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The paper presents the results of studies of argon-nitrogen plasma of a non-self-sustained low-pressure glow discharge with a hollow cathode by optical emission spectrometry. The plasma was generated in a mixture of Ar–N2 gases with an argon percentage from 0 to 100% at a total pressure of 1 Pa. The discharge current and voltage were maintained constant and amounted to 18 A and 165 V, respectively. A significant increase in the amount of Ar+ (up to 30%) at a nitrogen content of 10–25% was shown, which is associated with a shift in the reaction of charge exchange of nitrogen with argon towards the generation of argon ions. It was found that at a low partial pressure of nitrogen (≈10%), a sharp increase in the content of atomic nitrogen is observed which is probably due to the dissociation of nitrogen molecules upon collisions with an excited argon atom. [ABSTRACT FROM AUTHOR]

In this paper, the preparation of some isotopically selected targets by ion implantation is described. The selected isotopes to be implanted over graphite matrices described in the present work were 127I and 81Br. These isotopes were chosen for their similarity with the xenon and krypton isotopes of interest for the study of Double Charge Exchange reactions in the NUMEN project (Nuclear Matrix Elements for the Neutrino-less double beta decay). The characterization of the resulting targets after implantation was carried out using Rutherford Back Scattering Spectroscopy (RBS) with 1H, 12C, 28Si beams at different energies and scattering angles. [ABSTRACT FROM AUTHOR]

Single hot-wire velocity measurements have been conducted along a three-dimensional measurement grid to capture the flow-field induced by a 45 ∘ inclined slotted pulsed jet. Based on the periodic behavior of the flow, two different estimation methods have been implemented. The first one, considered as the reference baseline, is the conditional approach which consists in the redistribution of the experimental data into space- and time-resolved three-dimensional velocity fields. The second one uses a neural network to estimate 3D velocity fields given spatial coordinates and time. This paper compares the two methods for a complete flow-field estimation based on hot-wire measurements. Results suggest that the neural network is tailored to capture the phase-averaged dynamic response of the jet induced by the actuator, and identify the coherent structures in the flow field. Interesting performances are also observed when degrading the learning database, meaning that neural networks can be used to drastically improve the temporal or spatial resolution of a flow field estimation compared to the experimental data resolution. [ABSTRACT FROM AUTHOR]

Cobalt and Fe were co-electrodeposited as single crystal, faceted particles onto carbon paper to produce Co/Fe-oxyhydroxide oxygen evolution reaction (OER) catalysts with various Co/Fe ratios. Electron microscopy and Auger electron spectroscopy were used to investigate the morphology and composition of the electrodeposits. Iron content in the deposits increased with increasing Fe concentration in the electrolyte and Fe segregated to the particle surfaces. Electrochemical tests demonstrated that the deposit Co/Fe ratio influences OER activity by altering the electrochemically active surface area (ECSA) and charge transfer resistance. The OER activity increased with increasing Fe content up to ∼65 at% Fe, with a minimum overpotential of 0.33 V at 10 mA cm −2 in 1 M KOH. The fabricated OER catalysts were assembled into a Zn-air battery for discharge-charge cycling tests and showed lower charge potentials compared with bare carbon paper. [ABSTRACT FROM AUTHOR]

The NUMEN (NUclear Matrix Elements for Neutrinoless double beta decay) project was recently proposed with the aim to investigate the nuclear response to Double Charge Exchange reactions for all the isotopes explored by present and future studies of 0νββ decay. The expected level of radiation in the NUMEN experiment imposes severe limitations on the average lifetime of the electronic devices. During the experiments, it is expected that the electronic devices will be exposed to about 105 neutrons/cm2/s according to FLUKA simulations. This paper investigates the reliability of a System On Module (SOM) under neutron radiation. The tests were performed using thermal, epithermal, and fast neutrons produced by the Instituto de Pesquisas Energéticas e Nucleares 4.5 MW Nuclear Research Reactor. The results show that the National Instruments SOM is robust to neutron radiation for the proposed applications in the NUMEN project. [ABSTRACT FROM AUTHOR]

