Inelastic Collisions Research Articles

Electromagnetic interaction models for Monte Carlo simulation of protons and alpha particles

Electromagnetic interactions of protons and alpha particles are modeled in a form that is suitable for Monte Carlo simulation of the transport of charged particles. The differential cross section (DCS) for elastic collisions with neutral atoms is expressed as the product of the DCS for collisions with the bare nucleus and a correction factor that accounts for the screening of the nuclear charge by the atomic electrons. The screening factor is obtained as the ratio of the DCS for scattering of the projectile by an atom with a point nucleus and the parameterized Dirac–Hartree–Fock–Slater (DHFS) electron density, calculated from the eikonal approximation, and the Rutherford DCS for collisions with the bare point nucleus. Inelastic collisions, which cause electronic excitations of the material, are described by means of the plane-wave Born approximation, with an empirical simple model of the generalized oscillator strength (GOS) that combines several extended oscillators with resonance energies and strengths determined from the atomic configurations and from the empirical mean excitation energy of the material. The contributions from inner subshells are renormalized to agree with realistic ionization cross sections calculated numerically from the DHFS self-consistent model of atoms by means of the plane-wave Born approximation. The resulting DCS allows analytical random sampling of individual hard inelastic interactions.

Self-consistent modeling and analysis of spatial homogeneity of pure Na and Na−Ar mixture resonance photoplasma in a gas cell for Voigt profile

A self-consistent modeling of the resonance photoplasma in pure Na and Na−Ar mixtures with spatial homogeneity of photoexcitation of the resonance levels of Na in the volume of a cylindrical gas cell has been carried out. The Voigt line shape and the collision broadening of the D1 and D2 lines of Na were considered. The main photoplasma parameters were calculated for the Na pressure PNa=0.0045−0.165 torr, the PAr/PNa=0 and 10k (k = 1, 2 and 3) values and the gas temperature of 680 K at the pumping resonance radiation flux density F = 40 W/(m2nm). It has been established that the electron density Ne and temperature Te increase non-linearly with the growth of the PNa and reach, respectively, 6.4·1018 m−3 at PNa=0.165 torr and PAr/PNa=100 and 0.28 eV for the pure Na photoplasma. Herewith, the dependence of Te on the Ar pressure PAr is non-monotonic. It is a consequence of the cooperative action of electron inelastic collisions of the first and second kinds with Na atoms and elastic collisions with Na and Ar atoms. The comparison of the obtained results for the L = 4R = 0.02 m case with those calculated for the infinite cylinder case with the same R value showed the good validity of the infinite cylinder approximation. As a result of our analysis of the quenching of the resonance levels and theoretical results from the literature, it has been established that the spatial non-homogeneity of the investigated photoplasma caused by this quenching does not exceed 20 % for the PNa≤0.1 torr and PAr/PNa=0 − 103. The obtained data can be used in studies of alkali-containing photoplasmas and to create photoelectric converters based on them.

Lump wave solutions, lump-stripe soliton inelastic collision phenomena and rogue-type wave solutions for a generalized breaking soliton system in (3+1)-dimensions

Based on five types of structures of the functional multi-layer neural network model, some explicit exact solutions for a (3+1)-dimensional generalized breaking soliton system including lump waves, lump-stripe solitons and rogue-type waves are explored by using bilinear neural network method without the datasets training. The 3-dimensional plots, 2-dimensional curves and density plots of these results obtained are provided to display their dynamic characteristics. In particular, the complete processes of lump wave and stripe soliton fusion phenomena are presented. We hope the formulations established in this paper could be applied to study the exact traveling wave solutions of other integrable nonlinear evolution equations.

Effects of Propellant Slosh on Touchdown Stability for Landing Vehicles

This paper aims to characterize the effect of propellant slosh using a multistep analytical method for the two-and-over and two-two-and-over passive landing modes. Each touchdown of a landing leg is modeled as an inelastic collision, which is analyzed using generalized impulses and generalized momenta. Simulation results establish conditions at which slosh improves or degrades touchdown stability compared to treating the system as a single rigid body. Because slosh is generally uncontrolled but bounded, this study establishes a rule of thumb for designers to use in adjusting the vehicle height or landing-leg footprint in order to maintain stability in the presence of slosh dynamics when operating close to the stability boundary.

