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This paper proposes a method of distinguishing the contributions of ionized and injected charges to the charge transport in oil immersed paper in triple-layer and double-layer samples. With the double-layer sample, the apparent mobility including the ions contribution is obtained by the calculation according to the speed of accumulated charge density at the interface. The contribution of ions is excluded by subtracting the accumulated charge density in the triple-layer sample from that in the double-layer sample. It is found that the interface charge mainly comes from the ionization charges under a low field, and the contribution of injected charge takes a more important part at higher electric field.

The analytical performance and a suggested mechanism for zero volt paper spray using chromatography paper are presented. A spray is generated by the action of the pneumatic force of the mass spectrometer (MS) vacuum at the inlet. Positive and negative ion signals are observed, and comparisons are made with standard kV paper spray (PS) ionization and nanoelectrospray ionization (nESI). While the range of analytes to which zero volt PS is applicable is very similar to kV PS and nESI, differences in the mass spectra of mixtures are interpreted in terms of the more significant effects of analyte surface activity in the gentler zero volt experiment than in the other methods due to the significantly lower charge. The signal intensity of zero volt PS is also lower than in the other methods. A Monte Carlo simulation based on statistical fluctuation of positive and negative ions in solution has been implemented to explain the production of ions from initially uncharged droplets. Uncharged droplets first break up due to aerodynamics forces until they are in the 2-4 ?m size range and then undergo Coulombic fission. A model involving statistical charge fluctuations in both phases predicts detection limits similar to those observed experimentally and explains the effects of binary mixture components on relative ionization efficiencies. The proposed mechanism may also play a role in ionization by other voltage-free methods. (Figure Presented). � 2015 American Chemical Society.

Absolute electron impact ionization cross sections for CH3X, where X = H, F, Cl, Br, and I Claire Vallance et al 1997 J. Phys. B: At. Mol. Opt. Phys. 30 2465–2475 Absolute electron-impact ionization cross sections for a range of C1 to C5 chlorocarbons James E Hudson et al 2001 J. Phys. B: At. Mol. Opt. Phys. 34 3025–3039 Absolute electron impact ionization cross-sections for CO, CO2, OCS and CS2 James E Hudson et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 445–455 We have recently re-examined some published binary-encounter–Bethe (BEB) calculations on the electron impact ionization cross sections for halogenated hydrocarbons and sulfur-containing molecules, and found a discrepancy with our earlier results. Please see the PDF file for full details.

Several push‐pull oligocarbazole dye‐sensitizers have been studied using theoretical methods in order to better understand the relationship between structural electronic or optical properties and intramolecular path of active electrons during the ionization and injection processes. DFT/TD‐DFT calculations were performed on a series of five dye sensitizers. They differ by the presence of electron donating group (EDG) by inductive effect (noted+I) or electron releasing group (ERG) by mesomeric effect (noted+M) or electron withdrawing group by inductive effect (noted‐I) on the pushed part of the dyes studied. Our work focused on the internal distribution of electrons in the different parts of dye that are the push/pull moieties and the π‐bridge. The study concerned the ground state, the electronic transition process and the excited state. In each situation, the fragment acting in the ionization or transition phenomena were identified. In the ground state, the electrons of the push part appear to be the least bound because they have the highest probabilities of ionization. In the excited state, the ionized atoms are essentially positioned in the pushing part and some neighboring atoms of the bridge. In the electronic transition, the active atoms are located in the π‐conjugated part but only on the side adjacent to the acceptor group. To arrive to this conclusion, we optimized the structures of the five dyes in their ground and excited states. We calculated the atomic charges, the wavelengths and intensities of electronic transitions in the visible domain, the reorganization energies as well as the oxidation potential. It appears that +M donor ligands improve the performance of a dye because the great distribution of atoms to be ionized in the push parts.

The difference in the ionization rates of holes and electrons in Si results in different properties of n+-p-p+ and p+-n-n+ TRAPATT diodes. An approximate analysis is presented which shows these differences and indicates superior performance in the n+-p-p+ structure.

Theoretical justification for a relationship between ionization potential ( I ) and electronegativity ( x ) rests in the equation derived by Mulliken (1934, 1949), viz.: X = I + E / 2 where E is the electron affinity. Elements situate on the left-hand side of the Periodic Table have small E values, so that in these cases a direct relationship between x and I might be anticipated. On the right-hand side of the Periodic Table, the electron affinities may be appreciable, and for example in the halogens, are of the order 3 to 4 eV. The neglect of the term in E in these instances represents a serious departure from Mulliken’s equation. It is furthermore important to stress that the values of I which apply in the Mulliken equation are ‘valence-state’ ionization potentials, and are not in general to be identified with the first ionization potentials of the elements, which Walsh has employed. The relationships observed by Walsh might, in consequence, be misleading in cases where the ionization potential of the ground-state of an atom is far removed (in energy) from the ionization potential of the atom in its appropriate valence-state (e.g. Zn, Cd, Hg).

The time evolution of the electron density and the resulting time dependence of the X-ray polarizability of a crystal irradiated by highly intense XFEL femtosecond pulses is investigated theoretically. Rate equations for bound electrons and the Boltzmann equation for the unbound electron gas are used in calculations., The time evolution of the electron density and the resulting time dependence of Fourier components of the X-ray polarizability of a crystal irradiated by highly intense femtosecond pulses of an X-ray free-electron laser (XFEL) is investigated theoretically on the basis of rate equations for bound electrons and the Boltzmann equation for the kinetics of the unbound electron gas. The photoionization, Auger process, electron-impact ionization, electron–electron scattering and three-body recombination have been implemented in the system of rate equations. An algorithm for the numerical solution of the rate equations was simplified by incorporating analytical expressions for the cross sections of all the electron configurations in ions within the framework of the effective charge model. Using this approach, the time dependence of the inner shell populations during the time of XFEL pulse propagation through the crystal was evaluated for photon energies between 4 and 12 keV and a pulse width of 40 fs considering a flux of 1012 photons pulse−1 (focusing on a spot size of ∼1 µm). This flux corresponds to a fluence ranging between 0.8 and 2.4 mJ µm−2. The time evolution of the X-ray polarizability caused by the change of the atomic scattering factor during the pulse propagation is numerically analyzed for the case of a silicon crystal. The time-integrated polarizability drops dramatically if the fluence of the X-ray pulse exceeds 1.6 mJ µm−2.

