Browsing by Author "Seperuelo Duarte, Eduardo"

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    Chemical reactions in H2O:CO interstellar ice analogs promoted by energetic heavy ion irradiation
    (2022) Barros, Ana; Mejía Guamán, Christian Fernando; Seperuelo Duarte, Eduardo; Domaracka, Alicja; Boduch, Philippe; Rothard, Hermann; Da Silveira, Enio Frota
    H2O:CO, at concentrations of (3:2) and (10:1), was condensed on CsI substrate at 15 K and irradiated with 46 MeV 58Ni11 + ion beam. Radiolysis induced by fast heavy ions was analyzed by infrared spectroscopy (FTIR). The formation of nine molecular species, CO2, H2O2, HCOOH, HCO, H2CO, 13CO2, CH3OH, O3 and C3O2 was observed. For both concentrations, carbon dioxide (CO2), formaldehyde (H2CO), formic acid (HCOOH), and hydrogen peroxide (H2O2) are the most abundant products species, and tricarbon dioxide (C3O2) is much less abundant. Precursor destruction cross sections and formation cross sections of products are determined. The CO destruction cross section for the (3:2) concentration is almost five times higher than that of water, while those for the (10:1) concentration are practically the same. Atomic sputtering yields are estimated for the two ice films, the total mass sputtered is approximately 2.5 × 106 u per impact. These results contribute to figure out the chemical pathways of compounds synthesized from the two most abundant organic species (H2O and CO) observed in the ices of grain mantles of the circumstellar envelopes and interstellar medium. In additional, the finding results reveal that molecular astronomical percentages are comparable to those obtained after 15 eV molec−1 of deposited dose in current experiments compared with the relative concentration of molecules in solid phase observed in MYSO, LYSO, BG Stars, and Comets.
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    Compaction of porous ices rich in water by swift heavy ions
    (2015) Mejía Guamán, Christian Fernando; Ferreira de Barros, Ana Lucía; Seperuelo Duarte, Eduardo; Da silveira, Énio Frota; Dartois, Emmanuel; Domaracka, Alicja; Rothard, Hermann; Boduch, Philippe
    Porous water ice and water ice mixtures H2O:X (X = CO, CO2 and CH4) produced at 15 K, with film thicknesses in the 0.5–1 μm range, were irradiated by swift ions and monitored by mid-infrared spectroscopy (FTIR). The analysis of the evolution of the pure water ice infrared absorption on ion beam dose reveals a strong correlation among three quantities: (i) the absorbance of the most intense band (3250 cm−1), (ii) the wavelength of the maximum absorbance of this band and (iii) the absorbance of the OH-dangling bonds. This correlation is interpreted as indications of the water ice compaction by irradiation: as the beam fluence increases, the ice porosity decreases, the dangling bond peaks collapse and the area and position of the 3250 cm−1 band vary exponentially, all of them evolving with the same compaction cross section (). The linear dependence ( being the electronic stopping power) is observed for both pure and mixed water ices, confirming previous results. We suggests that the infrared absorption A-value varies with dose as during the compaction process ( eV/molec being the effective energy density to eliminate the OH-db, and is a parameter characterizing the porosity). These findings may be used as a diagnostic tool to probe the morphology of water ices occurring in the outer Solar System and in the ISM.