Physics cases of increasing interest in the recent years, such as the study of double charge exchange reactions for neutrino physics, require the study of very suppressed reaction channels in medium-heavy ion induced nuclear reactions. The main experimental challenges are the possibility to identify and detect the medium-heavy quasi-projectiles and the capability to measure very low cross-sections (few nb) with high sensitivity at very forward angles, including zero degree. The experimental techniques adopted in the setup of the MAGNEX magnetic spectrometer to face these issues are described in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Various doped materials have been investigated to improve the structural stability of layered transition metal oxides for lithium‐ion batteries. Most doped materials are obtained through solid state methods, in which the doping of cations is not strictly site selective. This paper demonstrates, for the first time, an in situ electrochemical site‐selective doping process that selectively substitutes Li+ at Li sites in Mn‐rich layered oxides with Mg2+. Mg2+ cations are electrochemically intercalated into Li sites in delithiated Mn‐rich layered oxides, resulting in the formation of [Li1−xMgy][Mn1−zMz]O2 (M = Co and Ni). This Mg2+ intercalation is irreversible, leading to the favorable doping of Mg2+ at the Li sites. More interestingly, the amount of intercalated Mg2+ dopants increases with the increasing amount of Mn in Li1−x[Mn1−zMz]O2, which is attributed to the fact that the Mn‐to‐O electron transfer enhances the attractive interaction between Mg2+ dopants and electronegative Oδ− atoms. Moreover, Mg2+ at the Li sites in layered oxides suppresses cation mixing during cycling, resulting in markedly improved capacity retention over 200 cycles. The first‐principle calculations further clarify the role of Mg2+ in reduced cation mixing during cycling. The new concept of in situ electrochemical doping provides a new avenue for the development of various selectively doped materials. [ABSTRACT FROM AUTHOR]

In this paper, the flower-shaped silver nanoparticle was used as substrate to investigate the SERS effect of pesticide molecules under different treatment conditions. Due to the variation of molecular structure and molecular interactions with pH value and solvent type, the combination mode of molecules and metal surface and electron transfer also changes, resulting in different SERS effects with a certain regularity. It was demonstrated that the optimum pH values for test conditions are in the range of 6.66–11.11 due to the auxiliary of H + ions and undestroyed complete functional groups of ethion. Meanwhile, the ethion in the acetone was the best in the three solvents (ultrapure water, absolute ethanol and acetone). Under optimal conditions, ethion can be detected with a minimum detectable concentration of 10 −10 M. The regression model obtained through principal component analysis (PCA) can be used for rapid and precise detection of the concentration of ethion, suggesting the importance of condition optimization for SERS test. Therefore, the solvent environment can be effectively improved to promote non-resonance enhancement of chemical bonding between adsorbate and metal substrate and resonance enhancement of light-induced charge transfer in molecular-metal system by excitation light. The solvent environment has significant effect on the SERS sensor from chemical enhancement. [ABSTRACT FROM AUTHOR]

Iron is an essential element for almost all organisms on Earth. It is necessary for a number of crucial processes such as hemoglobin and myoglobin transport and storage of oxygen in mammals; electron transfer support in a variety of iron-sulfur protein or cytochrome reactions; and activation and catalysis of reactions of a wide range of substrate like alkanes, olefins, and alcohols. Living organisms adopted iron as the main metal to carry out all of these functions due to the rich coordination chemistry of its two main redox states, Fe2+ and Fe3+, and because of its abundance in the Earth's crust and oceans. This paper presents an overview of the coordination chemistry of iron that makes it suitable for a large variety of functions within biological systems. Despite iron's chemical advantages, organisms were forced to manage with some drawbacks: Fe3+ insolubility and the formation of toxic radicals, especially the hydroxyl radical. Iron chemistry within biology is an example of how organisms evolved by creating molecular machinery to overcome these difficulties and perform crucial processes with extraordinary elegance and efficiency. © 2017 IUBMB Life, 69(6):382-388, 2017 [ABSTRACT FROM AUTHOR]

