Collision Processes Research Articles

The Role of Collision Ionization of K-Shell Ions in Nonequilibrium Plasmas Produced by the Action of Super Strong, Ultrashort PW-Class Laser Pulses on Micron-Scale Argon Clusters with Intensity up to 5 × 1021 W/cm2

The generation of highly charged ions in laser plasmas is usually associated with collisional ionization processes that occur in electron–ion collisions. An alternative ionization channel caused by tunnel ionization in an optical field is also capable of effectively producing highly charged ions with ionization potentials of several kiloelectronvolts when the laser intensity q > 1020 W/cm2. It is challenging to clearly distinguish the impacts of the optical field and collisional ionizations on the evolution of the charge state of a nonequilibrium plasma produced by the interaction of high-intensity, ultrashort PW-class laser pulses with dense matter. In the present work, it is shown that the answer to this question can be obtained in some cases by observing the X-ray spectral lines caused by the transition of an electron into the K-shell of highly charged ions. The time-dependent calculations of plasma kinetics show that this is possible, for example, if sufficiently small clusters targets with low-density background gas are irradiated. In the case of Ar plasma, the limit of the cluster radius was estimated to be R0 = 0.1 μm. The calculation results for argon ions were compared with the results of the experiment at the J-KAREN-P laser facility at QST-KPSI.

Cloud–cloud collision in S235: triggered the formation of high-mass stars and young star clusters

ABSTRACT We present the analysis of cloud–cloud collision (CCC) process in the Galactic molecular complex S235. Our new CO observations performed with the PMO-13.7 m telescope reveal two molecular clouds, namely the S235-Main and the S235-ABC, with ∼4 km s−1 velocity separation. The bridge feature, the possible colliding interface and the complementary distribution of the two clouds are significant observational signatures of cloud–cloud collision in S235. The most direct evidence of cloud–cloud collision process in S235 is that the S235-Main (in a distance of 1547$^{+44}_{-43}$ pc) and S235-ABC (1567$^{+33}_{-39}$ pc) meet at almost the same position (within 1σ error range) at a supersonic relative speed. We identified ten 13CO clumps from PMO-13.7 m observations, 22 dust cores from the archival SCUBA-2 data, and 550 YSOs from NIR–MIR data. 63 per cent of total YSOs are clustering in seven MST groups (M1−M7). The tight association between the YSO groups (M1 $\&$ M7) and the bridge feature suggests that the CCC process triggers star formation there. The collisional impact subregion (the South) shows 3 ∼ 5 times higher CFE and SFE (average value of 12.3 and 10.6 per cent, respectively) than the non-collisional impact subregion (2.4 and 2.6 per cent, respectively), suggesting that the CCC process may have enhanced the CFE and SFE of the clouds compared to those without collision influence.

Collisional Classical Dynamics at the Quantum Scale

During the past five decades, classical dynamics have been systematically used to gain insight on collision processes between charged particles and photons with atomic and molecular targets. These methods have proved to be efficient for systems in which numerical intensive quantum mechanical methods are not yet tractable. During the years, reaction cross sections for charge exchange and ionization have been scrutinized at the total and differential levels, leading to a clear understanding of the benefits and limitations inherent in a classical description. In this work, we present a review of the classical trajectory Monte Carlo method, its current status and the perspectives that can be envisaged for the near future.

The changing traditions of Islamic public administration: observing processes of collision, absorption and adaptation

ABSTRACT The development of the concept of Islamic Public Administration (IPA) requires consideration of its portability across spatial and temporal contexts as well as secular-religious divides. The content of IPA has shifted over time, and debate over its meanings and key attributes has been a consistent feature of the history of Muslim societies. This means a hard-edged IPA concept constituted by immutable structural features to enable valid and reliable observation over time is likely to be defeated. This article argues instead for a thematic IPA framework that is relatively underspecified to allow for context sensitivity and facilitates the analysis of enduring historical dilemmas of Islamic governance. Such a framework helps show how IPA differs from other public administration traditions; specifically, its self-conscious reinvention by appeals to Islamic theology, law and ethics; and its grounding in values that are not commensurable with secular, liberal “public” values.

