Charge Exchange Research Articles

Abstract. Ice particles play a crucial role in shaping cloud electrification, affecting the intensity of lightning activity. Previous studies have found a change of electric activity with varying aerosols concentration or active secondary ice production processes (SIP). However, the electric response to those parameters can differ with different cloud conditions and interact between themselves. The Meso-NH model was used with the two-moment microphysics scheme LIMA coupled with an explicit electrical scheme. Three idealized storms with varying warm-phase thicknesses were simulated to examine their response to aerosol concentrations and SIP mechanisms. Increasing the cloud condensation nuclei (CCN) or the ice nucleating particle (INP) concentration increases ice crystal concentration, non-inductive charging and lightning activity up to a threshold. The main ice production processes (heterogeneous, homogeneous nucleation or Hallett-Mossop mechanism) depend on the cloud base temperature, and the aerosol concentration. CCN concentration thresholds (1000–8000 cm−3) differ across all storms due to cloud base temperature, while the threshold for INP concentration is generally ∼ 100 L−1. Higher CCN concentrations increase cloud water content, affecting charge polarity, but has a relatively limited impact on graupel mass. SIP mechanisms significantly enhance non-inductive charging and lightning activity by increasing ice crystal concentrations, particularly at low altitudes where primary ice production is inactive. This promotes ice-graupel collisions and amplifies charge exchange in each grid cell. The intensity of SIP processes varies with the thickness of the warm-phase region. Raindrop shattering freezing is the most sensitive and requires a deep warm-phase, while Hallett-Mossop and collisional ice break-up produce abundant ice crystals in all storms.

Abstract The spectrum of high‐altitude blue auroral emissions was observed with HyperSpectral camera for auroral imaging (HySCAI) during morning astronomical twilight in Kiruna. Auroral resonance scattering of an 1NG (0, 1) (427.8 nm) emission starts to increase from the east, and then the increase of this resonance scattering emission extends to the magnetic zenith. The volume emission rate is evaluated from the rise in resonance scattering emission (time derivative of emission intensity). The volume emission rate of (427.8 nm) reaches its maximum when the sunlight shadow height reaches 200 km, although the GLOW model predicted a peak altitude of (427.8 nm) of 120 km. The higher altitude of the resonance scattering emission peak observed with HySCAI supports the idea that is produced by the charge exchange between and existing at high altitudes. However, we cannot rule out another possible mechanism of upflowing ions.

Abstract Investigating radiated power in fusion plasmas is of utmost importance to understand the effect of undesired impurities, such as metals, in present devices, or also desired impurities, such as noble gasses, to purposefully radiate a large fraction of power in future devices. These studies are especially important for high Z impurities which will play a crucial role in future generation fusion pilot plants (FPPs). In this work, we have developed a Power Radiation Analysis Module (PRAM), which is used to investigate 2D distributions of impurity densities and radiated power asymmetries caused due to both plasma rotation and the cooling rate dependence on temperature profile for the cases of experimental NSTX plasmas and designed scenarios for the Spherical Tokamak Advanced Reactor (STAR), both being low aspect ratio tokamaks. Two different atomic databases have been tested during this work to study their impact on the radiated power distribution, especially for high Z impurities. Also in PRAM, self-consistent calculations of two-dimensional electron, main ion, and impurity ion densities are carried out using one-dimensional input density, temperature, and rotation profiles. In the case of NSTX, discharges with high rotation of ~ 170 km/s, measured with charge exchange recombination spectroscopy, have been investigated. Rotation-induced charge separation, leading to an electrostatic potential, is calculated iteratively to a self-consistent solution while testing high Z impurities to observe any 2D asymmetry in the core radiated power due to centrifugal forces. The STAR design, being much larger (R=4 m), is projected to have a much lower rotation, and is shown to have low rotation-induced asymmetries, on the order of ten percent or less, between the low field and high field sides. However, another effect not due to rotation but to the dependence of impurity cooling rates on temperature can lead to radiation peaking off-axis, near the plasma edge. This effect is noticeable for argon in NSTX, for example, but can also be enhanced for certain impurities at much higher temperatures projected for STAR (T e0 ~ 32 keV), for example for undesired tungsten or possibly desired xenon.