Measurement and reduction of Ar metastable densities by nitrogen admixing in electron beam-generated plasmas

Electron beam (e-beam) generated plasmas are useful for material processing applications such as deposition and etching because the plasmas deliver a large fluence of very low energy of ions to surfaces. Metastable species produced in the beam-region can also transport significant energy to the plasma periphery and surfaces. In this work, we have investigated the spatially resolved density of metastable Ar 1s5 species produced in an Ar and Ar/N2 e-beam generated plasma at pressures of 60–67 mTorr using laser-induced fluorescence (LIF). The experiments provide the first direct measure of absolute density and reduction of Ar 1s5 in an e-beam generated plasma when argon is diluted with nitrogen. These results are consistent with previous predictions of numerical modeling and measurements using optical emission spectroscopy. The present spatially resolved LIF measurements directly quantify the reduction of Ar 1s5 in the e-beam generated plasma by nitrogen admixing. This reduction was observed in the region of the electron beam and in the plasma periphery, where substrates are usually placed. For example, up to a threefold reduction of the density of Ar 1s5 was measured when the argon background was diluted with 15.5% nitrogen at pressure of 60 mTorr. Ar 1s5 reduction is attributed to excitation exchange with nitrogen molecules as well as the cooling of plasma electrons via inelastic collisions with nitrogen molecules.

On the Importance of Inelastic Interactions in Direct Dark Matter Searches

The approach proposed earlier for describing the scattering of weakly interacting nonrelativistic massive neutral particles off nuclei is used as the basis to derive explicit expressions for the event countingrate expected in experiments aimed at directly detecting dark matter (DM) particles. These expressions make it possible to estimate the rates in question with allowance for both elastic (coherent) and inelastic (incoherent) channels of DM particle interaction with a target nucleus. Within this approach, the effect of a nonzero excitation energy of the nucleus involved is taken into account for the first time in calculating the contribution of inelastic processes. A correlation between the excitation energy and admissible values of the kinetic recoil energy of the excited nucleus constrains substantially the possibility of detection of the inelastic channel with some nuclei. In addition to the standard model of the DM distribution in theMilkyWay Galaxy, the effect of some other models that allow significantly higher velocities of DMparticles is considered. A smooth transition from from the dominance of the elastic channel of the DM particle–nucleus interaction to the dominance of its inelastic channel occurs as the nuclear recoil energy TA grows. If the DM detector used is tuned to detecting elastic-scattering events exclusively, then it cannot detect anything in the casewhere the nuclear recoil energy turns out to be belowthe the detection threshold. As TA grows, such a detector loses the ability to see anything, since elastic processes quickly become nonexistent. Radiation associated with the deexcitation of the nucleus becomes the only possible signature of the interaction that occurred. In the case of a spin-independent interaction, the inelastic contribution becomes dominant rather quickly as TA grows, while the differential event counting rate decreases insignificantly. If a DMparticle interacts with nucleons via a spin-dependent coupling exclusively, detectors traditionally setup to detect an elastic spin-dependent DMsignal will be unable to to see anything since the signal entirely goes through the inelastic channel. It looks like the sought interactions ofDM particles may have a sizable intensity, but the instrument is unable to detect them.Therefore, experiments aimed at directly detecting DM particles should be planned in such a way that it would be possible to detect simultaneously two signals—that of the recoil energy of the nucleus involved and that of gamma rays having a specific energy and carrying away its excitation. A experiment in this implementation will furnish complete information about the DM interaction that occurred.