Sliding of water droplets onto a textured metal surface

Technologies for catching fluid from a steam mixture in the form of small droplets using the lattices or metal plates located at a certain angle are used in many industrial installations. Conducting experimental studies of the processes of collision and draining the drops of fluid on the surfaces of the metal is relevant for increasing the efficiency of gathering fluid from the steam-air mixture in industrial plants. Accordingly, the purpose of this work was to analyze the effect of the texture of the metal surface on the characteristics of the process of spreading water drops after their fall. The experiments were carried out at the setup, which is based on the shadow technique. The height of liquid droplets and the angle of the substrate inclination were varied. To assess the effect of texture on the characteristics of the spreading of water drops on the surface of brass substrates, microgrooves were applied by a grinder. It was found out that after dosing, the drop stretched along the grooves. The left and right contact angles (LCAs and RCAs), measured perpendicular to the grooves, increased by 15% compared to the angles measured on the polished surface of the substrate. It was established that after pinning the drops on the tilted surface, the difference between the LCAs, measured in parallel and perpendicular to the grooves, increased by more than 35%.

Investigation on the dynamic behavior of the ring-stiffened double-shell structure due to subsea collisions

The ring-stiffened double-shell structure is currently widely utilized in the equipment for ocean engineering, of which the response analysis under subsea impact is important to accomplish the safety and highly difficult Marine missions. However, due to the complex characteristics of the research object including fluid-solid coupling contact, large deformation, short response time, and multiplet structure, the dynamic behavior of the impacted ring-stiffened double-shell structure is hard to analyze accurately by traditional numerical methods. To overcome challenges, a fresh modeling and solving approach for the impacting mechanism of the structure body is put forward by this paper. The method is based on the Arbitrary Lagrange-Euler and Fluid-Structure-Interaction (ALE-FSI) theory. A stiffness matrix of a penalty function and steady outer pressure setting is presented to build the underwater interaction model. Then, the ALE-based description method is proposed to simulate the collision process. The results indicate that the adopted modeling and solving methods for the subsea structural collision have better revealed the dynamic response process of subsea structure to impact. There isn’t any evident damage spreading to the surrounding region, and the structural damage is primarily contained in the collision area. When an underwater impact is applied to the double shell structure, the non-pressure shell provides better protection. The core academic achievement of this work is providing an effective approach for subsea impacting mechanism and nonlinear dynamic response of ring-stiffened double-shell structure which can be used in different scenarios. It can offer universal references to optimize the construction of underwater equipment and determine the level of impact damage to submarines.

Study on the peeling criterion of anti-ice and wear-resistant coating for polar ships and simulation analysis method of the ship-ice collision process

The wear-resistant coating on the hull surface can be peeled off under the collision between the ice during the navigation of polar ships. In this study, the damage and peeling of the anti-icing wear-resistant coating at different impact angles, impact speeds, and temperatures were simulated. The static icing adhesion shear strength and normal peel strength of the anti-ice wear-resistant coating were examined, and the coating peeling criterion with temperature term was proposed. Furthermore, the damage and peeling of the anti-ice wear-resistant coating at different impact angles, impact speeds, and temperatures were simulated numerically.

Galactic ‘Snake’ IRDC G11.11−0.12: a site of multiple hub–filament systems and colliding filamentary clouds

ABSTRACT To probe star formation processes, we present a multiscale and multiwavelength investigation of the ‘Snake’ nebula/infrared dark cloud G11.11−0.12 (hereafter, G11; length ∼27 pc). Spitzer images hint at the presence of subfilaments (in absorption), and reveal four infrared-dark hub–filament system (HFS) candidates (extent < 6 pc) towards G11, where massive clumps (> 500 M⊙) and protostars are identified. The 13CO(2–1), C18O(2–1), and NH3(1,1) line data reveal a noticeable velocity oscillation towards G11, as well as its left part (or part-A) around Vlsr of 31.5 km s−1, and its right part (or part-B) around Vlsr of 29.5 km s−1. The common zone of these cloud components is investigated towards the centre of G11 housing one HFS. Each cloud component hosts two subfilaments. In comparison to part-A, more APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps are observed towards part-B. The JWST near-infrared images discover one infrared-dark HFS candidate (extent ∼0.55 pc) around the massive protostar G11P1 (i.e. G11P1-HFS). Hence, the infrared observations reveal multiple infrared-dark HFS candidates at multiscale in G11. The Atacama Large Millimeter/submillimeter Array (ALMA) 1.16-mm continuum map shows multiple finger-like features (extent ∼3500–10 000 au) surrounding a dusty envelope-like feature (extent ∼18 000 au) towards the central hub of G11P1-HFS. Signatures of forming massive stars are found towards the centre of the envelope-like feature. The ALMA H13CO+ line data show two cloud components with a velocity separation of ∼2 km s−1 towards G11P1. Overall, the collision process, the ‘fray and fragment’ mechanism, and the ‘global non-isotropic collapse’ scenario seem to be operational in G11.