An expression for ion recombination in free-air ionization chambers irradiated by chopped X-rays is presented. The expression is validated by comparison with experiments using synchrotron radiation., Saturation curves for free-air ionization chambers with electrode gap widths of 4.2, 8.4 and 18 mm were obtained for 10 and 15 keV undulator synchrotron radiation thinned with a 230 Hz rotating-disk chopper. Ion recombination in free-air ionization chambers was found to be inversely proportional to the applied electric field, and an expression that satisfactorily reproduced the ion-recombination rate is determined. A comparison of the expressions for continuous and pulsed X-rays revealed that chopped high-intensity X-rays require a higher voltage to attain saturation when the product of the pulse width and electric field exceeds a value that depends on the X-ray energy. This behaviour was observed explicitly for 10 keV X-rays in measurements with the ionization chamber placed before and after the chopper.

In this paper, a modified COMSOL Multiphysics model with artificial stability is adopted, and the boundary condition developed in the previous paper are applied to the calculation of the photoionization rate. The main processes involved in air discharge were simulated by 39 plasma chemical reactions composed of 12 kinds of particles. The characteristics of low-temperature sub-atmospheric pressure air discharge under unipolar square wave pulse voltage with 13kV applied amplitude, 25 kHz-50 kHz frequency and a duty cycle of 50%-75% are discussed. The results show that: When the duty cycle increases, the average density of electron, N2+, N4+, O2+, O4+, and N2O2+ show an increasing trend, and the average electron temperature changes little; When the frequency increases, the average electron density, the average density of N4+ and O4+ show a downward trend, the average density of N2+, O2+, N2O2+ change little; The average electron temperature shows an increasing trend, but the duration of high electron temperature becomes shorter. When discussing a single period, it is found that the potential difference between the electrode and the plasma determines the direction of the electric field in the space. For the photoionization reaction, even if its influence on the negative streamer is not important, it still needs to be considered in the simulation. The effect of temperature on discharge is also taken as the research emphasis, it includes the following aspects: Firstly, at low temperature, the collision reaction and attachment reaction rates are increased, while the recombination reaction rate is almost unaffected; Secondly, low temperature results in the decrease of secondary electron emission coefficient, which indirectly increases the electric field gradient and the peak value of electric field; Finally, at low temperature, the mobility of carriers, including electrons, positive and negative ions, is increased, but the streamer velocity is decreased.

This paper represents a contribution toward finding a complete set of electron collision cross sections for the methane molecule by revising all of the collision cross sections and adding the partial collision cross sections data relating to dissociation by electron impact. For the latter, there are no available measurements data for each channel of dissociation and no validated recommended data for use in the modeling, although these data are very important in order to determine different species in a methane plasma. The rate coefficients of the partial dissociative collisions into neutrals and the partial ionization collisions are also calculated, and when fitted, these can be used as input for fluid models. This paper is concluded by the validation of our set of data through a comparison between the transport coefficients calculated by using our data and the measurements of the transport coefficients that already exist in the literature.

The past measurements of the plasma density and potential profiles near the exit of the keeper electrode in a hollow cathode device suggested that turbulent ion acoustic fluctuations and ionization instability in the cathode plume significantly increased the energy of the ions that flow from this region. The lifetime of keeper electrode is limited by sputtering or ion bombardment of the Molybdenum surface exposed to the discharge plasma. Increases in the cathode gas flow reduce the amplitude of the fluctuations and the number and energy of the energetic ions, which decreases the erosion rate of the keeper electrodes. However, as the cathode gas flow is raised for a given discharge current, the performance of a 5-kW Annular-Geometry Ion Engine (AGI-Engine) declines. There is a strong relationship between the performance and the lifetime of the ion thruster. To validate whether the 20-A hollow cathode satisfied China's communication satellite platform's application requirement for North-South station keeping, this paper analyzed the effect of the cathode gas flow on the performance and the lifetime of the AGI-Engine. Different from the previous methods, this paper first tracked the movement of energetic ions generated in the plume of the hollow cathode, predicted erosion rates, found where they hit the keeper electrode, and then determined the amount of material that they sputtered. A review of past experimental results was presented first. Next, based on the existing experimental data, theoretical analysis and numerical calculations were performed to determine the optimum gas flow range and the performance curve of the 20-A hollow cathode. The results showed that the primary erosion mechanism of the keeper electrode was caused by impact from Charge Exchange Xenon (CEX) ions, which caused the cathode orifice to be widened and attenuated over time. However, heavy double xenon (X e ++ ) ions, which struck the keeper electrode more severely than CEX ions, were the most crucial factor that limited the lifetime of the 20-A hollow cathode due to their high energy and large mass.

11 pags., 5 figs., 3 tabs. -- We adknowledge support by the CSIC Open Access Publication Initiative through its Unit Information Resources for Research (URICI). -- Open Access funded by Creative Commons Atribution Licence 3.0, Absolute total electron scattering cross sections (TCS) for nitrobenzene molecules with impact energies from 0.4 to 1000 eV have been measured by means of two different electron-transmission experimental arrangements. For the lower energies (0.4–250 eV) a magnetically confined electron beam system has been used, while for energies above 100 eV a linear beam transmission technique with high angular resolution allowed accurate measurements up to 1000 eV impact energy. In both cases random uncertainties were maintained below 5–8%. Systematic errors arising from the angular and energy resolution limits of each apparatus are analysed in detail and quantified with the help of our theoretical calculations. Differential elastic and integral elastic, excitation and ionisation as well as momentum transfer cross sections have been calculated, for the whole energy range considered here, by using an independent atom model in combination with the screening corrected additivity rule method including interference effects (IAM-SCARI). Due to the significant permanent dipole moment of nitrobenzene, additional differential and integral rotational excitation cross sections have been calculated in the framework of the Born approximation. If we ignore the rotational excitations, our calculated total cross section agrees well with our experimental results for impact energies above 15 eV. Additionally, they overlap at 10 eV with the low energy Schwinger Multichannel method with Pseudo Potentials (SMCPP) calculation available in the literature (L. S. Maioli and M. H. F. Bettega, J. Chem. Phys., 2017, 147, 164305). We find a broad feature in the experimental TCS at around 1.0 eV, which has been related to the formation of the NO2 anion and assigned to the p*(b1) resonance, according to previous mass spectra available in the literature. Other local maxima in the TCSs are found at 4.0 0.2 and 5.0 0.2 eV and are assigned to core excited resonances leading to the formation of the NO2 and O2 anions, respectively. Finally, for energies below 10 eV, differences found between the present measurements, the SMCPP calculation and our previous data for non-polar benzene have revealed the importance of accurately calculating the rotational excitation contribution to the TCS before comparing theoretical and experimental data. This comparison suggests that our dipole-Born calculation for nitrobenzene overestimates the magnitude of the rotational excitation cross sections below 10 eV., This study has partially been supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades (Project FIS2016-80440) and CSIC (Project LINKA 20085). F. C. acknowledges Radiation Biology and Biophysics Doctoral Training Programme (RaBBiT, PD/00193/2012); UCIBIO (UIDB/04378/2020) and together with P. L. V. the Portuguese National Funding Agency FCT through the Research Grants CEFITEC (UIDB/00068/2020) and PTDC/FISAQM/31281/2017. M. J. B. thanks the Australian Research Council for funding through grants DP160102787 and DP180101655. The authors acknowledge Dr N. C. Jones for providing her full experimental TCS data on NBz molecules and Dr L. S. Maioli and Prof. M. H. F. Bettega for providing numerical tables of their SMCPP calculation and taking part in helpful discussions related to this paper. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). Finally we also acknowledge Dr L. Campbell for his contributions to the final version of this paper.

