自相关函数、振动光谱和其它的热力学性质,并与经典模拟结果进行了比较。对二体相关函数的分析表明经典势的短程部分的刚性可能太强,从而导致了比实验值高的理论压力值。对于某些二体相关函数,CPMD模拟和经典模拟结果差别很大,可以归结为量子效应。当压力增高时,量子模拟得到的振动光谱向高频部分移动的现象与实验观测相符合。     

Analysis of pair correlation functions for macroscopic particles in dusty plasmas: Numerical simulation and experiment

Pair correlation is analyzed for systems of macroscopic particles with various isotropic interaction potentials. Under certain conditions, the behavior of the pair correlation function is determined by an effective order parameter and its decrease toward infinity follows an asymptotic power law. When the effective parameter is smaller than a certain critical value, the decay of pair correlation is much steeper. Experimental results concerning the form of the pair correlation function are presented for liquid-like dust structures localized in the near-electrode plasma sheath of a high-frequency capacitive discharge. An analysis of numerical and experimental results shows that melting dynamics in these systems are analogous to those characteristic of a topological phase transition.     

Statistical Theory of Two-Sided Multipactor

We develop a statistical theory of secondary-emission discharge (SED) taking the energy distribution of secondary electrons into account. The theory allows one to describe quantitatively the initial stage of development of a two-sided multipactor. For an arbitrary probability density of normal components of the ejection velocity and an arbitrary distance between the walls enclosing the microwave discharge plasma, we construct an analytical solution for the electron distribution function over transit times. The performed analysis is based on the results of a detailed study of conditions under which an electron reaches the opposite side. With allowance for the spread in thermal velocities, we derive a recurrence relation between the electron distribution functions over emission phases and formulate a general integral equation from which the resulting stationary distribution and the threshold of SED onset are determined.     

Ordered dust structures in a glow discharge

Highly ordered three-dimensional dust structures are created in a striated glow discharge, and their horizontal cross-sectional images are analyzed. Calculated correlation functions, local correlation parameters, and corresponding approximations are used to classify the state of a structure according to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) two-dimensional melting theory and a phenomenological approach. An orientational map based on an orientational parameter is proposed to expose domains in a cross section of a structure. It is shown that a plasma crystal is a polycrystal consisting of hexagonal domains (crystallites). Thermophoretic forces are used to create corners of various angles in the perimeter of the structure. Transition between hexagonal and square cell shapes is observed.     

On the theory of spin exchange structures

All possible types of spin ordering manifested in spin-spin correlation functions are determined. Some general characteristics of arbitrary spin structures predicted by macroscopic theory are examined, including energy associated with inhomogeneity, anisotropy, and energy in external fields.     

Diffraction of optical radiation on spatially ordered structures of macroparticles in a strongly nonideal thermal plasma

The first observation of the diffraction of optical radiation on ordered structures of macroparticles in a low-temperature thermal plasma was reported. The experiments were conducted in an air thermal plasma at atmospheric pressure with CeO₂ particles at temperatures 1800–2200 K. The parameters of the plasma medium were determined using probe and optical diagnostics methods. The binary correlation function of the system of macroparticles was reconstructed from measurements of the structure factor. Simulation of nonideal plasma with the parameters corresponding to experiment was performed by the molecular dynamic method. The computed and experimental correlation functions were compared, and it was noted that they are in good agreement with one another.     

Dynamical heterogeneity close to the jamming transition in a sheared granular material

The dynamics of a bidimensional dense granular packing under cyclic shear is experimentally investigated close to the jamming transition. Measurement of multipoint correlation functions are produced. The self-intermediate scattering function, displaying slower than exponential relaxation, suggests dynamic heterogeneity. Further analysis of four point correlation functions reveal that the grain relaxations are strongly correlated and spatially heterogeneous, especially at the time scale of the collective rearrangements. Finally, a dynamical correlation length is extracted from a spatiotemporal pattern of mobility. Our experimental results open the way to a systematic study of dynamic correlation functions in granular materials.     

Wave function(al)s in the large-N limit

The energy spectrum and correlation functions in various quantum theories have been determined within the large-N limit. Here we study the wave functions. Explicit results are presented for a quantum mechanical rotor, invariant under adjoint transformations of U(N), as well as for O(N) invariant vector models in quantum mechanics and quantum field theory.     