Microseismicity of the Persian Gulf and the Zagros Mountain Massif According to Bottom Seismological Observations

Bottom seismological observations in the Persian Gulf over a short period made it possible to detect weak earthquakes with magnitudes (ML = –0.2–2.9), whose sources are located in the mantle under its water area and under the Zagros mountain range. On the section built across the coastline of the Persian Gulf, under the Zagros Mountains, the projections of the sources of the detected earthquakes form seismic focal layers, steeply dipping into the mantle to the northeast to depths of 120–180 km. The spatial distribution of strong and medium earthquakes, obtained from the updated earthquake catalog of the US Geological Survey and the ISC International Seismological Catalog, does not contradict the distribution of sources of micro- and weak earthquakes, but complements it, forming a separate seismic focal layer. According to the data obtained as a result of bottom seismological observations, the entire thickness of the earth’s crust of the region and the upper mantle, and not only the upper layers of the crust, as presented in a number of publications, are seismically active. It is possible that collision processes and accompanying phenomena (mantle seismicity and destruction of the granitic layer of the earth’s crust) are associated with the presumed presence and rotation of the earth’s surface with the center of rotation in the area of about. Cyprus.

Theoretical cross sections for electron collisions relevant for ammonia discharges part 1: NH3, NH2, and NH

Besides being the worlds’ most important fertilizer precursor, ammonia could play an important role as hydrogen carrier in a decarbonized future. The efficient production and decomposition (or cracking) of ammonia are essential to this end. An electricity-driven technology of interest for both these processes are non-thermal plasmas. Plasma processes have the advantage of activating—even inert—molecules and initiating chemical reactions through electron collisions, rather than through conventional heating. However, a complete set of low-energy cross section data is not available for the electron collisions with ammonia (NH3) and its radicals, amidogen (NH2) and imidogen (NH). Here, we used the ab initio R-matrix method to determine theoretical cross sections for the low-energy electron collision processes with NH3, NH2, and NH. Additionally, we explored the contribution of the different processes towards dissociation (especially from electronic excited states). Where possible, we compared our theoretical cross section data with experimental data and/or previous recommendations. Lastly, our own recommended cross section data for the electron collisions are presented. Use of this complete set of electron collision data should contribute to a more accurate description of and better insights into the plasma-chemical kinetics behind plasma-assisted ammonia production and decomposition processes.

Plasma flow and instabilities in the magnetic mirror with ion recycling and neutral back-flow

Magnetic mirror configurations are observed in natural settings and have various applications in laboratory plasmas, such as a magnetic expander of the open mirror fusion devices. The axial plasma flow in open mirror systems is significantly influenced by atomic processes involving neutrals, such as ionization and charge-exchange collisions. A quasi-two-dimensional computational model was developed to study these effects on accelerated plasma flow in magnetic mirror configurations. This model includes an emitting wall, a quasineutral flow/acceleration region with a magnetic expander, and a recycling/absorbing wall. Implemented in a hybrid quasineutral code, the model incorporates drift-kinetic ions, fluid electrons, and fully kinetic neutral atoms with collision processes simulated using the direct simulation Monte Carlo approach. Ion recycling on the wall is accounted for using empirical methods. The model demonstrates that slow atoms with short mean free paths create a dense plasma layer near the wall, modifying the plasma potential which can lead to large-scale perturbations due to ion–ion streaming instabilities.

Experimental validation of particle-in-cell/Monte Carlo collisions simulations in low-pressure neon capacitively coupled plasmas

Plasma simulations are powerful tools for understanding fundamental plasma science phenomena and for process optimisation in applications. To ensure their quantitative accuracy, they must be validated against experiments. In this work, such an experimental validation is performed for a one dimensional in space and three dimensional in velocity space particle-in-cell simulation complemented with the Monte Carlo treatment of collision processes of a capacitively coupled radio frequency plasma driven at 13.56 MHz and operated in neon gas. In a geometrically symmetric reactor the electron density in the discharge centre and the spatio-temporal distribution of the electron impact excitation rate from the ground into the Ne 2p1 level are measured by a microwave cutoff probe and phase resolved optical emission spectroscopy, respectively. The measurements are conducted for electrode gaps between 50 mm and 90 mm, neutral gas pressures between 20 mTorr and 50 mTorr, and peak-to-peak values of the driving voltage waveform between 250 V and 650 V. Simulations are performed under identical discharge conditions. In the simulations, various combinations of surface coefficients characterising the interactions of electrons and heavy particles with the anodised aluminium electrode surfaces are adopted. We find, that the simulations using a constant effective heavy particle induced secondary electron (SE) emission coefficient of 0.3 and a realistic electron–surface interaction model (which considers energy-dependent and material specific elastic and inelastic electron reflection, as well as the emission of true SEs from the surface) yield results which are in good quantitative agreement with the experimental data.