Estimation of electron density, temperature and electrical characterization of silica seeded arc plasma at atmospheric pressure

Plasma technology stands at the forefront of numerous industrial applications, offering versatile solutions from materials processing to aerospace engineering. This study employs a single Langmuir probe technique operating at atmospheric pressure to scrutinize the transformative impact of silica seeding on low-temperature arc plasma. The investigation unveils a dynamic interplay of electrons and ions within the plasma, unveiling key electrical properties. The I–V electrical properties of the arcs plasma before seeding, having a floating voltage of –39 V, demonstrate electron and ion currents for varied probe voltages. The electrons’ density is calculated to be 2.11×1013 m–3, and the electrons’ temperature is at 6.25 eV. The I–V characteristics show a floating potential of about –35 V and –37 V after seeding an arc plasma using silica in the presence of aluminum oxide (2 % by weight) powder and grain, respectively. After seeding, it is discovered that the electron temperature falls to 1.18 eV for powder while 1.16 eV for grain and electron density rises to 2×1016 m–3 for powder and 1.84×1016 m–3 for grain. In addition, a notable fall in electron temperature and a discernible rise in electron density are seen. This non-equilibrium behavior is related to silica’s catalytic function, which is enhanced by the presence of aluminum oxide. Additionally, increased ionizing activity brought on by inelastic electron collisions causes the electron temperatures in the silica-seeded arcs plasma to rise with discharge voltage. These findings can be essential for enhancing plasma-based technologies in a variety of industrial applications because they provide insightful information on how silica seeding affects arc plasma properties

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.

Formula omitted]-breather solutions, inelastic interactions of the lumps and resonant interactions of the breathers for a (2+1)-dimensional nonlinear evolution equation

Studies are conducted on a (2+1)-dimensional nonlinear evolution equation. We investigate the inelastic interactions of the two/three/four lumps based on the M-lump solutions, where M is a positive integer. We observe the different patterns of inelastic interactions of the lumps. We construct the H-breather solutions and carry out the asymptotic analyses for two/three-breather solutions via the symbolic computation, where H is a positive integer. We demonstrate that the resonant interactions occur when the phase shifts of the two/three breathers approach the infinity. We graphically show the resonant interactions of the two/three breathers.

Innovative design and experimental validation of dynamic balance in rotary compressors based on particle damping energy dissipation technology

Dynamic imbalance is one of the primary issues in rotary compressor applications, which can generate significant vibration. A dynamic balance design is required to minimize the moment and additional inertia force, which can be eliminated by adding a counterweight. This paper utilized a solid plate that has cavities filled with particle damper as a novel design to satisfy the dynamic balance. Vibrational energy is dissipated in collisions between particles through momentum exchange and is converted into energy for consumption that consists of inelastic collision energy and frictional energy. The discrete element method (DEM) and multi-body dynamics (MBD) were applied for two-way coupling for a dynamic balance simulation. The impact of particle size, friction coefficient, and restitution coefficient on energy dissipation in rotary compressors was evaluated, and the particle radius of 1 mm produced the most satisfactory. The experiment measured the vibrational acceleration in the tangential and radial directions at a particular duration and frequency to reflect the particle damper’s dynamic balance and energy dissipation effect. Both simulation and experimental results confirmed that the novel design features are more acceptable than the original to satisfy the dynamic balance of a rotary compressor.

Inelastic interactions between a small, intense dipole and a large, weak, neutral monopole

Inelastic interactions between a small, intense dipole and a weak, neutral monopole in two-dimensional flows are analysed. The neutral vortex has vanishing exterior potential flow and the interactions involve the rotational flow of the vortices. It is shown that dipoles of small-size but large-amplitude, relative to the neutral vortex, may cross the vortex and scatter while leave the vortex stable.

State-to-state rovibrational transition rates for CO2 in the bend mode in collisions with He atoms.

