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The aim of this study was to develop a formula for estimating the effective radius of a diffusion-controlled irreversible contact reaction between diffusing solutes and a nonlinear immobile polymer molecule. Analytical expressions for the reaction radius were obtained that took into account averaging over conformations for chains with arbitrary segment-to-segment angles and distributions of dihedral angles. A comparison of the analytical results with the results of computer stochastic modeling of the reaction showed good agreement over a wide range of parameters. Based on an analysis of these expressions, parameter ranges were established in which it was possible to use either the linear chain or Gaussian coil approximation to describe the reaction kinetics. A comparison of several distributions over chain lengths showed that, as a first approximation, the radius of reaction can be estimated as that for a chain corresponding to the number-averaged molecular weight. Results of earlier experimental studies on charge scavenging by polymer molecules have been explained. [ABSTRACT FROM AUTHOR]

The article reveals the necessity and relevance of precise pulse pressure measurement in industry, power engineering, and transportation. The design, operating principle, and the result of the metrological studies of GET 43-2022 State Primary Standard for the unit of excess pressure within the static pressure range of 10–1600 MPa and the pulse pressure range of 1–1200 MPa and the effective area of piston-cylinder assemblies in deadweight testers within the range of 0.05–1 cm2 are presented. GET 43-2022 includes hydraulic and pneumatic systems, as well as an ultrahigh-pressure valve designed to compare systems used in GET 43-2022 that operate with different standard liquids within the range of 250–1200 MPa. The reproduction range of the pulse pressure unit in GET 43-2022 is 1–1200 MPa. The method for reproducing the pulse pressure unit in liquid and gas media using hydraulic and pneumatic systems is described. The metrological characteristics of GET 43-2022 are studied; the budget of measurement uncertainty in reproducing the pulse pressure unit is estimated. The obtained results help to meet the development needs of the pool of working standards for pulse pressure measuring instruments traceable to GET 43-2022. [ABSTRACT FROM AUTHOR]

To search for and elucidate the nature of radical cations arising in irradiated liquid ethylene carbonate (EC), the effect of the external magnetic field on the radiation-induced fluorescence of fluorophore solutions in EC has been studied. Using quantum-chemical calculations, it has been shown for the first time that primary EC radical cations are rapidly transformed into ion–molecular complexes containing, in addition to the initial radical cation, one or more solvent molecules. In the complexes, two particles are oriented to each other by carbonyl groups, on which almost all of the spin density is localized. This result shows that the prevailing concepts describing the primary stages of liquid carbonate radiolysis should be revised, and the possibility of the formation of such ion–molecular complexes should be taken into account when studying the oxidative decomposition of carbonates used in organic electrolytes. [ABSTRACT FROM AUTHOR]

Paramagnetic spin-lattice relaxation (SLR) in radical cations (RCs) of the cycloalkane series in liquid solution was studied and analyzed from the point of view of the correlation between the relaxation rate and the structure of the adiabatic potential energy surface (PES) of the RCs. SLR rates in the RCs formed in x-ray irradiated n-hexane solutions of the cycloalkanes studied were measured with the method of time-resolved magnetic field effect in the recombination fluorescence of spin-correlated radical ion pairs. Temperature and, for some cycloalkanes, magnetic field dependences of the relaxation rate were determined. It was found that the conventional Redfield theory of the paramagnetic relaxation as applied to the results on cyclohexane RC, gave a value of about 0.2 ps for the correlation time of the perturbation together with an unrealistically high value of 0.1 T in field units for the matrix element of the relaxation transition. The PES structure was obtained with the DFT quantum-chemical calculations. It was found that for all of the cycloalkanes RCs considered, including low symmetric alkyl-substituted ones, the adiabatic PESes were surfaces of pseudorotation due to avoided crossing. In the RCs studied, a correlation between the SLR rate and the calculated barrier height to the pseudorotation was revealed. For RCs with a higher relaxation rate, the apparent activation energies for the SLR were similar to the calculated heights of the barrier. To rationalize the data obtained it was assumed that the vibronic states degeneracy, which is specific for Jahn-Teller active cyclohexane RC, was approximately kept in the RCs of substituted cycloalkanes for the vibronic states with the energies above and close to the barrier height to the pseudorotation. It was proposed that the effective spin-lattice relaxation in a radical with nearly degenerate low-lying vibronic states originated from stochastic crossings of the vibronic levels that occur due to fluctuations of the interaction between the radical and the solvent. The magnitude of these fluctuations, ∼100 cm-1, determines the upper scale of the unperturbed splitting between the vibronic states, for which the manifestation of this paramagnetic relaxation mechanism could be expected. Our estimate for the relaxation rate derived using standard Landau-Zener model of nonadiabatic transitions at the level crossing agrees with the experimental data. This paramagnetic relaxation mechanism can also be operative in paramagnetic species of other types such as linear radicals, radicals with threefold degeneracy, paramagnetic centers in crystals, etc. It looks likely that the proposed SLR mechanism can be quenched by a fast vibrational relaxation in radicals. [ABSTRACT FROM AUTHOR]

