Inelastic Collision Processes Research Articles

Inelastic Processes in Low-energy Sulfur–Hydrogen Collisions

Abstract The cross sections and rate coefficients for inelastic processes in low-energy collisions of sulfur atoms and positive ions with hydrogen atoms and negative ions are calculated for the collisional energy range and for the temperature range 1000–10,000 K. Fifty-five covalent states and two ionic ones are considered. The ground ionic state provides only molecular symmetry, while the first-excited ionic state provides three molecular symmetries: , , and . The study of sulfur–hydrogen collisions is performed by the quantum model methods within the Born–Oppenheimer formalism. The electronic structure of the collisional quasimolecule is calculated by the semiempirical asymptotic method for each considered molecular symmetry. For nuclear dynamic calculations, the multichannel formula in combination with the Landau–Zener model is used. Nuclear dynamics within each considered symmetry is treated separately, and the total rate coefficients for each inelastic process have been summed over all symmetries. The largest values of the rate coefficients (exceeding ) correspond to the mutual neutralization processes in (the ground ionic state being the initial state), as well as in (the first-excited ionic state being the initial state) collisions. At the temperature 6000 K, the rate coefficients with large magnitudes have the values from the ranges and , respectively. The calculated rate coefficients with large and moderate values are important for NLTE stellar atmosphere modeling.

Influence of Collisions with Hydrogen on Titanium Abundance Determinations in Cool Stars

We performed the non-local thermodynamic equilibrium (non-LTE) calculations for Ti I-II with the updated model atom that includes quantum-mechanical rate coefficients for inelastic collisions with hydrogen atoms. We have calculated for the first time the rate coefficients for bound-bound transitions in inelastic collisions of titanium atoms and ions with hydrogen atoms and for the charge-exchange processes: Ti I + H <-> Ti II + H- and Ti II + H <-> Ti III + H-. The influence of these data on non-LTE abundance determinations has been tested for the Sun and four metal-poor stars. For Ti I and Ti II, the application of the derived rate coefficients has led to an increase in the departures from LTE and an increase in the titanium abundance compared to that, obtained with approximate formulas for the rate coefficients. In metal-poor stars, we have failed to achieve consistent non-LTE abundances from lines of two ionization stages. The known in the literature discrepancy in the non-LTE abundances from Ti I and Ti II lines in metal-poor stars cannot be solved by improvement of the rates of inelastic processes in collisions with hydrogen atoms in non-LTE calculations with classical model atmospheres.

Inelastic processes in calcium-hydrogen ionic collisions with account for fine structure

Inelastic processes in calcium-hydrogen ionic collisions with account for fine structure

State-to-state inelastic rotational cross sections in five-atom systems with the multiconfiguration time dependent Hartree method.

We present a MultiConfiguration Time Dependent Hartree (MCTDH) method as an attractive alternative approach to the usual quantum close-coupling method that approaches some computational limits in the calculation of rotational excitation (and de-excitation) between polyatomic molecules (here collisions between triatomic and diatomic rigid molecules). We have performed a computational investigation of the rotational (de-)excitation of the benchmark rigid rotor H2O-H2 system on a recently developed Potential Energy Surface of the complex using the MCTDH method. We focus here on excitations and de-excitations from the 000, 111, and 110 states of H2O with H2 in its ground rotational state, looking at all the potential transitions in the energy range 1-200 cm-1. This work follows a recently completed study on the H2O-H2 cluster where we characterized its spectroscopy and more generally serves a broader goal to describe inelastic collision processes of high dimensional systems using the MCTDH method. We find that the cross sections obtained from the MCTDH calculations are in excellent agreement with time independent calculations from previous studies but does become challenging for the lower kinetic energy range of the de-excitation process: that is, below approximately 20 cm-1 of collision energy, calculations with a relative modest basis become unreliable. The MCTDH method therefore appears to be a useful complement to standard approaches to study inelastic collision for various collision partners, even at low energy, though performing better for rotational excitation than for de-excitation.

