On the absence of charge symmetry in electrostatic interaction between charged drops and hard particles

It is shown that the analytical expressions for the energy and force of electrostatic interaction between charged conducting particles (drops), a point charge, and a finite-size particle, as well as between a particle (a drop or a point charge) and a conducting plane, are asymmetric with respect to the sign of one of the charges. This is because the polarization interaction is always attractive irrespective of the signs of interacting particles. The absence of this symmetry leads to the self-constriction of charged aerodispersed systems containing a condensed phase, for example, plasma or liquid-droplet systems.     

Kinetic arrest in polyion-induced inhomogeneously charged colloidal particle aggregation

Polymer chains adsorbed onto oppositely charged colloidal particles can significantly modify the particle-particle interactions. For sufficient amounts of added polymers, the original electrostatic repulsion can even turn into an effective attraction and relatively large aggregates can form. The attractive interaction contribution between two particles arises from the correlated adsorption of polyions at the oppositely charged particle surfaces, resulting in a non-homogeneous surface charge distribution. Here, we investigate the aggregation kinetics of polyion-induced colloidal complexes through Monte Carlo simulation, in which the effect of charge anisotropy is taken into account by a DLVO-like inter-particle potential, as recentely proposed by Velegol and Thwar (Langmuir 17, 7687 (2001)). The results reveal that the aggregation process slows down due to the progressive increase of the potential barrier height upon clustering. Within this framework, the experimentally observed cluster phases in polyelectrolyte-liposome solutions can be interpreted as a kinetic arrested state.     

Electric-field induced capillary interaction of charged particles at a polar interface

We study the electric-field induced capillary interaction of charged particles at a polar interface. The algebraic tail of the electrostatic pressure of each charge results in a deformation of the interface u approximately r(-4), where r is the lateral distance. The capillary interaction of nearby particles is repulsive and varies as rho(-6) with their distance rho. As a consequence, electric-field induced capillary forces cannot be at the origin of the secondary minimum observed recently for charged poly(methyl methacrylate) particles at an oil-water interface.     

On the boson-fermion model of superconductivity

Summary The existence of pair excitations in a Fermi gas interacting via a short-range attractive potential is investigated. Within the ladder approximation to the Bethe-Salpeter equation for the effective two-particle interaction, evidence of pair excitation is found at energies slightly larger than the chemical potential. The link between those excitations and a boson-fermion model of superconductivity (Phys. Lett. A,196 (1995) 359) is discussed. In particular it is shown that the charge carrier density dependence of the pair excitation (boson) energy, assumed phenomenologically in the boson-fermion model, is consistent with the properties of the interacting Fermi gas studied. These results give support to the microscopic origin of the phenomenological boson-fermion model of superconductivity. Within the polaron-bipolaron theory the assumption that bosons and fermions can be described as mobile particles has found support in ref.[6] where the small bipolaron (boson) delocalization is discussed and in ref.[7] where the large polaron delocalization is analysed.     

Colloidal interactions and transport in nematic liquid crystals

We describe a new nematic liquid-crystal colloid system which is characterized by both charge stabilization of the particles and an interaction force. We estimate the effective charge of the particles by electrophoretic measurements and find that in such systems the director anchoring energy W is very low and the particles have little director distortion around them. The interaction force is created by producing a radial distribution of the nematic order parameter around a locally isotropic region created by ir laser heating. We theoretically describe this as being due to the induced flexoelectric polarization, the quadrupolar symmetry of which provides the required long-range force acting on charged particles.     

Classical Electromagnetic Interaction of a Point Charge and a Magnetic Moment: Considerations Related to the Aharonov–Bohm Phase Shift