To enhance the piezoelectric and dielectric responses of perovskite for prospective applications in emerging microelectromechanical systems, integrating compounds to form ordered multilayer superlattices is a promising approach. The ferroelectric, dielectric, and piezoelectric properties of the (CaSnO3)n/(BaTiO3)n (n = 1–6) superlattices are investigated by first-principles calculations. The calculations reveal that the (CaSnO3)n/(BaTiO3)n (n = 2.6) superlattices have more robust ferroelectricity than their individual structures. Ps tend to saturate for n > 3, which is attributed to lattice constant stabilization. Due to the large e33 and extremely low C33 for (CaSnO3)3/(BaTiO3)3 superlattices, it exhibits a giant piezoelectric charge coefficient d33 (360 pC/N), which is the second-highest and only surpassed by that of SrTiO3/BaTiO3 among perovskite superlattices reported to date. The large e33 primarily originates from the displacement of Ti and Ba atoms, while the electronic contribution is negligible. Moreover, the (CaSnO3)3/(BaTiO3)3 superlattice has a high dielectric permittivity of 40.91, which is primarily attributed to the synergistic effects of ionic displacement and charge transfer. The (CaSnO3)3/(BaTiO3)3 superlattice also possesses a high electromechanical coupling coefficient, making it a promising candidate for future miniaturized and integrated multi-functional electronic devices.

Spectral line-shape in collinear laser spectroscopy after atomic charge exchange

Advancements in bioengineering have unlocked new microbial electrochemical applications in energy, sensing, remediation, and synthesis. Key to realizing these technologies is the engineering of conduits in metabolically versatile microbes like Escherichia coli to enable efficient charge exchange with the electrode. Inspired by mechanisms found in natural exogelectrogens, previous studies have largely focused on introducing conduits based on the metal-reducing (Mtr) pathway in Shewanella oneidensis MR-1. This study explores the concomitant expression of flavin secretion pathways for mediated charge transfer to complement the direct charge transfer from the bioengineered Mtr pathway. The engineered strains show a 3-fold increase in the total secretion of flavin mononucleotide (FMN) and riboflavin compared to a state-of-the-art Mtr-expressing strain lacking flavin overexpression. The concomitant flavin secretion further contributes up to a ≈3.4- and ≈1.5-fold increase in current compared to unmodified cells and the previous Mtr-expressing cells, respectively, with the greatest currents achieved for the strain favoring riboflavin secretion over FMN secretion. The introduction of flavin biosynthesis genes to Mtr-expressing strains thus reveals a distinct, yet complementary, EET mechanism for robust and multi-modal microbial applications.

Rapid and sensitive detection of volatile compounds in complex matrices remains challenging due to limited ionization efficiency. Herein, we developed a novel hybrid ionization source by coaxially integrating low-temperature plasma with desorption electrospray ionization (LTP-DESI). The LTP-DESI hybrid source was equipped with a triple quadrupole mass spectrometer to analyze volatile aroma compounds. Under the LTP-DESI mode, volatile aroma compounds exhibited significant signal enhancements, with intensities increased by up to 2 orders of magnitude compared with DESI or LTP. This enhancement arises from a three-stage synergistic mechanism: (1) droplet and plasma-driven desorption, (2) primary ionization by both charged droplets and plasma species, and (3) synergistic ionization enhancement via plasma-droplet interaction. The spatial and temporal overlap of the charged droplet and plasma plume significantly promotes [M + H]+ generation through Penning ionization, proton transfer and charge exchange under atmospheric pressure. The quantitative and qualitative capability of the LTP-DESI-MS platform was validated through analyses of commercial perfumes and banana tissues, achieving recoveries of 75.3-108.5% with relative standard deviations of 2.7-17.1%. These results highlight the potential of the LTP-DESI system as a robust, practical technique for rapid ambient analysis of aromas in diverse complex samples.

Efficient conversion of mechanical energy into direct current remains a significant challenge for current energy-harvesting devices. In ionic tribomaterials, the displacement and polarization of mobile ions can dynamically control both the magnitude and direction of generated charges. This process shares similarities with semiconductor-based tribovoltaic systems but differs from conventional dielectric triboelectric devices, where electrical conductivity and charge retention are often in competition. While ionic tribomaterials are receiving increasing attention, their ability to generate direct current directly from mechanical motion has not been fully investigated. Here, we show that incorporating ionic components, such as plasticizers, into a common dielectric polymer (polyvinyl chloride) transforms the output from alternating to direct current. This process is driven by contact electrification combined with electrode polarization, enabling stable direct current generation across contact–separation, sliding, and rotary motions—modes that are typically difficult to unify in a single design. The resulting devices maintain stable output under extended operation and varying environmental conditions, demonstrating a robust and versatile route for mechanical-to-electrical energy conversion. This approach bridges the performance gap between polymer-based triboelectric devices and tribovoltaic systems, offering a broadly applicable strategy for sustainable energy harvesting technologies.