A kinetic model for investigating the dielectric properties of rocket exhaust dusty plasmas

The electron kinetic model of rocket exhaust dusty plasma is developed based on the Boltzmann equation. Additional electron-dust elastic and inelastic collision processes are included in the kinetic equation except for the electron-neutral collisions. The dust surface potential and electron density are calculated according to the dust charging balance equation and the quasineutrality condition. The electron energy distribution function (EEDF) is calculated by solving the kinetic equation numerically. It shows that the obtained EEDF results for different dust densities deviate from the Maxwellian distribution obviously. In addition, the dielectric properties of rocket exhausts based on the obtained non-Maxwellian EEDFs are analyzed for different dust and plasma parameters. It is shown that the relative permittivity based on the EEDFs obtained from the kinetic model is larger than that based on Maxwellian distribution, while for the conductivity and attenuation constant, they become smaller. As for the influence of dust particles on the dielectric properties, a high ratio of dust and neutral density (10−9) leads to a smaller absolute value of relative permittivity, electrical conductivity, and attenuation constant for both Maxwellian distribution and EEDF obtained from the kinetic model. When the ratio is low (10−10), the dust particles almost have no influence on the dielectric properties. Meanwhile, it can be seen that the existence of dust particles makes the difference in dielectric properties obtained from the calculated EEDFs and Maxwellian distribution smaller.

Inelastic processes in low-energy collisions of singly ionized iron with hydrogen atoms

Inelastic processes in low-energy collisions of singly ionized iron with hydrogen atoms

Учет тонкой структуры атомов щелочных металлов при неупругих столкновениях с водородом

The method for calculations of rate coefficients for inelastic processes in collisions of alkali metal atoms and their positive ions with hydrogen atoms and its negative ions with accounting fine structure levels of alkali metals is proposed. The results of applications of the proposed method are reported in the present work on the examples of collisional systems KH and RbH.

Inelastic processes in low-energy iron-hydrogen collisions

The simplified model approach is applied to low-energy collisions of iron atoms and cations with hydrogen atoms and anions.Inelastic collisional processes for all transitions involving 97 low-lying covalent Fe + H states and two ionic Fe+ + H- molecular states are treated, and rate coefficients for excitation, de-excitation, ion-pair formation and neutralization processes are calculated within the Σ+6Π6,Δ6,Σ-4,Π4,Δ4 and 4Φ molecular symmetries.Rate coefficients with highest values correspond to the mutual neutralization processes Fe+(3d64s 6D) + H-→ Fe(3d6(3G)4s4p(3P°) w5G°, v5F°, y5H°) + H(1s2S) and Fe+(3d74F) + H-→ Fe(3d7(2G) 4p w3F°, y3H°, v3G°) + H(1s 2S). The highest rate coefficients for excitation and de-excitation correspond to the Fe(3d6(3G)4s4p(3P°) v5F°) + H(1s2S)→ Fe(3d6(3G)4s4p(3P°) y5H°) + H(1s 2S) process within the sextet molecular symmetries and the Fe(3d7(2D2)4p v3F°) + H(1s2S) → Fe(3d7(2G)4p v3G°) + H(1s 2S) process within the quartet molecular symmetries.

Data on inelastic processes in low-energy collisions of barium atoms and ions with hydrogen atoms and anions

