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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]

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]

B replying to b Shaun G. Ard et al. I Nature Communications i https://doi.org/10.1038/s41467-022-30566-3 (2022) In our 2020 Nature Communications paper[1], we reported a strong inverse kinetic isotope effect in the charge transfer reactions of NH SB 3 sb and ND SB 3 sb with Xe SP + sp ( SP 2 sp P SB 3/2 sb ) ions. 10.1039/D1SC01652K 3 Ard, S, Viggiano, A. A, Sweeny, B. C, Long, B. & Shuman, N. Inconsistent kinetic isotope effect in ammonia charge exchange reaction measured in a Coulomb crystal and in a selected-ion flow tube. For example, there is no sympathetic cooling of rotational or vibrational modes of trapped ions as the interaction range is too long (neighbouring ions are separated by 10-20 m); the reaction complex therefore will not undergo any inelastic collisions with other co-trapped ions. [Extracted from the article]

The charge exchange (CE) reaction is an effective probe to study the structure of atomic nuclei in the isospin dimension, which has been studied for decades. To expand the range of nuclei studied by CE reactions to a wider range and research the structure characteristics of unstable nuclei, including the isospin symmetry, spin-isospin excitation, and nuclear symmetry energy, a semi-cylindrical time projection chamber (scTPC) prototype was designed and constructed to probe ( 3 He,t) CE reactions in inverse kinematics. The 266 nm UV laser was used to achieve electron-drift-velocity calibration. The scTPC has an energy resolution (FWHM) of 5.6% for α particles emitted by 241 Am radioactive source. The position resolution of scTPC is described by the residual method. The spatial resolution on the pad plane is 409 μ m. And the position resolution in the drift direction is 326 μ m, equivalent to an angular resolution of 0.4 ∘ . These performances suggest that the scTPC can measure Δ E and particle tracks precisely. The successful development of the scTPC prototype provides better conditions for the next step of experimental data analysis and processing. [ABSTRACT FROM AUTHOR]

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]

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]

Current values of the neutron lifetime, determined by two entirely distinct measurement techniques of comparable precision, differ to a statistically significant degree, a result which has become known as the neutron lifetime anomaly. In a previous publication we have shown that the discrepancy can be resolved by taking account of electron transfer charge exchange reactions between residual gases and final state protons stored in a quasi-Penning trap. In this article we analyze unique experimental data obtained during the course of the first published neutron lifetime measurement that used a proton trap. These data employed trapping times greater by a factor of a thousand than became conventional in later experiments. The data show that significant event losses occur, probably due to residual gas other than molecular hydrogen or helium. Additionally, the molecular ion H2+ produced by charge exchange in H2 undergoes secondary molecular reactions, producing the molecular ion H3+ and the ion HeH+ which is also produced by secondary reactions in helium. These ions could result in event losses depending on the energy and time-of-flight acceptance windows. Energy losses are evaluated and ionic compositions are quantitively assessed as functions of trapping time and residual gas density to account for an energy spectrum obtained using a silicon surface barrier detector. The spectrum is strongly influenced by charge exchange, secondary molecular reactions and backscattering in the detector dead layer. [ABSTRACT FROM AUTHOR]

In a recent experiment, the repair efficiency of DNA thymine cyclobutane dimers (T＜＞T) on UV excitation of 8-oxoG base paired either to C or A was reported. An electron transfer mechanism from an excited charge transfer state of 8-oxoG–C (or 8-oxoG–A) to T＜＞T was proposed and 8-oxoG–A was found to be 2–3 times more efficient than 8-oxoG–C in repair of T＜＞T. Intra base pair proton transfer (PT) in charge transfer (CT) excited states of the base pairs was proposed to quench the excited state and prevent T＜＞T repair. In this work, we investigate this process with TD-DFT calculations of the excited states of 8-oxoG–C and 8-oxoG–A base pairs in the Watson–Crick and Hoogsteen base pairs using long-range corrected density functional, ̉B97XD/6-31G* method. Our gas phase calculations showed that CT excited state (1ππ*(CT)) of 8-oxoG–C appears at lower energy than the 8-oxoG–A. For 8-oxoG–C, TD-DFT calculations show the presence of a conical intersection (CI) between the lowest 1ππ*(PT–CT) excited state and the ground state which likely deactivates the CT excited state via a proton-coupled electron transfer (PCET) mechanism. The 1ππ*(PT–CT) excited state of 8-oxoG–A base pair lies at higher energy and its crossing with ground state is inhibited because of a high energy gap between 1ππ*(PT–CT) excited state and ground state. Thus the gas phase calculations suggest the 8-oxoG–A would have longer excited state lifetimes. When the effect of solvation is included using the PCM model, both 8-oxoG–A and 8-oxoG–C show large energy gaps between the ground state and both the excited CT and PT–CT states and suggest little difference would be found between the two base pairs in repair of the T＜＞T lesion. However, in the FC region the solvent effect is greatly diminished owing to the slow dielectric response time and smaller gaps would be expected. [ABSTRACT FROM AUTHOR]

