Acetone degradation by cosmic rays in the solar neighbourhood and in the Galactic Centre

• Published in: Monthly notices of the Royal Astronomical Society 2014-11, Vol.444 (4), p.3792-3801
• Main Authors: Andrade, Diana P. P., de Barros, Ana L. F., Ding, Jingjie, Rothard, Hermann, Boduch, Philippe, da Silveira, Enio F.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Chemical compounds; Cosmic rays; Ions; Molecules; Physics; Sciences of the Universe
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stu1519

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.