ABSTRACT Inelastic rate coefficients for 686 partial processes in low-energy Ba + H, Ba+ + H−, Ba++ H and Ba2+ + H− collisions are calculated. These data are needed for the non-local thermodynamic equilibrium (non-LTE) modelling of Ba i and Ba ii spectra, especially in cool stellar atmospheres. The calculations of the rate coefficients are performed by means of the quantum model approach, based on the asymptotic semi-empirical method for the electronic structure calculations and on multichannel formulas for the non-adiabatic nuclear dynamical calculations. The inelastic rate coefficients for all transitions between the 17 lowest covalent states and one ionic molecular state in Ba + H and Ba+ + H− collisions, as well as the inelastic rate coefficients for all transitions between the 19 lowest covalent states and one ionic molecular state in Ba+ + H and Ba2+ + H− collisions are calculated. In Ba+ + H− collisions, the highest rate coefficients correspond to the mutual neutralization processes into the Ba(6s6p1P°), Ba(6s7s3S) and Ba(6s7s1S) final states, with the largest value of 5.93 × 10−8 cm3 s−1 at T = 6000 K for the process Ba+ + H− → Ba(6s7s3S) + H. The highest rate coefficient for excitation and de-excitation processes in Ba + H collisions corresponds to the Ba(6s7s1S) → Ba(6s7s3S) transition, with the value of 7.62 × 10−9 cm3 s−1 at T = 6000 K. In Ba2+ + H− collisions, the highest rate coefficients correspond to the neutralization processes into the Ba+( 7p2P°), Ba+( 4f 2F°), Ba+( 6d 2D) and Ba+( 7s 2S) final states. The highest neutralization rate has the value of 3.96 × 10−8 cm3 s−1 at T = 6000 K for the Ba2+ + H− → Ba+( 7p 2P°) + H process. The largest rate coefficient for excitation and de-excitation processes in Ba+ + H collisions corresponds to the Ba+(7s 2S) → Ba+( 6p 2P°) transition, with the value of 1.23 × 10−9 cm3 s−1 at T = 6000 K.

A full-dimensional potential energy surface and quantum dynamics of inelastic collision process for H2-HF.

A full-dimensional ab initio potential energy surface for the H2-HF van der Waals complex was constructed by employing the coupled-cluster singles and doubles with noniterative inclusion of connected triples with augmented correlation-consistent polarised valence quadruple-zeta basis set plus bond functions. Using the improved coupled-states approximation including the nearest neighbor Coriolis couplings, we calculated the state-to-state scattering dynamics for pure rotational and ro-vibrational energy transfer processes. For pure rotational energy transfer, our results showed a different dynamical behavior for para-H2 and ortho-H2 in collision with hydrogen fluoride (HF), which is consistent with the previous study. Interestingly, some strong resonant peaks were presented in the cross sections for ro-vibrational energy transfer. In addition, the calculated vibrational-resolved rate constant is in agreement with the experimental results reported by Bott et al. These dynamics data can be further applied to the numerical simulation of HF chemical lasers.

The nonlocal electron kinetics for a low-pressure glow discharge dusty plasma

The nonlocal electron kinetic model based on the Boltzmann equation is developed in low-pressure argon glow discharge dusty plasmas. The additional electron-dust elastic and inelastic collision processes are considered when solving the kinetic equation numerically. The orbital motion limited theory and collision enhanced collection approximation are employed to calculate the dust surface potential. The electron energy distribution function (EEDF), effective electron temperature Teff, and dust surface potential are investigated under different plasma and dust conditions by solving the Boltzmann and the dust charging current balance equations self-consistently. A comparison of the calculation results obtained from nonlocal and local kinetic models is made. It is shown that the appearance of dust particles leads to a deviation of the EEDF from its original profile for both nonlocal and local kinetic models. With the increase in dust density and size, the effective electron temperature and dust surface potential decrease due to the high-energy electron loss on the dust surface. Meanwhile, the nonlocal and local results differ much from each other under the same calculation condition. It is concluded that, for low-pressure (PR ≤ 1 cm*Torr) glow discharge dusty plasmas, the existence of dust particles will amplify the difference of local and nonlocal EEDFs, which makes the local kinetic model more improper to determine the main parameters of the positive column. The nonlocal kinetic model should be used for the calculation of the EEDFs and dusty plasma parameters.

