Dust acoustic wave oscillations in C60 molecule

In this letter, dispersion properties of low-frequency electrostatic waves in a C₆₀ molecule are investigated. It is assumed that C₆₀ molecule is charged due to the field emission, and hence the C₆₀ molecule can be regarded as charged dust spheres surrounded by degenerate electrons and ions. We obtain the dispersion relation for the low-frequency electrostatic oscillations in the C₆₀ molecule by using the quantum hydrodynamic model in conjunction with the Poisson equation.     

Recent results on multiple ionization and fragmentation of negatively charged fullerene ions by electron impact

Employing the dynamic crossed-beams technique, the absolute cross sections of the electron-impact multiple ionization and fragmentation of mass-selected negatively charged fullerene ions C _m ^? → C _m?n ²⁺ (m=60, 70, 84; q=1, 2, 3; n=0, 2, 4) were measured. The electron energy varied from the respective threshold up to 1 keV. A scaling law was observed for the cross-section magnitude as a function of the fullerene size m and the charge state q of product ions. The data indicate that different mechanisms account for the detachment of an extra electron from the negatively charged fullerene and the formation of a positively charged ion, respectively. Moreover, the multiple ionization of a fullerene anion is found to be a sequential process. A novel ionization mechanism is proposed which might be expected to be valid for all negatively charged molecular or cluster ions able to shield the attached electron from the incident electron.     

pp Interactions at 303 GeV/c: Production angle distribution

We have measured the projected production angles of all charged particles in more than 1600 pp interactions at 303 GeV/c. We have obtained semi-inclusive distributions of pseudo-rapidity and dispersion of pseudo-rapidity event-by-event. The mean dispersion is found to be approximately constant for charged multiplicity, n_ch, from 6 to 16.     

Ab initio calculations of endo-and exohedral C60 fullerene complexes with Li+ ion and the endohedral C60 fullerene complex with Li2 dimer

The results of ab initio Hartree-Fock calculations of endo-and exohedral C₆₀ fullerene complexes with the Li⁺ ion and Li₂ dimer are presented. The coordination of the Li⁺ ion and the Li₂ dimer in the endohedral complexes and the coordination of Li⁺ ion in the exohedral complex of C₆₀ fullerene are determined by the geometry optimization using the 3–21G basis set. In the endohedral Li⁺C₆₀ complex, the Li⁺ ion is displaced from the center of the C₆₀ cage to the centers of carbon hexa-and pentagons by 0.12 nm. In the Li₂ dimer encapsulated inside the C₆₀ cage, the distance between the lithium atoms is 0.02 nm longer than that in the free molecule. The calculated total and partial one-electron densities of states of C₆₀ fullerene are in good agreement with the experimental photoelectron and X-ray emission spectra. Analysis of one-electron density of states of the endohedral Li⁺@C₆₀ complex indicates an ionic bonding between the Li atoms and the C₆₀ fullerene. In the Li⁺C₆₀ and Li⁺@C₆₀ complexes, there is a strong electrostatic interaction between the Li⁺ ion and the fullerene.     

Nanoemitter of giga- and terahertz ranges based on a carbon peapod: Numerical simulation

A mathematical model of a nanoemitter for the giga- and terahertz ranges based on a carbon nanopeapod formed by a (10, 10) nanotube with encapsulated C₆₀ fullerenes has been proposed. The fundamental possibility of the generation of giga- and terahertz radiation by a charged free fullerene oscillating in the potential well created by the atomic framework of the nanotube and several fullerenes polymerized with its walls and with each other has been proven. The radiation frequency is controlled by means of an external electric field. The dependence of the amplitude and frequency of oscillations on the charge of C₆₀ and on the external field strength has been revealed by the molecular dynamics method. If the fullerene has a charge of +1e or +2e, it emits electromagnetic waves only in the gigahertz range in strong external fields. At the same time, the physical conditions under which the frequency of radiation can be 0.36 GHz have been established: the charge of the fullerene must be +3e, the tube should be oriented strictly along the external field lines, and the strength should be 0.1 V/nm.     

