Collision Processes Research Articles

Electronic quenching of N(2D) in collision with CO(1Σ+) via spin-forbidden transitions.

In nitrogen-rich atmospheres under extreme conditions, the N2 molecule dissociates into atomic nitrogen in different electronic states. In particular, N(2D) is known to be reactive and to drive a complex chemistry in such regimes. If the atmosphere also contains carbon monoxide (such as Earth and Mars), several collisional processes with nitrogen-, carbon-, and oxygen-bearing species are relevant. Here, we employ a set of three accurate and global potential energy surfaces for the CNO system to study the N(2D) + CO → N(4S) + CO electronic quenching process, using the quasiclassical trajectories approach coupled with two different surface hopping schemes. Experimental measurements of the quenching rate coefficient are available only at room temperature, and our computational predictions show good agreement. We further provide the temperature dependence of the rate coefficients for the first time, extending to the hyperthermal regime. The effect of the initial rovibrational state of CO on the reactivity, as well as the distribution of energy in the products, is also unveiled.

Quasiclassical sampling and Wigner sampling of initial vibrational coordinates and momenta for polyatomic molecules in Monte Carlo molecular dynamics simulations

In a quasiclassical trajectory simulation, the vibrational modes are initialised with quantised vibrational energies, but vibrational phases are sampled by Monte Carlo. This requires an algorithm to assign coordinates and momenta to the various atoms. In this work, we present two methods for implementing this for nonrotating polyatomic molecules, namely, fixed-energy vibrational-state-selected initial conditions and thermal initial conditions. We also present a method for initiating classical trajectories with a ground-state Wigner distribution. These vibrational treatments are sufficient to initialise trajectories for unimolecular processes, and we also show how they can be applied to simulate bimolecular collision processes. The treatments of unimolecular and bimolecular collision processes are available in two Python codes called wigner_state_selected.py and bimolecular_collision.py, respectively, which will generate initial condition files that are recognisable by the SHARC and SHARC-MN computer programs for dynamics calculations. Both codes are available as standalone programs, as well as being included in SHARC-MN, and they will be included in future versions of SHARC. The methods implemented in these codes are mostly also available in the ANT computer program, and those that are not available in ANT will be incorporated in future versions of ANT.

State-selective single- and double-electron capture in collisions of low-energy S5+ ions with helium

Abstract State-selective single- and double-electron capture processes in collisions of S5+ ions with helium at energies ranging from 50.8 to 100 keV were investigated using cold target recoil ion momentum spectroscopy (COLTRIMS). Q-value spectra and projectile scattering angle distributions were obtained. For single electron capture, single electron capture into n = 3 states of the projectile ion is dominant. As the projectile energy increases, the contribution of single electron capture into n = 4 states was observed. Experimental relative cross-sections for single-electron capture into different projectile final states were compared with theoretical predictions based on the molecular orbital close-coupling (MOCC) method. In double-electron capture, two-electron populated into the 3s 23p and 3s3p 2 states of projectile dominates. The reaction window calculated from the classical molecular Coulombic barrier model can qualitatively explain the experimental results. The scattering angle distribution of the multi-peak structure of the double-electron capture process is observed. The database is openly available in Science Data Bank at 10.57760/sciencedb.j00113.00233.

Vulnerability Assessment of Reinforced Concrete Piers Under Vehicle Collision Considering the Influence of Uncertainty

In recent years, the serious damage and even collapse accidents of bridge under vehicle-to-pier collision occurred frequently and have attracted growing attention world widely. Numerous studies have been conducted to examine the structural resistance of bridge piers against vehicle-with-pier collisions. Nevertheless, most of those studies employed a deterministic approach without incorporating the inherent uncertainty in structural and loading parameters. This study proposes a probabilistic approach to investigate the vulnerability of reinforced concrete (RC) piers under collisions with trucks and tractors. To do this, a dynamic mass-spring numerical model was developed to simulate the pier–vehicle collision process, which was further validated through simulating experimental data. A total of four parameters, including concrete strength, pier diameter, stirrup yield strength, and stirrup spacing, were considered and regarded as uncertainty parameters with their probability distributions determined according to the available studies. The Monte Carlo simulation method was used to generate 1000 samples for each of the uncertainty parameters and these random samples were coupled in the simplified numerical model. Through probabilistic analysis, the collapse vulnerability of RC piers was estimated. The results revealed that a tractor with a higher mass can result in higher failure probabilities than a truck. The uncertainty of the pier diameter and concrete strength have a great impact on the vulnerability of RC piers under different damage states.

