Abstract
Acetone (CH3COCH3) was the first molecule with 10 atoms found in the interstellar medium. This molecule was found towards the hot molecular core Sagittarius B2 (N–LHM) and in the Orion–KL star-forming region towards the hot core. Laboratory data, such as the formation and destruction cross-sections and the half-life of the molecules, combined with theoretical calculations and astronomical observations, can help us to elucidate the processes that occur in the astronomical sources. In this work, we study the radiolysis of acetone ice by 40-MeV 58Ni11 + ions at 16 K. Pure acetone ice was bombarded with nickel ions, which are cosmic ray constituents that are highly efficient at inducing chemical reaction in ices, in order to provide experimental data for a model describing interaction with similar heavy constituents of cosmic rays (with z ≥ 10). The dissociation rate of pure acetone and its half-life in the interstellar medium in close proximity to the solar system and the Galactic Centre due to the main ions (H, He, C, Mg, O, Si, Fe, Ni) are predicted from recorded spectra and the current analysis. The formation of new molecular species by cosmic rays is discussed and the atom budget is analysed. The formation cross-section of species, as well as the penetration depth of some light and heavy ions, are also calculated. We present a discussion on the energy lost and the penetration depth of acetone ice.
Highlights
Acetone (CH3COCH3) has a central C = O structure, a strong bond present in several important molecules of astrophysical and biological interest
We present results concerning the production of new molecules from radiolysis of pure acetone ice, as well as a discussion on the penetration depth and energy loss by cosmic rays in this ice
We have studied the radiolysis of 16-K pure acetone ice by 40-MeV 58Ni11 + ions
Summary
Bennett et al (2007) calculated the vibrational frequencies and band strengths for various species expected to be formed from pure ices of amorphous methanol, irradiated at 11 K by 5-keV electrons This process of electronic energy transfer is similar to that occurring in interstellar ices, in comets and in icy Solar system bodies when irradiated by MeV ions and by secondary electrons produced in this interaction. The photodissociation cross-section value of 1.2 × 10−17 cm was determined, allowing them to estimate the acetone half-life in astrophysical environments such as T Tauri stars, where soft X-rays play an important role in inducing chemical processes in grains. The destruction cross-sections of pure acetone ice and its half-life in the ISM in the proximity of the Solar system and the Galactic Centre corresponding to different projectiles (H, He, C, Mg, O, Si, Fe, Ni) have been estimated from an interpolation of the current data with results from the literature. We present results concerning the production of new molecules from radiolysis of pure acetone ice, as well as a discussion on the penetration depth and energy loss by cosmic rays in this ice
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