Mapping the evolution of pure CO2 ices irradiated by ions, UV, and electrons using the upgraded PROCODA code (employing an effective rate constant ordering by thermochemistry data)

Understanding the Molecular Kinetics and Chemical Equilibrium Phase of Frozen CO during Bombardment by Cosmic Rays by Employing the PROCODA Code

“…In this study, we utilize the updated PROCODA code (described in detail by Pilling et al 2022Pilling et al , 2023 to investigate the chemical evolution of pure CO ice under irradiation by cosmic-ray analogs, to calculate the ERCs, and to characterize the CE phase that occurs at larger radiation fluences. The term ERC is employed once again to account for the various chemical environments in which a given reaction can take place within the ice.…”

“…To solve the coupled chemical equations set, comparing modeled species with experimental data, the code employs a minimization process of a function referred to as the score function (SF) that evaluates how close the system is to its minimum global solution (see the full discussion in Pilling et al 2022Pilling et al , 2023. This function includes several terms and constraints such as the term for the χ 2 function for a direct comparison with experimental data, the term for mass similarity criterion (MSC) between model and experiments, the term for the similarity between experimental desorption and modeled desorption yield (Y), and the condition for the achievement of the CE phase in the ice at larger fluences (by employing the slope similarity criterion (SSC)).…”

“…The thermochemical data used in the ordering hypothesis for the ERCs considers that all studied species are in the lowest energy level and formation enthalpies and reaction enthalpies are at the gas phase at the theoretical temperature of 0 K. Additional details of the ordering procedure are given at Pilling et al (2023). A list of the chemical species and gas-phase formation enthalpies at 0 K (Δ f H 0 ) considered in this work is presented in Table 1.…”

“…The goal of this study is to assess and quantify the presence of chemical species (and its reaction routes including its molecular kinetics) observed and predicted in pure CO ice subjected to bombardment by cosmic-ray analogs, using the PROCODA code (Pilling et al 2022(Pilling et al , 2023Carvalho et al 2022) and experimental data from Seperuelo Duarte et al (2010). The experimental data involved the irradiation of pure CO ice at 13 K by 50 MeV Ni ions, obtained at the GANIL laboratory in France.…”

“…The current code version employs the ERCs ordering hypothesis based on thermochemistry data (taken from the literature), which incorporates actual chemical information into the code, specifying that some reactions should be faster than others. As discussed by Pilling et al (2023), this procedure reduces code degeneracy and yields a more accurate chemical solution.…”