Dynamics of tin plasmoids and thermal shielding onset from a liquid metal CPS target using ITER intra-ELM energy-range H0/H0-H+ beams

Abstract Liquid-Metal (LM) divertor configurations are being explored to identify potential solutions to develop more resilient Plasma Facing Components for harsh environments characterized by nominal and transient power loads that can seriously compromise the feasibility of conventional tungsten elements. In this work, tin (Sn) plasmoids generated in front of a LM filled Capillary Porous System target exposed to ITER-Intra ELM energy range (20-33 keV) particle beams (H0 and H0-H+ mixtures), are investigated at the OLMAT High-Heat Flux facility. Local characterization of plasmoids, including absolute quantification of the ionic species densities and their non-stationary evolution with target surface temperature, are conducted using a novel configuration consisting of a single Langmuir Probe (LP) directly embedded in the target while also employing a solid Titanium-Zirconium-Molybdenum alloy target for LP measurement benchmarking. Optical Emission Spectroscopy provides additional plasma characterization while infrared pyrometry monitors target thermal response. The temporal dynamic evolution of Sn plasmoids is described by four phases that depend on target temperature, parameters that determine the net eroded tin flux and eventually tin plasma content and global plasma build-up. The final phase, initiated at target temperature of 1600 K, is associated with the first stages of a thermal shielding state with partial mitigation of incoming heat fluxes. The thermal shielding and heat-flux mitigation fraction characteristics are inferred by studying deviations of target thermal response against a simple 1-D heat conduction model. Finally, the main Sn erosion mechanisms (thermal sputtering and evaporation) and atomic collisional processes (charge-exchange, electron/high-energy neutral-ion impact and recombination processes of Sn atoms) involving keV-range energy particles (neutrals, protons) as contributions to plasma build-up and heat flux mitigation characteristics are considered, these being questions of importance when considering detached LM divertor configurations operating in ELM-containing regimes.

HD163296 and its giant planets: Creation of exo-comets, interstellar objects and transport of volatile material

The birth of giant planets in protoplanetary discs is known to alter the structure and evolution of the disc environment, however most of our knowledge is focussed on its effects on the observable gas and dust. The impact on the evolution of the invisible planetesimal population remains insufficiently studied, yet mounting evidence from the Solar System shows how the appearance of its giant planets played a key role in shaping the habitability of the terrestrial planets. We investigate the dynamical and collisional transport processes of volatile elements by planetesimals in protoplanetary discs that host young giant planets using the HD,163296 system as our case study. HD,163296 is one of the best-characterised protoplanetary discs and has been proposed to host at least four giant planets on wide orbits as well as a massive planetesimal disc. The goal of this study is to assess the impact of the dynamical and collisional transport on the disc as well as on existing and forming planetary bodies. We performed high-resolution n-body simulations of the dynamical evolution of planetesimals embedded in HD,163296's protoplanetary disc across and after the formation of its giant planets, accounting for the uncertainty on both the disc and planetary masses as well as for the effects of aerodynamic drag of the disc gas and the gas gravity. To quantify the impact probabilities with existing and possible undiscovered planetary bodies, we processed the output of the n-body simulations with well-tested statistical collisional algorithms from studies of the asteroid belt. In our simulations the formation of giant planets in the HD,163296 system creates a large population of dynamically excited planetesimals, the majority of which originate from beyond the CO snowline. The excited planetesimals are then transported to the inner disc regions as well as scattered outward beyond the protoplanetary disc and into interstellar space. In the inner disc, potential solid planets can be enriched in volatile elements to levels that are comparable or larger than those of the Earth, while giant planets can be enriched to the levels of Jupiter and Saturn. The formation of giant planets on wide orbits impacts the compositional evolution of protoplanetary discs and young planetary bodies on a global scale. The collisional enrichment of the atmospheres of giant planets can alter or mask the signatures of their formation environments; this process can also provide independent constraints on the disc mass. In our simulations protoplanetary discs with giant planets on wide orbits prove efficient factories of interstellar objects.