This paper is an extension of our previous paper (Mašek and Rohlena, 2015), where we applied a transform method for the solution of Vlasov–Maxwell set of equations in a one-dimensional geometry to describe the Raman backscattering of the heating ns laser wave in the external corona of the generated laser plasma in a strongly non-linear regime. The method is stabilized by a simplified Fokker–Planck collision term, which, in turn, is used for a study of the influence of collisional and collisionless damping mechanisms of the daughter electron plasma wave (EPW) on the instability development and their competition resulting in a different instability behavior in various plasma configurations. The physics of trapped electrons is studied in detail and compared to the resulting Raman reflectivity. The Raman reflectivity was found to depend strongly on the intensity of laser irradiation in the different regions of the plasma corona. This is discussed in detail from the point of view of trapped electrons behavior in the EPW. Moreover, a study of the Raman reflectivity dependence on the electron–ion collision frequency (average plasma ionization) is presented, too. The results supplement the physical picture of the collision and collisionless processes influencing the Raman instability non-linear development.

In this paper composition of a non-ideal lithium-hydrogen-uranium plasma was studied using the Saha equation. The results obtained in this paper can be used both in theoretical calculations and in the implementation of various experimental projects related to non-ideal plasma, in particular, for studying the thermodynamic properties of nuclear fuel detected in gaseous plasma form in nuclear jet engines. The degree of ionization of lithium, hydrogen, and uranium atoms was determined as the ratio of the number of free electrons to the total number of nuclei in the plasma. The composition of the ionized plasma was calculated in the framework of the system of the chemical model of plasma. A system of nonlinear Saha equations is obtained, which was solved by numerical methods. The calculations were carried out in the Debye approximation, taking into account the screening effects. As a result, the dependence of the degree of ionization of lithium, hydrogen, and uranium atoms on concentration and temperature at different percentages of these atoms in the substance is presented: 10-85-5%, 9-90-1%, respectively.

Atmospheric corona discharge plasmas are the most common diversely occurrence in the electric power system. In this paper, four elementary processes occurred in corona discharge are taken into account, including elastic collision, excitation, attachment, and ionization. As one of the most important parameters in corona characteristics analysis, the effective Townsend ionization coefficient is completely calculated by the Boltzmann equation under the consideration of humidity. This paper also derives the electron energy distribution function (EEDF) in water vapor and dry air, respectively. With reference to previous researches and the existing literature, comparisons and validations on ionization and attachment coefficient are conducted. Besides, the effects of humidity, pressure, and temperature on the effective ionization coefficient are also discussed in this paper. It is concluded that humidity can enhance both ionization and attachment. The results show that the ionization coefficient in this paper is well consistent with traditional ones, while there are variations for attachment coefficient. In normal condition, the effective ionization coefficient varies slightly with humidity, but it increases significantly with a decreased pressure or an increased temperature, which cause the change in critical electric field correspondingly.

In 1964, Professor L.V. Keldysh, with whom I share winning the Lomonosov Gold Medal, published what was to become a very influential paper. In his paper, he developed the theory of multiphoton ionization for atoms and the creation of electron-hole pairs for solids. Fifty years later, we generate the world’s shortest light pulses using electron wave packets that are extracted from rare gas atoms by an intense infrared pulse much as Professor Keldysh described. The ultrashort bursts of XUV radiation from many atoms add coherently to produce intense pulses as short as 65 attoseconds—the current world record. Similar highly nonlinear processes occur in other atoms, molecules and solids. In addition to its importance as a new source of soft X-ray radiation and ultrashort pulses, the radiation generated from ionizing material encodes information on the quantum system from which it was made. By analyzing the XUV radiation, not only can we image molecular orbitals but also determine the band structure of solids.

This paper employs Bayesian probability theory for analyzing data generated in femtosecond pump-probe photoelectron-photoion coincidence (PEPICO) experiments. These experiments allow investigating ultrafast dynamical processes in photoexcited molecules. Bayesian probability theory is consistently applied to data analysis problems occurring in these types of experiments such as background subtraction and false coincidences. We previously demonstrated that the Bayesian formalism has many advantages, amongst which are compensation of false coincidences, no overestimation of pump-only contributions, significantly increased signal-to-noise ratio, and applicability to any experimental situation and noise statistics. Most importantly, by accounting for false coincidences, our approach allows running experiments at higher ionization rates, resulting in an appreciable reduction of data acquisition times. In addition to our previous paper, we include fluctuating laser intensities, of which the straightforward implementation highlights yet another advantage of the Bayesian formalism. Our method is thoroughly scrutinized by challenging mock data, where we find a minor impact of laser fluctuations on false coincidences, yet a noteworthy influence on background subtraction. We apply our algorithm to data obtained in experiments and discuss the impact of laser fluctuations on the data analysis.

The morphology of magnetic equipotential lines in axisymmetric magnetic mirror field was analyzed. Based on the magnetic fluid theory of electrons, an electron cloud model formed by magnetic mirror field confined electrons was built in this paper. And twodimension differential potential equations were solved by using Runge-Kutta method. The calculation gave the Boltzmann distribution and potential distribution of electron density. The principle of both electron escape and confinement were analyzed in magnetic mirror field environment, the runaway electron current situation of the electronic cloud boundary was analyzed. Based on the leakage current of electron boundary, the balance of ionization electrons and escape electrons was used to deprive the confined region leakage current factor relationship equation in magnetic mirror environment. The relationship between the runaway electron current and the runaway factor, the effects electron temperature, electron velocity, and magnetic field lines on runaway factor were given. Furthermore, the minimum confined magnetic field needed to build electron cloud in magnetic mirror field was also given in this paper.

