scholarly journals Cross Sections and Rate Coefficients for Vibrational Excitation of H2O by Electron Impact

Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 62
Author(s):  
Mehdi Ayouz ◽  
Alexandre Faure ◽  
Jonathan Tennyson ◽  
Maria Tudorovskaya ◽  
Viatcheslav Kokoouline
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Vibrational Excitation ◽  
Normal Modes ◽  
Scattering Matrix ◽  
Rate Coefficients ◽  
Vibrational States ◽  
R Matrix ◽  
Frame Transformation ◽  
The Uk

Cross-sections and thermally averaged rate coefficients for vibration (de-)excitation of a water molecule by electron impact are computed; one and two quanta excitations are considered for all three normal modes. The calculations use a theoretical approach that combines the normal mode approximation for vibrational states of water, a vibrational frame transformation employed to evaluate the scattering matrix for vibrational transitions and the UK molecular R-matrix code. The interval of applicability of the rate coefficients is from 10 to 10,000 K. A comprehensive set of calculations is performed to assess uncertainty of the obtained data. The results should help in modelling non-LTE spectra of water in various astrophysical environments.

scholarly journals Cross Sections and Rate Coefficients for Rotational Excitation of HeH+ Molecule by Electron Impact

Atoms ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 49 ◽  
Author(s):  
Marjan Khamesian ◽  
Mehdi Ayouz ◽  
Jasmeet Singh ◽  
Viatcheslav Kokoouline
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Theoretical Approach ◽  
Analytical Formula ◽  
Rate Coefficients ◽  
Rotational Excitation ◽  
R Matrix ◽  
Wide Range ◽  
The Uk ◽  
Quantum Defect Theory

Cross sections for rotational excitation and de-excitation of the HeH+ ion by an electron impact are computed using a theoretical approach that combines the UK R-matrix code and the multi-channel quantum defect theory. The thermally-averaged rate coefficients derived from the obtained cross sections are fitted to an analytical formula valid for a wide range of temperatures.

scholarly journals Electron-impact fine-structure excitation of Fe ii at low temperature

2019 ◽  
Vol 485 (2) ◽  
pp. 2252-2258
Author(s):  
Yier Wan ◽  
C Favreau ◽  
S D Loch ◽  
B M McLaughlin ◽  
Yueying Qi ◽  
...  
Keyword(s):  
Fine Structure ◽  
Low Temperature ◽  
Electron Impact ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Ground Term ◽  
R Matrix ◽  
Uncertainty Estimates ◽  
Frame Transformation ◽  
Effective Collision

Abstract Fe ii emission lines are observed from nearly all classes of astronomical objects over a wide spectral range from the infrared to the ultraviolet. To meaningfully interpret these lines, reliable atomic data are necessary. In the work presented here we focused on low-lying fine-structure transitions, within the ground term, due to electron impact. We provide effective collision strengths together with estimated uncertainties as functions of temperature of astrophysical importance (10−100 000 K). Due to the importance of fine-structure transitions within the ground term, the focus of this work is on obtaining accurate rate coefficients at the lower end of this temperature range, for applications in low-temperature environments such as the interstellar medium. We performed three different flavours of scattering calculations: (i) an intermediate coupling frame transformation (icft) R-matrix method, (ii) a Breit–Pauli R-matrix (bprm) method, and (iii) a Dirac Atomic R-matrix Code (darc). The icft and bprm calculations involved three different autostructure target models each. The darc calculation was based on a reliable 20 configuration, 6069 level atomic structure model. Good agreement was found with our bprm and darc collision results compared to previous R-matrix calculations. We present a set of recommended effective collision strengths for the low-lying forbidden transitions together with associated uncertainty estimates.

Cross sections for resonant vibrational excitation ofN2by electron impact

1981 ◽  
Vol 23 (3) ◽  
pp. 1089-1099 ◽  
Author(s):  
A. U. Hazi ◽  
T. N. Rescigno ◽  
M. Kurilla
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Vibrational Excitation

scholarly journals Electron-impact double ionization of the carbon atom

2018 ◽  
Vol 620 ◽  
pp. A188 ◽  
Author(s):  
Valdas Jonauskas
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Cross Sections ◽  
Double Ionization ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Ionization Cross ◽  
Ionization Cross Sections ◽  
Good Agreement

Electron-impact single- and double-ionization cross sections and Maxwellian rate coefficients are presented for the carbon atom. Scaling factors are introduced for the electron-impact excitation and ionization cross sections obtained in the distorted wave (DW) approximation. It is shown that the scaled DW cross sections provide good agreement with measurements for the single ionization of the C atom and C1+ ion. The direct double-ionization (DDI) process is studied using a multi-step approach. Ionization–ionization, excitation–ionization–ionization, and ionization–excitation–ionization branches are analyzed. It is demonstrated that the three-step processes contribute ≼40% of the total DDI cross sections for the case where one of the electrons takes all of the excess energy after the first ionization process.

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