Proyecto de Investigación: PROCESOS EN HIELOS ASTROFISICOS
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AYA2017-85322-R
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2-aminooxazole in Astrophysical Environments: IR Spectra and Destruction Cross Sections for Energetic Processing
(IOP Science Publishing, 2021-03-11) Maté, B.; Carrasco Herrera, R.; Timón, V.; Tanarro, I.; Herrero, V. J.; Carrascosa, H.; Muñoz Caro, G. M.; González Díaz, C.; Jiménez Serra, I.; Agencia Estatal de Investigación (AEI); 0000-0002-5478-8644; 0000-0002-1217-6834; 0000-0002-1888-513X; 0000-0002-7456-4832; 0000-0002-2885-4847; 0000-0001-7003-7368; 0000-0002-8789-9148; 0000-0003-4493-8714; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
2-aminooxazole (2AO), a N-heterocyclic molecule, has been proposed as an intermediate in prebiotic syntheses. It has been demonstrated that it can be synthesized from small molecules such as cyanamide and glycoaldehyde, which are present in interstellar space. The aim of this work is to provide infrared (IR) spectra, in the solid phase for conditions typical of astrophysical environments and to estimate its stability toward UV photons and cosmic rays. IR (4000–600 cm−1) absorption spectra at 20 K, 180 K, and 300 K, IR band strengths, and room-temperature UV (120–250 nm) absorption spectra are given for the first time for this species. Destruction cross sections of ≈9.5 10−18 cm2 and ≈2 10−16 cm2 were found in the irradiation at 20 K of pure 2AO and 2AO:H2O ices with UV (6.3–10.9 eV) photons or 5 keV electrons, respectively. These data were used to estimate half-life times for the molecule in different environments. It is estimated that 2AO could survive UV radiation and cosmic rays in the ice mantles of dense clouds beyond cloud collapse. In contrast, it would be very unstable on the surface of cold solar system bodies like Kuiper Belt objects, but the molecule could still survive within dust grain agglomerates or cometesimals.
Photon-induced desorption of larger species in UV-irradiated methane ice
(Oxford Academics: Oxford University Press, 2020-02-19) Carrascosa, H.; Cruz Díaz, G. A.; Muñoz Caro, G. M.; Dartois, E.; Chen, Y. J.; Agencia Estatal de Investigación (AEI); Ministry of Science and Technology, Taiwan (MOST); National Aeronautics and Space Administration (NASA); Carrascosa, H. [0000-0002-2885-4847]; Chen, Y. J. [0000-0003-4497-3747]; Dartois, E. [0000-0003-1197-7143]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
At the low temperatures found in the interior of dense clouds and circumstellar regions, along with H2O and smaller amounts of species such as CO, CO2 or CH3OH, the infrared features of CH4 have been observed on icy dust grains. Ultraviolet (UV) photons induce different processes in ice mantles, affecting the molecular abundances detected in the gas phase. This work aims to understand the processes that occur in a pure CH4 ice mantle subjected to UV irradiation. We studied photon-induced processes for the different photoproducts arising in the ice upon UV irradiation. Experiments were carried out in ISAC, an ultra-high vacuum chamber equipped with a cryostat and an F-type UV lamp reproducing the secondary UV field induced by cosmic rays in dense clouds. Infrared spectroscopy and quadrupole mass spectrometry were used to monitor the solid and gas phases, respectively, during the formation, irradiation and warming-up of the ice. Direct photodesorption of pure CH4 was not observed. UV photons form CHx· and H· radicals, leading to photoproducts such as H2, C2H2, C2H6 and C3H8. Evidence for the photodesorption of C2H2 and photochemidesorption of C2H6 and C3H8 was found; the latter species is so far the largest molecule found to photochemidesorb. 13CH4 experiments were also carried out to confirm the reliability of these results.
