Electron Collision Cross Sections Research Articles

Electron transport in CF3I and CF3I-N2 mixtures

Electron collision cross sections for CF3I are estimated using the electron swarm method. Electron drift velocity, effective ionisation coefficient, and longitudinal diffusion coefficient in CF3I are calculated using Monte Carlo method, and the calculated electron transport coefficients are compared with those measured. Calculated electron drift velocity agrees with measured data within the difference of 6% below 1600 Td, and calculated effective ionisation coefficient agrees with measured data within the difference of 10% above 460 Td. Further, those swarm parameters in CF3I–N2 mixtures are calculated, and calculated values of electron drift velocity and effective ionisation coefficient agree well with measured data in CF3I–N2 mixtures. This confirms the validity of the estimated set.

시뮬레이션에 의한 SF6-He 혼합기체에서 전자에너지 분포함수

This paper describes the electron transport characteristics in SF6-He gas calculated E/N values 0.1～700[Td] by the Monte Carlo simulation and Boltzmann equation method using a set of electron collision cross sections determined by the authors and the values of electron swarm parameters obtained by TOF method. This study gained the values of the electron swarm parameters such as the electron drift velocity, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients for SF6-He gas at a range of E/N. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

Ab initio Calculations of Electron-Impact Excitation Cross Sections for N2 Molecule

One of the great difficulties in understanding nitrogen plasma elementary processes is the lack of an available database of the cross-sections of electron-impact excitations and radiations. Ab initio calculations of vibrational excitation cross sections for electron collisions with nitrogen molecules in low-lying states using similarity function approach, such as a-a′, a-w, B-B′ and B-W transition systems, are reported here for the first time. In the meantime, the average excitation energies of neighboring levels of these systems have been calculated. In order to obtain the cross sections, accurate spectroscopic constants and transition dipole moments have been investigated. Potential energy curves and other electronic transition dipole moments for the low-lying states of N2 have been re-evaluated using complete active space self-consistent field (CASSCF) approach with aug-cc-pVqZ basis set. The calculated cross-sections could provide a database for studying the elementary processes and the properties in N2 plasma.

Calculations of electron transport coefficients in Cl2-Ar, Cl2-Xe and Cl2-O2 mixtures

In order to understand quantitatively plasma phenomena and ionized gases, accurate electron collision cross-sections and electron transport coefficients for not only pure atoms and molecules but also for the binary gas mixtures are necessary. Electron transport coefficients (electron drift velocity, density-normalized longitudinal diffusion coefficient, and density-normalized effective ionization coefficient) in mixture gases of Cl2 with Ar, Xe and O2, therefore, were calculated and analyzed by using a two-term approximation of the Boltzmann equation over a wide E/N range (ratio of the electric field E to the neutral number density N). The limiting field strength values of E/N, (E/N)lim, for these binary gas mixtures were also derived and compared with those of pure SF6 gas. These binary gas mixtures are being considered for use in many industries, depending on the mixture ratio and the particular application of the gas and the electrical equipment.

Total cross sections for O2 and S2 by electron impact

We report total cross sections for electron collision with O2 and S2 molecules in the energy range 0.1–2000eV by combining two theoretical methods. Below the ionization threshold of the target, total cross section is calculated by the ab initio R-matrix method through Quantemol-N software. For intermediate and high energies, we have applied a Spherical complex optical potential formalism. Comparison is made with the available theoretical and experimental data and a reasonable agreement is observed. The high energy cross section for S2 molecule is reported for the first time.

Cross sections for electron collisions with dimethyl ether

We report a joint theoretical-experimental investigation of electron collision with dimethyl ether (DME) in the low- and intermediate-energy ranges. Experimental absolute differential, integral, and momentum-transfer cross sections for elastic ${e}^{\ensuremath{-}}$-DME scattering are reported in the 100--1000 eV energy range. Our measurements were performed using a crossed electron-beam--molecular-beam geometry. The angular distribution of the scattered electrons was converted to absolute cross section using the relative flow technique. Theoretically, elastic differential, integral, and momentum-transfer cross sections, as well as the grand-total and total absorption cross sections for electron collision with DME are calculated in the 1--1000 eV energy range. A single-center-expansion technique combined with the Pad\'e approximant method is used in our calculations. A comparison between the present experimental and theoretical data shows very good agreement. Moreover, comparison with theoretical and experimental data for ${e}^{\ensuremath{-}}$-ethanol (an isomer of DME) scattering shows interesting isomeric effects.

