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Item 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)(Elsevier) Pilling, Sergio; Rocha, Will Robson Monteiro; Carvalho, Geanderson Araújo; Abreu, Heitor Avelino deChemical reactions and desorption processes are being triggered by incoming ionizing radiation over astrophysical ices in cold space environments. The quantification of these processes is crucial to achieve a detailed understanding of the underlying chemistry occurring within the ice. With this goal, we have upgraded the PROCODA code (Pilling et al. 2022a) which solves a system of coupled differential equations and describes the evolution of the molecular abundances under processing by radiation, now including an effective rate constant (ERCs) ordering by employing thermochemistry data taken from literature. This methodology helps to identify the most important reactions within the reaction network and therefore decreases the degeneracy of the solutions and enhancing the accuracy of the calculations. Here, we described the chemical evolution of four irradiated pure CO2 considering 11 different chemical species, 100 reaction routes and 11 radiation-induced desorption processes. The best-fit models provide the effective rate constants, several desorption parameters, as well as, the characterization of the chemical equilibrium (CE) phase. A comparison with previous code version was given and indicates that the ordering of rate constants by thermochemistry data is more important when more energy is deposited in the ice. The current work present more realistic values for the effective rate constants and a better characterization of the CE phase, such data can be used to refine astrochemical models to better describe cold space environments in the presence of incoming ionizing radiation field such molecular clouds and protoplanetary regions and the surface of comets and frozen moons and planets.Item Characterization of acetonitrile ice irradiated by X-rays employing the procoda code – II. Desorption processes(Royal Astronomical Society) Carvalho, Geanderson Araújo; Pilling, Sergio; Gerasimenko, SvitlanaIn this work, we focus on the study of radiation-induced desorption processes that occurred in acetonitrile ice irradiated by broad-band X-rays (6 eV to 2 keV) monitored by Fourier transform infrared spectroscopy at different radiation fluences. In a previous work, we used the procoda code to derive the chemical evolution of the ice. Here, we have observed that the acetonitrile desorbed column density is at least two orders of magnitude larger than the desorbed column densities of daughter or granddaughter molecular species at chemical equilibrium stage. This indicates that total desorption column density is mainly governed by the father molecule, as also previously hypothesized in experimental studies. This occurs basically because the acetonitrile column density is larger than the other ones. In particular, at chemical equilibrium acetonitrile desorption column density represents almost 98 per cent of the total, while it is close to 1 per cent for H, CN, and CH2, the species with larger molecular desorption percentages at chemical equilibrium. Another derived quantity is what we called intrinsic desorption rate, which is a number per second for individual species. Some of the larger intrinsic desorption rates were 6.2 × 10−6 (CH3CN), 6.2 × 10−6 (CN), 5.7 × 10−6 (H), 5.7 × 10−6 (CH2), and 4.4 × 10−6 (C2N2). These results help to put constraints in astrochemical models and can also be useful to clarify some astronomical radio observations.