Some properties of an ultimately nonideal metastable supercooled plasma

The formation of a metastable plasma state from an initial strongly nonideal state and certain properties of this metastable supercooled state are considered by directly modeling the dynamics of a system of many Coulomb particles. It is shown that the relaxation of the average kinetic energy of the particles can be characterized by a universal dimensionless function and, in particular, that an ultimate value degree of plasma nonidealness occurs which can be reached in the metastable state when no external action is present. The calculated binary correlation functions are in good agreement with the results of the Debye model, even outside its range of applicability. The time dependence of the total dipole moment of the system of particles is investigated. It is shown that there are oscillations of the total dipole moment. These collective oscillations take place at a frequency which is somewhat below the Langmuir frequency, the oscillations of the free and bound electrons occurring in antiphase. A hypothesis is advanced to the effect that recombination relaxation is frozen on account of the interaction of quasibound electrons with the Langmuir oscillations of the free electrons. Institute of General Physics, Academy of Sciences of the Russian Federation. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 3–16, October, 1996.     

Collective oscillations of electrons for modeling from first principles and the nature of anomalous drift along the energy axis

A hypothesis is advanced that a metastable supercolled state of a system of classical Coulomb particles can be provided by the quasiresonant interaction of coupled electrons with collective oscillations of plasma electrons. This interaction is particularly strong when the Kepler frequency is of the order of the Langmuir oscillation frequency (which occures when the radius of an electron orbit is of the order of the average distance between the charges). Modeling from first principles has shown that the characteristic oscillation time of the dipole moment of a system of Coulomb particles is of the order of the Langmuir oscilation frequency. General Physics Institute, Russian Academy of Sciences, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 76–81, July, 1996.     

Energy characteristics of radiation from an oscillating dipole moving in a dielectric medium with resonant dispersion

Radiation produced by oscillations of an electric dipole moving along its dipole moment through an insulator with the resonance-type dispersion is considered. The total power of radiation and the power density spectrum are studied both analytically and numerically. It is shown that the radiation spectrum consists of either two separate frequency ranges or a single frequency range depending on the parameters of the problem. The dependences of the radiation power on the velocity of the source are revealed for various values of the resonant and Langmuir frequencies.     

Electron clouds around charged particulates

Poisson’s equation is used to derive an expression for the characteristics of the Debye electron cloud around a multiply charged particle. It is shown that the limiting dimension of the Debye cloud (for an infinitely large charge of the particles) varies from 0.7 to 2.2 Debye radii, depending on the geometry of the problem. A first-principles modeling of the dynamics of many electrons moving around an immobile charged center is carried out. It is shown that a metastable state which relaxes at least one thousand times more slowly than would follow from the kinetic theory is established. Calculations show that in this metastable state (which is far from thermodynamic equilibrium) there is a detailed balance of electron transitions from a state with one energy to another. The distribution of electrons over kinetic energy has a Maxwellian form, while the distribution over total energy is radically different from the Boltzmann distribution and is close to that which was established previously by the authors for a plasma of singly charged ions. The potential distribution around the immobile charge in the metastable plasma is obtained. Zh. Tekh. Fiz. 69, 53–57 (January 1999)     

Dynamics of electron beams in plasmas

The characteristic features of the relaxation of the energy and momentum distribution functions of the electrons in a plasma produced by a low-voltage beam discharge in helium are investigated. It is established that, contrary to widely held opinion, the energy of an intense electron beam may relax due to the wave excitation. The critical currents corresponding to a jumplike transition from one relaxation mechanism to another are measured. The density of metastable helium atoms is determined from the comparative analysis of theoretical and experimental results on the structure of the energy spectrum of the electrons of an intense beam. An intense electron beam is found to become more isotropic in the course of its interaction with Langmuir waves in a collisionless plasma. The cross section for quasi-elastic collisions between the electrons and Langmuir plasmons is estimated. The wave nature of the beam-plasma mechanism for the relaxation of the anisotropic electron energy distribution function is demonstrated, and the mechanism itself is shown to come into play when the discharge current exceeds a certain critical level. The experimental threshold criterion for the energy relaxation of an intense monoenergetic beam is obtained for the first time. It is shown that the relaxation occurs in two stages: the isotropization stage, in which the beam energy decreases insignificantly, is followed by the stage in which the beam relaxes to a state with a plateau-like energy distribution function. The threshold criterion for the relaxation of the anisotropic electron energy distribution function is universal in character regardless of the cause of anisotropy.     