Theoretical study of inelastic processes in collisions of Y and Y+ with hydrogen atom

ABSTRACT Utilizing a simplified quantum model approach, the low-energy inelastic collision processes between yttrium atoms (ions) and hydrogen atoms have been studied. Rate coefficients corresponding to the mutual neutralization, ion-pair formation, excitation, and de-excitation processes for the above collision systems have been provided in the temperature range of 1000–10 000 K. Three ionic states and 73 covalent states are considered in calculations for the collisions of yttrium atoms with hydrogen atoms, which include six molecular symmetries and 4074 partial inelastic reaction processes. For the collisions of yttrium ions with hydrogen atoms, one ionic state and 116 covalent states are included, which are related to three molecular symmetries and 13 572 partial inelastic collision processes. It is found that the rate coefficients for the mutual neutralization process have a maximum at T = 6000 K, which is an order of magnitude higher than those of other processes. Notably, the positions of optimal windows for the collisions of yttrium atoms and ions with hydrogen atoms are found near electronic binding energy −2 eV (Y) and −4.4 eV (Y+), respectively. The scattering channels located in or near these optimal windows have intermediate-to-large rate coefficients (greater than 10−12 cm3 s−1). The reported data should be useful in the study of non-local thermodynamic equilibrium modelling.

Collisional Penrose process of extended test particles near an extremal Kerr black hole

We investigate the collisional Penrose process of extended test particles near an extremal Kerr black hole using the pole-dipole-quadrupole approximation. We analyze the motion of the test particles and examine the dynamics and maximal efficiency of energy extraction in this process. Our results demonstrate that the maximal extracted energy in the collisional Penrose process is influenced by the spin s and quadrupolar parameter C of the test particles. Specifically, we observe that, at a fixed collisional position, the energy extraction efficiency decreases as the spin increases for either the pole-dipole or the pole-dipole-quadrupole approximation case. Furthermore, for a fixed spin, the energy extraction efficiency is higher in the pole-dipole-quadrupole approximation compared to the pole-dipole approximation. These findings provide insight into the role of the internal structures of the test particles in the collisional Penrose process.

A volume of fluid method for three dimensional direct numerical simulations of immiscible droplet collisions

This paper presents an advanced Volume of Fluid (VOF) method that enables performant three dimensional Direct Numerical Simulations (DNS) of the interaction of two immiscible fluids in a gaseous environment with large topology changes, e.g., binary droplet collisions. One of the challenges associated with the introduction of a third immiscible phase into the VOF method is the reconstruction of the phase boundaries near the triple line in arbitrary arrangements. For this purpose, an efficient method based on a Piecewise Linear Interface Calculation (PLIC) is shown. Moreover, the surface force modeling with the robust Continuous Surface Stress (CSS) model was enhanced to treat such three-phase situations with large topology changes and thin films. A consistent scaling of the fluid properties at the interfaces ensures energy conservation.The implementation of these methods in the multi-phase flow solver Free Surface 3D (FS3D) allowed a successful validation. A qualitative comparison of the morphology in binary collisions of immiscible droplets as well as a quantitative comparison regarding the threshold velocities that distinguish different collision regimes shows excellent agreement with experimental results.These simulations enable the evaluation of experimentally inaccessible data like the contributions of kinetic, surface and dissipative energy of both immiscible liquids during the collision process. Furthermore, the comparison against binary collisions of the same liquids highlights similarities and differences between immiscible and equal droplet collisions. Both can support the modeling of the immiscible liquid interaction in the future.

Viscous QCD medium effects on the bottom quark transport coefficients

The bottom quark transport coefficients, i.e., drag and diffusion coefficients, have been studied for the collisional and soft gluon radiative processes within the viscous QCD medium. The thermal medium effects are incorporated using the effective fugacity quasiparticle model (EQPM). Both the shear and bulk viscous effects at leading order are embedded through the near-equilibrium distribution functions of the quark–gluon plasma (QGP) constituent quasiparticles. The transport coefficients’ dependence on the bottom quark’s initial momentum and QGP temperature have been investigated. The relative dominance of the radiative over the collisional process for the bottom quark seems to occur at a higher initial momentum compared to that of the charm quark. In contrast, the effect of the viscous corrections seems to be more for the charm quark. Furthermore, we also investigate the validity of the Einstein fluctuation–dissipation theorem for our analysis.