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data from space telescopes requires knowledge of the rate coefficients of rovibrationally inelastic molecular collisions. Here, we present such rate coefficients in a temperature range from 10 to 500K for collisions of CO2 with He atoms in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC) calculations as well as from calculations with the less demanding coupled-states approximation (CSA) and the vibrational close-coupling rotational infinite-order sudden (VCC-IOS) method. All of the calculations are based on a newly calculated accurate abinitio four-dimensional CO2-He potential surface including the CO2 bend (ν2) mode. We find that the rovibrationally inelastic collision cross sections and rate coefficients from the CSA and VCC-IOS calculations agree to within 50% with the CC results at the rotational state-to-state level, except for the smaller ones and in the low energy resonance region, and to within 20% for the overall vibrational quenching rates except for temperatures below 50K where resonances provide a substantial contribution. Our CC quenching rates agree with the most recent experimental data within the error bars. We also compared our results with data from Clary et al. calculated in the 1980s with the CSA [A. J. Banks and D. C. Clary, J. Chem. Phys. 86, 802 (1987)] and VCC-IOS [D. C. Clary, J. Chem. Phys. 78, 4915 (1983)] methods and a simple atom-atom model potential based on abinitio Hartree-Fock calculations and found that their cross sections agree fairly well with ours for collision energies above 500 cm-1, but that the inclusion of long range attractive dispersion interactions is crucial to obtain reliable cross sections at lower energies and rate coefficients at lower temperatures.

NLTE Analysis of Y i and Y ii in the Atmospheres of FGK Stars

The nonlocal thermodynamical equilibrium (NLTE) line formation of Y i and Y ii is considered in 1D LTE model atmospheres of FGK-type stars. The model atom was constructed with the most up-to-date atomic data, including quantum cross sections and rate coefficients for transitions in inelastic collisions of Y i and Y ii with hydrogen atoms. For seven reference stars, we obtained an agreement between NLTE abundances inferred from the two ionization stages, while the difference in LTE abundance (Y i and Y ii) can reach up to −0.31 dex. In the atmospheres of FGK-type stars, for both Y i and Y ii lines, the NLTE abundance corrections are positive. In solar metallicity stars, the NLTE abundance corrections for Y ii lines do not exceed 0.12 dex, while in atmospheres of metal-poor stars, they do not exceed 0.21 dex. For Y i lines, the NLTE abundance corrections can reach up to ∼0.5 dex. We determined the yttrium NLTE abundances for a sample of 65 F and G dwarfs and subgiants in the −2.62 ≤ [Fe/H] ≤ +0.24 metallicity range, using high-resolution spectra. For stars with [Fe/H] ≤ −1.5, [Y/Fe] versus [Fe/H] diagram reveals a positive trend with an average value of [Y/Fe] ≃ 0. For metal-poor stars, among Sr, Y, and Zr, the arrangement [Sr/Fe] < [Y/Fe] < [Zr/Fe] remains consistent. The current study is useful for Galactic chemical evolution research. The model atom will be applied for NLTE yttrium abundance determination in very metal-poor stars studied with LAMOST and Subaru.

Quantum scattering cross-sections for O(3P) + N2 collisions for planetary aeronomy

ABSTRACT ‘Hot atoms’, atoms in their excited states, transfer their energy to the surrounding atmosphere through collisions. This process (known as thermalization) plays a crucial role in various astrophysical and atmospheric processes. Thermalization of hot atoms is mainly governed by the amount of species present in the surrounding atmosphere and the collision cross-sections between the hot atoms and surrounding species. In this work, we investigated the elastic and inelastic collisions between hot oxygen atoms and neutral N2 molecules, relevant to oxygen gas escape from the Martian atmosphere and for characterizing the chemical reactions in hypersonic flows. We conducted a series of quantum scattering calculations between various isotopes of O(3P) atoms and N2 molecules across a range of collision energies (0.3–4 eV), and computed both their differential and collision cross-sections using quantum time-independent coupled-channel approach. Our differential cross-section results indicate a strong preference for forward scattering over sideways or backward scattering, and this anisotropy in scattering is further pronounced at higher collision energies. By comparing the cross-sections of three oxygen isotopes, we find that the heavier isotopes consistently have larger collision cross-sections than the lighter isotopes. As a whole, this study contributes to a better understanding of the energy distribution and thermalization processes of hot atoms within atmospheric environments. Specifically, the cross-sectional data presented in this work is directly useful in improving the accuracy of energy relaxation modelling of O and N2 collisions over the Mars and Venus atmospheres.