Plasma Polarization Around Dust Particle in an External Electric Field

The effect of plasma polarization around a negatively charged dust particle is investigated with the help of Monte Carlo simulation of ion trajectories in the electric field of the dust particle and an external electric field. The induced dipole moment of such a system was estimated in a wide range of dust particle and plasma parameters. It is shown that the dipole moment is very large, and has a non‐monotonous dependence on the external electric field. For a small external electric field, it weakly depends on the charge of the dust particle. The dipole moment reduces with the decrease of ion mean free path (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Plasma properties of a quasi-one-dimensional ring

The spectrum of plasma oscillations and the frequency of the dielectric relaxation of electrons in a quasi-one-dimensional ring are calculated. The plasmon spectrum is revealed to be equidistant. It is shown that, in contrast to the three-dimensional case, the dielectric relaxation is dispersive and, therefore, the distribution of carriers in quasi-one-dimensional rings can be studied by means of dielectric relaxation spectroscopy.     

Toward a theory of nuclear relaxation in dielectric glasses at ultralow temperatures

The temperature and frequency dependence of the nuclear relaxation rate in dielectric glasses is investigated. It is shown that at low and ultralow temperatures nuclear relaxation is due to an interaction between the nuclear quadrupole moment and fluctuations of the electric field created by dipole moments of two-level systems. Fluctuations of this field can be associated with the background relaxation or are due only to the dipole-dipole interaction between two-level systems. It is shown that at lower temperatures the second relaxation mechanism begins to dominate. Expressions are obtained for the temperature and frequency of crossover between different nuclear relaxation regimes. The possibility of experimental confirmation of our results is discussed. Zh. éksp. Teor. Fiz. 115, 2254–2262 (June 1999) Russian Scientific Center “Kurchatov Institute”     

Kinetic theory of monochromatic waves bunching in a low-voltage beam discharge in rare gases

The kinetic theory of phase focusing, that is bunching in a low-voltage beam discharge in rare gases (LVBD) during the propagation of longitudinal electrostatic oscillations at the Knudsen numbers of the order of unity have developed. The anomalous relaxation of the almost monoenergetic electron beam in momentum and energy is described for the case when this process cannot be explained by electron–atom collisions. The paper has shown the important role of electrons that have the beam energy and isotropic directional distribution, which is formed as a result of elastic collisions between the beam electrons and atoms. The dependence of the anomalous relaxation length on parameters of the LVBD in rare gases is studied.The developed theory makes it possible to quantitatively interpret experimental data on the LVBD under conditions when the electron mean free path is of the order of the interelectrode gap. According to these data, regardless of the density of the charged particles in the LVBD plasma in rare gases, five Langmuir plasma wavelengths fit along the length of the anomalous relaxation of the electron beam. The study of the electron beam dynamics laws in a plasma is important for the development of plasma-electrical devices, where the beam discharge is applied, namely: widely used all-movable stabilizers, sources of intense electromagnetic radiation, controlled elements of electronic circuits, plasma chemical reactors, etc.     

Metastable states of dust plasma

The free energy of three-component dust plasma has been calculated analytically based on the spherical model of an elementary electroneutral volume. It has been shown that metastable states of dust particles, ions, and simultaneously all plasma particles can exist for finite interparticle distances. These states can be attained due to spatial correlation of electrons, while some states can be attained due to the correlation of ions. A large charge of dust particles, high electron temperature, and a small fraction of the charge of the electrons compared to the total absolute charge of the plasma particles are important conditions for the existence of metastable states. A possible connection between the existence of metastable states of particles in the plasma and their agglomeration has been analyzed.     

The effect of zero Langmuir oscillations of an electromagnetic field on the transverse dielectric permittivity of a degenerate electron–ion plasma

It is shown theoretically that the electromagnetic background of longitudinal zero oscillations of a temperature-degenerate electron–ion plasma in a thermodynamic equilibrium state resonantly distorts the wave functions of its electrons. This gives rise to a characteristic quantum frequency that nonanalytically depends on Planck’s constant ?. Vacuum phenomena in plasma attributed to zero oscillations turn out to be anomalously large. Quantum corrections to the transverse dielectric permittivity of a degenerate electron–ion plasma, which are nonanalytic with respect to ? and are attributed to the zero-point oscillations of the plasma, are determined.     

Free energy of nonideal two-component thermal plasma

The free energy of nonideal two-component thermal plasma is calculated using the Poisson-Boltzmann equation. The possibility of the existence of a metastable state is shown for a component of heavy multicharged particles with particle charge values bounded from below and plasma temperature values bounded from above. The component of oppositely-charged light singly-charged particles and plasma generally do not feature the metastable state.     

Metal particle polarization

The effect of electron collisions with lattice atoms in metals on metal particle polarization in an ac electric field was analyzed. It was shown that, in contrast to collisionless (free) electron gas, an increase in the negative electronic permittivity with decreasing electric field frequency in relaxation metal particles is limited by the conductivity relaxation time. It was shown that the plasma frequency appears in relaxation metal only if the dielectric relaxation time is less than the free path time in metal.     