Abstract Within the racetrack memory paradigm, systems exploiting magnetic guiding potentials instead of geometrical ones, allow for enhancing the versatility of the final devices adding magnetic reconfigurable capabilities. Hard/soft magnetic multilayers with stripe domain configurations fulfill these requirements. In these systems, the topology of the generated textures that would act as information
carriers, is strongly conditioned by the stripe lattice configuration. Micromagnetic simulations have been used to study the magnetization reversal process in NdCo5/Py reconfigurable racetracks. By using skyrmionic charges and magnetic vorticity lines, the topological transformations controlling the nucleation of vortices, antivortices, Bloch lines and Bloch points has been analyzed. It
has been shown that magnetic topological charge exchanges between textures rule the formation of vortex/antivortex pairs with opposite polarities, key for the guided propagation through the stripe pattern.

The coexistence of structural polarity and magnetism within a single material can give rise to coupled electromagnetic states, such as those observed in multiferroics. Unlike widely studied insulating polar materials, polar magnetic metals host unique coupling among their symmetry-breaking lattice distortions, spin order and intrinsic conductivity, offering a unique platform for emergent magnetotransport phenomena. Here we report a polar antiferromagnetic metallic state in the double-layered Ruddlesden-Popper perovskite Sr3Co2O7. The cobalt ions at different sublayers develop inequivalent ionic displacements, geometrically generating a polar state while preserving metallic conductivity. Furthermore, the quasi-two-dimensional crystalline architecture hosts an A-type antiferromagnetic order with the Néel vector along the c axis, stabilized by interlayer hybridization of Co-d orbitals. Strikingly, despite negligible remanent magnetization, we observe a notable zero-field anomalous Hall conductivity, ascribed to the coupling between antiferromagnetism and polarity. This work highlights the pivotal role of symmetry engineering and geometric distortion in layered perovskites for designing multifunctional quantum materials.

Abstract A 1D model of the scrape off layer (SOL) is created with a physics based calculation of the impurity radiation and the inclusion of the perpendicular heat flux q⊥ compared to previous 1D models. The calculation of the impurity radiation includes the addition of a model using parallel and perpendicular motion to calculate the impurity confinement time τ and the inclusion of charge exchange between neutral hydrogen and impurity ions. Reasonable agreement is found between the model and the 2D fluid code SOLPS-ITER. Additionally, an improvement is shown over the constant τ used in previous works The model is used to examine the effects of shallow field line angles at ITER levels of parallel heat flux (q||). A large increase in radiation results in an increase in the upstream parallel heat flux which can still be in detachment at shallow field line angles for both q⊥ and the calculated τ for traditional impurities (argon and nitrogen) as well as boron. The physics behind this increase in radiation at shallow field line angles is shown to be a decrease in τ and a change in the temperature profile with the inclusion of q⊥.

Abstract This study investigates the impact of neutral gas heating on plasma characteristics in inductively coupled Ar/O2 discharges using a 2D axisymmetric fluid model incorporating thermal flow and heat transfer. Unlike conventional isothermal models, the model incorporates multiple gas heating pathways, such as Franck-Condon heating, ion-neutral charge exchange, and metastable quenching. The analysis was performed across a wide range of operating conditions, including variations in input power, pressure, and O2 mole fraction.
 Results show that elevated neutral gas temperatures lead to reduced electron, ion, and radical densities due to decreased neutral density and collision frequency, while simultaneously increasing electron temperature through reduced energy loss mechanisms. Additionally, the temperature gradient induces asymmetric radical transport and wall-localized accumulation, particularly for oxygen radicals, driven by the Soret effect and surface recombination dynamics.
 300K and 500K isothermal models were compared to demonstrate that neglecting thermal effects may result in significant inaccuracies in predicting plasma behavior. The findings emphasize the critical role of incorporating gas heating and thermal transport in plasma modeling to ensure accurate predictions in semiconductor processing applications.

