Search

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]

The theory of heavy ion double charge exchange (DCE) reactions proceeding by effective rank-2 isotensor interactions is presented. Virtual pion–nucleon charge exchange interactions are investigated as the source for induced isotensor interactions, giving rise to the Majorana DCE (MDCE) reaction mechanism. MDCE is of a generic character, proceeding through pairs of complementary ( π ± , π ∓ ) reactions in the projectile and target nucleus. The dynamics of the elementary processes is discussed, where the excitation of pion–nucleon resonances are of central importance. Investigations of initial and final state ion–ion interactions show that these effects are acting as vertex renormalizations. In closure approximation, well justified by the finite pion mass, the second-order transition matrix elements reduce to pion potentials and effective two-body isotensor DCE interactions, giving rise also to two-body correlations in either of the participating nuclei. Connections to neutrinoless Majorana double beta decay (MDBD) are elucidated at various levels of the dynamics, from the underlying fundamental electro-weak and QCD scales to the physical scales of nuclear MDBD and MDCE physics. It is pointed out that heavy ion MDCE reactions may also proceed by competing electro-weak charge exchange processes, leading to lepton MDCE by electrons, positrons, and neutrinos. [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]

Composite particle, (3 H e , t) , charge exchange reactions on targets 1 2 C , 1 3 C , 1 8 O , 2 6 M g , 5 8 N i and 1 1 8 , 1 2 0 S n at 140 MeV/u beam energy have been analyzed by employing distorted wave impulse approximation (DWIA). Specifically, unit cross-section and angular distribution have been calculated using normal optical model potential (NOMP) and single folding optical model potential (SFOMP) for both relativistic and non-relativistic cases. The sensitivity of present results on exchange terms has also been examined and it is pertinent to report here that the inclusion of these effects reduces the cross-section in magnitude up to 60%, which in turn brings it closer to the data except for 1 2 C. [ABSTRACT FROM AUTHOR]

Although photochemistry-enabled escape of oxygen is a dominant atmospheric loss process at Mars today, ion outflow plays an essential role in the long-term evolution of Mars' atmosphere. Apart from heavy planetary ions such as O +, O2 +, and CO2 +, the loss of planetary protons is also important because it could be related to water loss. To study planetary proton loss due to solar wind interaction, we improve the 4-species (O +, O2 +, CO2 +, and H +) single-fluid magnetohydrodynamic (MHD) model of Mars, to a 5-species (separating planetary protons and solar wind protons) MHD model so that the two types of protons can be tracked separately. The global distributions of solar wind protons and planetary ions at low altitudes are investigated. The calculated planetary proton escape rates are larger than heavy ion loss rates and solar wind proton inflows for both solar maximum and minimum conditions. Planetary proton escape rates are 1-2 orders less than neutral hydrogen loss, suggesting that planetary protons could contribute to no >10% of the hydrogen loss under current conditions. By comparing normal cases with cases for which H-O charge exchange reactions or electron impact ionizations are switched off, we find that H-O charge exchange mainly affects densities at low altitudes, while impact ionizations exert great influence on escape rates at high altitudes. The overall results suggest the specific treatment of proton origins in models of Mars atmosphere escape provides better insight into the contributing processes, and should be included in future studies focusing on water's fate. [ABSTRACT FROM AUTHOR]