Backward angle (u-channel) scattering provides complementary information for studies of hadron spectroscopy and structure, but has been less comprehensively studied than the corresponding forward angle case. As a result, the physics of u-channel scattering poses a range of new experimental and theoretical opportunities and questions. We summarize recent progress in measuring and understanding high energy reactions with baryon charge exchange in the u-channel, as discussed in the first Backward angle (u-channel) Physics Workshop. In particular, we discuss backward angle measurements and their theoretical description via both hadronic models and the collinear factorization approach, and discuss planned future measurements of u-channel physics. Finally, we propose outstanding questions and challenges for u-channel physics. [ABSTRACT FROM AUTHOR]

The results of a numerical simulation of the dynamics of the airglow of the atomic oxygen red line (630 nm) due to ionospheric heating by high-power, high-frequency (HF) radio emission are presented. The simulation was based on a system that incorporates an equation for the electron temperature Te (thermal conductivity) with a localized heating source near the reflection point of the pump wave; an equation to balance the ion concentration in molecular oxygen which emerges from the charge exchange reaction (О+ + О2 → + О); and an equation for the concentration of oxygen atoms in the excited state O(1D), which results from the dissociative recombination ( + е− → О + О(1D)) and is responsible for the airglow. The height distributions of molecular (O2) and atomic (O) oxygen were taken from the NRLMSISE-00 empirical model of the atmosphere, and the profiles of the electron content Ne were taken from the International Reference Ionosphere (IRI) model modified according to the 2010 and 2012 experimental data from the SURA ionospheric heating facility. The results have been compared with experimental data. The calculations make it possible to interpret the experimentally observed suppression of the background airglow during ionospheric heating by a high-power radio wave and the "afterglow" effect upon the cessation of heating. [ABSTRACT FROM AUTHOR]

The differential cross sections of the charge exchange reaction d p → (p p) n has been measured at 1.75 GeV/c per nucleon for small transferred momenta using the one arm magnetic spectrometer STRELA at the Nuclotron accelerator in JINR Dubna. The ratio of the differential cross section of the charge exchange reaction d p → (p p) n to that of the n p → p n elementary process is discussed in order to estimate the spin-dependent part of the n p → p n charge exchange amplitude. The n p → p n amplitude turned out to be predominantly spin-dependent. [ABSTRACT FROM AUTHOR]

The current rate constants agree reasonably well with the Coulomb crystal measurements for both the NH SB 3 sb and ND SB 3 sb reactions given the absolute uncertainties. The rate constants were measured by monitoring the first order decay of Xe SP + sp ( SP 2 sp P SB 3/2 sb ) as a function of the concentration of NH SB 3 sb /ND SB 3 sb . Ions were produced using an electron impact ion source yielding both ground Xe SP + sp ( SP 2 sp P SB 3/2 sb ) and excited state Xe SP + sp ( SP 2 sp P SB 1/2 sb ), then mass-selected and injected into a flow tube maintained at ~0.3 Torr of fast flowing helium gas. [Extracted from the article]

In this work, the suitability of atmospheric pressure photoionization (APPI) has been assessed for the determination of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) by gas chromatography–high-resolution mass spectrometry (GC-HRMS). The APPI of target compounds has been tested in both positive and negative ion modes. Under positive ion mode, the analytes generated the molecular ion, which was favoured using dopants that promote charge exchange gas-phase reactions (i.e., benzene), while in negative ion mode, the ion [M−Cl+O]− for PCDFs and dl-PCBs were mainly formed, providing the best results using benzene and diethyl ether as dopants, respectively. Concerning PCDDs, highly chlorinated congeners were mainly ionized by means of the [M−Cl]− ion, whereas [M−Cl+O2]− was the base peak for tetraCDD and [M−Cl+O]− for penta- and hexaCDDs. Method quality parameters, in accordance with the current EU Regulation guidelines for food and feed analysis, showed the good performance of the two GC-APPI-HRMS (Orbitrap) methods since they provided high detection capability (low fg levels), good linearity, and satisfactory precision (RSD% < 9%). In addition, the GC-APPI-HRMS (Orbitrap) methods were validated by analysing selected environmental and feed samples and the results were compared to those obtained using conventional GC-EI-HRMS, demonstrating the good performance in the analysis of the target compounds. Hence, the GC-APPI-HRMS technique can be proposed as alternative to the conventional methods for the determination of PCDD/Fs and dl-PCBs in environmental and feed matrices. [ABSTRACT FROM AUTHOR]