Size and Albedo Constraints for (152830) Dinkinesh Using WISE Data

Probing small main-belt asteroids provides insight into their formation and evolution through multiple dynamical and collisional processes. These asteroids also overlap in size with the potentially hazardous near-Earth object population and supply the majority of these objects. The Lucy mission will perform a flyby of the small main-belt asteroid, (152830) Dinkinesh, on 2023 November 1, in preparation for its mission to the Jupiter Trojan asteroids. In this Letter, we present data to support the planning of Lucy’s imminent encounter of Dinkinesh. We employed aperture photometry on stacked frames of Dinkinesh obtained by the Wide-field Infrared Survey Explorer and performed thermal modeling on a detection at 12 μm to compute diameter and albedo values. Through this method, we determined Dinkinesh has an effective spherical diameter of km and a visual geometric albedo of at the 16th and 84th percentiles. This albedo is consistent with typical stony (S-type) asteroids. These measurements will enable the Lucy team to optimize planning for the flyby of Dinkinesh, including refinement of exposure times and flyby geometry. The data obtained from this mission will, in turn, allow us to better understand the calibration of our thermal models by providing ground truth data. The Lucy flyby presents a rare opportunity to study the smallest main-belt asteroid ever observed in situ.

Effect of cell settlement on the electrochemical collision behaviors of single microbes

Electrochemical collision technique has emerged as a powerful approach to detect the intrinsic properties of single entities. The diffusion model, together with migration and convection processes are generally used to describe the transport and collision processes of single entities. However, things become more complicated concerning microbes because of their relatively large size, inherent motility and biological activities. In this work, the electrochemical collision behaviors of four different microorganisms: Escherichia coli (Gram-negative bacteria), Staphylococcus aureus, Bacillus subtilis (Gram-positive bacteria) and Saccharomyces cerevisiae (fungus) were systematically detected and compared using a blocking strategy. By using K4Fe(CN)6 as redox probe, the downwards step-like signals were recorded in the collision process of all the three bacteria, whereas the collision of S. cerevisiae was rarely detected. To further investigate the underlying reason for the abnormal collision behavior of S. cerevisiae, the effect of cell settlement was discussed. The results indicated that ellipsoidal S. cerevisiae with a cell size larger than 2 μm exhibited a cell sedimentation rate of 261.759 nm s−1, which is dozens of times higher than the other three bacteria. By further enhanced convection near the microelectrode or positioned the microelectrode at the bottom of electrochemical cell, the collision signals of S. cerevisiae were successfully detected, indicating cell sedimentation is a nonnegligible force in large cell transport. This study fully addressed the effect of cell settlement on the transport of microbial cells and provided two strategies to counteract this effect, which benefit for the deeper understanding and further application of electrochemical collision technique in single-cell detection.

Review of the 1st EUV Light Sources Code Comparison Workshop

We review the results of the 1st Extreme Ultraviolet (EUV) Light Sources Code Comparison Workshop. The goal of this workshop was to provide a platform for specialists in EUV light source plasma modeling to benchmark and validate their numerical codes using well-defined case studies. Detailed consideration of a plethora of atomic collisional and radiative processes is required for modeling EUV light source plasmas. Eight institutions spanning four countries contributed data to the workshop. Two topics were addressed, namely (i) the atomic kinetics and radiative properties of tin plasmas under EUV-generating conditions and (ii) laser absorption in a fully ionized, one-dimensional hydrogen plasma. In this paper, we summarize the key findings of the workshop and outline plans for future iterations of the code comparison activity.

Diversity of Behavior after Collisions of Sn and Si Nanoparticles Found Using a New Density Functional Tight-Binding Method.

We present a new approach to studying nanoparticle collisions using density functional based tight binding (DFTB). A novel DFTB parametrization has been developed to study the collision process of Sn and Si clusters (NPs) using molecular dynamics (MD). While bulk structures were used as training sets, we show that our model is able to accurately reproduce the cohesive energy of the nanoparticles using density functional theory (DFT) as a reference. A surprising variety of phenomena are revealed for the Si/Sn nanoparticle collisions, depending on the size and velocity of the collision: from core-shell structure formation to bounce-off phenomena.