Collisional ionization data for research of interstellar medium and planetary atmospheres

Abstract 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.