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1. Vibrational Excitation of HDO Molecule by Electron Impact

   https://doi.org/10.3390/atoms13040032  

   Ayouz, Mehdi Adrien; Faure, Alexandre; Schneider, Ioan F; Mezei, János Zsolt; Kokoouline, Viatcheslav (April 2025, Atoms)

   Cross sections and thermally averaged rate coefficients for the vibrational excitation and de-excitation by electron impact on the HDO molecule are computed using a theoretical approach based entirely on first principles. This approach combines scattering matrices obtained from the UK R-matrix codes for various geometries of the target molecule, three-dimensional vibrational states of HDO, and the vibrational frame transformation. The vibrational states of the molecule are evaluated by solving the Schrödinger equation numerically, without relying on the normal-mode approximation, which is known to be inaccurate for water molecules. As a result, couplings and transitions between the vibrational states of HDO are accurately accounted for. From the calculated cross sections, thermally averaged rate coefficients and their analytical fits are provided. Significant differences between the results for HDO and H2O are observed. Additionally, an uncertainty assessment of the obtained data is performed for potential use in modeling non-local thermodynamic equilibrium (non-LTE) spectra of water in various astrophysical environments. 

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2. Cross Sections and Rate Coefficients for Vibrational Excitation of H2O by Electron Impact

   https://doi.org/10.3390/atoms9030062  

   Ayouz, Mehdi; Faure, Alexandre; Tennyson, Jonathan; Tudorovskaya, Maria; Kokoouline, Viatcheslav (September 2021, Atoms)

   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. 

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3. Cross sections for vibrational excitation and dissociative recombination of the CF3+ ion in collisions with low-energy electrons

   https://doi.org/10.1088/1361-6595/ac54c0  

   Jiang, Xianwu; Liu, Hainan; Zhang, Ya; Jiang, Wei; Ayouz, Mehdi; Kokoouline, Viatcheslav (April 2022, Plasma Sources Science and Technology)

   Abstract Cross sections for the vibrational excitation and dissociative recombination (DR) of the C F 3 + ion in collisions with electrons at low scattering energies are computed using a previously-developed approach combining the normal mode approximation for the vibrational states of the target ion and the UK R -matrix code for the evaluation of the scattering matrices at fixed geometries. The obtained cross section for the DR shows excellent agreement with the experimental data from the ASTRID storage ring. Thermally-averaged rate coefficients are obtained from the cross sections for temperatures 10–3000 K. 

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4. Electron Scattering Cross-Section Calculations for Atomic and Molecular Iodine

   https://doi.org/10.3390/atoms9040103  

   Ambalampitiya, Harindranath; Hamilton, Kathryn; Zatsarinny, Oleg; Bartschat, Klaus; Turner, Matt; Dzarasova, Anna; Tennyson, Jonathan (December 2021, Atoms)

   Cross sections for electron scattering from atomic and molecular iodine are calculated based on the R-matrix (close-coupling) method. Elastic and electronic excitation cross sections are presented for both I and I2. The dissociative electron attachment and vibrational excitation cross sections of the iodine molecule are obtained using the local complex potential approximation. Ionization cross sections are also computed for I2 using the BEB model. 

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5. Partial Photoionization Cross Sections of Chromium from the Ground and Excited States

   https://doi.org/10.3390/atoms8030051  

   Zatsarinny, Oleg; Tayal, Swaraj (September 2020, Atoms)

   null (Ed.)

   Partial and total photoionization cross sections of iron-peak elements are important for the determination of abundances in late-type stars and nebular objects. We have investigated photoionization of neutral chromium from the ground and excited states in the low energy region from the first ionization threshold at 6.77 eV to 30 eV. Accurate descriptions of the initial bound states of Cr I and the final residual Cr II ionic states have been obtained in the multiconfiguration Hartree-Fock method together with adjustable configuration expansions and term-dependent non-orthogonal orbitals. The B-spline R-matrix method has been used for the calculation of photoionization cross sections. The 194 LS final ionic states of Cr II 3d44s, 3d34s2, 3d5, 3d44p, and 3d34s4p principal configurations have been included in the close-coupling expansion. The inclusion of all terms of these configurations has significant impact on the near-threshold resonance structures as well as on the nonresonant background cross sections. Total photoionization cross sections from the ground 3d54sa7S and excited 3d54sa5S, 3d44s2a5D, 3d54pz5P, and 3d44s4py5P states of Cr I have been compared with other available R-matrix calculation to estimate the likely uncertainties in photoionization cross sections. We analyzed the partial photoionization cross sections for leaving the residual ion in various states to identify the important scattering channels, and noted that 3d electron ionization channel becomes dominant at higher energies. 

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