Rheology of a dilute binary mixture of inertial suspension under simple shear flow

Abstract The rheology of a dilute binary mixture of inertial suspension under simple shear flow is analyzed in the context of the Boltzmann kinetic equation. The effect of the surrounding viscous gas on the solid particles is accounted for by means of a deterministic viscous drag force plus a stochastic Langevin-like term defined in terms of the environmental temperature Tenv. Grad’s moment method is employed to determine the temperature ratio and the pressure tensor in terms of the coefficients of restitution, concentration, the masses and diameters of the components of the mixture, and the environmental temperature. Analytical results are compared against event-driven Langevin simulations for mixtures of hard spheres with the same mass density m1/m2 = (σ(1)/σ(2))3, mi and σ(1) being the mass and diameter, respectively, of the species i. It is confirmed that the theoretical predictions agree with simulations of various size ratios σ(1)/σ(2) and for elastic and inelastic collisions in a wide range of parameter space. It is remarkable that the temperature ratio T1/T2 and the viscosity ratio η1/η2 (ηi being the partial contribution of the species i to the total shear viscosity η = η1 + η2) discontinuously change at a certain shear rate as the size ratio increases; this feature (which is expected to occur in the thermodynamic limit) cannot be completely captured by simulations due to the small system size. In addition, a Bhatnagar–Gross–Krook (BGK)-type kinetic model adapted to mixtures of inelastic hard spheres is exactly solved when Tenv is much smaller than the kinetic temperature T. A comparison between the velocity distribution functions obtained from Grad’s method, the BGK model, and simulations is carried out.

Experimental Study of the Response of Sheared E × B Flow to Varying Ion–Neutral Collisions

Partially ionized plasma is a common occurrence in astrophysical and space environments. The emergence and development of plasma instabilities are significantly impacted by the inelastic collisions between the ions and neutrals in the partially ionized plasma, such as the charge exchange. In this study, the effect of the ion–neutral collisions on the sheared E × B flow was experimentally investigated. In the weak collision range, the shear-driven plasma instability, such as Kelvin–Helmholtz instability, was excited by the velocity-sheared flow. However, increasing ion–neutral collisions resulted in a decrease in the magnitude of the sheared E × B flow due to charge exchange–induced drag forces. Consequently, the Kelvin–Helmholtz instability is suppressed, and the Rayleigh–Taylor instability is triggered. The underlying mechanism was elucidated through experimental findings and numerical analysis. The result of this study proposes that a transition between the two modes occurred with increasing ion–neutral collision strength. It could be applied to the study of the solar chromosphere and prominence and planetary ionospheres, where plasma is partially ionized and the sheared E × B flow is often encountered.

Soliton interactions and Mach reflection in gas bubbles–liquid mixtures

In this study, we assume that blood is assumed to be a viscoelastic and incompressible homogeneous media in which several uniform sized oxygen bubbles are uniformly distributed. Based on this, we establish a (3 + 1)-dimensional modified Kadomtsev–Petviashvili (mKP) equation to describe the long nonlinear pressure waves in the gas bubbles–liquid mixtures. Using bell polynomials, a new bilinear form of the mKP equation is constructed, and then the one- and two-soliton solutions of the equation are obtained by the Hirota method. Via the one-soliton solutions, parametric conditions of the existence of shock wave, elevation and depression solitons, and the Mach reflection characters in the mixtures are discussed. Soliton interactions have been discussed on the basis of the two-soliton solutions. We find that the (i) parallel elastic interactions can exist between the shock and elevation solitons; (ii) oblique elastic interactions can exist between the (a) shock and depression solitons and (b) the elevation and depression solitons; and (iii) oblique inelastic interactions can exist between the two depression solitons.