Recently a new injection scheme for Laser Wake Field Acceleration, employing a single 100-TW-class laser system, has been proposed. In the Resonant Multi-Pulse Ionization injection (ReMPI) a resonant train of pulses drives a large amplitude plasma wave that traps electrons extracted from the plasma by further ionization of a high-Z dopant (Argon in the present paper). While the pulses of the driver train have intensity below the threshold for the dopant's ionization, the properly delayed and frequency doubled (or more) ionization pulse possesses an electric field large enough to extract electrons, though its normalized amplitude is well below unity. In this paper we will report on numerical simulations results aimed at the generation of GeV-scale bunches with normalized emittance and {\it rms} energy below $80\, nm \times rad $ and $0.5\, \%$, respectively. Analytical consideration of the FEL performance for a $1.3\, GeV$ bunch will be also reported., EAAC 2017 Conference, Elba, Italy

10 pags., 5 figs., 2 tabs., We report absolute elastic differential cross sections (DCSs) for electron collisions with phosphorus trifluoride, PF3, molecules (e + PF3) in the impact energy range of 2.0–200 eV and over a scattering angle range of 10–150. Measured angular distributions of scattered electron intensities were normalized by reference to the elastic DCSs of He. Corresponding integral and momentum-transfer cross sections were derived by extrapolating the angular range from 0 to 180 with the help of a modified phase-shift analysis. In addition, due to the large dipole moment of the considered molecule, the dipole-Born correction for the forward scattering angles has also been applied. As a part of this study, independent atom model calculations in combination with screening corrected additivity rule were also performed for elastic and inelastic (electronic excitation plus ionization) scattering using a complex optical potential method. Rotational excitation cross sections have been estimated with a dipole-Born approximation procedure. Vibrational excitations are not considered in this calculation. Theoretical data, at the differential and integral levels, were found to reasonably agree with the present experimental results. Furthermore, we explore the systematics of the elastic DCSs for the four-atomic trifluoride molecules of XF3 (X = B, N, and P) and central P-atom in PF3, showing that, owing to the comparatively small effect of the F-atoms, the present angular distributions of elastic DCSs are essentially dominated by the characteristic of the central P-atom at lower impact energies. Finally, these quantitative results for e PF3 collisions were compiled together with the previous data available in the literature in order to obtain a cross section dataset for modeling purposes. To comprehensively describe such a considerable amount of data, we proceed by first discussing, in this paper, the vibrationally elastic scattering processes whereas vibrational and electronic excitation shall be the subject of our following paper devoted to inelastic collisions., This work was conducted under the support of the Ministry of Education, Culture, Sports, Science and Technology- Japan. F.B. and G.G. acknowledge the partial financial support from the Spanish Ministerio de Economia y Competitivided (Project No. FIS 2012-31230).

Ionization of neutrals by precipitating electrons and ions is the main source of Titan's nightside ionosphere. This paper has two goals: (1) characterization of the role of electron impact ionization on the nightside ionosphere for different magnetospheric conditions, and (2) presentation of empirical ion production rates determined using densities measured by the Cassini Ion and Neutral Mass Spectrometer (INMS) on the nightside. The ionosphere between 1000 and 1400 km is emphasized. We adopt electron fluxes measured by the Cassini Plasma Spectrometer Electron-Spectrometer and the Magnetospheric Imaging Instrument as classified by Rymer et al. [2009]. The current paper follows an earlier paper (Paper I), in which we investigated sources of Titan's dayside ionosphere and demonstrated that the photoionization process is well understood. The current paper (Paper II) demonstrates that modeled and empirical ionization rates on the nightside are in agreement with an electron precipitation source above 1100 km. Ion production rate profiles appropriate for different Saturnian magnetospheric conditions, as outlined by Rymer et al., are constructed for various magnetic field topologies. Empirical production rate profiles are generated for deep nightside flybys of Titan. The results also suggest that at lower altitudes (below 1100 km) another source, such as ion precipitation, is probably needed.

Titan's ionosphere is created when solar photons, energetic magnetospheric electrons or ions, and cosmic rays ionize the neutral atmosphere. Electron densities generated by current theoretical models are much larger than densities measured by instruments on board the Cassini orbiter. This model density overabundance must result either from overproduction or from insufficient loss of ions. This is the first of two papers that examines ion production rates in Titan's ionosphere, for the dayside and nightside ionosphere, respectively. The first (current) paper focuses on dayside ion production rates which are computed using solar ionization sources (photoionization and electron impact ionization by photoelectrons) between 1000 and 1400 km. In addition to theoretical ion production rates, empirical ion production rates are derived from CH4, CH3+, and CH4+ densities measured by the INMS (Ion Neutral Mass Spectrometer) for many Titan passes. The modeled and empirical production rate profiles from measured densities of N2+ and CH4+ are found to be in good agreement (to within 20%) for solar zenith angles between 15 and 90°. This suggests that the overabundance of electrons in theoretical models of Titan's dayside ionosphere is not due to overproduction but to insufficient ion losses.

A generalized analytical model based on multistage scattering phenomena has been developed in this paper for estimating the impact ionization rate of charge carriers in semiconductors. The probabilities of impact ionization initiated by electrons and holes have been calculated separately by taking into account all possible combinations of optical phonon scattering and carrier-carrier collisions prior to the impact ionization. Finally the analytical expressions of impact ionization rate of electrons and holes have been developed by using the aforementioned impact ionization probabilities. The impact ionization rates of electrons and holes in 4H-SiC have been calculated within the field range of $$2.5\times 10^{8}$$2.5×108---$$6.5\times 10^{8}\hbox { V m}^{-1}$$6.5×108Vm-1 by using the analytical expressions of those developed in the present paper. Those are also calculated by using the analytical expressions developed by some other researchers earlier without considering the multistage scattering phenomena. Finally the theoretical results obtained from the analytical model proposed in this paper and the analytical model developed by earlier researchers within the field range under consideration have been compared with the ionization rate values calculated by using the empirical relations fitted from the experimentally measured data. Closer agreement with the experimental data has been achieved when the impact ionization rate of charge carriers in 4H-SiC are calculated from the proposed model as compared to the earlier one.