Resolved hyperfine structure is observed for the first time in the OD EPR spectra of charge pairs recombining in a solid polymer matrix at room temperature. [ABSTRACT FROM AUTHOR]

The method of time-resolved magnetic field effect (TR MFE) in recombination fluorescence of spin-correlated radical ion pairs has been used to detect and identify radical cations generated at early stages after the pulse irradiation of polyethylene and tricosane. From analysis of TR MFE curves, the widths of unresolved EPR spectra of radical cations have been determined, and their g factors have been evaluated. The results have demonstrated that, as distinct from n-alkanes, primary radical cations in polyethylene are localized on chemical defects of the polymer chain in a time of about 1 ns or less. [ABSTRACT FROM AUTHOR]

The article focuses on a study which demonstrates the potentialities of the time-resolved magnetic field effect (TR MFE) method. It provides details about the radical anions of tetrafluorobenzene and pentafluoroaniline generated by X-ray irradiation of solutions. Information about the fluorescence intensity decay caused by recombination of radical ion pairs is presented.

The national primary standard GET 43-2013 for the units of pressure in the range of 10-1600 MPa and of the effective area of piston pairs in dead-weight pressure gauges in the range of 0.05-1 cm has been created to upgrade the national primary special standard GET 43-73 for the unit of pressure in the range of 250-1500 MPa. The unexcluded systematic error has been reduced by a factor of 10. [ABSTRACT FROM AUTHOR]

The article focuses on a study which uses the method of time-resolved magnetic field effect (TR-MFE) in recombination fluorescence of spin-correlated radical ion pairs to check the concepts available in the literature. It is reported that the analysis of fluorescence response of the irradiated solution of a luminophore in liquid tetrahydrofuran enabled gaining understanding of the positive charge carrier generated upon ionization of the solvent molecule.

This work examines the possibilityof using the fluorescence response of irradiated solutions of luminophoresand the effect of an external electric field on the fluorescence decayto determine the mobility of geminate radical ions when using aliphaticethers as the solvents. As an example, p-terphenylsolutions were studied in a series of ethers (diethyl, dibutyl, methyl tert-butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran,1,4-dioxane, eucalyptol, and 1,2-dimethoxyethane). Verification ofthe nature of the charge carriers in the irradiated solutions wasmade by means of the method of the time-resolved magnetic field effectin recombination fluorescence of spin-correlated radical ion pairs.It was found that at a p-terphenyl concentrationof about 10 mM, the observed fluorescent response from the solutions,in most cases, was due to the recombination of radical ions formedfrom the aromatic solute. The relative mobility of p-terphenyl radical ions in ethers was estimated by using a stochasticcomputer simulation of the radiation spur composed of 4 primary ionpairs. The ions’ mobility was found to be dependent on solventviscosity in accordance with Walden’s rule, with no noticeableeffect of solvent polarity. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the demonstration of spin statistical factor in the excess electron scavenging reaction with stable nitroxyl radicals. It says that the assessment of the kinetics of ion-molecular reactions was utilized to reveal the spin effects in the reaction. It adds that the spin effects in the reaction of excess electron scavenging are absent if the solvation with solvent molecules can stabilized the intermediate triplet state of the anion.