Electrodynamics and dispersion properties of a magnetoplasma containing elongated and rotating dust grains

The electrodynamics and dispersion properties of a magnetized dusty plasma containing elongated and rotating charged dust grains are examined. Starting from an appropriate Lagrangian for dust grains, a kinetic equation for the dust grain and the corresponding equations of motion are derived. Expressions for the dust charge and dust current densities are obtained with the finite size (the dipole moment) of elongated and rotating dust grains taken into account. These charge and current densities are combined with the Maxwell-Vlasov system of equations to derive dispersion relations for the electromagnetic and electrostatic waves in a dusty magnetoplasma. The dispersion relations are analyzed to demonstrate that the dust grain rotation introduces new classes of instabilities involving various low-frequency waves in a dusty magnetoplasma. Examples of various unstable low-frequency waves include the electron whistler, the dust whistler, dust cyclotron waves, AlfvÉn waves, electromagnetic ion-cyclotron waves, as well as lower-hybrid, electrostatic ion cyclotron, modified dust ion-acoustic waves, etc. Also found is a new type of unstable waves whose frequency is close to the dust grain rotation frequency. The present results should be useful in understanding the properties of low-frequency waves in cosmic and laboratory plasmas that are embedded in an external magnetic field and contain elongated and rotating charged dust grains.     

Dispersion relation of dust acoustic waves in metallic multi-walled carbon nanotubes

In this paper,a charged multi-walled carbon nanotube(MWCNT),which is surrounded by charged nanoparticles,is modeled as a cylindrical shell of electron-ion-dust plasma.By employing classical electrodynamics formulations and the linearized hydrodynamic model,the dispersion relation of the dust acoustic wave oscillations in the composed system is investigated.We obtain a new low-frequency electrostatic excitation in the MWCNT,i.e.dust acoustic wave oscillations.     

Functionalization of pentagon–pentagon edges of fullerenes by cyclic polysulfides: A DFT study

We have performed a computational study to investigate the cyclosulfurization of the pentagon–pentagon (p–p) junctions in the non-IPR fullerenes C₆₀(D₃) and C₇₀(C_2v), and also Stone-Wales defective C₆₀ fullerene. Our results indicate the exothermic character of cyclosulfurization processes which can be related to the increase of pyramidalization angle (spherical excesses) and p characters of natural hybrid orbitals of C atoms at the p–p junctions. In fact these lead to the structural strain relief and stability of the cyclosulfurization derivatives of the non-IPR fullerenes. Moreover, the cyclosulfurization reaction of p–p bonds on the C₇₀(C_2v) is more energetically favorable than that of C₆₀(D₃), due to the higher curvature of carbon sites and the larger values of the p characters of natural hybrid orbitals in the C₇₀(C_2v). On the other hand, localization of the excess electrons on the C atoms at the p–p junctions leads to the low tendency of the charged non-IPR fullerenes to cyclosulfurization process. The desulfurization pathway of the exohedral derivatives of C₇₀(C_2v) indicates that it is energetically unfavorable for the functionalized fullerenes to break into individual fullerene and sulfur molecules. HOMO–LUMO gaps almost are independent of the number of pentathiepin rings while sensitive to the type of parent fullerene.     

Propagation and conversion of non-axisymmetric modes in non-uniform helicon-sustained plasma

An effect of the radial plasma density gradient on the oblique wave propagation in the helicon-frequency range is investigated. It is shown that the dispersion features of electrostatic and electromagnetic modes are essentially changed in strongly non-uniform helicon plasma. In particular, the transition between helicon eigenmode frequency scales ω ～ k _z and ω ～ k _z ² is demonstrated. The process of total conversion of long-wavelength helicon mode into short-wavelength electrostatic wave in near-axis region of a plasma column is analysed. Due to modification of the wave dispersion relations, the densities at which the mode conversion occurs are considerably reduced if the density gradient is steep enough. The estimation of collisionless axial damping rate of helicon mode connected with linear mode conversion is presented. This damping is compared with the usual collision damping.     