Recording and optical processing of images of projected fringes in the study of objects with a periodic surface texture

Specific features of application of the fringe projection method to the study of objects with a periodic surface texture are analyzed. It is shown that a moire pattern is formed in the image recording process. It is caused by the superposition of two periodic structures, namely, the image of the texture of the surface under study and the system of projected fringes. The bending of moire fringes in the pattern is determined by the summary effect of two functions, which describe the bending of the images of surface texture and the system of projected fringes, because of the deviation of the relief shape from the comparison plane. A method for the optical processing of a photographic image by two coherent light beams is described, which makes possible a separate interferometric visualization of the aforementioned functions. Results of experimental studies are presented.     

高离化类锂原子体系(Z=21～30)1s23p态的能级结构和振子强度

用全实加关联方法计算了类锂原子体系(Z=21～30)偶极跃迁1s22s -1s23p的跃迁能、振子强度以及1s23p态的精细结构劈裂.非相对论能量用Rayleigh -Ritz变分法确定;相对论修正和质量极化效应用微扰论计算;同时考虑了来自量子电动力学(QED)效应的修正.得到的理论结果与实验数据及物理规律符合的很好.     

Quantum State Reconstruction of Many Body System Based on Complete Set of Quantum Correlations

We propose and study a universal approach for the reconstruction of quantum states of many body systems from symmetry analysis. The concept of minimal complete set of quantum correlation functions (MCSQCF) is introduced to describe the state reconstruction. As an experimentally feasible physical object, the MCSQCF is mathematically defined through the minimal complete subspace of observables determined by the symmetry of quantum states under consideration. An example with broken symmetry is analyzed in detail to illustrate the idea.     

Study of the topology of metal-containing granular films by light scattering and atomic force microscopy

The correlation properties of films consisting of granular structures with granules smaller than 6 nm prepared by the laser electrodispersion method are investigated. The correlation functions of the nanoparticle distribution on a transparent substrate are calculated from the angular structure of scattered radiation using the single-scattering approximation, as well as from the data of atomic force microscopy for copper, nickel, and palladium structures with different packing density. The size of coarse particles in nanostructures is estimated.     

Fluctuations in a fluid under a stationary heat flux II. Slow part of the correlation matrix

The general formulas, derived in a previous paper, are used to calculate the correlation functions of the hydrodynamic variables in the Rayleigh-Bénard system. The behavior of the correlation functions on a time scale slow compared to that of sound propagation is determined, using systematically nonequilibrium hydrodynamic eigenmodes. These (slow) eigenmodes of the linearized Boussinesq equations in the presence of gravity and a temperature gradient are the viscous and the visco-heat modes. They are determined for ideal heat-conducting plates with stick boundary conditions. The visco-heat modes are found to behave qualitatively different from those obtained with slip boundary conditions. Using these eigenmodes, the slow part of the correlation functions can be determined explicitly. On a small length scale, as probed by light scattering, we recover the same expression for the Rayleigh line as quoted in the literature. On larger length scales, as probed by microwaves, the coupling of gravity to the temperature gradient gives rise to a convective instability (heating form below) or to propagating visco-heat modes (heating from above). The corresponding correlation functions and the Rayleigh line are calculated and discussed.     

Quantum Rings with Two Deeply Bound Electrons under a Magnetic Field

A model is proposed to study the quantum rings with two deeply bound electrons under a variable magnetic field. The emphasis is placed to clarify the effect of the size （diameter） and the width of the ring on the fractional Aharonov-Bohm oscillation. It was found that the reduction of size will lead to a very strong oscillation in the ground state energy and in the persistent current. The electronic correlation has also been demonstrated by showing the nodal structures of wave functions.     

Formation of complex structures in dusty plasmas under temperature gradients

Thermophoretic effects on dust structures under temperature gradients in glow and radio-frequency discharge plasmas are studied experimentally. The geometry of dust structures consisting of micrometer-sized polydisperse grains depends on heat release in the plasma. Thermophoretic forces associated with heat release can control the formation of dust structures of different geometries. A theoretical model is proposed to describe dust separation with respect to grain size caused by the effects of radial electrostatic and thermophoretic forces. The glow discharge currents under critical conditions for grain separation predicted by the model agree with those observed experimentally.     

The dynamics of macroparticles in a direct current glow discharge plasma under microgravitation conditions

The dynamics of large-sized (70-180 μm) spherical bronze particles in a direct current glow discharge plasma was studied experimentally under microgravitation conditions. The temperatures, velocities, pair correlation functions, and self-diffusion coefficients of macroparticles were measured at various discharge currents. The charges of dust particles (on the order of 10⁶ e) corresponded to high surface potentials of about 30–40 V. The experimental data were in close agreement with the simulation data on Yukawa systems with weak screening of dust charges. The influence of macroparticles on equilibrium ionization in a dense dust cloud was considered.