The article presents a study which examines whether the efficient spin-lattice relaxation in radical ions (RCs) is related to a multi-well structure of the adiabatic potential energy surface (PES) and a low barrier to pseudorotation. RCs of a series of alkylsubstituted cyclohexanes were compared with the experimental data on the relaxation rate of RCs as a function of temperature. Analysis showed that efficient relaxation in the RC arises when it moves along the pseudorotation coordinate.

Diffusion-controlled reaction of electron transfer from diphenylsilane radical anions to the series of α- and α,ω-bromoalkanes with alkane chain length up to 18 atoms has been studied in n-dodecane solutions. At room temperature, reaction rate constants have been determined and corresponding reaction radii have been evaluated. It has been shown that a not-too-long chain molecule, which contains two terminal reaction sites and participates in the diffusion-controlled reaction, may be considered as a rapidly rotating pair of reacting sinks with a distance between their centers equal to the mean-square end-to-end distance of the molecule. [ABSTRACT FROM AUTHOR]

Radical cations of Me3СSiMe3 and Me3СGeMe3 were detected in hexane solution using the method of time-resolved magnetic field effect. The structures and electronic distributions of neutral molecules Me3CEMe3 and their radical cations: Me3СEMe3·+ (E = C, Si, Ge, Sn) were investigated by DFT PBE/TZ2P calculations. The calculated and the experimental hyperfine coupling constants a(H) are in good agreement. The structures of Me3СSiMe3·+, Me3СGeMe3+·, and Me3СSnMe3+· are in essence a tight radical cation pairs of the type CMe3·/EMe3+. [Copyright &y& Elsevier]

The processes of the formation of excited states on the nanosecond timescale in irradiated alkane solutions of positive charge and energy acceptors were studied by means of computer simulation in the single-spur approximation as an the example. The model involved pairwise contact interactions between all transient species produced in the same spur with allowance for their spin state. The effects of external magnetic and electric fields on the kinetics of delayed fluorescence were calculated, depending on the spur size and the initial number of ion pairs in the spur. It was shown that energy transfer from excited solvent molecules to an acceptor and the annihilation of luminophore triplet molecules should be taken into consideration in the simulation of the kinetics of delayed fluorescence of irradiated solution even at a low average ionization density. [ABSTRACT FROM AUTHOR]

Results are presented from interferometric studies of a coaxial injector operating in the nonsteady arc-discharge mode. The discharge was initiated and stabilized by pulsed gas puffing into the interelectrode gap of the injector. The dynamics of the plasma bunch formation and the spatial characteristics of the bunch are investigated, and the density of the generated plasma is determined. [ABSTRACT FROM AUTHOR]

A unit for creating in the area of the analyzed sample a pulsed microwave field with a 2.45-GHz frequency, a 10-ns fall time, and a rotating component of the magnetic induction with a maximum amplitude of 0.8 mT is described. The fast pulse decay is obtained by creating a pulsation mode in the system consisting of two coupled resonators. The duration of the flat top of the microwave pulse is regulated from 0 to 400 ns, and the maximum pulse repetition rate is 16 kHz. The unit is used in the nanosecond X-ray fluorimeter to control the spin state of the spin-correlated ion-radical pairs in nonpolar solutions. [ABSTRACT FROM AUTHOR]

The article reports on the identification of radical cations (RCs) of branched alkenes in liquid solutions through the time-resolved magnetic field effect (TR MFE) technique. Findings showed that the lifespans of the RCs in solution at room temperature were tens of nanoseconds. It was also shown that the quantum-chemical computations and the outcomes of TR MFE curves simulation highlight the detection of the observed spin dynamics by hyperfine coupling (HFC) in the RCs of the alkenes.

The article presents a research study of degenerate electron exchange(DEE) reaction with n-Nonane(C9) radical present in a solution. The experiments showed that the rate constant of the DEE between the C9 radical cations and molecule is lower in magnitude by two orders than the diffusion-controlled limit. An important factor responsible for the decrease in the rate constant for n-alkanes as compared to cyclic alkanes is reported as the multitude of conformations of normal alkanes in solutions.