Isotopic substitution has long been used to understand the detailed mechanisms of chemical reactions; normally the substitution of hydrogen by deuterium leads to a slower reaction. Here, we report our findings on the charge transfer collisions of cold Xe + ions and two isotopologues of ammonia, NH 3 and ND 3 . Deuterated ammonia is found to react more than three times faster than hydrogenated ammonia. Classical capture models are unable to account for this pronounced inverse kinetic isotope effect. Moreover, detailed ab initio calculations cannot identify any (energetically accessible) crossing points between the reactant and product potential energy surfaces, indicating that electron transfer is likely to be slow. The higher reactivity of ND 3 is attributed to the greater density of states (and therefore lifetime) of the deuterated reaction complex compared to the hydrogenated system. Our observations could provide valuable insight into possible mechanisms contributing to deuterium fractionation in the interstellar medium. Inverse kinetic isotope effects (KIEs) are rarely observed. Here, the authors report an inverse KIE in the charge transfer reaction of Xe + with ammonia. ND 3 reacts more than 3 times faster than NH 3 , despite no N-H or N-D bonds being broken, with implications for our understanding of interstellar chemistry. [ABSTRACT FROM AUTHOR]

We analyse $K^{-} p \rightarrow (\eta, \eta',\pi^{0}) \Lambda$ on the basis of the fit of data in a wide region of energies, and $\pi^{-} p \rightarrow (\eta, \eta') n$ at the energies of GAMS- $4\pi$ . We show that disagreements between the data and the predictions of Regge theory may be explained by the mode change of summation of intermediate contributions at increasing energy, from coherent to non-coherent. A method of experimental measurement of the non-coherent contributions is proposed. On the basis of available data on the charge-exchange reactions the $\eta$ - $\eta'$ mixing is estimated. [ABSTRACT FROM AUTHOR]

The role of the ammonium cation on the reversible electrochemistry of Prussian Blue thin films was analyzed through in situ combination of three different impedance techniques. Electrochemical impedance spectroscopy provides information on the electron transfer. Mass impedance spectroscopy allows the exchange of free water, ammonium, and proton ions to be elucidated. Color impedance spectroscopy provides the kinetics of electrochromic changes of Prussian Blue structure (main backbone structure, ferrocyanide vacancies, and trapped structures). The simultaneous measurement of the three impedances gives detailed information on the mechanism of the whole process, specifically one faster and two slower, which have been identified during the electrochemical reactions of Prussian Blue films in NH Cl acidic solutions. [ABSTRACT FROM AUTHOR]

Manipulating the macroscopic phases of solids using ultrashort light pulses has resulted in spectacular phenomena, including metal-insulator transitions, superconductivity and subpicosecond modification of magnetic order. The development of this research area strongly depends on the understanding and optical control of fundamental interactions in condensed matter, in particular the exchange interaction. However, disentangling the timescales relevant for the contributions of the exchange interaction and spin dynamics to the exchange energy, Eex, is a challenge. Here, we introduce femtosecond stimulated Raman scattering to unravel the ultrafast photo-induced dynamics of magnetic excitations at the edge of the Brillouin zone. We find that femtosecond laser excitation of the antiferromagnet KNiF3 triggers a spectral shift of the two-magnon line, the energy of which is proportional to Eex. By unravelling the photo-induced modification of the two-magnon line frequency from a dominating nonlinear optical effect, we find that Eex is increased by the electromagnetic stimulus. [ABSTRACT FROM AUTHOR]

The charge exchange reaction p̄+Ps→e−+H̄, of interest for the future experiments (GBAR, AEGIS, ATRAP,...) aiming to produce antihydrogen atoms, is investigated in the energy range between the e−+H̄(n=2) and e−+H̄(n=3) thresholds. An ab-initio method based on the solution of the Faddeev-Merkuriev equations is used. Special focus is put on the impact of the Feshbach resonances and the Gailitis-Damburg oscillations, appearing in the vicinity of the p̄+Ps(n=2) threshold, on the H̄ production cross section. [ABSTRACT FROM AUTHOR]

Abstract: Within the framework of dynamical adiabatic approach the hidden crossing theory of inelastic transitions is applied to charge exchange in H+ + He+(1s) collisions in the wide range of center of mass collision energies Ecm = (1.6-70) keV. The good agreement with experiment and molecular close coupling calculations is obtained. At low energies our 4-state results are closest to the experiment and correctly reproduce the shoulder in energy dependence of the cross section around Ecm = 6 keV. The 2-state results correctly predict the position of the maximum of the cross section at Ecm ≈ 40 keV, whereas 4-state results fail to correctly describe the region around the maximum. The reason for this is the fact that adiabatic approximation for a given two-state hidden crossing is applicable for values of the Schtueckelberg parameter >1. But with increase of principal quantum number N the Schtueckelberg parameter decreases as ~N−3. That is why the 4-state approach involving higher excited states fails at smaller collision energies Ecm ≈ 15 keV, while the 2-state approximation which involves low lying states can be extended to higher collision energies. Graphical abstract: [ABSTRACT FROM AUTHOR]

We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volume of the molten Na alloy can be used with a limited ion-exchange membrane size. In this proof-of-concept study, the feasibility of multi-electron transfer redox reactions per active ion and multiple active ions for catholytes has been demonstrated. The critical barriers to mature this new HNFBs have also been explored. [ABSTRACT FROM AUTHOR]