Comparisons of sets of electron–neutral scattering cross sections and swarm parameters in noble gases: III. Krypton and xenon

This paper, the third in a series of three, describes work carried in the context of Plasma Data Exchange Project of the Gaseous Electronics Conference (PDEP-GEC) to compare electron collision cross-sections sets from ground-state, noble gases atoms and to check their consistency with measured swarm parameters. Such consistency is a minimum requirement if the cross-section data are to be used for modelling low-temperature plasmas. In this paper, we present intercomparisons of the independently compiled sets of electron cross-sections from ground-state, neutral Kr and Xe atoms presently available on the LXCat open-access website (www.lxcat.laplace.univ-tlse.fr). Swarm parameters (reduced mobility, characteristic energy, reduced longitudinal diffusion coefficient, reduced ionization coefficient) calculated in a Boltzmann solver or Monte Carlo simulation using these cross-sections sets are compared with experimental data, also available online on the LXCat site.

Scattering cross sections for electrons in C2 H2F4 and its mixtures with Ar from measured transport coefficients

Previous measurements of the drift velocities, W, and the density-normalized effective ionization (multiplication) coefficients (ionization minus attachment), (α − η)/N, measured in C2H2F4 (1,1,1,2 tetrafluoroethane) and in C2H2F4–Ar mixtures have been analysed with a standard swarm procedure. As a result of this analysis a set of electron collision cross sections for the C2H2F4 molecule has been obtained. This set has been further used to calculate other transport parameters such as the characteristic energies and rate coefficients for individual processes.

Electron Swarm Parameters and Electron Collision Cross Sections

An electron swarm study using molecular gas-rare gas mixtures is briefly reviewed, and the advantage of using these mixtures to evaluate inelastic electron collision cross-section data for molecules through electron swarm study is explained. This advantage also suggests a new procedure for deriving a consistent set of electron collision cross sections for molecules by using electron swarm data measured in pure molecular gas and in the molecular gas-rare gas mixtures alternately. The procedure is detailed by using an example of C2H4. The derived cross-section set for C2H4 covers the energy range where a conventional electron beam experiment is not practical and can be crucial for the quantitative modeling of relevant plasmas.

Electron Collision Cross Sections for the BF3Molecule and Electron Transport Coefficients in BF3–Ar and BF3–SiH4Mixtures

A consistent set of low-energy electron collision cross sections for the boron trifluoride (BF3) molecule has been derived from the measured electron transport coefficients for a pure BF3 molecule using an electron swarm study and a two-term approximation of the Boltzmann equation for energy. The electron transport coefficients, which were calculated using the derived set, are consistent with the experimental data over a wide range of \(E/N\) values (ratio of the electric field \(E\) to the neutral number density \(N\)). The present set of electron collision cross sections for the BF3 molecule, therefore, is the best available so far for the quantitative numerical modeling of plasma discharges for processing procedures with materials containing BF3 molecules. The electron-transport coefficients for BF3–Ar and BF3–SiH4 mixtures were also calculated and analyzed in a wide range of \(E/N\) ratios for the first time. The presence of a remarkable synergism in the Townsend first ionization coefficient has been pointed out in BF3–SiH4 mixtures.

MCS-BEq에 의한 CH4기체에서 전자에너지 분포함수

This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. Using quantitative simulations of weakly ionized plasma, we can analyze gas characteristic. In this paper, the electron transport characteristic in CH₄ has been analysed over the E/N range 0.1～300[Td], at the 300[。K] by the two term approximation Boltzmann equation method and Monte Carlo Simulation. Boltzmann equation method has also been used to predict swarm parameter using the same cross sections as input. The behavior of electron has been calculated to give swarm parameter for the electron energy distribution function has been analysed in CH₄ at E/N=10, 100 for a case of the equilibrium region in the mean energy. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

Total, elastic, and inelastic cross sections for positron and electron collisions with tetrahydrofuran