Background: Electron-capture reaction rates on medium-heavy nuclei are an important ingredient for modeling the late evolution of stars that become core-collapse or thermonuclear supernovae. The estimation of these rates requires the knowledge of Gamow-Teller strength distributions in the β+ direction. Astrophysical models rely on electron-capture rate tables largely based on theoretical models, which must be validated and tested against experimental results. Purpose: This paper presents a systematic evaluation of the ability of theoretical models to reproduce experimental Gamow-Teller transition strength distributions measured via (n,p)-type charge-exchange reactions at intermediate beam energies. The focus is on transitions from stable nuclei in the pf shell (45 ≤ A ≤ 64). In addition, the impact of deviations between experimental and theoretical Gamow-Teller strength distributions on derived stellar electron-capture rates is investigated. Method: Data on Gamow-Teller transitions from 13 nuclei in the pf shell measured via charge-exchange reactions and supplemented with results from β-decay experiments where available, were compiled and compared with strength distributions calculated in shell models (using the GXPF1a and KB3G effective interactions) and quasiparticle random-phase approximation (QRPA) using ground-state deformation parameters and masses from the finite-range droplet model. Electron-capture rates at relevant stellar temperatures and densities were derived for all distributions and compared. Results: With few exceptions, shell-model calculations in the pf model space with the KB3G and GXPF1a interactions qualitatively reproduce experimental Gamow-Teller strength distributions of 13 stable isotopes with 45 ≤ A ≤ 64. Results from QRPA calculations exhibit much larger deviations from the data and overestimate the total experimental Gamow-Teller strengths. For stellar densities in excess of 107 g/cm³, ground-state electron-capture rates derived from the shell-model calculations using the KB3G (GXPF1a) interaction deviate on average less than 47% (31%) from those derived from experimental data for which the location of daughter states at low excitation energies are well established. For electron-capture rates derived from Gamow-Teller strengths calculated in QRPA, the deviations are much larger, especially at low stellar densities. Conclusions: Based on the limited set of test cases available for nuclei in the pf shell, shell-models using the GXPF1a and KB3G interactions can be used to estimate electron-capture rates for astrophysical purposes with relatively good accuracy. Measures of the uncertainties in these rates can serve as input for sensitivity studies in stellar evolution models. Ground-state electron-capture rates based on the QRPA formalism discussed in the paper exhibit much larger deviations than those based on the shell-model calculations and should be used with caution, especially at low stellar densities. [ABSTRACT FROM AUTHOR]

In this paper, two kinds of hybrid α-Fe2O3@Co3O4 and α-Fe2O3@MnCo2O4 composites with high yield have been successfully synthesized on a flexible carbon cloth via simple solution methods. These as-obtained products serve as supercapacitor electrodes without the use of any adscititious surfactants and binders. These two hybrid electrode architectures make full use of the synergistic effects between α-Fe2O3 frameworks and coated Co3O4 or MnCo2O4 layers. They exhibit obviously enhanced discharge areal capacitance of 490 mF cm−2 and 1073 mF cm−2 for α-Fe2O3@Co3O4 and α-Fe2O3@MnCo2O4 composites at 1 mA cm−2 with an identical potential voltage of 0–0.9 V. Long-life cycling stability with capacitance retention of 74.6% for α-Fe2O3@Co3O4 and 77.8% for α-Fe2O3@MnCo2O4 are presented after 6000 charge/discharge cycles, respectively. Such prominent electrochemical performances are mainly ascribed to the hybrid composites, which can provide a large reaction surface area, fast ion and electron transfer and good structure combination stability. The as-synthesized flexible hybrid composites might have promising applications in micro/nanoscale energy storage devices. [ABSTRACT FROM AUTHOR]