Regular and chaotic dynamics of the dipole moment of square dipole arrays

Dipole lattices, which represent square dipole arrays, are investigated. Various types of equilibrium configurations of arrays are obtained, and conditions are shown under which these configurations are established. On the basis of parametric bifurcation diagrams, the main types of regular and chaotic oscillation regimes of the total dipole moment of a system are considered and their dependence on the amplitude, frequency, and polarization of an alternating field, as well as on the initial equilibrium configuration of arrays, is analyzed. Scenarios of the onset of chaotic regimes are demonstrated, including those that occur via the establishment and variation of quasiperiodic oscillations of the dipole moment of a system. The dynamic bistability state is revealed in which a stochastic resonance—an increase in the response of a system to a harmonic signal in the presence of noise—can be implemented.     

Radiation from an oscillating point dipole from a photonic crystal layer of dielectric nanocolumns

The radiation pattern and intensity of the electromagnetic radiation from a point dipole source (e.g., a semiconductor quantum dot) located inside a photonic crystal layer consisting of a periodically ordered array of dielectric nanocolumns have been calculated. It has been shown that the main features of radiation can be explained considering a simple model of the interaction of the dipole with Fabry-Perrot resonances of eigenmodes of the photonic crystal layer. The total power of radiation and radiation pattern strongly depend on the position of the dipole, orientation of its dipole moment, and frequency of oscillations.     

Instability Parameters of Optical Oscillation Frequency in Plasma Central Discharge and Periphery Region

We have observed relaxation oscillations in a capacitive discharge in Ar gas, connected to a peripheral ground chamber. The plasma oscillations observed from time-varying optical emission from the main discharge chamber show, for example, a high frequency （75.37kHz） relaxation oscillation, at lOOmTorr and 8 W absorbed power, and a low frequency （2.72Hz） relaxation oscillation, lOO mTorr and 325 W absorbed power. Time-varying optical emission intensity and plasma density are also detected with a Langmuir probe. The theoretical result agrees well with experiments.     

Radiative quenching and excitation of metastable states upon differential scattering of atoms: II. The He(1<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>–2<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>)-Ne molecule

The differential cross sections of radiative-collisional quenching (absorption) of a metastable state of a colliding atom are calculated for the first time. As a particular example, the reaction of quenching (excitation) of the metastable state He(2¹S) in collisions with Ne atoms in the ground state is considered. The calculations are performed for the thermal collisional energy E = 10^?3 au for a wide range of radiation frequencies, including both wings and the center of the line of a forbidden atomic transition, and are based on the uniform quasi-classical approximation, which generalizes the Franck-Condon approximation to the case of an exponential dependence of the transition dipole moment on the internuclear distance, as well as to the case of nonintersecting terms. The calculated differential cross sections have an oscillating structure, which, for the blue wing of the forbidden spectral line, is interpreted as Stückelberg oscillations. At a radiation frequency close to the frequency of the forbidden atomic transition, a sharp maximum in the differential cross section—the giant glory effect—is observed in the range of small scattering angles. This effect is shown to occur as a result of superimposition of the rainbowlike feature of the differential cross section on the glory feature.     

Effect of ion mean free path length on plasma polarization behind a dust particle in an external electric field

In this paper, a self‐consistent numerical model that describes the behavior of plasma around an isolated, highly charged dust particle is presented. Using the developed model, self‐consistent distributions of the space charge density and plasma potential in the presence of an external electric field are obtained. These distributions are thoroughly analysed though Legendre decomposition. For different dust plasma parameters, such as the radius of the dust particle, the amplitude of the external field, and the mean free path of ions, the dipole moment of the ion cloud surrounding the dust particle is calculated. It turns out that the dependencies of the dipole moment on the value of the external electric field obtained for different parameters are reduced to a single curve by simple scaling.     

Evaluation of the dipole interaction of a pair of metal particles in the region of the plasmon resonance

We consider the electric field of an induced dipole moment of a single small particle characterized by the absence of frequency dispersion of the permittivity and the field of a metal particle, which has frequency dispersion and is described in the free electron approximation taking into account the size effects of restriction of the electron free path. The influence of the induced field on the optical properties of a system of small particles is analyzed. It is shown that, for an ensemble of particles without frequency dispersion, the effective medium theory can be used up to concentrations corresponding to filling factors ? ≤ 0.52. In the case of metal particles, with frequency dispersion of dielectric functions and, especially, for the frequency range of the plasmon resonance, this theory can be used only for concentrations not exceeding the threshold ? ≈ 0.01.     

Stability of a quasineutral beam of negative ions

The stability of a beam of negative ions propagating in the parent gas is investigated. It is shown that growth of plasma oscillations with a small growth rate is possible at subcritical currents in a quasineutral regime. The influence of traveling secondary electrons, whose density is small, is also studied. The low-frequency oscillations considered pose the greatest danger to a beam whose velocity is close to the velocity of the secondary electrons. Zh. Tekh. Fiz. 68, 96–98 (September 1998)