This study investigates the covalent functionalisation of few-layer black phosphorus (FLBP) using isocyanates to overcome its inherent susceptibility to oxidation, which limits its application in electrochemical devices. Key synthesis parameters affecting protection efficacy include reactant concentration, ultrasonic irradiation parameters, and solvent selection. While higher reactant concentrations enhance surface coverage, excessive functionalisation impedes interfacial charge transfer. Ultrasonic treatment facilitates optimal reactant-surface interactions, significantly improving electrochemical stability. Comparative solvent analysis indicates acetonitrile outperforms N, N-dimethylformamide in preserving electrochemical performance while enhancing protection against degradation. The research demonstrates that selected isocyanate reactants can effectively passivate the highly nucleophilic three-coordinated phosphorus atoms on FLBP surfaces through the formation of RNHC(O)-P < and RNHC(O)O-P < moieties at reactive surface sites. Electrochemical characterisation reveals that 2xIP(O)(ch)₂_DMF modification provides protection against phosphorus oxidation while maintaining redox functionality. This modification reveals enhanced charge transfer kinetics relative to pristine FLBP or glassy carbon electrodes. The proposed approach widens the electrochemical potential window by eliminating phosphorus oxidation typically observed at 0.65 V while improving charge exchange at the electrode/electrolyte interface. These findings establish a systematic approach for FLBP stabilisation via isocyanate functionalisation, expanding potential applications in energy storage systems, electrocatalysis, and electrochemical sensing technologies.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-20117-3.

Abstract The heliospheric energetic neutral atoms (ENAs) are products of charge exchange between solar wind and pick-up ions and interstellar neutral atoms. They are created in different regions of the heliosphere and its boundary region with the interstellar medium, constituting different ENA populations, and they carry information about their parent populations and production processes. Thus, ENAs enable mapping of the global structure of the heliosphere and the processes within and at its edge. Three instruments have provided sky maps of the heliospheric ENAs from 200 eV up to 44 keV over the solar activity cycle. The IBEX-Lo and IBEX-Hi instruments on board the Interstellar Boundary Explorer (IBEX) have provided ENA sky maps from 200 eV to 4.3 keV (central energy) from 2009 throughout Solar Cycle 24. The Ion and Neutral Camera (INCA) on board the Cassini–Huygens mission provided sky maps of the ENAs from 8–44 keV (central energy) on the spacecraft route to and in orbit around Saturn through Solar Cycles 23 and 24. We compare large-scale structures of ENA enhancements present across the sky maps in a wide energy range based on IBEX-Lo, IBEX-Hi, and INCA. They include Ribbon, heliotail lobes, and upwind ENA enhancement. We report on similarities and differences observed, including the evolution of the Ribbon from low to higher energies, and the presence of confined north and south heliotail lobes up to 44 keV.

Charge exchange between solar wind mathrm C ^4^+ ions and neutrals drives soft X-ray and extreme ultraviolet emissions in astrophysical environments. Laboratory studies of charge exchange processes provide accurate atomic structure parameters, which are essential for the modeling of astrophysical plasmas. We aim to measure the absolute charge exchange cross section of mathrm C ^4^+ colliding with He, mathrm O _2, mathrm N _2, and mathrm CH _4 for their potential applications in astrophysical plasma modeling, as such processes take place between fast solar wind and neutral gases in planetary atmospheres. The experiments were performed on a 150 kV highly charged ion collision apparatus at Fudan University. The mathrm C ^4^+ ions were generated from a 14.5 GHz electron cyclotron resonance ion source, collided with the target gas in the gas cell, and detected by a position-sensitive detector. We utilized the growth rate approach to investigate the electron capture cross section data. We provide new absolute electron capture cross section data of mathrm C ^4^+ colliding with He, mathrm O _2, mathrm N _2, and mathrm CH _4 in the energy range of 2.3–33.3 keV/u or 671–2535 km/s, with experimental uncertainties of 9% and 10% for single- and double-electron capture, respectively. The measured single-electron capture cross sections for mathrm C ^4^++He show significant deviations from existing theoretical calculations. We obtained the absolute single- and double-electron capture cross sections of mathrm C ^4^+ colliding with He, mathrm O _2, mathrm N _2, and mathrm CH _4. These new data significantly deviate from the predictions of current modeling approaches.

