Electron interaction with methane molecule and accurate determination of its elastic cross-section is a demanding task for both experimental and theoretical standpoints and relevant for our better understanding of the processes in Earth’s and Solar outer planet atmospheres, the greenhouse effect or in plasma physics applications like vapor deposition, complex plasma-wall interactions and edge plasma regions of Tokamak. Methane can serve as a test molecule for advancing novel electron-molecule collision theories. We present a combined experimental and theoretical study of the elastic electron differential cross-section from methane molecule, as well as integral and momentum transfer cross-sections in the intermediate energy range (50–300 eV). The experimental setup, based on a crossed beam technique, comprising of an electron gun, a single capillary gas needle and detection system with a channeltron is used in the measurements. The absolute values for cross-sections are obtained by relative-flow method, using argon as a reference. Theoretical results are acquired using two approximations: simple sum of individual atomic cross-sections and the other with molecular effect taken into the account.

Absolute differential cross section for elastic electron scattering from the isoflurane molecule, both experiment and theory, at an incident electron energy of 100 eV. A significant match between the two is evident.

Ionization is among the most important processes within the interstellar medium and planetary atmospheres since it defines both their physical and chemical nature. The elementary processes that lead to ionization events need to be understood and the cross sections which define the probability of different ionization pathways need to be defined in order to support the modelling of these regions. In this article we discuss the elementary processes leading to ionization events and their importance in planetary atmospheres. We focus on calculations of ionization and dissociative rate coefficients. Ionization rate coefficients derived from electron swarms as a function of the reduced electric field for planetary atmospheres in Solar system are presented as an example of ionization data required for this study. Dissociative rate coefficients for molecular hydrogen cation over a wide range of temperatures are discussed as an example of data needs. Our model is tailored for collisional reactions and may handle various atomic and molecular species, as shown for different compositions of planetary atmospheres. The model incorporates a significantly enriched set of collisional cross sections, including energy-dependent and temperature-dependent rates, as shown in calculations of dissociative rate coefficients. We also present several databases that may be used to source ionization data, with an emphasis on those developed in Belgrade.

We report the results of the measurements and calculations of the absolute differential elastic electron scattering cross-sections (DCSs) from sevoflurane molecule (C₄H₃F₇O). The experimental absolute DCSs for elastic electron scattering were obtained for the incident electron energies from 50 eV to 300 eV, and for scattering angles from 25° to 125° using a crossed electron/target beams setup and the relative flow technique for calibration to the absolute scale. For the calculations, we have used the IAM-SCAR+I method (independent atom model (IAM) applying the screened additivity rule (SCAR) with interference terms included (I)). The molecular cross-sections were obtained from the atomic data by using the SCAR procedure, incorporating interference term corrections, by summing all the relevant atomic amplitudes, including the phase coefficients. In this approach, we obtain the molecular differential scattering cross-section (DCS), which, integrated over the scattered electron angular range, gives the integral scattering cross-section (ICS). Calculated cross-sections agree very well with experimental results, in the whole energy and angular range.