Examinando por Autor "Carrascosa, H."

Mostrando 1 - 3 de 3

Acceso Abierto
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, Cristobal; Jimenez-Serra, Izaskun; 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.
Acceso Abierto
Infrared spectroscopy of astrophysical ice analogues at oblique angles
(Oxford University Press, 2025-02-26) González Díaz, Cristobal, C.; Carrascosa, H.; Muñoz Caro, G. M.; Agencia Estatal de Investigación (AEI)
In astrochemical exploration, infrared (IR) spectroscopy is vital for understanding the composition and structure of ice in various space environments. This article explores the impact of incident angles on IR spectroscopy, focusing on molecular components present in interstellar and circumstellar ice mantles such as CO, CO 2 , H 2 O, CH 3 OH, NH 3 , CH 4 , H 2 S. The experiment involves changing the angle at which the IR beam hits the surface used for ice deposition. It is important to measure the density of the ice layer accurately, especially for experiments that involve using different angles in IR spectroscopy. Furthermore, the experimental methodology allowed us to derive the effective refraction index values in the IR range for each ice component. Existing corrections typically consider geometric configurations but o v erlook the refractiv e inde x of the ice ( n ), a factor dependent on ice composition. The study reveals that the incident angle and the refractive index, determine the path length of the IR beam across the ice sample. This insight challenges conventional corrections, impacting the integrated absorption values of the IR bands and column densities. In addition, for certain ice components, variations in the incidence angle affect the longitudinal (LO) and transverse (TO) optical modes of the ice, leading to observable changes in the IR band profiles that provide information on the amorphous or crystalline structure of the ice. The practical implications of this work apply to experimental setups where normal IR measurements are unfeasible. Researchers using, for example, the standard 45 ◦ angle for IR spectroscopy, will benefit from a more accurate estimation of ice column density.
Acceso Abierto
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, Emmanuel; 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.