Extensive information, such as ion temperature and wave-particle interactions, can be obtained by direct measurement of ion distribution functions using laser-induced fluorescence (LIF). This nonintrusive plasma diagnostic provides an important window into the ion motions in phase-space. Previous simulation results suggest that LIF measurements, which are performed on metastable ions produced directly from neutral gas particles and also from ions in other electronic states, place restrictions on the metastable lifetime. In the case where metastable population is produced from direct ionization of neutral atoms, the velocity distribution measured using LIF will only faithfully represent processes which act on the ion dynamics in a time shorter than the metastable lifetime. In this paper, the metastable lifetime effects are explored experimentally for the first time using wave-particle interaction in an Argon multidipole plasma. We demonstrate that this systematic effect can be corrected using the theory addressed in the paper based on the metastable lifetime and relative fraction of metastables produced from pre-existing ions., 7 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1811.07915

Impurity seeding into a tokamak divertor for radiative cooling is considered as a tool for achieving detached/semi-detached regimes required to meet the condition of acceptable heat loads on divertor plates. Experiments aimed at searching for an operational window with a significant reduction of poloidal heat fluxes due to the impurity radiation and without decrease of confinement are performed on many tokamaks. A critical issue in these experiments is how large a fraction of impurities is retained in the divertor region and how much is extracted upstream to the scrape-off layer. In the present paper a physical mechanism of impurity transport from a divertor towards upstream and back to the divertor is analyzed. It is demonstrated that the widespread concept that the impurity leaks if the parallel thermal force exceeds the friction due to main ions and is retained otherwise—is not correct. In this paper, we contend that the impurity leaks if it crosses the stagnation point of the impurity ion poloidal velocity profile before being ionized, and is retained if it ionizes closer to the target than the location of that stagnation point. Thus the leakage efficiency depends on the relative spatial positions of the impurity atom ionization source and the stagnation point of the impurity ion poloidal velocity profile. The impurity ion poloidal velocity is to large extent the sum of the poloidal projection of its parallel velocity and the E × B drift velocity, where the former is derived from the parallel impurity force balance equation. It is demonstrated that the solution of this equation may be approximated by the balance of friction and thermal forces in all regimes, while other terms are smaller. This allows for expressing the impurity parallel velocity through the main ion one and makes the distribution of the parallel (poloidal) fluxes of the main ions, including Pfirsch–Schluter fluxes and E × B drift fluxes, to be an important element of the impurity transport. It is shown that the impurity distribution in the edge plasma is rather sensitive to the value of the impurity ion ionization rate. This analysis is supported by simulation results obtained for the ASDEX Upgrade tokamak with various seeding rates of N and Ne with the SOLPS-ITER code. The importance of the inclusion of self-consistent drift flows is demonstrated by comparison to results of corresponding simulations with the drifts turned off.

The present paper is based on the materials of the Invited Lecture presented at 29th Summer School and International Symposium on the Physics of Ionized Gases (28 August 2018–1 September 2018, Belgrade, Serbia). In the paper, the effect of nitrogen admixture on various characteristics of a dc glow discharge in argon (the volt-ampere characteristic, rate of plasma decay in the afterglow, discharge constriction condition, and formation of a partially constricted discharge) is considered.

This paper presents research results on the ion charge state and energy distribution in the anode plasma generated at the spark stage of a high-current vacuum discharge. The cathode and the anode are both made of liquid metal Ga–In alloy. The use of a circuit with a relatively low impedance (6 $\Omega$ ) and a small interelectrode gap $({\sim}{\rm 1}~{\rm mm})$ made it possible to obtain a relatively high discharge current $({\sim}{\rm 1}~{\rm kA})$ at an initial voltage of 10–15 kV. Therefore, an electron beam consisting of a train of pulses with a duration of 5 ns and power density of ${\sim}2.5\cdot 10^{8}~{\rm W}/{\rm cm}^{2}$ is formed in ${\sim}{\rm 50}~{\rm ns}$ , giving rise to high-density anode ablation plasma. The parameters of the ion component of this plasma are investigated with a mass energy analyzer. It is found that ions with ${\rm Z}=1\hbox{--}4$ are present in the plasma, and the ion energy increases roughly in proportion with increasing ion charge. Increasing the initial voltage causes an increase in the fraction of highly charged ions and in their energy. The absolute values of the ion energy reach ${\sim}{\rm 1}~{\rm keV}$ . Two mechanisms of ion acceleration are discussed: adiabatic expansion of the anode plasma and ion acceleration by an ambipolar electric field. It is shown that the regularities found in this paper can be explained only with resort to both mechanisms.

In this paper we study the temperatures of electrons convected with the solar wind to large solar distances and finally transported over the solar wind termination shock. Nearly nothing, unless at high energies in the cosmic ray regime, is known about the thermodynamical behaviour of these distant electrons from in~situ plasma observations. Hence it is tacitly assumed these electrons, due to their adiabatic behaviour and vanishing heat conduction or energization processes, have rapidly cooled off to very low temperatures once they eventually arrive at the solar wind termination shock (at about 100 AU). In this paper we show that such electrons, however, at their passage over the termination shock due to the shock–electric field action undergo an over-adiabatic heating and therefore appear on the downstream side as a substantially heated plasma species. Looking quantitatively into this heating process we find that solar wind electrons achieve temperatures of the order of 2–4 × 106 K downstream of the termination shock, depending on the upstream solar wind bulk velocity and the shock compression ratio. Hence these electrons therewith play an important dynamical role in structuring this shock and determining the downstream plasma flow properties. Furthermore, they present an additional ionization source for incoming neutral interstellar hydrogen and excite X-ray emission. They also behave similar to cosmic ray electrons and extend to some limited region upstream of the shock of the order of 0.1 AU by spatial diffusion and thereby also modify the upstream solar wind properties.

This paper is concerned with the computer modeling of a quadrupole mass spectrometer (QMS) to include the effect of pressure in the ion source. The paper simulates the spectra over the pressure range from 10-6 to 10-4 mbar. An important contribution is the development of a novel procedure to include pressure dependence of the ion source to allow better prediction of instrument performance. Electron-impact total ionization cross sections in the ionic current expression are calculated using the binary-encounter-Bethe theory for argon gas. The predicted results show good agreement with the experimental results obtained from a commercial QMS used for residual gas analysis.

© 2015 Elsevier B.V. All rights reserved. In the early days of ion beam analysis, i.e. the early 60s, channeling was discovered and brought to maturity via a combined effort in experimental, computational and theoretical research. It was soon realized that the probability for nuclear interaction (such as nuclear scattering, nuclear reactions, ionization followed by X-ray emission...) would significantly decrease when steering the ion beam along a crystallographic direction of a single crystal. Hence, this effect would be optimally suited to investigate a wide range of materials properties related to their crystal structure, such as defects, elastic strain, the lattice site of impurities, as well as phonon-related properties. In this paper, I will briefly review some of the pioneering work, which led to the discovery and theoretical understanding of ion channeling. Subsequently, a number of applications will be discussed where the strength of the ion beam analysis technique allows deducing information which is often hardly (or not) attainable by other techniques. Throughout the paper, I will reflect on the future of channeling in materials research, and pay special attention to potential pitfalls, challenges and opportunities. ispartof: Nuclear Instruments & Methods in Physics Research B vol:371 pages:12-26 ispartof: location:Opatija: CROATIA status: published