By analyzing the latitudinal distributions of ionospheric ions observed by the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions satellite at 670 km altitude in different seasons, we found that the large‐scale depletion of nighttime oxygen ions is prevalent at the low and middle latitudes of winter hemisphere (center ∼ 30°) under different geomagnetic conditions. The latitudinal width of the winter oxygen ion depletion (WOD) region is about 20°–60° at different longitudes, and its upper boundary latitudes are mostly lower than the midlatitude trough (|λ| ≥ 50°) of nighttime hydrogen ions (H+) near the plasmapause. In the WOD region, the density ratio of oxygen and hydrogen ions and that of their neutral densities (O and H) approximately agree with the chemical equilibrium relationship of charge exchange reactions (H + O+ ↔ H+ + O) predicted by previous theory, indicating that the charge exchange reactions are mainly responsible for the large‐scale oxygen ion depletion at the low and middle latitudes in winter hemisphere. Plain Language Summary: Previous studies focused on the nighttime midlatitude trough of ionospheric electrons (e−) and light ions (H+ and He+). Although the percentage of nighttime oxygen ions was found to decrease in winter hemisphere at 400 km altitude, it is not clear whether the winter oxygen ion depletion (WOD) is a common phenomenon in the topside ionosphere. Moreover, the mechanism of the WOD has not been understood clearly. Here, our statistical results indicate that the large‐scale depletion of nighttime oxygen ions is prevalent at the low and middle latitudes of winter hemisphere under different geomagnetic conditions. By analyzing the relationship among the latitudinal changes in the ion bulk velocity, densities and their neutral densities, we found that the charge exchange reactions mainly cause the nighttime oxygen ion depletion at the low and middle latitudes in winter hemisphere in the topside ionosphere. Key Points: The nighttime oxygen ions decrease remarkably at the low and middle latitudes of winter hemisphere in the topside ionosphereThe latitudes of large‐scale oxygen ion depletion (center ∼ 30°) are mostly lower than the midlatitude trough of nighttime hydrogen ionsThe winter depletion of nighttime oxygen ions is largely due to the charge exchange reactions between oxygen ions and atomic hydrogen [ABSTRACT FROM AUTHOR]

(1) Pions produced in the development of extended atmospheric cosmic ray air showers subsequently decay to muons. The measured yield of those muons is generally underestimated by current phenomenological models and event generators optimized for cosmic ray physics. The importance of those disagreements motivates the feasibility studies for testing these models at the Large Hadron Collider (LHC) energies, at the highest center-of-mass energies achievable in a laboratory. The interaction of a nucleus and a virtual pion created in a charge exchange reaction at the LHC is a similar process to those contributing to the development of air showers in case of cosmic rays. The crucial problem of such an analysis is the selection of charge exchange events with the highest possible efficiency and high purity from proton–proton collisions at the LHC. (2) For this we consider distributions of various measurable quantities given by event generators commonly used in cosmic ray physics. (3) We examine the expected distributions of energy deposited in different calorimeters of an LHC experiment. We consider the geometrical acceptance and energy resolution of the detectors at the Compact Muon Solenoid (CMS) experiment, as an example. We determine a working point cut from the various options for event selection, and compare signal and background predictions using different models for a representative simple observable, such as average transverse momentum or charge particle yield. (4) A set of event selection cuts along these considerations is proposed, with the aim of achieving optimal efficiency and purity. [ABSTRACT FROM AUTHOR]

A chemical reaction mechanism of chlorine plasma under low-pressure conditions that is widely used in the literature is validated against the experimental data of Y. Wang and J. K. Olthoff [J. Appl. Phys. 85, 6358 (1999)] for an inductively coupled plasma reactor. The model used in the present study is a self-consistent two-dimensional fluid plasma model coupled with Maxwell's equations. The quantities of interest in the plasma are the fluxes and energy distribution functions of Cl2+ and Cl+ ions. We find that the charge exchange reaction between Cl+ and Cl2 that is typically included in chlorine plasma reaction mechanisms results in poor predictability of the model compared to experiments. Neglecting this reaction allows for a correct prediction of the dominant ion species in the low-pressure chlorine plasma and dependence of their fluxes on the gas pressure. Additionally, neglecting the charge exchange reaction allows for a rather accurate prediction of ion energy distribution functions at the grounded electrode. Overall, we conclude that the rate coefficient of the charge exchange reaction between Cl+ and Cl2 reported in the literature significantly exceeds what may in fact explain the role of this process in a low-pressure plasma discharge. [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]

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]

These lectures, held at a school at the Galileo Galilei Institute for Theoretical Physics, give a survey of the formalism, the methods and achievements of nuclear direct reaction theory. After recapitulating the principles of quantum scattering theory, projection techniques are used to reduce the complexities of nuclear reactions to the manageable level of a set of a few selected coupled channels interacting via effective operators. Direct reactions are introduced as fast reactions proceeding preferentially through the excitation of doorway components of the nuclear many-body configurations, corresponding to a separation of scales in energy and momentum transfer. The concept of the optical model is introduced and applied to elastic scattering on nuclei. The coupled channel T-matrix formalism is discussed for pion-induced reactions on the nucleon. Applications of direct reaction to theory are illustrated for transfer reactions, inelastic scattering, and single and double charge exchange reactions with light and heavy ions. [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]