Examines the unusually fast paramagnetic relaxation of cyclohexane and adamantane radical cations. Use of the method of the time-resolved magnetic field effect in recombination fluorescence of spin-correlated radical ion pairs; Analysis of the kinetics of recombination fluorescence decay for solutions in hexane; Indication of cyclohexane and adamantane radical cations' short spin-lattice relaxation times.

The states of supported vanadium and the nature of activation of ammonia adsorbed on vanadium sites of VОx/TiО2 catalysts are studied by 51V NMR spectroscopy and diffuse-reflectance IR Fourier-transform (DRIFT) spectroscopy using cluster quantum chemical calculations of NН3 adsorption. We employ the VОx/TiО2 catalyst of two types: the monolayer catalyst in which vanadium is located on the surface of well-crystallized anatase and the catalyst in which vanadium embedded in the anatase lattice at a rather great depth. It is shown that ammonia is predominantly adsorbed on Lewis acid sites of the monolayer catalyst, whereas most of NН3 adsorbed on the catalyst containing bulk vanadium is in the form of ammonium ions. Analysis of experimental and calculated data suggests that, in the monolayer catalyst, NН3 molecules in the selective reduction of nitrogen oxides are activated on Lewis acid sites. Ammonia activation involves the dissociation of the N–H bond in a coordinated molecule, which results in the formation of the amide V–NН2 group and a water molecule coordinated by a V5+ ion. It is likely that, in the case of the catalyst containing bulk vanadium, this reaction occurs with the predominant participation of ammonium ions. [ABSTRACT FROM AUTHOR]

A plasma injector with pulsed gas filling is investigated experimentally. Interferometric measurements of the formation dynamics of the plasma channel are carried out. Under optimal operating conditions, the injector is capable of producing a plasma channel 4 cm in diameter with an electron density of ∼10[sup 17]cm[sup –3]. The effect of the cathode diameter of the plasma opening switch on the conductivity of the plasma channel is studied. It is shown that the current flowing through the plasma channel of a single injector attains 400 kA. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The time-resolved magnetic field effect in the recombination fluorescence of spin-correlated radical ion pairs has been measured to study n-alkane radical cations in irradiated solutions at room temperature. The magnetic field effect was recorded as a ratio of fluorescence decay curves in the 0.1 T and zero magnetic fields for solutions of C[sub 8], C[sub 9], C[sub 10], C[sub 12], and C[sub 16] n-alkanes in n-hexane with addition of 3 × 10[sup -5] M p-terphenyl-d[sub 14]. A distinct maximum at 10-30 ns followed by a slowly decaying plateau was observed for all the solutions. Simulation shows that the maximum corresponds to an unresolved ESR spectrum with the peak-to-peak linewidth ranging from about 1.6 mT to 0.5 mT for C[sub 8] to C[sub 16] radical cations. The unresolved structure is believed to result from the hyperfine couplings with many protons of the radical cation, the increase in the number of interacting protons compared with low temperature matrices being caused by the methyl group rotation and conformational motion of the carbon chain. With increase in concentration of dissolved n-alkane, the maximum in the curves first moves to longer times and finally disappears; this was attributed to the narrowing of ESR spectrum contour due to degenerate electron exchange. [ABSTRACT FROM AUTHOR]

Singlet-triplet oscillations in spin-correlated radical pairs have been studied at magnetic field strengths low for one radical and high for the other. Oscillations with frequencies close to the Larmor frequency ω[sub 0] of electron spin precession have been predicted under these conditions. Both numerical and exact analytical solutions in arbitrary magnetic fields are presented for three cases of hyperfine couplings in wide-spectrum radical. For the case of unresolved spectrum, singlet-triplet evolution was found to contain a single oscillating term with frequency ω[sub 0]. In the case of one spin-I magnetic nucleus, there are two low frequency oscillating terms with frequencies ω- = ω[sub 0]- ω[sub 0]/(2I + 1) and ω[sub +] = ω[sub 0] + ω[sub 0]/(2I + 1), the amplitude of the first term being larger than that of the second. The case of a number of equivalent protons also has been analysed as a superposition of one-nucleus oscillations. The predicted oscillations were observed in a time resolved magnetic field effect for several radical ion pairs produced by Xray irradiation of alkane solutions with charge acceptors. For pairs (p-terphenyl-d[sub 14])[sup -.]/(isooctane)+ [sup .] and (p-terphenyl-d[sub 14])[sup -.] /(2,4-dimethylpentane)[sup +.] the oscillation frequency in a field B[sub 0] of 0.5-4 mT is about 20% lower than ω[sub 0]. Oscillations were observed also in pairs with equivalent nuclei(p-terphenyl-d[sub 14])[sup +.] /(C[sub 6]F[sub 6])- [sup .] and (p-terphenyl-d[sub 14])[sup -.]/(hexamethylethane)[sup =.]. [ABSTRACT FROM AUTHOR]

