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1. The UV Spectrum of the Lyman-Birge-Hopfield Band System of N2 Induced by Cascading from Electron Impact

   https://doi.org/https://doi.org/10.1029/2019JA027546  

   Joseph M. Ajello1, J. Scott ( January 2020 , Journal geographic)

   null (Ed.)

   We have measured in the laboratory the far ultraviolet (FUV: 125.0–170.0 nm) cascade-induced spectrum of the Lyman-Birge-Hopfield (LBH) band system (a 1Πg → X 1Σg+) of N2 excited by 30–200 eV electrons. The cascading transition begins with two processes: radiative and collision-induced electronic transitions (CIETs) involving two states (a′ 1Σu− and w 1Δu → a 1Πg), which are followed by a cascade induced transition a 1Πg → X 1Σg+. Direct excitation to the a-state produces a confined LBH spectral glow pattern around an electron beam. We have spatially resolved the electron induced glow pattern from an electron beam colliding with N2 at radial distances of 0–400 mm at three gas pressures. This imaging measurement is the first to isolate spectral measurements in the laboratory of single-scattering electron-impact-induced-fluorescence from two LBH emission processes: direct excitation, which is strongest in emission near the electron beam axis; and cascading-induced, which is dominant far from the electron beam axis. The vibrational populations for vibrational levels from v′=0–2 of the a 1Πg state are enhanced by CIETs, and the emission cross sections of the LBH band system for direct and cascading-induced excitation are provided at 40, 100, and 200 eV 

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2. 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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3. Electron scattering on molecular nitrogen: common gas, uncommon cross sections

   https://doi.org/10.1140/epjd/s10053-023-00687-5  

   Song, Mi-Young ; Cho, Hyuck ; Karwasz, Grzegorz P. ; Kokoouline, Viatcheslav ; Tennyson, Jonathan ( June 2023 , The European Physical Journal D)

   Abstract We discuss peculiar features of electron scattering on the N 2 molecule and the N 2 + ion, that are important for modeling plasmas, Earth’s and other planets’ atmospheres. These features are, among others: the resonant enhancement of the vibrational excitation in the region of the shape resonance around 2.4 eV, the resonant character of some of electronic excitation channels (and high values of these cross sections, both for triplet and singlet states), high cross section for the dissociation into neutrals, high cross sections for elastic scattering (and electronic transitions) on metastable states. For the N 2 + ion we discuss both dissociation and the dissociative ionization, leading to the formation of atoms in excited states, and dissociative recombination which depends strongly on the initial vibrational state of the ion. We conclude that the theory became an indispensable completion of experiments, predicting many of partial cross sections and their physical features. We hope that the data presented will serve to improve models of nitrogen plasmas and atmospheres. Graphical abstract 

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4. Theoretical study of the electron-induced vibrational excitation of H2O

   https://doi.org/10.1051/0004-6361/202449361  

   Ayouz, Mehdi ; Faure, Alexandre ; Kokoouline, Viatcheslav ( July 2024 , Astronomy & Astrophysics)

   This study presents calculations for cross sections of the vibrational excitation of H2O (X1A1) via electron impact. The theoretical approach employed here is based on first principles only, combining electron-scattering calculations performed using the UK R-matrix codes for several geometries of the target molecule, three-dimensional (3D) vibrational states of H2O, and 3D vibrational frame transformation. The aim is to represent the scattering matrix for the electron incident of the molecule. The vibrational wave functions were obtained numerically, without the normal-mode approximation, so that the interactions and transitions between vibrational states assigned to different normal modes could be accounted for. The thermally averaged rate coefficients were derived from the calculated cross sections for temperatures in the 10–10 000 K interval and analytical fits for rate coefficients were also provided. We assessed the uncertainty estimations of the obtained data for subsequent applications of the rate coefficients in modelling the non-local thermal equilibrium (non-LTE) spectra of water in various astrophysical environments. 

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5. 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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