Spatiotemporal variations of Early to Middle Paleozoic magmatism in northern Beishan: Implications for accretionary and collisional processes in the southern Central Asian Orogenic belt

Spatiotemporal variations of Early to Middle Paleozoic magmatism in northern Beishan: Implications for accretionary and collisional processes in the southern Central Asian Orogenic belt

Electron populations and neutralization process in the plume of a gridded ion thruster

Abstract In order to assess the importance of collisional processes in the neutralization of a gridded ion thruster plume this study presents a series of simulations carried out with a planar, full-PIC code provided of a library of electron, ion and neutral collisions. In particular, we find that the inclusion of electron inelastic collisions, such as ionization and excitation, results fundamental in the generation of a population of electrons trapped in the plume’s potential well, which play a major role in the neutralization of the plume and in the formation of the electric potential map. A further investigation is therefore carried out on the properties of the electron populations present in the plume, suggesting that the trapped population results mostly insensitive to the emission properties of the cathode, but displays a strong dependence on the inclusion of inelastic collisions and a slow approach to stationary conditions dictated by the timescales of these collisions. Given the symmetry of the plume bulk even in presence of an externally mounted cathode, we further extend the study to an axisymmetric simulation case with an annular cathode, that allows the evaluation of a three-dimensional expansion process. The build up of the trapped electron population in this case is even slower, because of the smaller neutral density observed when expanding the plume in three dimensions, and an acceleration strategy that speeds-up the approach to steady state without altering it is therefore proposed. Nevertheless, the main governing physical processes observed in the planar case remain prominent also in this latter case.

Electron collision cross sections for 1,1,1,2-tetrafluoroethane (C2H2F4) obtained by swarm analysis of transport coefficients in pure gas and its mixtures with argon

Abstract In this work, we present a revised set of electron collision cross sections for 1,1,1,2 tetrafluoroethane (C2H2F4). The cross-section set is the result of a standard swarm analysis of measured drift velocities (W) and effective ionization coefficients ((α–η)/N) under pulsed-Townsend conditions, where α is the ionization coefficient, and η is the attachment coefficient. Calculations and numerical analysis are performed for pure C2H2F4 and its mixtures with argon over a wide range of reduced electric fields E/N (where E is the electric field and N is the gas number density). A special attention was given to the region of low and moderate electron energies, where electron attachment and vibration excitation are dominant inelastic channels of scattering. The cross-section set we derive provides a good balance of energy, momentum, and the number of charged particles. Using a Monte Carlo simulation technique and the derived cross-section set as input, we calculate other transport coefficients and properties, such as characteristic energy, diffusion coefficients, and rate coefficients for individual collisional processes. We expect this cross-section set and electron swarm transport coefficients to be useful in modelling non-equilibrium plasmas as well as in studying resistive plate chambers in high-energy physics.

Beyond BOLSIG+: Monte Carlo simulation of electron and ion swarms to obtain transport and rate coefficients for plasma modeling

It is common practice in low-temperature plasma modeling to calculate the electron transport and reaction rate coefficients from electron-neutral cross-section data by means of an electron Boltzmann equation solver, based on some approximate form of the kinetic theory of charged particle swarms. This paper explores the validity of these calculations and introduces Monte Carlo Simulator of Ionized Gases MCIG, a Monte Carlo simulation code that is being released as a complement to BOLSIG+, a popular Boltzmann solver. MCIG provides rigorous reference values of the transport coefficients and rate coefficients under swarm conditions, without invoking the approximations used by most Boltzmann solvers, such as two-term Legendre expansion of the velocity distribution function. It can handle ions as well as electrons and allows for constant and oscillating electric and magnetic fields, pulsed and steady-state swarm configurations, non-zero gas temperature, superelastic collisions, and anisotropic angular scattering. The physical and methodological principles of MCIG are described in detail, including original techniques to handle non-conservative collision processes and obtain statistical error bars for all results. Subsequently, MCIG is used to quantify the accuracy of the two-term approximation for a wide range of gases and reduced electric fields, to illustrate differences between alternative definitions of the transport coefficients used in swarm data analysis and to explore the possible effects of anisotropy of scattering for electrons and ions. The Appendix gives analytical expressions of the transport coefficients used as a verification benchmarks.

