Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium
We computationally investigated the chemical evolution of H _2 O:O _2 ices (6:1 ratio) under irradiation by cosmic-ray analogs (0.8 MeV H ^+ ) at 9, 50, and 100 K to understand the implications the chemical evolution of O _2 -containing ices in space, such as the surface of the Moon, comets, outer s...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adc924 |
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| author | J. R. C. Silva L. M. S. V. Queiroz L. F. A. Ferrão S. Pilling |
| author_facet | J. R. C. Silva L. M. S. V. Queiroz L. F. A. Ferrão S. Pilling |
| author_sort | J. R. C. Silva |
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| description | We computationally investigated the chemical evolution of H _2 O:O _2 ices (6:1 ratio) under irradiation by cosmic-ray analogs (0.8 MeV H ^+ ) at 9, 50, and 100 K to understand the implications the chemical evolution of O _2 -containing ices in space, such as the surface of the Moon, comets, outer solar system bodies such Europa and Enceladus, as well as Kuiper Belt objects, and cold regions of the interstellar medium (ISM). Using experimental data and the PROCODA code with 200 reactions coupled equations involving 12 species, we calculated physicochemical parameters such as effective rate coefficients (ERCs), chemical abundances, and desorption. Six species were observed experimentally (H _2 O, O _2 , HO _2 , H _2 O _2 , O _3 , and HO _3 ), while six were predicted but not observed in the experiments (H, H _2 , H _3 , O, OH, and H _3 O). Our findings highlight the influence of temperature on chemical equilibria and desorption yields, with certain reaction rates diminishing at 50 K. Among the results were the lists with the ERCs, and the reaction branching ratio obtained by best-fit models can be employed in astrochemical models. Curiously, we observe that the average ERCs for bimolecular collisions decrease by half as the ice temperature increases, varying from 5.8e-25 to 2.9e-25 cm ^3 molecules ^−1 s ^−1 for the ices studied. These results enhance our understanding of the physical chemistry of astrophysical ices under ionizing radiation, providing valuable data for astrochemical models that assess the effects of cosmic radiation on the composition and stability of icy bodies in the solar system and denser and colder regions of the ISM. |
| format | Article |
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| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-ec6ab5699c8d4216b09f38535bd272a72025-08-20T02:34:31ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985225410.3847/1538-4357/adc924Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and EquilibriumJ. R. C. Silva0https://orcid.org/0000-0002-9558-8665L. M. S. V. Queiroz1https://orcid.org/0000-0001-5613-6132L. F. A. Ferrão2https://orcid.org/0000-0003-1294-8707S. Pilling3https://orcid.org/0000-0002-6321-3666Instituto Tecnológico de Aeronáutica , São Jose dos Campos, SP, 12228-900, Brazil ; josianercs@ita.brInstituto Tecnológico de Aeronáutica , São Jose dos Campos, SP, 12228-900, Brazil ; josianercs@ita.brInstituto Tecnológico de Aeronáutica , São Jose dos Campos, SP, 12228-900, Brazil ; josianercs@ita.brUniversidade do Vale do Paraíba—UNIVAP , São José dos Campos, SP, 12244-000, BrazilWe computationally investigated the chemical evolution of H _2 O:O _2 ices (6:1 ratio) under irradiation by cosmic-ray analogs (0.8 MeV H ^+ ) at 9, 50, and 100 K to understand the implications the chemical evolution of O _2 -containing ices in space, such as the surface of the Moon, comets, outer solar system bodies such Europa and Enceladus, as well as Kuiper Belt objects, and cold regions of the interstellar medium (ISM). Using experimental data and the PROCODA code with 200 reactions coupled equations involving 12 species, we calculated physicochemical parameters such as effective rate coefficients (ERCs), chemical abundances, and desorption. Six species were observed experimentally (H _2 O, O _2 , HO _2 , H _2 O _2 , O _3 , and HO _3 ), while six were predicted but not observed in the experiments (H, H _2 , H _3 , O, OH, and H _3 O). Our findings highlight the influence of temperature on chemical equilibria and desorption yields, with certain reaction rates diminishing at 50 K. Among the results were the lists with the ERCs, and the reaction branching ratio obtained by best-fit models can be employed in astrochemical models. Curiously, we observe that the average ERCs for bimolecular collisions decrease by half as the ice temperature increases, varying from 5.8e-25 to 2.9e-25 cm ^3 molecules ^−1 s ^−1 for the ices studied. These results enhance our understanding of the physical chemistry of astrophysical ices under ionizing radiation, providing valuable data for astrochemical models that assess the effects of cosmic radiation on the composition and stability of icy bodies in the solar system and denser and colder regions of the ISM.https://doi.org/10.3847/1538-4357/adc924AstrochemistryLaboratory astrophysicsCosmic raysMolecular reactionsNatural satellites (Solar system) |
| spellingShingle | J. R. C. Silva L. M. S. V. Queiroz L. F. A. Ferrão S. Pilling Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium The Astrophysical Journal Astrochemistry Laboratory astrophysics Cosmic rays Molecular reactions Natural satellites (Solar system) |
| title | Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium |
| title_full | Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium |
| title_fullStr | Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium |
| title_full_unstemmed | Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium |
| title_short | Molecular Evolution of H2O:O2 Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium |
| title_sort | molecular evolution of h2o o2 ices at different temperatures in simulated space environments i chemical kinetics and equilibrium |
| topic | Astrochemistry Laboratory astrophysics Cosmic rays Molecular reactions Natural satellites (Solar system) |
| url | https://doi.org/10.3847/1538-4357/adc924 |
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