Optical nonuniformities in the nuclear-pumped gas lasers are calculated. The nonuniformities are formed due to inhomogeneous energy deposition by the fission fragments from thin plane uranium layers that irradiate the laser active gas. The results of calculations agree with experimental data. [ABSTRACT FROM AUTHOR]

Provides information on a study on the cooling and freshening in the upper layer of the Norwegian Sea in relation to atmospheric forcing. Details on the data used in the study; Results of the study; Conclusions.

The article discusses the unusual proton-transfer complex between the 2,2,6,6-tetramethylpiperidine radical cation and neutral molecule. A resonance was detected by monitoring the decrease in the intensity of recombination fluorescence that arises from recombination of radical ion pairs in a resonance microwave field in the optically detected erythrocyte sedimentation rate (OD ESR) method. It notes the time-resolved magnetic field effect (TR-MFE) techniques and detected the said unusual complex.

The generator ensures the switching-off of the magnetic field, having an amplitude of 4 × 0.5 mT in 22 × 2 ns at a frequency of 50 kHz in a volume of about 2 cm3, in a setup intended for measuring delayed fluorescence in the photon counting mode. It helped to observe spin evolution of spin-correlated radical ion pairs (para-terphenyl/para-terphenyl) in a zero magnetic field using the time-resolved magnetic effect method. It was shown that the generator allows one to study the spin dynamics of a wide class of organic radical ions in a weak magnetic field. [ABSTRACT FROM AUTHOR]

The results of investigations of a spark discharge in air in the gap between the tip (anode) and a 1.5‑mm-long plane are presented. It is shown that, after breakdown, the discharge develops in the form of a beam of individual microchannels that close the discharge gap, then, after 20–30 ns, a continuous outer boundary of the channel forms and its radial expansion begins. The electron concentration at this moment reaches its maximum value at the level of 2 × 1019 cm—3. It was found that, starting from 60 ns, a cylindrical shock wave departs from the channel boundary. With time, the difference in the radii of the shock wave and the channel increases, resulting in the formation of a radial structure in the form of a highly conductive internal channel, separated from the shock wave by an intermediate shell. A computational and theoretical model is proposed to describe the dynamics of the spark channel expansion from the moment of the formation of a solid outer boundary, and a satisfactory agreement between the calculations and experimental data is obtained. [ABSTRACT FROM AUTHOR]

The results of studies of the microstructure in the initial phase of the discharge in air in the gap between the pin and a plane 1.5 mm long are presented. Measurements show that within 15 ns after breakdown, the channel is a bundle of a large number of microchannels, the current in the channel grows almost linearly up to 1 kA, and the electron concentration reaches 2 × 1019 cm−3. Taking into account the experimental data, the electron temperature dynamics in a separate microchannel was calculated. It was found that the average electron temperature is from 4 to 8 eV, the electric field strength is ∼300 kV/cm, and the electrical conductivity is ∼10 Ω−1 cm−1. The obtained results indicate that it is the microstructure of the discharge that determines the relatively high values of the average temperature of electrons in combination with a sufficiently high degree of ionization. [ABSTRACT FROM AUTHOR]

The results of studies of the dynamics of near-electrode processes in the initial phase of a spark discharge in atmospheric-pressure air in the point-plane geometry are presented. After breakdown, regions of about 50 μm or more in size with an increased electron concentration of (3–8) × 1019 cm–3 near the surface of the flat cathode have been observed. With allowance for the experimental data on erosion effect of the discharge on the surface of a flat electrode and the associated gas-dynamic effects, a physical model of near-electrode processes has been proposed, based on which the gas-dynamic parameters are estimated. [ABSTRACT FROM AUTHOR]