Application of topological optimization and biomechanical simulation to enhance the design of collision safety systems and injury prediction in new energy vehicles

This study explores how to establish a quantitative balance mechanism between the lightweight demand of new energy vehicles and the collision safety of occupants/batteries through multidisciplinary collaborative optimization. Integration of topology optimization and biomechanical simulation to facilitate the design and injury prediction of new energy vehicle (NEV) crash safety systems. Using extensive data from the National Highway Traffic Safety Administration (NHTSA) and the Center for Automotive Research (ARC), first, topology optimization is applied to reduce vehicle weight while maintaining crashworthiness. Subsequently, biomechanical simulations were performed using finite element analysis to simulate the human response to impact. These models are then combined to predict injury risk. Our results show that the weight of key vehicle components is substantially reduced, while the effect on structural stiffness is negligible. Biomechanical simulations provide detailed injury severity scores (ISS) for different body parts under different impact scenarios. The comprehensive model shows that compared with the unoptimized vehicle structure, the optimized vehicle structure is expected to reduce the overall weight of the new energy vehicle and reduce the damage probability of the optimized structure in the collision process by 18.2%. This study highlights the great potential of combining topology optimization and biomechanical simulation to improve the crash safety and injury prediction of new energy vehicles.

Planetary Formation Constrained by Collisions between Millimeter-sized Lunar Particles and Lunar Surface from Chang’E-4 Mission

Abstract Exploring low-velocity collisions is crucial for unraveling intricate processes in planetary formation, particularly the bouncing barrier that impedes the aggregation of dust into sizable planetesimals. Observational data on extraterrestrial collision processes remain limited. Here, we quantify collision parameters for millimeter-sized lunar particles impacting the porous lunar surface at speeds ranging from 2.3 to 76.8 cm s−1 under lunar gravity, leveraging Chang’E-4 imagery. This study represents the first tangible acquisition of extraterrestrial collision data. Our findings reveal that speeds exceeding 7.0 ± 2.6 cm s−1 result in bouncing, yielding coefficients of restitution ranging from 0.51 to 0.80. In contrast to particle–particle collisions, interactions between lunar particles and the porous lunar surface exhibit a heightened sticking threshold speed, facilitating particles to overcome the bouncing barrier. Diminished coefficients of restitution expedite collapses, significantly reducing dust cloud collapse times. This implies that porous particles foster favorable conditions for overcoming the bouncing barrier and promoting growth. Our results unveil the conducive conditions enabling extraterrestrial samples to overcome the bouncing barrier, advancing our comprehension of planetary formation and providing crucial observational constraints for relevant theories.

Analysis of the Hourglass–Spindle-Shaped Trajectory Generated by the Collision of Circularly Polarized Laser Pulses with Electrons

This study investigates the hourglass–spindle-shaped trajectory of electron motion based on a model of electron and circularly polarized chirped laser pulse coaxial collision. The velocity, acceleration, and radiation distribution of the electron in this state of motion are systematically analyzed. The formation process of the hourglass–spindle-shaped trajectory is examined in detail. Four distinct stages of the electron–laser pulse collision process are proposed, with an in-depth analysis of the interaction dynamics and underlying mechanisms in each stage. The critical conditions for the formation of the hourglass–spindle-shaped trajectory are identified, along with the conditions for the emergence of two other possible trajectories resulting from the collision: the spiral-shaped and spindle-shaped trajectories. Additionally, a general model for analyzing electron–laser pulse collisions is proposed.

Revealing the sound, flow excitation, and collision dynamics of human handclaps

Hand clapping, a ubiquitous human behavior, serves diverse daily-life purposes. Despite prior research, a comprehensive understanding of its physical mechanisms remains elusive. To bridge this gap, we integrate human data, parametric experiments, finite-element simulations, and theoretical frameworks to investigate the acoustic properties of clapping sound and their connections with the fluid flow and soft matter collision. Motion-audio synchronization reveals the flow-excitation nature of the hand cavity resonance. The classical Helmholtz resonator model, incorporating occasional pipe standing wave contributions for finger grooves, reliably predicts clapping sound frequencies across various real and engineered hand configurations. Material elasticity, coupled with the dynamic collision process, has minor effects on the sound frequency but a major impact on the temporal evolution of the sound signals, as reflected by the quality factors of resonance. Both spatial and dynamic factors for sound intensity are examined. We establish a quadratic scaling relationship between hand cavity gauge pressure and clapping speed, elucidating the positive correlation between faster claps and louder sounds. Our work advances the knowledge of hand-clapping acoustics and offers insights into sound signal synthesis, processing, and recognition. Furthermore, these findings may facilitate low-cost acoustical diagnostics in architecture and enhance rhythmic sound patterns in music and language education. Published by the American Physical Society 2025

Resonance-enhanced electron transfer in laser-assisted proton-hydrogen collisions.