Estimating inelastic heavy-particle – hydrogen collision data

Aims. A simplified model is derived for estimating rate coefficients for inelastic processes in low-energy collisions of heavy particles with hydrogen, in particular, the rate coefficients with high and moderate values. Such processes are important for non-local thermodynamic equilibrium modeling of cool stellar atmospheres.Methods. The derived method is based on the asymptotic approach for electronic structure calculations and the Landau-Zener model for nonadiabatic transition probability determination.Results. It is found that the rate coefficients are expressed via statistical probabilities and reduced rate coefficients. It is shown that the reduced rate coefficients for neutralization and ion-pair formation processes depend on single electronic bound energies of an atomic particle, while the reduced rate coefficients for excitation and de-excitation processes depend on two electronic bound energies. The reduced rate coefficients are calculated and tabulated as functions of electronic bound energies. The derived model is applied to barium-hydrogen ionic collisions. For the first time, rate coefficients are evaluated for inelastic processes in Ba+ + H and Ba2+ + H− collisions for all transitions between the states from the ground and up to and including the ionic state.

Inelastic processes in collisions of lithium positive ions with hydrogen anions and atoms

Inelastic processes in the low-energy collisions Li3+ + H−, Li2+ + H, Li2+ + H- and Li+ + H are investigated for all collisional channels with the excited ionic lithium states Li2+ (nl) and Li+ (1s nl) up to and including the corresponding ion-pair states for the temperature range 1000–20 000 K. For all possible processes in the Li3+ + H- and Li2+ + H collisions inelastic cross sections and rate coefficients are calculated for the transitions between the ion-pair channel Li3+ + H- and the 35 below lying contributing Li2+ (nl) + H channels. It is found that the highest values of cross sections and rate coefficients are obtained for the recombination processes and their inverse, the ion-pair formation processes, involving the Li2+ (3l), Li2+ (4l), and Li2+ (5l) states. For the processes in the Li2+ + H- and Li+ + H collisions, cross sections and rate coefficients are calculated for all transitions between 34 Li+ (1s nl) + H channels lying below Li2+ + H- plus this ion-pair channel. In this case the highest rate coefficients correspond to the recombination processes with the Li+(1s3l1,3L) and Li+(1s4l1,3L) final states, as well as their inverse processes of ion-pair production. Rate coefficient values for these most efficient processes are rather high, of the order of 10−8 cm3/s. This leads to total recombination rate coefficients in Li3+ + H- and Li2+ + H- collisions with values larger than 10−7 cm3/s.Graphical abstract

Data on inelastic processes in low-energy potassium-hydrogen and rubidium-hydrogen collisions

Two sets of rate coefficients for low-energy inelastic potassium-hydrogen and rubidium-hydrogen collisions were computed for each collisional system based on two model electronic structure calculat ...

Estimating inelastic heavy-particle–hydrogen collision data

Aims. We derive a simplified model for estimating atomic data on inelastic processes in low-energy collisions of heavy-particles with hydrogen, in particular for the inelastic processes with high and moderate rate coefficients. It is known that these processes are important for non-LTE modeling of cool stellar atmospheres.Methods. Rate coefficients are evaluated using a derived method, which is a simplified version of a recently proposed approach based on the asymptotic method for electronic structure calculations and the Landau-Zener model for nonadiabatic transition probability determination. Results. The rate coefficients are found to be expressed via statistical probabilities and reduced rate coefficients. It turns out that the reduced rate coefficients for mutual neutralization and ion-pair formation processes depend on single electronic bound energies of an atom, while the reduced rate coefficients for excitation and de-excitation processes depend on two electronic bound energies. The reduced rate coefficients are calculated and tabulated as functions of electronic bound energies. The derived model is applied to potassium-hydrogen collisions. For the first time, rate coefficients are evaluated for inelastic processes in K+H and K+ +H− collisions for all transitions from ground states up to and including ionic states.

Atomic data on inelastic processes in low-energy manganese-hydrogen collisions

Aims. The aim of this paper is to calculate cross sections and rate coefficients for inelastic processes in low-energy Mn + H and Mn+ + H− collisions, especially, for processes with high and moderate rate coefficients. These processes are required for non-local thermodynamic equilibrium (non-LTE) modeling of manganese spectra in cool stellar atmospheres, and in particular, for metal-poor stars.