A fundamentally new understanding of the classical electromagnetic interaction of a point charge and a magnetic dipole moment through order v ² /c ² is suggested. This relativistic analysis connects together hidden momentum in magnets, Solem's strange polarization of the classical hydrogen atom, and the Aharonov–Bohm phase shift. First we review the predictions following from the traditional particle-on-a-frictionless-rigid-ring model for a magnetic moment. This model, which is not relativistic to order v ² /c ² , does reveal a connection between the electric field of the point charge and hidden momentum in the magnetic moment; however, the electric field back at the point charge due to the Faraday-induced changing magnetic moment is of order 1/c ⁴ and hence is negligible in a 1/c ² analysis. Next we use a relativistic magnetic moment model consisting of many superimposed classical hydrogen atoms (and anti-atoms) interacting through the Darwin Lagrangian with an external charge but not with each other. The analysis of Solem regarding the strange polarization of the classical hydrogen atom is seen to give a fundamentally different mechanism for the electric field of the passing charge to change the magnetic moment. The changing magnetic moment leads to an electric force back at the point charge which (i) is of order 1/c ² , (ii) depends upon the magnetic dipole moment, changing sign with the dipole moment, (iii) is odd in the charge q of the passing charge, and (iv) reverses sign for charges passing on opposite sides of the magnetic moment. Using the insight gained from this relativistic model and the analogy of a point charge outside a conductor, we suggest that a realistic multi-particle magnetic moment involves a changing magnetic moment which keeps the electromagnetic field momentum constant. This means also that the magnetic moment does not allow a significant shift in its internal center of energy. This criterion also implies that the Lorentz forces on the charged particle and on the point charge are equal and opposite and that the center of energy of each moves according to Newton's second law F=Ma where F is exactly the Lorentz force. Finally, we note that the results and suggestion given here are precisely what are needed to explain both the Aharonov–Bohm phase shift and the Aharonov–Casher phase shift as arising from classical electromagnetic forces. Such an explanation reinstates the traditional semiclassical connection between classical and quantum phenomena for magnetic moment systems.     

Investigation of electrostatic charge distribution within the reactor wall fouling and bulk regions of a gas–solid fluidized bed

The distribution of charge within the wall fouling region and bulk of a fluidized bed reactor was investigated. Experiments were conducted in a 0.1 m in diameter carbon steel fluidization column under atmospheric conditions. Polyethylene particles were fluidized with extra dry air at 1.5 the minimum fluidization velocity (bubbling flow regime) for 1 h. Using an online Faraday cup measurement technique, the net charge-to-mass ratio (q/m), as well as the size distribution of all particles adhered to the column wall and those in the bulk of the bed was determined. The wall particles were found to be predominantly negatively charged while those which did not adhere to the wall were predominantly positively charged. The charge distribution within each region was then investigated by a custom made charged particle separator that separated the particles according to their charge magnitude and polarity. It was determined that although the net charge of the wall layer particles was negative, a significant amount of positively charged particles existed within each sample and therefore the entire wall particle layer. This suggests that the wall layer was formed through layering between positively and negatively charged particles. Particles in the bulk of the bed also consisted of bipolarly charged particles.     

Interaction of a dielectric macroparticle with a point charge in plasma

The electrostatic interaction of a charged spherical dielectric macroparticle with a point charge in a plasma in the presence of an external uniform electric field is considered. The electrostatic force and the torque acting on the macroparticle have been determined, and the form of the interaction potential has been established for a nonuniform distribution of free charge on the macroparticle surface. A simple (for calculations) expression for the interaction potential that describes well the exact potential at all interparticle distances is proposed. The angular velocity of the spinning of dust particles caused by a nonuniform distribution of free charge over their surface has been estimated.     

Microscopic Origin of Universality in Casimir Forces

The microscopic mechanisms for universality of Casimir forces between macroscopic conductors are displayed in a model of classical charged fluids. The model consists of two slabs in empty space at distance d containing classical charged particles in thermal equilibrium (plasma, electrolyte). A direct computation of the average force per unit surface yields, at large distance, the usual form of the Casimir force in the classical limit (up to a factor 2 due to the fact that the model does not incorporate the magnetic part of the force). Universality originates from perfect screening sum rules obeyed by the microscopic charge correlations in conductors. If one of the slabs is replaced by a macroscopic dielectric medium, the result of Lifshitz theory for the force is retrieved. The techniques used are Mayer expansions and integral equations for charged fluids.     