Background: Stellar electron-capture reactions on medium-heavy nuclei are important for many astrophysical phenomena, including core-collapse and thermonuclear supernovae and neutron stars. Estimates of electroncapture rates rely on accurate estimates of Gamow-Teller strength distributions, which can be extracted from charge-exchange reactions at intermediate beam energies. Measured Gamow-Teller transition strength distributions for stable pf:shell nuclei are reasonably well reproduced by theoretical calculations in the shell model, except for lower mass nuclei where admixtures from the sd shell can become important. Purpose: This paper presents a β+ charge-exchange experiment on 45Sc, one of the lightest pf-shell nuclei. The focus was on Gamow-Teller transitions tofinal states at low excitation energies, which are particularly important for accurate estimations of electron-capture rates at relatively low stellar densities. The experimental results are compared with various theoretical models. Method: The double-differential cross section for the 45Sc(t, 3He +γ) reaction was measured using the NSCL Coupled-Cyclotron Facility at 115 MeV/u. Gamow-Teller contributions to the excitation-energy spectra were extracted by means of a multipole-decomposition analysis, γ rays emitted due to the deexcitation of 45Ca were measured using GRETINA to allow for the extraction of Gamow-Teller strengths from very weak transitions at low excitation energies. Results: Gamow-Teller transition strengths to 45Ca were extracted up to an excitation energy of 20 MeV, and that to the first excited state in 45Ca at 174 keV was extracted from the γ-ray measurement, which, even though weak, is important for the astrophysical applications and dominates under certain stellar conditions. Shell-model calculations performed in the pf shell-model space with the GXPF1A, KB3G, and FPD6 interactions did not reproduce the experimental Gamow-Teller strength distribution, and a calculation using the quasiparticle random phase approximation that is often used in astrophysical simulations also could not reproduce the experimental strength distribution. Conclusions: Theoretical models aimed at describing Gamow-Teller transition strengths from nuclei in the lower pf shell for the purpose of estimating electron-capture rates for astrophysical simulations require further development. The likely cause for the relatively poor performance of the shell-model theory is the influence of intruder configurations from the sd shell. The combination of charge-exchange experiments at intermediate beam energy and high-resolution γ-ray detection provides a powerful technique to identify weak transitions to low-lying final states that are nearly impossible to identify without the coincidences. Identification of these weak low-lying transitions is important for providing accurate electron-capture rates for astrophysical simulations [ABSTRACT FROM AUTHOR]

When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330 to 1051 cm-1. The response time of the TRIR detection setup is ~40 ns, with a typical sensitivity of ~100 µOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. This new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here. [ABSTRACT FROM AUTHOR]

This paper analyzes the slow-varying electric fields and the associated currents of a total of 35 negative upward lightning initiated by the Peissenberg tower, Germany. Thirty-four of which were from winter upward lightning and only one from summer upward lightning. It appears that all of the winter upward lightning were initiated without nearby preceding lightning activity (called “self-initiated” lightning) and only the summer lightning was triggered by nearby lightning activity (called “other-triggered” lightning). The slow-varying electric fields of the winter upward lightning showed a fast rise characterized by the 10–90% risetime, with an arithmetic mean of 13.8 ms. After attaining the maximum, the electric field turned into a slow decay being characterized by the time on half value which was evaluated to having the arithmetic mean of 441 ms. Transported charges to ground were on average 44.8 C and on maximum 165 C. The maximum value of the electric field was 39.9 kV/m on average, with the highest value being 64.5 kV/m. For the electric fields, higher values were prevented by recovery effects such as the corona from objects at ground and the redistribution of the charge in the thundercloud. Due to these effects, no or only weak correlations were found between the 10–90% risetime, the time on half value, the charge, and the maximum of the electric field. From additional measurements with a field mill, it was found that the electric field recovers to the starting level within some seconds. [ABSTRACT FROM PUBLISHER]