We have designed a device with a gliding unipolar arc of the Jacob's ladder type. The dynamics of arc rising has been investigated. It is found that the arc climbs at a constant velocity on the major part of its path. The convective nature of the arc rise due to heating of air by the plasma is demonstrated. The dependence of the arc rise velocity on the opening angle between the electrodes is obtained. The dependence is found to be decaying. [ABSTRACT FROM AUTHOR]

Analytical solution is obtained for time-resolved magnetic field effects (TR-MFE) on recombination fluorescence of radical-ion pair (RIP) containing radical ion with two groups of magnetically equivalent nuclei. The present theoretical approach is applied to three experimental systems: RIPs containing radical cations of 2,3-dimethylbutane, 2,2,6,6-tetramethylpiperidine, or diisopropylamine and radical anion of p-terphenyl-d14 in nonpolar alkane solutions. Good agreement between theory and experiment is found for all the three systems, hyperfine coupling constants of radical cations are obtained by fitting the experimental TR-MFE traces. The potential of the TR-MFE technique for studying radical ions with nonequivalent nuclei is discussed in detail. The wide applicability of the theoretical model and the experimental technique make them useful for studying short-lived radical species that are often beyond the reach of the conventional electron paramagnetic resonance spectroscopy. [ABSTRACT FROM AUTHOR]

Using high-speed photography and shadow photography, the structure of the glow and the microstructure of the spark discharge in a 1.5 mm long "pin(cathode)-plane" gap in air in the pressure range from 300 to 760 Torr has been studied. The presence of a micro channel structure of the discharge in the indicated pressure range was established—the discharge is a aggregation of a large number of micron-diameter channels. It is shown that with decreasing pressure, the evolution of the microstructure and glow of the discharge lags behind the onset of breakdown, however, their morphology retains similarity at different pressures. [ABSTRACT FROM AUTHOR]

The method of time resolved magnetic field effects in the recombination fluorescence of spin-correlated radical ion pairs is used to detect for the first time the perfluorobenzocyclobutene radical anion. The quantum chemical analysis of the potential energy surface testifies that the particle is structurally flexible with respect to the pseudo-rotation coordinate. The calculated values of hyperfine interaction constants averaged over global minima are close to those estimated from the experimental data of time resolved magnetic field effects. [ABSTRACT FROM AUTHOR]

Using high-speed shooting and shadow photography, the spatial structure of a pulsed discharge in a 1.5 mm long "pin(cathode)-plane" gap in nitrogen and argon in the pressure range from 0.25 to 2 atm was studied. It has been found that a spark discharge is realized in nitrogen and a diffuse form of discharge is realized in argon. For both cases, the presence of a microstructure of discharges in the studied pressure range was found, when the discharge is an aggregation of a large number of micron-diameter channels. It is shown that for each gas the dynamics of the discharge glow structure remains similar at different pressures. It has been established that the glow and microstructure of the discharge in nitrogen are similar to those in air. [ABSTRACT FROM AUTHOR]

the formation of the microchannel structure of a spark discharge in the gap spike (cathode)-plane of 1.5 mm length in the air of atmospheric pressure was studied by the method of shadow photography. The images with the concurrent descent of microchannel diameter sand the number of microchannel increase in the cathode region on the time interval of 5 ns were recorded. The obtained data are explained in the frames of the microstructure formation mechanism at the expense of the front instability of the ionization wave. The parameters characterizing the process of the microstructure formation are estimated, and they agree with the experimental data. [ABSTRACT FROM AUTHOR]

The initial phase of a spark discharge in the gap between the pin (cathode) and a plane 1.5 mm long in atmospheric pressure air under conditions of preliminary photoionization by an auxiliary discharge was investigated by the method of shadow photography. In the absence of preionization, the discharge from the first nanoseconds after breakdown is an aggregate of a large number of micron-diameter channels. It was found that the electron concentration resulting from preionization, estimated at 108–109 cm–3, increases the degree of uniformity of the discharge channel in the near-cathode region; however, in the near-anode region, the channel remains microstructured. Within the framework of the mechanism of microstructure formation due to the instability of the ionization wave front, a criterion for the formation of a uniform discharge is obtained and an explanation of the results obtained is presented. [ABSTRACT FROM AUTHOR]