We present total, elastic, and inelastic cross sections for positron and electron scattering from tetrahydrofuran (THF) in the energy range between 1 and 5000 eV. Total cross sections (TCS), positronium formation cross sections, the summed inelastic integral cross sections (ICS) for electronic excitations and direct ionization, as well as elastic differential cross sections (DCS) at selected incident energies, have been measured for positron collisions with THF. The positron beam used to carry out these experiments had an energy resolution in the range 40-100 meV (full-width at half-maximum). We also present TCS results for positron and electron scattering from THF computed within the independent atom model using the screening corrected additivity rule approach. In addition, we calculated positron-impact elastic DCS and the sum over all inelastic ICS (except rotations and vibrations). While our integral and differential positron cross sections are the first of their kind, we compare our TCS with previous literature values for this species. We also provide a comparison between positron and electron-impact cross sections, in order to uncover any differences or similarities in the scattering dynamics with these two different projectiles.

Elastic Scattering of Low-Energy Electron by Lignin Precursors

We present cross sections for electron collisions with monolignol precursors obtained with the Schwinger Multichannel method. For Cs phenol system, π* resonances are found in the A" irreducible representation. So, mechanisms for dissociative electron attachment could give rise if σ* resonances are found in the monolignols.

Absolute cross sections for electron collisions with diacetylene: Elastic scattering, vibrational excitation and dissociative attachment

We present absolute experimental cross sections for elastic scattering, vibrational excitation by electron impact and for dissociative electron attachment to 1,3-butadiyne, as well as calculations of the elastic cross sections.

Electron collisions with nitromethane

We present elastic cross sections for low energy electron-collisions with the nitromethane molecule. We compare our results for the π* and the σ* shape resonances position with the available experimental data.

Electron collisions with the HCOOH... H2O complex

We present elastic cross sections for electron-collisions with the HCOOH...H2O. We compare the π* shape resonance position of the complex to that of the HCOOH molecule.

Electron collisions with the formamide dimer and the HCOOH...HCONH2 complex

We present elastic cross sections for electron-collisions with the formamide dimer and the HCOOH...HCONH2 complex. We compare the π* shape resonances position of the dimer and the complex to those of the HCONH2 and HCOOH molecules.

Calculated electron impact spin-coupled rotational cross-sections for 2S + 1Σ+ linear molecules: CN as an example

Here we present the development and adaptation of existing atom–molecule collision theory in order to calculate spin-coupled rotationally resolved cross-sections for electron–molecule collisions. A full theory is developed from the existing work for this new process and then implemented using the infinite order sudden approximation to simplify the method; this approximation is shown to hold for the results of a simple test. The formalism is used to compute spin-rotation cross-sections for electron collisions with the CN radical in its 2Σ+ ground electronic state. Results for transitions out of the ground spin rotational state are presented. A general fortran program, ROTLIN_S, is developed for this task.

R-matrix calculations of differential and integral cross sections for low-energy electron collisions with ethanol

Electron collisions with C2H5OH are studied up to impact energies of 10 eV using several theoretical models. Calculated differential cross sections suggest that the extrapolation to low angles used to extend experimental data and hence give integral cross sections significantly underestimates the large, dipole-driven forward scattering cross section. An improved set of values for the rotationally-unresolved elastic cross section is proposed; the corresponding rotationally resolved cross sections are also presented. Static exchange plus polarisation calculations find a very broad shape resonance in each of the 2A′ and 2A′′ symmetries in the 7 eV collision region however no resonance at lower energies, in qualitative agreement with the interpretation of some but not all dissociative electron attachment measurements.

Electron collision cross sections for the TMS molecule and electron transport coefficients in TMS-Ar and TMS-O2 mixtures

A consistent set of low-energy electron-collision cross sections for the tetramethylsilane (TMS) molecule has been derived from the measured electron transport coefficients for a pure TMS molecule by using an electron swarm study and a two-term approximation of the Boltzmann equation for energy. The electron transport coefficients, which were calculated by using the derived set, are consistent with the experimental data over a wide range of E/N values (ratio of the electric field E to the neutral number density N). The present set of electron collision cross sections for the TMS molecule, therefore, is the best available so far for quantitative numerical modeling of plasma discharges for processing procedures with materials containing TMS molecules. The electron-transport coefficients in TMS-Ar and TMS-O2 mixtures were also calculated and analyzed in a wide range of E/N ratios for the first time. The presence of a remarkable synergism in the Townsend first ionization coefficient has been pointed out in the TMS-O2 mixtures.