Condensed Matter 1(1), 6 (2016). doi:10.3390/condmat1010006 special issue: "Selected Papers from The 13th Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures (ACSIN 2016)", The photon--ion merged-beams technique for photoabsorption studies of ionized nanoparticles} with synchrotron radiation is introduced. As an example, recent results from photoionization and photofragmentation of the endohedral fullerene ions Lu$_3$N@C$^{+}_{80}$, Lu$_3$N@C$^{2+}_{80}$, and Lu$_3$N@C$^{3+}_{80}$ are briefly discussed, highlighting the sensitivity and versatility of the experimental technique., Published by MDPI, Basel

Plasmas induced by EUV radiation are unique since they are created without the need of any discharge. Moreover, it is essential to characterize these plasmas to understand and predict their long term impact on highly delicate optics in EUV lithography tools. In this paper we study plasmas induced by 13.5 nm EUV radiation in hydrogen gas. The electron density is measured temporally resolved using a non-invasive technique known as microwave cavity resonance spectroscopy. The influence of the EUV pulse energy and gas pressure on the temporal evolution of the electron density has been explored over a parameter range relevant for industry. Our experimental results show that the maximum electron density is in the order of 1014 m-3 and depends linearly on the EUV pulse energy. Furthermore, the maximum electron density depends quadratically on the pressure; the linear term is caused by photoionization and the quadratic term by subsequent electron impact ionization. The decay of the plasma is governed by ambipolar diffusion and, hence, becomes slower at elevated pressures. Similarities and differences of the same processes in argon are highlighted in this paper.

In this paper, we present a detailed analytical computation of the triple differential cross sections, in the first Born approximation, for the relativistic electron-impact ionization of hydrogen atom in the metastable 2S-state in the symmetric and asymmetric coplanar geometries. The process is investigated by using the relativistic Dirac-formalism where the effects of spin and relativity are taken into account. It is shown that the nonrelativistic limit is accurately reproduced when applying low incident kinetic energies. At high energies, relativistic and spin effects are found to significantly affect the triple differential cross sections. The numerical results obtained for the triple differential cross section are compared with some other theoretical results in the nonrelativistic regime for asymmetric coplanar geometry. For this particular process and in the absence of any experimental data and theoretical models at high energies for the triple differential cross sections, the results of our calculated relativistic total cross section are compared with available theoretical and experimental results. We hope that the present study will provide significant contribution to future experiments.

The linewidth of ions has been observed to be systematically narrower than that of the coexisting neutrals in molecular clouds (Houde et al. 2000) and been interpreted as the signature of the decoupling of the neutral turbulence from magnetic fields in partially ionized medium (Li & Houde 2008; Paper I, hereafter). As a sequel of Paper I, here we present further observational evidence that lend support to these earlier proposals with the velocity coordinate spectrum analysis (Lazarian & Pogosyan 2006). We recover the turbulent energy spectra of HCN and HCO+(4-3) in a starless molecular filament in NGC 6334 where magnetic fields play a dynamically important role (Li et al. 2015). Our analysis showed that the neutral spectrum is consistent with Kolmogorov-type (k^-5/3, where k is the wave number), while that of the ions is the same on the large scale but steeper (k^-2) for scales smaller than 0.404pc. We carefully ruled out the possibilities that the spectrum difference can stem from the differences of ion and neutral optical depth and hyper-fine structures.

In plasma spray, operation parameters, including current, flow rate of primary gas, and flow rate of secondary gas, would influence the heat and acceleration status of particles greatly, thus influencing the coating's final quality. As the first stage to optimize the spraying technology, this paper investigates the typical Ar–He plasma spray process, analyzing the influence mechanism of current, flow rate of Ar, as well as flow rate of He on the temperature field and velocity field. The chemical reactions and turbulence are fully taken into account. It is found that the electrical current is apparently influential to both the jet temperature and velocity, and further the ionization of Ar atoms. With increasing Ar or He flow rates independently, the temperature of the plasma jet will be decreased, and the velocity of the plasma jet will be increased. Related inner mechanisms are revealed in detail. The results presented in this paper would be theoretically helpful for further study of the interaction between the plasma jet and the particles, and the optimization of the plasma-spraying technology.

Recombination of the primordial helium plasma (HeII→HeI, z ≃ 1500 − 3000) isconsidered. This process has an effect on the CMBR anisotropy and CMBR spectrumdistortion. In this work an influence of neutral hydrogen on kinetics of HeII→HeIrecombination is investigated in the frame of the standard cosmological model. It isshownthat small amount ofneutral hydrogen(10 −5 −10 2 oftotal number ofhydrogenions and atoms) leads to acceleration of HeII→HeI recombination at z . 2000 and atz . 1600 quasi-equilibrium HeII→HeI recombination (according to the Saha formula)becomes valid.Key words: cosmology, primordial plasma, recombination, cmbr, anisotropy 1 INTRODUCTIONThe HeII→HeI primordial recombination has an ef-fect on formation of the cosmic microwave background ra-diation (CMBR) anisotropy (e.g. Hu et al., 1995; Seager etal., 1999) and CMBR spectrum distortion (Lyubarsky andSunyaev, 1983; Fahr and Loch, 1991; Dubrovich and Stol-yarov, 1997; Wong et al., 2006). The relative difference ofCMBR anisotropy power spectrum corresponding to SahaHeII→HeI recombination and corresponding to HeII→HeIrecombination by Seager et al. (1999) has a level of up to5% for multipoles l ≃ 1500−3000 (Seager et al., 2000). Suchchanges can be measured in future experiments (e.g. Planckand others).Kinetics of HeII→HeI recombination has been consid-ered in a number of papers (Boschan and Biltzinger, 1998;Novosyadlyj, 2006; Wong and Scott, 2006; and referencestherein). The most used model of helium recombination isthe model suggested by Matsuda et al. (1969) and devel-oped by Seager et al. (1999). A significant modification ofthis model was suggested by Dubrovich and Grachev (2005)who took into account recombination through HeI ortho-states.In the model by Seager et al. (1999) the effect of neu-tral hydrogen on HeII→HeI recombination was neglectedalthough in a number of previous papers (e.g. Hu et al.,1995; Boschan and Biltzinger, 1998; and others) authorspointed out that this effect may be essential. This contra-diction made us investigate the effect of neutral hydrogenon HeII→HeI recombination again and derive HeII→HeI re-combination kinetic equation which takes this effect into ac-count.2 ADDITION TO THE RECOMBINATIONMODELThe main addition to the Seager’s et al. (1999) model istaking into account an interaction of resonant HeI quantawith neutral hydrogen. This interaction is described by thefollowing elementary processes:1. HeI resonant photon ionizes hydrogen atom with emis-sion of electron which has a kinetic energy more than 6 eV:H + γ → H

Ionization potentials (IPs) or electron affinities (EAs) for transition metal clusters are an important property that can be used to identify and differentiate between clusters. Accurate calculation of these values is therefore vital. Previous attempts using a variety of DFT models have correctly predicted trends, but have relied on the use of scaling factors to compare to experimental IPs. In this paper, we introduce a new density functional (BFW) that is explicitly designed to yield accurate, absolute IPs for transition metal clusters. This paper presents the numerical results for a selection of transition metal clusters and their carbides, nitrides, and oxides for which experimental IPs are known. When tested on transition metal clusters, the BFW functional is found to be significantly more accurate than B3LYP and B3PW91.

