E. A. Lisin

Analysis of pair interparticle interaction in nonideal dissipative systems

A new method is proposed for determining the interaction forces between particles in nonideal dissipative systems with isotropic pair potentials. The method is based on the solution of the inverse problem describing the motion of interacting particles by a system of Langevin equations and allows one to recover the parameters of the external confining potential without referring to a priori information on the friction coefficients of the particles. This procedure was tested by a numerical simulation of the problem in a wide range of parameters typical of experimental conditions in a laboratory dusty plasma. The results of the first experimental approbation of the method as applied to the analysis of the interaction of dust particles in a laboratory high-frequency capacitive discharge plasma are presented.

Energy exchange in systems of particles with nonreciprocal interaction

A model is proposed to describe the sources of additional kinetic energy and its redistribution in systems of particles with a nonreciprocal interaction. The proposed model is shown to explain the qualitative specific features of the dust particle dynamics in the sheath region of an RF discharge. Prominence is given to the systems of particles with a quasi-dipole–dipole interaction, which is similar to the interaction induced by the ion focusing effects that occur in experiments on a laboratory dusty plasma, and with the shadow interaction caused by thermophoretic forces and Le Sage’s forces.

Influence of external perturbations on the interaction between grains in plasma

An experimental study of dust grain dynamics in plasma was carried out for cluster systems relaxing to their equilibrium state after the action of a laser beam. The influence of this external perturbation on the potential between interacting dust grains was analyzed. We found that the spatial asymptotes of the pair potential for perturbed and equilibrium dust systems differ. The possible reasons for this phenomenon are discussed.

Dust-particle charge in weakly ionized gas-discharge plasma

The results of the measurements of the charge on dust suspended in a laboratory rf-discharge plasma are presented. Experiments were performed for both small-size clusters of particles and large quasi–two-dimensional systems formed in a wide range of plasma conditions. The estimations of dust charges were derived from the interaction potential profiles of dust particles and their characteristic oscillation frequencies obtained by two methods: one based on a solution of the inverse Langevin problem and another one on studying mass-transfer processes in a dusty subsystem. The experimental results were compared with numerical data and theoretical estimates based on the near-electrode layer theory and the OML approach for isotropic and anisotropic plasma.

Solid-hexatic-liquid transition in a two-dimensional system of charged dust particles

Two-stage melting is observed experimentally in a confined monolayer of dust particles in plasma. The pair correlation and bond-angular correlation functions, the number of topological defects, and the pair potentials are measured and analyzed. The bond-orientational correlation functions show a clear solid-to-hexatic-to-fluid transition, in perfect agreement with the Berezinskii-Kosterlitz-Thouless transition theory.

Contactless methods for studying interactions between dust particles in a gas-discharge plasma

This paper reviews some of the contactless methods for passive diagnostics of pair interactions between dust particles in laboratory gas-discharge plasmas. Two methods are considered for reconstructing the spatial dependence of a pair interaction potential. Techniques for estimating the characteristic pair interaction energy in quasi-equilibrium strongly coupled systems are also discussed.

Influence of external perturbations on dynamical characteristics of dust clusters (simulation)

The results of a numerical study of the dynamics of interacting particles in cluster systems under the action of an external perturbing field on them are presented. The relaxation rates and characteristic relaxation times of a cluster to its equilibrium state are analyzed. The conditions for the formation of dynamical structures of charged particles in the field of external nonpotential forces are investigated. The peculiarities of diagnosing the pair potential of particles in nonequilibrium systems are considered. The numerical simulation conditions for the problem were close to the conditions of experiments in a dusty plasma.

Verifying the reciprocity of interparticle interaction forces in strongly coupled systems

We propose a simple criterion for revealing the breaking of pair interaction symmetry in strongly coupled dissipative systems. The criterion is based on the analysis of correlations between the velocities of strongly interacting particles, which can be measured relatively easily in experiments with macroparticles in various media. We derive analytic relations that make it possible to calculate the derivatives of the interaction force between a pair of particles from the data on the correlations of their velocities and coordinates. The proposed criterion and relations are verified using the results of numerical simulation of the dynamics of dust particles in a plasma.

Processes of diffusion in a limited ensemble of charged particles in a static magnetic field

The dynamics of a limited ensemble of charged particles in a spatially uniform static magnetic field has been studied analytically and numerically. Calculations have been performed for particles with various masses and charges in a wide range of the parameters of the systems under study. It has been shown that the transverse diffusion coefficient in an ensemble of particles in the magnetic field for weakly nonideal systems is described by the Townsend formula. Analytical estimates have been proposed for the analysis of the effective diffusion radius of the ensemble of particles owing to their thermal motion. The proposed relations have been tested by the numerical simulation of the problem.

On the possibility of determining the forces of anisotropic interaction between plasma microparticles

The possibility of experimental diagnostics of forces of the anisotropic interaction between dusty particles in plasma is considered for the first time. To this end, a modification of the method based on the solution of the Langevin inverse problem for systems with anisotropic interparticle interaction is presented. It is tested on the results of numerical simulation of chain structures of particles with the quasi-dipole–dipole interaction similar to the interaction appearing between dusty particles in near-electrode layers of gas discharges.