Chemical reactions in the nitrogen–acetone ice induced by cosmic ray analogues: relevance for the Solar system

Abstract

b s e r v a t o r i o d o V a l o n go, Ladeira ABSTRACTThe radiolysis of a 10:1 nitrogen:acetone mixture, condensed at 11 K, by 40 MeV 58 Ni 11+ ions is studied. These results are representative of studies concerning solar system objects exposed to cosmic rays. In the Kuiper Belt, region of Trans-Neptunian Objects (TNOs), acetone, N2 and other small molecules were detected and may be present on icy surfaces. Bombardment by cosmic rays triggers chemical reactions leading to synthesis of larger molecules. In this work, destruction cross sections of acetone and nitrogen molecules in solid phase are determined from a sequence of infrared spectra obtained at increasing ion beam fluence. The results are analyzed and compared with those of previous experiments performed with pure acetone. It is observed that the N2 column density decreases very fast, suggesting that nitrogen quickly leaves a porous sample under irradiation. The behavior of acetone in the mixture confirms that the ice formed by deposition of the vapor mixture is more porous than that of pure acetone ice. The most abundant molecular species formed from the mixture during irradiation are: C3H6, C2H6, N3, CO, CH4 and CO2. Some N-bearing species are also formed, but with low production yield. Comparing with pure acetone results, it is seen that dissolving acetone in nitrogen a ffects the formation cross sections of the new species: CH4, CO2 and H2CO, for example, have formation cross section smaller than the respective values for irradiated pure acetone, while those for CO and C2H6 species are higher. This fact can explain the presence of C2H6 even in regions on Pluto where CH4 is not pure, but diluted in a N2 matrix together with less abundant species. These results also show the formation of more complex molecules, such as HNCO, acetic acid and, possibility, glycine. The production of these complex molecules suggests the formation of small prebiotic species in objects beyond Neptune from acetone diluted in a N 2 matrix irradiated by cosmic rays. Formation cross sections for the new formed species are determined.

Fragmentation dynamics of doubly charged camphor molecule following C 1s Auger decay

“…Investigating such interactions has profound implications in obtaining insights into processes such as radiation damage in biology and the stability of molecular aggregates like ices in interstellar medium. 1,2 When a core-level electron in a molecule is excited, a valence electron fills the core hole resulting in either photoemission or the removal of one or more partner electrons from the system leading to an Auger decay. Auger processes are the dominant multiple ionisation channels in light atoms, even when they are a part of larger aggregates, like molecules.…”