No abstract

The understanding of electron interactions with molecules in plasma is of vital importance from academic and technological point of view. The reliable electron collision data is required to model the electron and ion components of low-temperature and non-equilibrium plasmas. Various electron impact cross-sections like the differential, integral, momentum transfer, partial and total ionizations are reported for tetraethyl silicate (TEOS), a plasma relevant molecule in the energy range between ionization threshold and 5~keV. The elastic (differential, integral and momentum transfer) cross-sections are obtained by invoking the molecular approach and local potential approximation within the single center expansion formalism. The dissociative ionization cross-sections are reported with in the binary-encounter-Bethe (BEB) model formalism. The elastic and ionization cross-sections are summed incoherently to estimate total cross-sections. A good agreement is observed between the present and available results. This work validates the efficacy of the modified-BEB model in computing the partial ionization cross-sections.

In the present work, we assess the effectiveness of singly differential cross sections (SDCS) due to electron-impact ionization by invoking the binary-encounter-Bethe (BEB) model on various atomic and molecular targets. The computed results were compared with the experimental and theoretical data. A good agreement was observed between the present and the available results. This agreement improves as the incident energy of the projectile increases. The model can be applied to compute the SDCS for the ions produced due to the electron-impact dissociative ionization process and the average energy due to the secondary electrons. Both these quantities are of interest in plasma processing and radiation physics.

No abstract

The positron impact cross-sections of pyrimidine molecules are reported from 1 eV to 5000 eV. These cross-sections include differential elastic, integral elastic, and direct ionisation. The elastic cross-sections are computed using the single-centre expansion scheme whereas the direct ionisation cross-sections are obtained using the binary-encounter-Bethe formula. The integral and differential cross-sections exhibit consistency with the experimental and other theoretical results. The direct ionisation cross-sections, which are reported for the first time, are compared with the experimental inelastic cross-sections (the sum of excitation and ionisation) to assess the trends in theoretically computed ionisation cross-sections and with the corresponding results for the electrons. The incoherently summed elastic and ionisation cross-sections match very well with the total cross-sections after 40 eV indicating the minimal impact of the positronium formation and electronic excitation processes. Based on this study, we recommend that the experimental data of the inelastic cross-sections reported by Palihawadana et al. be revisited.