Astatine isotopes can be produced in liquid lead-bismuth eutectic targets through proton-induced double charge exchange reactions on bismuth or in secondary helium-induced interactions. Models implemented into the most common high-energy transport codes generally have difficulties to correctly estimate their production yields as was shown recently by the ISOLDE Collaboration, which measured release rates from a lead-bismuth target irradiated by 1.4 and 1 GeV protons. In this paper, we first study the capability of the new version of the Liège intranuclear cascade model, INCL4.6, coupled to the deexcitation code ABLA07 to predict the different elementary reactions involved in the production of such isotopes through a detailed comparison of the model with the available experimental data from the literature. Although a few remaining deficiencies are identified, very satisfactory results are found, thanks in particular to improvements brought recently on the treatment of low-energy helium-induced reactions. The implementation of the models into MCNPX allows identifying the respective contributions of the different possible reaction channels in the ISOLDE case. Finally, the full simulation of the ISOLDE experiment is performed, taking into account the likely rather long diffusion time from the target, and compared with the measured diffusion rates for the different astatine isotopes, at the two studied energies, 1.4 and 1 GeV. The shape of the isotopic distribution is perfectly reproduced as well as the absolute release rates, assuming in the calculation a diffusion time between 5 and 10hours. This work finally shows that our model, thanks to the attention paid to the emission of high-energy clusters and to low-energy cluster induced reactions, can be safely used within MCNPX to predict isotopes with a charge larger than that of the target by two units in spallation targets, and, probably, more generally to isotopes created in secondary reactions induced by composite particles. [ABSTRACT FROM AUTHOR]

Abstract: A detailed study using the ab initio DFT-based calculations of the electronic and optical properties of pure and Mn4+ doped Ba2LaNbO6 is presented in this paper. Comparison of the calculated electronic bands structure, density of states diagrams, and dielectric functions for the pure and doped crystal reveals the changes induced by the Mn4+ impurity ions. In addition, the energy levels of the Mn4+ ion in the ordered perovskite Ba2LaNbO6 are calculated by the exchange charge model (ECM) of crystal field theory and compared with the experimental data that has been presented in the literature. The calculated Mn4+ energy levels are in good agreement with the experimental spectra. Additionally, the excitation band shapes of the 4A2g(4F)–4T2g(4F) and 4A2g(4F)–4T1g(4F) transitions are modeled to estimate the zero-phonon lines (ZPL) positions and the effective number of phonons, which are involved in the corresponding excitation transition. The results of our calculations yield the crystal field parameter of Dq=1780cm−1 and Racah parameters B=670 and C=3290cm−1, with C/B=4.9 for the Mn4+ ion in the double-perovskite Ba2LaNbO6. [Copyright &y& Elsevier]

Abstract: We describe a setup for studies of dissociation dynamics of multiply charged molecules formed due to highly charged ion impact. The setup consists of a multihit, position-sensitive, time of flight measurement system along with an electrostatic analyzer with offset detector. Brief description of different components of the setup and electronics for multihit data acquisition is presented in this paper. Coulomb explosion of multiply ionized N2 and charge exchange studies on Ar with highly charged projectile ion is carried out to test the performance of the spectrometer and its multifold coincidence capabilities. [Copyright &y& Elsevier]

The Regge features of elastic K±N → K±N, and charge exchange K - p → K0n and K + n → K0p reactions are described by using a combined analysis of all these channels at high momenta. Based on the meson exchanges in the t -channel with their decays to a KK pair allowed, the exchanges of ρ (775) + ω (782) are excluded in contrast to existing model calculations and the present paper follows a new scheme for the meson exchanges a0 (980) + ϕ (1020) + f2 (1275) + a2 (1320) Reggeized for the forward elastic-scattering amplitude together with Pomeron. The charge exchange reactions are described by a0 (980) + a2 (1320) exchanges in the t -channel. Dominance of the isoscalar f2 and Pomeron exchanges beyond PLab ≈ 3 GeV/c is shown in the elastic process. Both the isovector a0 and a2 exchanges in charge exchange reactions play the respective roles in the low- and high-momenta region. Differential and total cross sections are presented to compare with existing data. A discussion is given to the polarization of K-p → K-p at PLab = 10 GeV/c and K-p → K0n at PLab = 8 GeV/c. [ABSTRACT FROM AUTHOR]