A quasi-classical study of energy transfer in collisions of hyperthermal H atoms with SO2 molecules.

A deep understanding of energy transfer processes in molecular collisions is at central attention in physical chemistry. Particularly vibrational excitation of small molecules colliding with hot light atoms, via a metastable complex formation, has shown to be an efficient manner of enhancing reactivity. A quasi-classical trajectory study of translation-to-vibration energy transfer (T-V ET) in collisions of hyperthermal H(2S) atoms with SO2(X̃1A') molecules is presented here. For such a study, a double many-body expansion potential energy surface previously reported for HSO2(2A) is used. This work was motivated by recent experiments by Ma et al. studying collisions of H + SO2 at the translational energy of 59 kcal/mol [J. Ma et al., Phys. Rev. A 93, 040702 (2016)]. Calculations reproduce the experimental evidence that during majority of inelastic non-reactive collision processes, there is a metastable intermediate formation (HOSO or HSO2). Nevertheless, the analysis of the trajectories shows that there are two distinct mechanisms in the T-V ET process: direct and indirect. Direct T-V processes are responsible for the high population of SO2 with relatively low vibrational excitation energy, while indirect ones dominate the conversion from translational energy to high values of the vibrational counterpart.

Reactive, Inelastic, and Dissociation Processes in Collisions of Atomic Oxygen with Molecular Nitrogen.

We report the results of detailed calculations of reactive, inelastic, and dissociative processes in collisions of atomic oxygen with molecular nitrogen in their respective electronic ground states. Cross sections are calculated as a function of collision energy in the range 0.001-10 eV, considering the whole rovibrational ladder. Some problems related to the vibrational energy levels of the asymptotes of 3A″ and 3A' potential energy surfaces used in this work are solved by an appropriate scaling at the level of cross sections. The results are compared with data in the literature, obtaining excellent agreement with experimental thermal data for reactive processes on a very large temperature range, and reasonable agreement with indirect dissociative data. Significant discrepancies are observed with previous reactive state-to-state results calculated on less detailed potential energy surfaces. Inelastic results are compatible with extrapolation of experimental thermal rate coefficient for temperatures higher than 4500 K but completely fail to reproduce experimental data at room temperature. The issue is discussed, indicating the reasons and possible solutions to the problem, and a resonable rate coefficient is obtained combining experimental and theoretical results in the range 300-20000 K. Complete, accurate fits are provided for both reactive and dissociative state-to-state rate coefficients to use them in applicative numerical codes concerning air kinetics.

Precision measurements of cross-sections for inelastic processes in collisions of alkali metal ions with atoms of rare gases

A multifaceted experimental study of collisions of Na[Formula: see text] and K[Formula: see text] ions in the energy range of 0.5–10 keV with He and Ar atoms is presented. Absolute cross-sections for charge-exchange, ionization, stripping and excitation processes were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss and optical spectroscopy methods. The experimental data and the schematic correlation diagrams are employed to analyze and determine the mechanisms for these processes.

Evaluation of angular scattering models for electron-neutral collisions in Monte Carlo simulations

In Monte Carlo simulations of electron transport through a neutral background gas, simplifying assumptions related to the shape of the angular distribution of electron-neutral scattering cross sections are usually made. This is mainly because full sets of differential scattering cross sections are rarely available. In this work simple models for angular scattering are compared to results from the recent quantum calculations of Zatsarinny and Bartschat for differential scattering cross sections (DCS’s) from zero to 200 eV in argon. These simple models represent in various ways an approach to forward scattering with increasing electron energy. The simple models are then used in Monte Carlo simulations of range, straggling, and backscatter of electrons emitted from a surface into a volume filled with a neutral gas. It is shown that the assumptions of isotropic elastic scattering and of forward scattering for the inelastic collision process yield results within a few percent of those calculated using the DCS’s of Zatsarinny and Bartschat. The quantities which were held constant in these comparisons are the elastic momentum transfer and total inelastic cross sections.