The generation of pure spin currents is critical for low-dissipation spintronic applications, yet existing methods relying on spin-orbit coupling or ferromagnetic interfaces face challenges in material compatibility and operational robustness. We propose a paradigm-shifting approach to generate symmetry-protected pure spin currents by applying mechanical stress on insulating antiferromagnetic materials, i.e., the pure piezospintronic effect. We first classify magnetic point groups enabling pure piezospintronic effects. A novel first-principles method is developed to compute the spin dipole moments and coefficients of the piezospintronic effect. Integrating these methodologies with high-throughput screening, we identify FeOOH, Cr_{2}O_{3}, and NaMnX (X=As, Bi, P, Sb) with significant pure piezospintronic effects. Interestingly, we reveal that the ionic displacement contribution dominates the piezospintronic effect, in contrast to the piezoelectric effect. Our study not only provides a first-principles approach for investigating spin dipole moment related phenomena (e.g., ferrotoroidicity, fractional quantum spin dipole moment, piezospintronics), but also provides promising piezospintronic materials for experimental verification and industrial applications.

Abstract Guiding-center orbit-following simulations of fast ion losses for two neutral beam injections (NBIs) with three-dimensional (3D) magnetic perturbations and charge exchange (CX) by the GYCAVA code are presented. Here, 3D magnetic perturbations include the ripple field and resonant magnetic perturbations (RMPs). Loss fractions, loss regions, heat loads and steady-state densities of beam ions have been investigated on the EAST tokamak.&amp;#xD;The steady-state density of co-current perpendicular NBI ions near the edge can be significantly reduced by CX and the ripple field. &amp;#xD;In the presence of the ripple field, CX enhances NBI ion losses without RMPs, while it can reduce the particle loss of NBI ions with RMPs. This behavior is attributed to the overlap of loss regions induced by 3D magnetic perturbations and CX and the re-ionization effect. Both CX and RMPs can significantly broaden loss regions on the high-field side (HFS) of NBI ions, leading to increased losses of passing ions born on the HFS. Hit points of lost neutrals are influenced by the direction of the toroidal magnetic field, which is related to the gyromotion of fast ions. CX can significantly mitigate the heat loads of NBI ions in the presence of 3D magnetic perturbations. The mitigation effect, caused by background neutrals, may help reduce fast-ion-induced hot spots near the mid-plane, which can adversely affect the plasma performance in a tokamak. The neutral density at the edge can be enhanced by external gas puffing in experiments. This work provides numerical support for mitigation of heat loads of fast ions near the mid-plane by using external gas puffing.

Abstract This study analyzes the emission of energetic neutral atoms (ENAs), generated by charge exchange between energetic protons and Ganymede's atmosphere. We also constrain the observability of such ENAs by an imaging instrument aboard a spacecraft. Our approach employs tracing tools that calculate the trajectories of magnetospheric parent protons near Ganymede. We determine the ENA flux through a hypothetical spherical detector encompassing the moon's atmosphere. We additionally generate synthetic ENA images, as seen by a point‐like detector with a finite field of view. The complexity of Ganymede's electromagnetic environment is successively increased; we consider (i) uniform Jovian fields, (ii) the superposition of the moon's internal dipole with Jupiter's field, and (iii) draped fields from a hybrid model of Ganymede's plasma interaction. Our major results are: (a) In uniform fields, the ENA flux is elevated within a circular band on the detector sphere. Synthetic ENA images record a cluster of high flux near the moon's limb, with the position of this enhancement determined by the viewing geometry. (b) When including Ganymede's internal dipole, the flux through the sphere displays a localized increase above the ramside apex, mainly generated by protons on open field lines at mid‐latitudes. In the synthetic images, the reduced ENA emissions from the closed field line region produce local flux depletions along the equator. (c) Pile‐up of Jupiter's field significantly reduces the ENA flux from Ganymede's ramside atmosphere. (d) At energies above several keV, the emissions from Ganymede's atmosphere clearly exceed the ENA flux released from the moon's surface.

Abstract Semi-inclusive hadron production in deep inelastic lepton-nucleon scattering (SIDIS) provides important probes of parton distributions and fragmentation functions. We compute the next-to-next-to-leading order (NNLO) massless QCD corrections to the full set of SIDIS coefficient functions in analytical form, accounting for electroweak neutral current and charged current exchange. Focusing on the kinematical setting of SIDIS measurements at the future Electron-Ion Collider (EIC), we quantify the impact of these corrections on the phenomenological predictions and their associated uncertainties. We study the impact of electroweak interference in the neutral current SIDIS process and investigate lepton polarisation asymmetries designed to enhance the sensitivity on charged current SIDIS.

Resonant charge exchange in proton collisions with transition metal dichalcogenide 2D surfaces