The AEgIS experiment aims at producing antihydrogen (and eventually measuring the effects of the Earth gravitational field on it) with a method based on the charge exchange reaction between antiproton and Rydberg positronium. To be precise, antiprotons are delivered by the CERN Antiproton Decelerator (AD) and are trapped in a multi-ring Penning trap, while positronium is produced by a nanoporous silica target and is excited to Rydberg states by means of a two steps laser excitation. New Monte Carlo simulations are presented in this paper in order to investigate the current status of the AEgIS experiment [1] and to interpret the recently collected data [2]. [ABSTRACT FROM AUTHOR]

Gas giant exoplanets orbiting at close distances to the parent star are subjected to large radiation and stellar wind fluxes. In this paper, hydrodynamic simulations of the planetary upper atmosphere and its interaction with the stellar wind are carried out to understand the possible flow regimes and how they affect the Lyα transmission spectrum. Following Tremblin and Chiang, charge exchange reactions are included to explore the role of energetic atoms as compared to thermal particles. In order to understand the role of the tail as compared to the leading edge of the planetary gas, the simulations were carried out under axisymmetry, and photoionization and stellar wind electron impact ionization reactions were included to limit the extent of the neutrals away from the planet. By varying the planetary gas temperature, two regimes are found. At high temperature, a supersonic planetary wind is found, which is turned around by the stellar wind and forms a tail behind the planet. At lower temperatures, the planetary wind is shut off when the stellar wind penetrates inside where the sonic point would have been. In this regime mass is lost by viscous interaction at the boundary between planetary and stellar wind gases. Absorption by cold hydrogen atoms is large near the planetary surface, and decreases away from the planet as expected. The hot hydrogen absorption is in an annulus and typically dominated by the tail, at large impact parameter, rather than by the thin leading edge of the mixing layer near the substellar point. [ABSTRACT FROM AUTHOR]

C60 is a scaffold or an electron acceptor  depending on the number of addends. The role of different fullerene subunits is dramatically different in a supramolecular photosynthetic model obtained from a C60 monoadduct bearing an imidazole moiety and a C60 hexa‐adduct decorated with 12 peripheral metalloporphyrins. In their Full Paper on page 223 ff., J. ‐F. Nierengarten, N. Armaroli et al. show that only the monosubstituted C60 derivative plays an active role (electron acceptor) in the cascade of photoinduced events. [ABSTRACT FROM AUTHOR]

Capacitively coupled plasma (CCP) tools utilized for plasma etching of dielectric features utilize large amounts of power for processing. As a result, neutral gas heats up significantly during processing. The resulting gas density variations across the reactor can affect reaction rates, radical densities, plasma characteristics and uniformity within the reactor. In this paper, results from a two-dimensional computational investigation of an Ar/CF4 CCP discharge incorporating an energy equation solution for all ions and neutrals are discussed. The dominant neutral gas heating process is identified to be elastic collisions with ions while conduction is found to be the major mechanism of heat transport. Some species such as F and CF3 demonstrate higher temperatures than the feedstock gases owing to additional heating via charge-exchange reactions and/or Franck–Condon heating. Typical process parameters such as pressure, frequency of excitation, power and gas composition are varied to investigate their impact on gas temperature. At higher excitation frequency and/or pressure, increased elastic collisions with ions lead to greater heat generation. The heat generated per molecule of the radicals, however, decreases with increase in pressure leading to a decrease in gas temperature. The increase in neutral collision frequencies with pressure also results in the decrease in temperature difference between species in the plasma. As CF4 fraction increases, both the elastic collision cross-section and Franck–Condon heating sources increase, leading to higher gas temperatures. [ABSTRACT FROM AUTHOR]