A microchannel structure of a spark discharge initiated in atmospheric-pressure air in a point-plane gap has been discovered by shadow photography. The structure has been observed since the onset of the discharge glow. The evolution of the microstructure over times from several nanoseconds to several tens of nanoseconds has been traced. Specifically, the development of microchannels from the point into the discharge gap, expansion of the microchannels, and their interaction have been observed. A correlation has been found between the microstructure of the spark channel in the discharge gap and its autograph on the surface of the plane electrode. [ABSTRACT FROM AUTHOR]

This work reports on the spectroscopic properties and gas sensing performances of cobalt bis-porphyrin derivative ((Co-H)Por 2 ) in a thin films form obtained by Langmuir–Schäfer (LS) method towards Volatile Organic Compounds (VOCs) and an oxidizing gas in a Magneto-Optical Surface Plasmon Resonance (MO-SPR) configuration. In particular the optical and spectroscopic properties of (Co-H)Por 2 multilayers deposited onto proper Au/Co/Au magneto-plasmonic (MP) transducers were inspected in dry air conditions and after exposure to different analyte gas concentrations. The molecular organization of these thin films deposited by Langmuir–Schäfer technique has been investigated and a comparison between the MOSPR experimental data and simulation has been also reported. In order to validate our experimental results and obtain further insight into the physical mechanism of interaction between the organometallic molecules and magneto plasmonic nanostructured systems, numerical simulations based on Finite Element Method (FEM) techniques, have been performed. The optical and magneto-optical properties of these hybrid systems have been theoretically analyzed to confirm the experimental outcomes. Finally, a peculiar sensitivity of the MOSPR sensing probe in respect to investigated analytes has been recorded. [ABSTRACT FROM AUTHOR]

The microchannel structure of a spark discharge in a 1.5-mm-long point–plane gap has been studied by the method of shadow photography. The discharge dynamics (propagation of microchannels from the point into the discharge gap, branching and expansion of the microchannels, formation of a joint front of the spark's shock wave and its motion) has been observed over a time from several nanoseconds to several hundred nanoseconds. Objects of a half-ring shape have been discovered. They have been identified as semispherical shock waves resulting from the formation of microcraters near sites where the microchannels touch the plane electrode. [ABSTRACT FROM AUTHOR]

Microwave pulses at a frequency of 2.45 GHz with a duration of 30–55 ns (at the base level) were obtained using the effect of fast energy transfer in a pair of coupled cavities. The pulse repetition rate reached 40 kHz, and the maximum magnetic-induction amplitude was 0.32 mT at a 20-W generator power. [ABSTRACT FROM AUTHOR]

A plasma opening switch fed by a helical magnetic explosion generator is developed. A plasma sheath with an axial length of ≈4 cm and an electron density of ∼10[SUP17] cm[SUP-3] is produced in the electrode gap of the switch by six coaxial gaseous-plasma injectors. A series of explosion experiments shows that the system developed allows one to study the switch at currents of about 2 MA. [ABSTRACT FROM AUTHOR]

The evolution of a microsecond pulsed barrier discharge initiated in atmospheric pressure air in the point–plane electrode geometry has been investigated using streak camera photorecording and shadow photography with micrometer resolution and nanosecond exposure. It has been shown that the discharge develops in series and its structure evolves both within a series and from series to series. It has been found that, irrespective of the polarity of a feed voltage pulse, the discharge develops from the point electrode, having the form of a set of many micrometer-diameter channels. At the late stage, the discharge consists of a number of glowing microstructured channels, which occupy the space between the point and barrier and deviate from the point axis, and many faint channels radially propagating over the surface of the barrier. Numerical parameters of the structured have been obtained. [ABSTRACT FROM AUTHOR]

