Browsing by Author "Da Silveira, Enio Frota"

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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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    Radiolysis of ices by cosmic-rays: CH4 and H2O ices mixtures irradiated by 40 MeV 58Ni11+ ions
    (2020) Mejía Guamán, Christian Fernando; Barros, Ana; Rothard, Hermann; Boduch, Philippe; Da Silveira, Enio Frota
    Physico-chemical modifications induced by swift heavy ions on methane-water (CH4:H2O) ices at 15 K are analyzed. Ice films, at concentrations of (1:3) and (1:15), were irradiated by 40 MeV 58Ni11+ ions. Fourier transform transmission spectroscopy in the mid-range was used to monitor the evolution ices at 15 K as a function of projectile fluence. New IR bands appearing for the irradiated (CH4:H2O) (1:3) ice are attributed to the synthesized molecules: C3H8, HCO, H2CO, CO, CO2, H2O2, HCOOH, CH3OH, C2H5OH, and CH3CHO. For the irradiated (CH4:H2O) (1:15) ice, the abundances of the compounds containing two carbons atoms are lower than those for the (1:3) ice; in contrast, CH3OH and H2O2 abundances increase when compared to the values obtained with the (1:3) ice. After irradiation, the ices were warmed up until 110 K, when the IR spectra reveal features of complex organic molecules. The destruction and formation cross sections and the sputtering yields of the ice mixtures are estimated. These findings provide possible pathways for the occurrence of compounds rich in C, O, and H, which are indeed observed in the cold regions of the universe such as ices in grain mantles of the interstellar medium and circumstellar envelopes. © 2020. The American Astronomical Society. All rights reserved.