acta physica slovaca

Abstract: The glow region of a argon-oxygen mixture rf asymmetrically capacitively coupled plasma was studied using a self-compensated Langmuir probe. Optical emission spectroscopy has been used to obtain information about different plasma parameters as well as the processes which take place in plasma in the range of the studied pressures and powers.

Abstract: Concentric and non-concentric multiple double layers were investigated in a double plasma machine, under various experimental conditions. The obtained results prove that a common mechanism is at the origin of the appearance and dynamics of both types of multiple double layers. In this mechanism, electron-neutral impact excitations and ionizations play an important role.

Abstract: We present a free software for modeling the electron dynamics in the uniform electric field named Web-EEDF. It uses a Monte Carlo algorithm to calculate electron energy distribution functions (EEDFs) and other plasma parameters in various gas mixtures. Obtained results are in good agreement with literature. This software represents the first stage in a more complex modeling of plasma chemical processes leading to the decomposition of various air pollutants in electrical discharges at atmospheric pressure.

Abstract: The paper is focused on investigation and comparison of two chemical processes occurring in water solutions treated by DC diaphragm discharge - hydrogen peroxide generation and degradation of organic compounds dissolved in water. Concentration of hydrogen peroxide produced by the discharge depends on the discharge conditions (polarity and magnitude of the applied voltage etc.) and it is determined by photometry using a specific titanium reagent. Organic dyes in solid phase and dissolved in water are chosen as model compounds for the degradation processes. Their concentration is determined by photometry, too.

Abstract: The study reports the plasma density measurement employing simple ion probes. Ion flux probes are used to determine if the extraction process of an electron beam is source limited in a cold cathode e-beam source. The probes indicate the approximate order in the magnitude of plasma density. However, in spite of this indication, there is  a variation of the measured plasma density from a shot-to-shot. The simple ion probes offer a quick evaluation of the plasma gun when a plasma density in the order of 10^13 cm^- 3 at the anode-cathode gap region is anticipated. The velocities of plasma maxima were found to be approximately 1.4 to 5 cm/ms.

Abstract: The study of dissociative electron attachment (DEA) to CCl3Br molecule has been performed in the electron energy range from 0 to about 2 eV and in the gas temperature range from 293 K to 478 K using a crossed electron-molecular beams apparatus with a temperature regulated, effusive molecular beam  source. Strong enhancement of the negative ion production with the gas temperature has been observed for the overall negative ion yield and for Cl-CCl3Br reaction channel at low electron energies (~0 eV). Activation energies for dissociative electron attachment of (123 +- 20) meV and (65 +- 20) meV have been estimated for the overall negative ion formation and for the Cl- reaction channel. The DEA cross section for Br-CCl3Br reaction channel was at low electron energies temperature independent.  At the 0.6 eV (Br- CCl3Br) and 0.65 eV (Cl-CCl3Br) resonances the cross-sections were temperature independent. At the elevated gas temperatures above 422 K, strong decrease of the negative ion yield has been observed for DEA CCl3Br assigned to the catalytic thermal decomposition of molecules on the iron surface of the molecular beam source.

Abstract: We calculate the total energy (the matter plus fields) of the universe considering Bergmann-Thomson's energy-momentum formulation in both Einstein's theory of general relativity and tele-parallel gravity on two different space-times; namely Reboucas-Tiomno-Korotkii-Obukhov and the Godel-type metrics. We also compute some kinematical quantities for these space-times and find that these space-times have shear-free expansion and non-vanishing four-acceleration and vorticity. Different approximations of the Bergmann-Thomson energy-momentum formulation in these different gravitation theories give the same energy density and agree with each other. The results advocate the importance of energy-momentum definitions.

Abstract: We study gravitational lensing by quadrupole potentials within the linearized gravity approximation  and the integration over the unperturbed photon trajectory. It is well known that the quadrupole potential contribution to the deviation angle is much smaller than that of the monopole one. We show that quadrupole potentials can change the photon polarization vector, but there is no contribution from the monopole term to the first order. The effect is maximal when the axis of the quadrupole is tangential to the photon trajectory and it is proportional to the frequency (rate) of the quadrupole moment of the deflector. The second order correction of the monopole potential to the polarization is canceled away by the renormalization of the polarization vector.

Abstract: Experiments have been carried out to further characterize the magnetically confined hollow cathode duoplasmatron. The plasma column constricted by magnetic field between intermediate electrode and anode is investigated by the Langmuir probe and optical emission spectroscopy. The electron temperature, electron and ion density and  plasma potential were measured as a function of source discharge current and argon pressure. In the discharge current range of 25--150~mA used in this expriment, electron temperature increased with an increase in discharge current and also with the reduction in argon pressure. The electron density showed an order of magnitude increase in this discharge current range for fixed gas pressure. The electron temperatures measured by both methods are reasonably consistent. Thereby indicating the usefulness of emission spectroscopy as a simple and reliable technique to measure electron temperature without disturbing the plasma.

Abstract: The paper is purposed to elaborate the problem of gravitational energy localization in de Sitter(dS) C-space-time (the C space-time in a background with a cosmological constant Lambda. In this connection, using the energy-momentum definition of Einstein, we find the same energy in both general relativity and tele-parallel gravity.

Abstract: We present longitudinal emission diagnostics of the plasma channel in the special design of the plasma pencil - rf barrier torch discharge. This configuration has been developed  for deposition of thin films on various surfaces. Using optical emission spectroscopy the spectroscopic quantities were determined as well as the longitudinal distribution of rotational temperature in the plasma channel is presented.

Abstract: Low-density polyethylene (LDPE) and isotactic polypropylene (PP) and their blends with compositions 90/10, 70/30, 50/50, 30/70 and 10/90 weight per~cent were studied by means of mechanical and nuclear magnetic resonance (NMR) methods. The three types of tapes were prepared: undrawn, drawn up to complete neck development and ultimately drawn up to break. The macroscopic properties characterized by tensile modulus, ultimate strength and drawability as well as phase structure and macromolecular orientation were studied by these methods. It was found out that properties of studied materials vary with composition and with degree of drawing. Quantitative relations were found out between macroscopic properties obtained from mechanical measurement and parameters characterizing phase structure and macromolecular orientation obtained from NMR measurements.