Isospin conservation and “poisson-like” multiplicity distributions

Data on charged particle multiplicities and on the production of neutral particles are used to calculate a lower bound on the dispersion of the distribution of the total number of particles in the final state of hadron-hadron collisions. It is shown that this bound is an approximately linear function of 〈n_ch〉, the mean of the number n_ch of charged particles in the final state. It is argued that this rules out the possibility that the production of particles can be described by a single “Poisson-like” mechanism, no matter what isospin conserving hypothesis is used. It is also argued that such models will inevitably fail to reproduce the available data on the mean number of neutrals produced when n_ch is known.     

Formation of doubly charged negative ions under the conditions of the resonant electron capture by fluorofullerenes

Doubly charged negative ions formed when electrons with controlled energies interact with isolated fluorinated fullerene molecules C₆₀F _n (n = 36, 48) have been detected and investigated by resonant electron capture mass spectrometry. The dependence of the intensity of the formation of doubly charged negative ions of fluorofullerenes on the energy of attached electrons has been measured. An original method, which is based on the experimental data and does not require additional calibration quantities, has been developed for estimating the absolute cross section for the formation of doubly charged negative ions. The absolute cross sections for the formation of the most intensely formed ions C₆₀F ₃₆ ^2? and C₆₀F ₄₈ ^2? are estimated to be about 1.1 × 10^?24 and 1.5 × 10^?24 m² at their maximum-yield energies of 2.0 and 1.6 eV, respectively.     

Electrostatic proximity force,toner adhesion,and a new electrophotographic development system

It has recently been shown that the electrostatic adhesion of a discrete distribution of charge points that are uniformly distributed around a sphere in contact with a conductive plane is larger than the conventional result, (1/4πε₀)(Q²/4r²), by (1+4/π), where Q is the total charge and r is the radius of the spherical particle. This new electrostatic force, the 4/π term, is due to discrete nature of charge and is called the electrostatic proximity force. This electrostatic proximity force is active at every contact point between a real, charged insulating particle and a conductive plane. By minimizing the number of contact points, the adhesion of electrophotographic toner particles to a conductive surface has been reduced by at least a factor of 10 compared to commercially available toners, allowing the viability of a new electrophotographic development system: a dc-jump, non-magnetic, monocomponent development system.     

Largeurs des raies spectrales de CO autoperturbe et perturbe par N2, O2, H2, HCI,NO et CO2

Linewidths of CO self-broadening and broadened by N₂, O₂, H₂, HCI, NO, and CO₂ have been calculated using different contributions in the intermolecular dispersion potential.The quadrupole moment of some perturbers has been determined by comparison between calculated and observed linewidths. The values obtained for the quadrupole moments may depend on the dispersion potential, especially when it is low (as is the case for N₂, O₂ and H₂). For CO-CO and CO-NO, the electrostatic interactions including the octupole moment yield good results for the linewidths for high |m|-values.     

Lower bound in energy for chaotic dynamics of ions

When a charged particle is acted upon by an electrostatic wave propagating across a uniform magnetic field, its dynamics is chaotic provided that its initial Larmor radius is larger than a threshold value ϱ_m. We analytically compute ϱ_m when the wave frequency is an integer multiple of the particle cyclotron frequency, and show that ϱ_m increases with the wave amplitude. This leads to the counter-intuitive result that the dynamics of a low energy particle can be made stochastic by decreasing the amplitude of the wave.     

Activation of fullerene coatings on field emitters by potassium atom and ion fluxes

The activation of tip field emitters with a fullerene coating by the atomic and ionic fluxes of potassium is studied. The deposition of atomic potassium decreases characteristic voltage U ₁ generating fixed fieldemission current I by a factor of 3.5–4.0. However, field emitters activated by potassium atoms are rapidly deactivated and the resulting decrease in U ₁ after storage in a vacuum does not exceed 25–30%. A stable approximately twofold decrease in the characteristic voltage can be reached if the fullerene coating is exposed to a potassium ion flux. The enhanced efficiency of emitter activation by a potassium ion flux is explained by the formation of KC ₆₀ endohedral and/or C₆₀ K exohedral molecules in the fullerene coating.     