Fiber–Based Model for Simulating Inelastic Interaction Buckling of Rectangular CFST Slender Columns with Unequal Wall Thickness

Rectangular concrete-filled steel tubular (RCFST) columns can be designed to have unequal wall thickness to maximize their resistance to combined axial and uniaxial bending loads. However, there is very little published research on their local–global interaction buckling behavior. This paper presents an efficient fiber-based simulation model for analyzing the inelastic interaction buckling of eccentrically loaded RCFST slender columns with unequal wall thickness. The model considers the progressive local–global interaction buckling, distributed plasticity, concrete cracking and crushing, second-order effects, and geometric imperfections. The mathematical model is programmed to compute not only the axial load–displacement responses but also the interaction curves of axial load and moment of slender RCFST columns. The simulation modeling is validated by experimentally measured data. The validated computer model is used to parametrically study the interaction local–global buckling responses of RCFST columns while the range analysis is conducted to identify the relative significance of key parameters. It is demonstrated that the proposed computer model accurately simulates experimentally measured responses. Hence, it can be used with confidence in practice to analyze and design RCFST slender columns fabricated with steel plates of unequal thickness. The existing design standard AS/NZS 2327:2017 provides acceptable strength predictions of RCFST slender columns and beam-columns while the procedure specified in Eurocode 4 overestimates their capacities.

Mending cracks atom-by-atom in rutile TiO2 with electron beam radiolysis

Rich electron-matter interactions fundamentally enable electron probe studies of materials such as scanning transmission electron microscopy (STEM). Inelastic interactions often result in structural modifications of the material, ultimately limiting the quality of electron probe measurements. However, atomistic mechanisms of inelastic-scattering-driven transformations are difficult to characterize. Here, we report direct visualization of radiolysis-driven restructuring of rutile TiO2 under electron beam irradiation. Using annular dark field imaging and electron energy-loss spectroscopy signals, STEM probes revealed the progressive filling of atomically sharp nanometer-wide cracks with striking atomic resolution detail. STEM probes of varying beam energy and precisely controlled electron dose were found to constructively restructure rutile TiO2 according to a quantified radiolytic mechanism. Based on direct experimental observation, a “two-step rolling” model of mobile octahedral building blocks enabling radiolysis-driven atomic migration is introduced. Such controlled electron beam-induced radiolytic restructuring can be used to engineer novel nanostructures atom-by-atom.

Sputtering and structural modifications induced in silicon dioxide (SiO2) thin films under (10–40 MeV) Auq+heavy ion irradiation

Surface sputtering and structural modifications induced in silicon dioxide thin films (SiO2/Si) deposited on silicon substrates and irradiated by swift (10–40 MeV) heavy Auq+(q = +4, +6, +7, and +9) ions were investigated by grazing‐incidence X‐ray diffraction (GIXRD) spectroscopy, Rutherford backscattering (RBS) spectrometry and time‐of‐flight elastic recoil detection (ToF‐ERDA) technique. The GIXRD analysis of the as‐deposited and irradiated samples revealed increasing structural modifications of the SiO2thin films under Auq+ion impacts with increasing ion‐beam energy. The changes consisted of decreased grain sizes with increased strain accompanied by a phase transformation from crystalline to amorphous films. RBS analysis showed a decrease in the mean stoichiometric (O/Si) ratio from (2.2 ± 0.1) to (1.7 ± 0.1), due to preferential sputtering of oxygen, as the incident ion energy increased. The obtained RBS‐results were then completed by those of ToF‐ERDA analysis technique using a 40 MeV Au9+heavy ion beam. The preferential sputtering yield ratios (YSi/YO) were determined experimentally both versus electronic stopping power and ion fluence. The obtained results were then compared to numerical values derived from the inelastic thermal spike (i‐TS) model, Sigmund's analytical formula and SRIM simulation code. A good agreement was observed between the measured preferential sputtering data and the i‐TS calculated values, when considering both nuclear elastic and electronic inelastic collision mechanisms. Besides, a close correlation is observed between the electronic stopping power dependent measured sputtering yields and the XRD peak intensity degradation per unit fluence. These observations suggest that the same mechanism of MeV heavy ion‐irradiation induced extended atomic disordering, occurs both in the case of structural modifications and surface sputtering. Finally, the obtained experimental results are discussed on the basis of the i‐TS model.