In this paper we suggest Penning ionization as an important route of formation for ionic species in upper planetary atmospheres. Our goal is to provide relevant tools to researchers working on kinetic models of atmospheric interest, in order to include Penning ionizations in their calculations as fast processes promoting reactions that cannot be neglected. Ions are extremely important for the transmission of radio and satellite signals, and they govern the chemistry of planetary ionospheres. Molecular ions have also been detected in comet tails. In this paper recent experimental results concerning production of simple ionic species of atmospheric interest are presented and discussed. Such results concern the formation of free ions in collisional ionization of H2O, H2S, and NH3 induced by highly excited species (Penning ionization) as metastable noble gas atoms. The effect of Penning ionization still has not been considered in the modeling of terrestrial and extraterrestrial objects so far, even, though metastable helium is formed by radiative recombination of He+ ions with electrons. Because helium is the second most abundant element of the universe, Penning ionization of atomic or molecular species by He*(23S1) is plausibly an active route of ionization in relatively dense environments exposed to cosmic rays.

Any injection of electromagnetically interacting particles during the cosmic dark ages will lead to increased ionization, heating, production of Lyman-alpha photons and distortions to the energy spectrum of the cosmic microwave background, with potentially observable consequences. In this note we describe numerical results for the low-energy electrons and photons produced by the cooling of particles injected at energies from keV to multi-TeV scales, at arbitrary injection redshifts (but focusing on the post-recombination epoch). We use these data, combined with existing calculations modeling the cooling of these low-energy particles, to estimate the resulting contributions to ionization, excitation and heating of the gas, and production of low-energy photons below the threshold for excitation and ionization. We compute corrected deposition-efficiency curves for annihilating dark matter, and demonstrate how to compute equivalent curves for arbitrary energy-injection histories. These calculations provide the necessary inputs for the limits on dark matter annihilation presented in the accompanying Paper I, but also have potential applications in the context of dark matter decay or de-excitation, decay of other metastable species, or similar energy injections from new physics. We make our full results publicly available at http://nebel.rc.fas.harvard.edu/epsilon, to facilitate further independent studies. In particular, we provide the full low-energy electron and photon spectra, to allow matching onto more detailed codes that describe the cooling of such particles at low energies., Comment: 18 pages, 6 figures, data files and tools available at http://nebel.rc.fas.harvard.edu/epsilon. Accompanying paper to "Indirect Dark Matter Signatures in the Cosmic Dark Ages I. Generalizing the Bound on s-wave Dark Matter Annihilation from Planck". v2 adds references, fixes a small bug, and clarifies a definition. No qualitative changes to results. This version to be submitted to Phys Rev D

This paper discusses the out-gassing behavior of a repetitively pulsed electron beam diode with a CsI-coated tufted carbon fiber cathode and a carbon fiber anode. Through this paper, a cross section model was developed that utilizes experimental data including pressure, temperature and voltage (energy) for determination. Mass and optical spectroscopy identified neutral and ion species likely responsible for the pressure pulses. The identified neutral and ionization cross sections from the published literature and databases were compared with the experimentally determined cross sections. The types of cross sections were electron-neutral and was single impact leading to single, double and triple ionization as well as elastic scattering. This comparison leads to the conclusion that initial pressure bursts consist of plasma with constituents of Cs, Cs/sup ++/, Cs/sup +++/, I, I/sup ++/, N/sub 2/, N/sub 2//sup +/, H/sub 2/O/sup +/, H, H/sup +/, and H/sub 2//sup +/. Larger pressure bursts after the initial ones also include Cs/sup +/ and I/sup +/. Smaller bursts observed during steady state operations fluctuate between plasmas that contain H and H/sup +/, and those that contain H, H/sup +/, and H/sub 2//sup +/. Consistently, the initial pressure pulses exceeded those found under steady-state operations. The optical spectroscopy timing and results are self-consistent with what is obtained from the cross section model. The cross section model coupled with the experimental data determines the transient plasma makeup responsible for the observed pressure pulses.

As a continuation of the preceding paper in this issue (J. Phys. Chem. A 2005, 109, 6805), we studied photodissociation dynamics of the acetone S2 (n, 3s) Rydberg state excited at 195 nm using femtosecond time-resolved photofragment translational spectroscopy. The technique, which is implemented by the combination of fs pump-probe ionization spectroscopy and kinetic energy resolved time-of-flight mass spectrometry (KETOF), measured temporal evolutions of the product kinetic energy distributions (KEDs) with a time resolution limited only by the laser pulse widths. Two methyl product KED components were resolved and assigned to the primary and secondary methyl products on the basis of their temporal behaviors. The results support the mechanism in which the primary dissociation occurs on the acetone S1 surface and provide complementary dynamical information to that discussed in the preceding paper.

The charge exchange (or transfer) due to collision with hydrogen has important effects on the physical characteristics of astrophysical plasma. In this paper, collisional ionization equilibrium in the temperature range of ˜ 1,000--80,000 K are investigated for C, N, and O ions including the effects of charge exchange. The calculated ionic abundance fractions are compared with those of previous works. The ionic abundance fractions calculated in the paper can be used in understanding the spectroscopic properties of warm interstellar medium. It is also found that the ratio between the degree of ionization of oxygen and that of hydrogen shows big difference with the previously well-known result for the environment where the collisional ionization is not important. This implies that investigations on the collisional ionization in the warm interstellar medium are required.

This paper describes the information for quantitative simulation of weakly ionized plasma. In previous paper, we calculated the electron transport coefficients by using two-term approximation of Boltzmann equation. But there is difference between the result of the two-term approximation of the Boltzmann equation and experiments in pure CF molecular gas and in CF+Ar gas mixture. Therefore, In this paper, we calculated the electron drift velocity (W) in pure CF molecular gas and CF+Ar gas mixture (1 %, 5 %, 10 %) for range of E/N values from 0.17～300 Td at the temperature was 300 K and pressure was 1 Torr by multi-term approximation of the Boltzmann equation by Robson and Ness. The results of two-term and multi-term approximation of the Boltzmann equation have been compared with each other for a range of E/N.

