2017/03/31 by N. F. W. Ligterink, A. Coutens, Vincent Kofman +8 · 3 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Chemistry #Isocyanate #Low Mass #Molecular Spectroscopy and Structure #Molecule #Organic chemistry #Physics #Protostar #Star formation #Stars #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stx890
published as Mon. Not. R. Astron. Soc. 469 (2017) 2219-2229 · Accepted 2017 April 7. Received 2017 March 26; in original form 2017 January 24. 13 pages, 8 figures
openalex created_date 2017/04/07 · openalex publication_date 2017/04/12 · arxiv created 2017/05/04 · arxiv updated 2018/06/05 · openalex updated_date 2026/08/05
Methyl isocyanate (CH3NCO) belongs to a select group of interstellar molecules considered to be relevant precursors in the formation of larger organic compounds, including those with peptide bonds. The molecule has only been detected in a couple of high-mass protostars and potentially on comets. A formation route on icy grains has been postulated for this molecule but experimental evidence is lacking. Here we extend the range of environments where methyl isocyanate is found and unambiguously identify CH3NCO through the detection of 43 unblended transitions in the ALMA Protostellar Interferometric Line Survey (PILS) of the low-mass solar-type protostellar binary IRAS 16293−2422. The molecule is detected towards both components of the binary with a ratio HNCO/CH3NCO ∼ 4–12. The isomers CH3CNO and CH3OCN are not identified, resulting in upper abundance ratios of CH3NCO/CH3CNO > 100 and CH3NCO/CH3OCN > 10. The resulting abundance ratios compare well with those found for related N-containing species towards high-mass protostars. To constrain its formation, a set of cryogenic UHV experiments is performed. VUV irradiation of CH4:HNCO mixtures at 20 K strongly indicate that methyl isocyanate can be formed in the solid state through CH3 and (H)NCO recombinations. Combined with gas-grain models that include this reaction, the solid-state route is found to be a plausible scenario to explain the methyl isocyanate abundances found in IRAS 16293−2422.