Electron transfer in collisional processes plays a crucial role in numerous physical and chemical phenomena. In this study, we investigate the resonance of electron transfer during ion-atom collisions under the influence of a laser field by numerically solving the time-dependent Schrödinger equation (TDSE). Using appropriate laser parameters, we have demonstrated that applying a laser field results in a considerable increase in electron transfer probability due to a single- or two-photon resonance between the ground and excited states. Additionally, we observe distinct circular dichroism (CD) effects in capture probability for low laser frequencies (ℏω < 0.1 a.u.), while these effects are attenuated or absent at higher laser frequencies (ℏω > 0.2 a.u.). We attribute these phenomena to resonance-enhanced capture and ionization mechanisms.

The impact of target parameters on the collision process and hot-spot performance in the double-cone ignition scheme

The density distribution, temperature, and asymmetry of the stagnated plasmas in inertial confinement fusion are crucially important for fusion performance and influencing the energy coupling efficiency from heating laser to hot-spot in the fast ignition scheme. In the double-cone ignition scheme, the fuel is compressed and accelerated in a pair of gold cones, ejected out, and collided with each other to form the stagnated plasmas. To investigate the impact of target parameter variations on the stagnated plasmas, the evolutions of intensities, sizes, and shapes of the self-emission signals were analyzed. The observation result shows that the material of the shell significantly affects the ejecting velocity and self-emission signal intensity, and the distance between the geometric centers of the gold cones influences the emission intensity and sizes. According to analytical calculations, changing the geometric center's distance can not only improve the temperature and heating performance of the collided plasmas but can also reduce the areal density of the fuel.

Effect of surface hydrophobicity on the bubble-substrate collisional interaction process and interaction force

Effect of surface hydrophobicity on the bubble-substrate collisional interaction process and interaction force

Timing and petrogenesis of late orogenic calc-alkaline volcanism in the Slovak Transcarpathians: Implications for the evolution of the Carpathian collisional process

Timing and petrogenesis of late orogenic calc-alkaline volcanism in the Slovak Transcarpathians: Implications for the evolution of the Carpathian collisional process

Microphysical Properties and Turbulence Evolution Characteristics of a Typical Coastal Fog Event in the Beibu Gulf, China

AbstractA fog field observation experiment was carried out in the Beibu Gulf, Guangxi, China from February to April of 2023, with observational instruments including fog monitor, visibility meters, and the three‐dimensional ultrasonic anemometer. This study is the first to use the field observation data conducting a fog microphysics in this area. A dense coastal fog case during 10–11 February 2023 is chosen to understand the evolution of the microphysical characteristic parameters, dominant microphysical processes, as well as the turbulence characteristics. The main results are as follow: (a) The average values of fog droplets number concentration(N), liquid water content (LWC), average diameter (), are 6.5 cm−3,0.0005 gm−3 and 3.1 μm, respectively. The N and LWC over the Beibu Gulf are much lower than those in other coastal areas of China. (b) The droplet size distribution of the Beibu Gulf fog is monotonically decreasing, with peak diameter of 2.8 μm. The average droplet number distribution roughly conforms to the Junge distribution. (c) For the whole coastal fog event, condensation nucleation and droplet condensation growth are the dominant processes, and well‐developed turbulence is observed. (d) During the development stage of this fog, condensation nucleation and condensation growth is the dominant processes; in the mature stage, turbulence is relatively stable, and the collision process plays a dominant role; during the dissipation stage, there is evaporation of fog droplets.

ON THE FEATURES OF THE INFLUENCE OF IMPURITIES OF THE ELECTRODE MATERIAL ON THE ELECTRICAL CONDUCTIVITY OF THE PLASMA OF PULSE ELECTRICAL DISCHARGE IN WATER

he influence of impurities of the electrode material on the electrical conductivity of pulsed discharge plasma in water is considered. Experimental studies of electrical conductivity were conducted and calculations were performed based on the Grade method of moments. It is shown that a small amount of metal and carbon impurities can significantly change the value of the plasma electrical conductivity coefficient compared to the case of pure water vapor. It is found that metal and carbon impurities can cause both an increase and a decrease of the plasma electrical conductivity, which is related to the processes of interparticle collisions and the presence of clusters.