Oscillating two-stream instability of beat waves in a hot magnetized plasma

It is shown that an electrostatic electron plasma beat wave is efficiently unstable for a low-frequency and short-wave-length purely growing perturbation (ω, k), i.e. an oscillating two-stream instability in a transversely magnetized hot plasma. The nonlinear response of electrons and ions with strong finite Larmor radius effects has been obtained by solving the Vlasov equation expressed in the guiding-center coordinates. The effect of ion dynamics has been found to play a vital role around ω ∼ ω_ci, where ω_ci is the ion-cyclotron frequency. For typical plasma parameters, it is found that the maximum growth rate of the instability is about two orders higher when ion motion is taken into account in addition to the electron dynamics.     

Intermolecular interactions in the liquid crystal-fullerene C70 system

The formation of complexes in the fullerene C₇₀-toluene-liquid crystal system is investigated. The precision study of spectral manifestations of the intermolecular interaction in this system is performed for two low-frequency absorption bands of C₇₀. These manifestations are found to be specific for each of the bands analyzed.     

A new construction technique for exact axially symmetric static electrovac solutions of the Einstein-Maxwell equations

Coordinates adapted to the full electrostatic symmetries of a charged axially symmetric static system are constructed and applied to the coupled Einstein-Maxwell equations. A new solution is presented and the framework for general solutions is developed. The Weyl solutions g₀₀(Φ) are readily extracted from the formalism.     

Influence of superalkali oxides on structural,electrical and optical properties of C24 fullerene nanocluster: A theoretical study

The influence of superalkali oxides on structural, electrical and the optical properties of 6-5 isomer of C₂₄ fullerene nanocluster was investigate using DFT calculations. It was shown that the structure of fullerene was drastically affected by adsorption of M₃O on its surface and as a result of all bonding lengths, was subsequently changed. DOS results showed that the E_g of C₂₄ in presence of M₃O (M=Li, Na, K) was fairly changed so that the electronic properties and electrical conductance of C₂₄ were not affected by M₃O adsorption. Based on the results of NBO calculations, specifically on MEP surfaces and HOMO-LUMO distribution, the charge was transferred from M₃O to C₂₄ fullerene; therefore, the M₃O is the positive head of complexes and in an electric field it is oriented toward the negative pole. The calculated polarisability(α) and the first hyperpolarisability(β₀) values indicated that the adsorption of M₃O on exterior surface of C₂₄ fullerene has had a drastic effect on the optical response of C₂₄ fullerene and caused a large increase in α and β₀ values. TD-DFT calculations were also carried out in order to confirm the β₀ values. This work theoretically devises novel C₂₄-based nanostructures via interaction with Superalkali Oxides in order to promote, their potential applications in electronic devices and high-performance NLO materials.     

Investigation of the possibility of functionalization of C20 fullerene by benzene via Diels–Alder reaction

C₂₀ fullerene, this novel species with all its pentagonal faces has displayed some unique operations in making fast pericyclic reactions. As an example, the high dienophile character of the C₂₀ fullerene and the ability of this species in making an ultra-fast Diels–Alder reaction with 1,3-butadiene, has been recently reported. Moreover, new experimental reports claim that the C₆₀ fullerene, one of the fullerene family, could make a Diels–Alder reaction with the central ring of anthracene and make the ring non-aromatic. These reports may encourage researchers to do more studies on the properties of this small carbon cage.To address this question, the present research has discussed all the reaction channels of the Diels–Alder cycloaddition of benzene molecule as a 1,3-diene with the C₂₀ fullerene in order to answer this question: “Is C₂₀ fullerene able to make a Diels–Alder reaction with this molecule?”.