Debye-Hückel theory for slab geometries

The electrostatic interaction of charged particles through or at a low-dielectric slab, such as a lipid bilayer immersed in water or a self-assembled monolayer (SAM) on a metal substrate, is considered theoretically in the presence of salt within the Gaussian approximation using a generalized Green's formalism. A number of separate situations are discussed: i) The presence of a low-dielectric slab leads to pronounced interactions of a single charge with the slab via the formation of polarization surface charges. For SAMs on metal substrates, there is an intricate crossover from image-charge attraction to the metal substrate (for large distances) to image-charge repulsion from the SAM (for small distances) with a stable minimum at a distance of roughly 20 times the thickness of the hydrophobic film. For bilayers in water, the interaction of a single charge is always repulsive. ii) The surface potential of a SAM is calculated for the case when the hydrophobic layer contains dipole moments, which might explain the recently observed long-ranged repulsion of hydrophobic scanning tips from PEG-terminated SAMs on gold. iii) The interaction between charged particles through the bilayer is weakened. Oppositely charged particles still attract each other through the membrane. The free-energy minimum occurs as a result of the competition between self-repulsion from the slab and interparticle attraction and is located at a separation from the membrane surface which equals 15 times the membrane thickness. iv) Surface charges on the two surfaces of a bilayer attract each other through the bilayer unless the surface charge densities are the same, even if the signs are the same. v) All these effects are strongly influenced by the presence of salt. Received 25 January 2000     

Equilibrium charge of small metal particles and hopping transport in a metal-insulator composite

It is shown that the thermodynamically equilibrium state of a system of small metal particles placed in a dielectric matrix are unavoidably charged. The charge of spherical metal particles with different radii is calculated at low temperatures. Hopping transport in a system of metal particles is studied. It is shown that it is limited by the charging energy, which serves as a typical hopping energy and can be gapless. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 8, 510–515 (25 October 1999)     

Electrostatic adhesion of ion and triboelectric-charged particles

The adhesion of ∼10 μm charged toner particles is of considerable importance in the electrophotographic process for copying or printing documents. If the non-electrostatic short-range adhesion force is reduced with nanoparticle surface additives, the toner adhesion is dominated by an electrostatic force. However, the measured adhesion of triboelectrically charged toner is greater than the prediction of an electrostatic image force model that assumes a uniform surface charge distribution. The enhanced electrostatic adhesion of triboelectrically charged toner is attributed to a non-uniform surface charge distribution. To provide support for this interpretation, the adhesion of ion-charged toner is of interest since a more uniform surface charge distribution is expected. Electric field detachment measurements on ion-charged toner for different charge levels show that the adhesion of ion-charged toner is indeed less than that of triboelectrically charged toner.     

Electrostatic energy of a disordered system of metallic granules

Electrostatic interaction energies in a disordered monodisperse system of metallic granules are calculated. The calculation is performed in the dipole approximation for particles that cannot be regarded as point charges. The dependences of the charging energies of the particles on the concentration of the metallic phase as well as the dependences of the interaction energy of the charged particles on the distances between them are obtained. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 100–105 (25 July 1999)     

Processes involving a change in the charge states during interactions of He2+ ions with fullerenes

The cross sections for the elementary processes involving a change of the charge states of both particles during the interaction of He²⁺ ions with fullerene molecules are for the first time measured over a broad energy range of electron-volt energies. It is found that processes involving the capture of one or two electrons by the He²⁺ ions are accompanied by additional ionization of the fullerene and that the collisional contribution of the transfer-ionization processes increases with increasing velocity. Single-electron capture is rarely accompanied by fragmentation of the fullerene. Double-electron capture leads, with a higher probability, to fragmentation with the formation of several light charged fragments and, with a smaller probability, to fragmentation with the formation of a heavy charged fragment containing an even number of carbon atoms and light fragments in an uncharged state. Zh. Tekh. Fiz. 68, 12–14 (April 1998)     

High Pressure as a Tool for Characterizing Charge Carriers in a Conducting Polymer

A characteristic feature of conducting polymers is the existence of localized charge carriers. The localization process is closely related to the charge carrier-phonon interaction, which is a function of local molecular properties of the polymer chain on which the carriers are localized. Depending on this interaction in conducting polymers with a non-degenerate ground state singly charged polarons or doubly charged bipolarons may exist. It will be shown that high pressure is a useful tool for studying charge carrier properties by influencing the local molecular conformation. A transition between both types of charge carriers is observed in polypyrrole.     