The paper presents a systematic characterization of pure hydrogen capacitively coupled discharges, produced in a parallel plate cylindrical setup. A two-dimensional, time-dependent fluid model is used to describe the production, transport, and destruction of electrons and positive ions H+,H2+, and H3+, at different frequencies(13.56 - 60 MHz), pressures (0.2 - 8 Torr), rf applied voltages (50 - 450 V) and geometric dimensions (1.6 - 12.8 cm radii and 1.6 - 6.4 cm interelectrode distances). A good agreement is found between calculation results and experimental measurements for the coupled electrical power, the plasma potential, and the self-bias potential, at various frequencies and rf applied voltages. However, the model generally underestimates the electron density with respect to its measured values. The paper discusses different space-time events, such as the development of double-ionization structures or the occurrence of field inversion and field reversal phenomena. The dependencies on pressure and frequency of the time-average electric field distribution are analyzed and related to the electron displacement within space-charge sheaths.This study is later used to understand the variations of the hydrogen dissociation rate, with changes in discharge operating conditions. The influence of reactor dimensions on the spatial profiles of the plasma potential, the rf electric field, the electron density, and the electron mean energy are analyzed in terms of discharge symmetry. An investigation of the space-time averaged rf electric field variations, with changes in the applied voltage, pressure, and geometric dimensions is carried out.These variations are shown to follow a universal similarity curve, if an adequate normalization is used when plotting the rf electric field as a function of pressure.This innovative representation of rf discharges allows a univocal definition of a reactor working point, for given operating conditions., Portugal. Ministério da Ciência Tecnologia e Ensino Superior (MTCES). Instituto Superior Técnico (IST). Centro de Física dos Plasmas – PRAXIS XXI (BD/15716/98), SFRH/BD/5012/2001., French Embassy, Gabinete de Relações Internacionais da Ciência e do Ensino Superior (GRICES) - ScientificTechnical Luso-French Cooperation Program - Project 539-B4 - Université Paris-Sud. Laboratoire de Physique des Gaz et des Plasmes.

This compilation revises the 1991 listing of atomic data for the lighter elements from hydrogen to gallium. The tabulation emphasizes resonance lines, i.e., lines whose lower level is the ground state, or an excited fine-structure state of the ground term, and is restricted to wavelengths longward of the H I Lyman limit at 911.753 ?. All but the very weakest known and predicted electric-dipole transitions are included, but no forbidden lines. This paper has attempted to review all data published by the end of 2002.?????The tables contain the best data available to the author on ionization potentials, level designations, vacuum and air wavelengths, lower and upper energy levels, statistical weights, transition probabilities, natural damping constants (reciprocal lifetimes), oscillator strengths, and the often used combinations of log gf and log ?f. All ion stages with relevant classified lines are included. Individual components resulting from isotope shift and hyperfine structure are listed explicitly for certain species. The accompanying text provides references, explanations for the critical selection of data, and notes indicating where new measurements or calculations are needed.?????This compilation should be particularly useful in the analysis of interstellar and quasar absorption lines and other astrophysical sites where the density of particles and radiation is low enough to excite only the lowest atomic levels. The data also are relevant to the study of stellar atmospheres, and gaseous nebulae.?????An Appendix summarizes new data relevant to the similar compilation in Paper II for the elements germanium to uranium.

This paper deals with the conditions for steady burning of a high-current vacuum arc (HCVA) as well as the conditions and causes for the development of an instability that is specific for the anode region of high-current arcs and results in contraction of a freely burning HCVA in the near-anode region. The steady burning of the HCVA requires that electrode processes are efficient enough to generate plasma-forming matter. This perspective is used to analyze the cathode processes and to show that the cathode spots (CSs)-the primary plasma sources-do not generate sufficient plasma for the steady burning of the HCVA. Therefore, the generation of the secondary plasma (SP), whose existence in the HCVA is evident from results of many experiments, is important to study. Analysis is done on the efficiency of a variety of possible sources of SP. The basic SP source is shown to be the anode-emitting atoms that are efficiently ionized by the plasma electrons in its vicinity. The anode emits atoms under the action of fast primary ions of plasma jets flowing out of the CS. Therefore, the dynamics of the CS under the action of the intrinsic magnetic field of the arc defines the state of both the anode region and the arc as a whole, since it defines the flux of the primary ions to the anode. A dynamic HCVA model that includes SP generation is proposed and substantiated. The arc contraction near the anode and the formation of an erosion anode spot are assumed to result from the development of instability of the evaporation-ionization (EI) nature that is specific to the anode region of high-current arcs. The HCVA loses stability with respect to EI processes because of an increase in the lateral loss of the primary ions and the corresponding drop in the efficiency of the SP generation. The increase in the lateral loss of the primary ions is a corollary fact of the CS dynamics. The conclusions that follow immediately from the dynamic model of HCVA have been shown to be in satisfactory agreement with the results of various experiments. The consideration carried out in this paper is based on the analysis of the vast amount of experimental material obtained by different researchers while investigating both the electrode processes and those in the HCVA gap.

A free energy relationship (FER) between the activation free energy ΔG⧧ and the reaction asymmetry ΔGRXN was derived in the preceding paper for acid ionization proton transfer (PT) reactions in a polar environment, in which the proton is treated quantum mechanically, but does not tunnel. In the present paper, the inclusion of the proton donor−acceptor vibrationthe vibration of the hydrogen (H−) bondand its impact on the FER are analyzed. The structure of the resulting FER, which includes quantization of both the proton and the H-bond coordinates, is found to be identical to that for the fixed donor−acceptor case, but with a re-interpretation for certain components, which reflects a significant coupling that exists between the H-bond vibration and the solvent reaction coordinate. This coupling derives from the increased mixing of the reactant and product valence bond electronic structures as the transition state is reached. Analytical expressions for the FER ingredients including these features are obtaine...

Ionization of trace gases by electron impact followed by ion extraction is an important pumping approach in ultrahigh vacuum (UHV) systems, which operate at nTorr pressure levels. However, pumping efficiency can only be achieved if the lifetime of electrons is sufficiently long to allow ionizing collisions with neutral species. In miniaturized systems, the electron lifetime is limited due to wall collisions. A traditional approach for an extended electron lifetime via trapping uses crossed electric and magnetic fields. These magnetic fields are undesirable in certain miniaturized systems such as atomic clocks. In this paper, the authors report a method and miniaturized structure for electron trapping in UHV conditions, which does not rely on magnetic fields. Electrons from an electron-beam source are transferred through a grid electrode into a central region of the device where they are trapped in lengthened trajectories using applied radio frequency (RF) electric fields. This paper describes analytical a...