hemical Evolution of CO2 Ices under Processing by Ionizing Radiation: Characterization of Nonobserved Species and Chemical Equilibrium Phase with the Employment of PROCODA Cod

Author(s)

Pilling, Sergio ^[1] ; Carvalho, Geanderson A. ^[1] ; Rocha, Will R. M. ^[2]

Affiliation

^[1] Univ Vale Paraiba, Inst Pesquisa & Desenvolvimento, BR-12244000 Sao Jose Dos Campos, SP - Brazil

^[2] Leiden Univ, Lab Astrophys, Leiden Observ, POB 9513, NL-2300 RA Leiden - Netherlands

• Document type: Journal article
• Source: ASTROPHYSICAL JOURNAL; v. 925, n. 2 FEB 1 2022.
• Web of Science Citations: 0

Abstract

Astrophysical ices are being exposed to ionizing radiation in space environments, which trigger new reactions and desorption processes. In the lab, such processing by radiation has revealed the appearance of several new species and complements the study of the chemical evolution of icy astrophysical scenarios. Here, we develop a computational methodology that helps to clarify the chemical evolution of ices investigated experimentally under photolysis/radiolysis processes until reaching chemical equilibrium (CE). Briefly, the code (named PROCODA) solves a system of coupled differential equations and describes the evolution of the molecular abundances with the irradiation time for ices under processing by radiation. Two experimental ice samples containing pure CO2 and irradiated by two ionizing agents (cosmic rays and ultraviolet photons) were considered prototype systems. Here, we considered 11 different chemical species within the ice (four observed: CO2, CO, O-3, and CO3; seven nonobserved or unknown: O, O-2, C, C2, C2O, C2O2, and C2O3), 100 reaction routes (e.g., direct dissociation reactions, bimolecular and termolecular reactions) and radiation-induced desorption processes. The best-fit models provide the reaction rates, several desorption parameters, as well as the characterization of the CE phase. At CE, the percentage of nonobserved species in the UV model was almost triple the one calculated in the CR model (which also includes a lot of O and C atoms). The determined values can be employed in future astrochemical models to map chemical evolution embedded species in astrophysical regions under the presence of an ionizing radiation field. (AU)

• FAPESP's process: 09/18304-0 - Synthesis and degradation of prebiotic molecular species at planetary atmospheres, comets and interstellar ice analogs
• Grantee: Sergio Pilling Guapyassu de Oliveira
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 15/10492-3 - Study about the chemical evolution of astrophysical ices in the vicinity of young stellar objects employing experimental data in the infrared and computational modeling codes
• Grantee: Will Robson Monteiro Rocha
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/07657-5 - Computational modeling of circumstellar environment of protostars by employing data of bombarded ices with cosmic rays simulated in laboratory.
• Grantee: Will Robson Monteiro Rocha
• Support Opportunities: Scholarships in Brazil - Doctorate