A model for the structure of point-like fermions: Qualitative features and physical description

A model for the structure of point-like fermions as tightly bound composite states is described. The model is based upon the premise that electromagnetism is the only fundamental interaction. The fundamental entity of the model is an object called the vorton. Vortons are semiclassical monopole configurations of electromagnetic charge and field, constructed to satisfy Maxwell's equations. Vortons carry topological charge and one unit each of two different kinds of angular momenta, and are placed in magnetically bound pair states having angular momentum l=1/2. The topological charge prevents the mutual annihilation of the vorton pair. The helicity eigenstates of the vortons' intrinsic angular momenta form the basis for a set of internal quantum numbers for the pair which distinguish the different (point-like) pair states. Sixteen fourcomponent spinor states, eight leptonic and eight hadronic, are obtained. Eleven of these are identified with the quantum numbers of the experimentally known particles: e, v_e, μ, v_μ, τ, v_τ; p, n, Λ, Λ_c, and b. Thus one new heavy lepton with its neutrino and three new quark states are predicted. Some possibilities for the extension of this model are discussed.     

Counter-Ions Between or at Asymmetrically Charged Walls: 2D Free-Fermion Point

This work contributes to the problem of determining effective interaction between asymmetrically (likely or oppositely) charged objects whose total charge is neutralized by mobile pointlike counter-ions of the same charge, the whole system being in thermal equilibrium. The problem is formulated in two spatial dimensions with logarithmic Coulomb interactions. The charged objects correspond to two parallel lines at distance \(d\) , with fixed line charge densities. Two versions of the model are considered: the standard “unconstrained” one with particles moving freely between the lines and the “constrained” one with particles confined to the lines. We solve exactly both systems at the free-fermion coupling and compare the results for the pressure (i.e. the force between the lines per unit length of one of the lines) with the mean-field Poisson-Boltzmann solution. For the unconstrained model, the large- \(d\) asymptotic behaviour of the free-fermion pressure differs from that predicted by the mean-field theory. For the constrained model, the asymptotic pressure coincides with the attractive van der Waals-Casimir fluctuational force. For both models, there are fundamental differences between the cases of likely-charged and oppositely-charged lines, the latter case corresponding at large distances \(d\) to a capacitor.     

Electrical properties of water drops inside the dropwise cluster

The Letter shows that inside a dropwise cluster formed over the heated water surface, water drops are electrically charged. The charge of a separate drop reaches 10³ units of an elementary charge. The drops are positioned from each other at the distance of double Debye radius length. It is fixed up that drops levitate over the water surface in consequence of the Stokes force acting from the side of gas-vapor flow rising from water surface. The Stokes force thousand times exceeds the Coulomb drop repulsion force from the water surface.     

Balance functions at RHIC

The balance function is based on the principle that charge is locally conserved when particles are pair produced. Balance functions have been measured for all charged pairs, identified pion pairs, and identified charged kaon pairs in Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV and p+p collisions at $\sqrt {s_{NN} } = 200$ GeV at the Relativistic Heavy Ion Collider using STAR. Balance functions for all charged particles from Au+Au scale smoothly with centrality to the p+p value. Balance functions for charged particles and pions are narrower in central collisions than in peripheral collisions consistent with trends predicted by models incorporating the concept of late hadronization. Balance functions for kaon pairs represent a strangeness balance. Balance functions for kaons are narrower than those for pion pairs and may show less dependence on centrality.     

Tunneling Radiation of the Charged Particles for Charged Spherical Black Hole in VGM

Applying Parikh’s semi-classical tunneling method, Hawking radiation of charged massive particles via tunneling from charged spherical black hole in vacuum for Vector Graviton Metric theory (VGM) of gravitation is investigated. Because the derivation respects conservation of energy and charge, the tunneling rate of particles is relevant to the change of Bekenstein-Hawking entropy and the exact spectrum is not precisely thermal. The result employs an underlying unitary theory. PACS numbers: 04.70.-s, 97.60. Lf