The results of studying the initial phase of a spark discharge microstructure formation in a tip–plane gap 1.5 mm length in air are presented. Measurements show that, within 15 ns after breakdown, the channel is an aggregate of a large number of microchannels, the current in the channel rises almost linearly to a value of 1 kA, and the electron density reaches 2 × 1019 cm–3. Calculations of the kinetics of processes in a separate microchannel taking into account experimental data have been carried out. It has been found that the average electron temperature ranges from 4 to 8 eV, the electric field strength is ~ 300 kV/cm, and electrical conductivity is ~10 Ω–1 cm–1. The results obtained show that it is the discharge microstructure that causes relatively high values of the average electron temperature along with a sufficiently high ionization degree. [ABSTRACT FROM AUTHOR]

A spark discharge in a 1.5-mm-long tip (cathode)-plane gap in the time interval from the breakdown onset to 200 ns has been studied. Тhe discharge has been found to arise in the form of a bundle of microchannels. The dynamics of the discharge spatial structure, the electron concentration, the gas temperature in the channel, and the velocity of its radial expansion have been determined. [ABSTRACT FROM AUTHOR]

Dynamics of the initial stage of discharge in air is studied at atmospheric pressure in a point–plane gap at different parameters of the tip electrode and lengths of the interelectrode gap. Spark or diffuse discharges are implemented in experiments depending on the length of the interelectrode gap. Shadow photography is used to show that, for all electrodes in the experiments, the discharge channels represent multiple microchannels that develop from the tip and close the discharge gap. [ABSTRACT FROM AUTHOR]

The spectroscopic behavior of mono-zinc ethane-bridged bis-porphyrin (ZnH2Po 2 ) was studied as a solid film upon deposition from a chloroform solution by means of the spin-coating method. The angular speed used during the deposition strongly influences the conformational arrangement of bis-porphyrin. A preferential arrangement as the anti- (opened) conformer was obtained when high speeds were used. The obtained thin film was successfully employed to detect ammonia and acetone as the relevant analytes in aqueous solutions. This was a result of the supramolecular interaction between each of these two compounds used and the bis-porphyrin active layer, inducing the corresponding conformational switching easily detectable by UV–vis absorption spectroscopy. The spectral variations of ZnH2Po 2 were evident in the range of concentrations between 1 ppm and 20 ppm for both the analytes. This is particular important in light of the fact that ammonia and acetone concentrations are changed within this limit throughout the menstrual women’s cycle, reaching their maximum during the fertility days. Hence, ZnH2Po 2 can be effectively applied as a potential active layer for medical devices to monitor the hormonal variations during the women’s menstrual cycle. Additionally, the reversible sensing mechanism with reusable up to 8 cycles, makes this ZnH2Po 2 based active layer practically efficient. [ABSTRACT FROM AUTHOR]

The dynamics of mechanical destruction of a conductor in an explosively formed fuse opening switch on a finned obstacle under the action of detonation products is studied in the injection channel of the U-70 proton synchrotron. Protonograms are recorded with digital multiframe electron-optic cameras. The exposure time per frame, about 30 ns, is determined by the duration of a proton bunch. The time from the beginning of motion of the conductor to its destruction is about 3 μs. It is shown that the switch with typical sizes of the obstacle (the thickness of the fin is 1.5 mm, and the width and depth of the groove are 1.5 and 4.5 mm, respectively) provides operation with satisfactory gasdynamic parameters. [ABSTRACT FROM AUTHOR]

The results of industrial tests of a cascade of chemical absorbents for catching spent halogen-containing processes gases during discharge into the atmosphere are discussed. It is noted that the volume of the discharged gases decreases as a result of CO absorption. The HF and Cl content in passing gas can serve as a criterion for the completion of each catching step; Cl detection after the last step is a service life criterion for all chemical absorbents of a facility without exception. The average catching efficiency is 99.7 and 98.5% with respect to fluorine- and chlorine-containing components, respectively. An approximate calculation of the near-ground concentration of HF and Cl is performed. The gases discharged by the isotope separation plant at the Siberian Chemical Combine were purified at the level of the maximum admissible concentration for the working zone and not at the level of the technical norm established individually for each industrial enterprise. Equipping nuclear fuel cycle enterprises with such systems will make it possible to decrease environmental contamination considerably. [ABSTRACT FROM AUTHOR]