2018/11/30 by V. M. Rivilla, J. Martín‐Pintado, J. Martín-Pintado +11 · 2 citations
Chemistry · Physics and Astronomy · #Abundance (ecology) #Advanced Chemical Physics Studies #Astrochemistry #Astrophysics #Astrophysics and Star Formation Studies #Chemistry #Dimer #Galaxy #Gas phase #Interstellar cloud #Interstellar medium #Isomerization #Kinetic energy #Mean kinetic temperature #Molecular Spectroscopy and Structure #Molecular cloud #Organic chemistry #Physics #Thermodynamic equilibrium #Thermodynamics #astro-ph.GA
paper · pdf · doi:10.1093/mnrasl/sly228
Accepted in Monthly Notices of the Royal Astronomical Society Letters
arxiv created 2018/11/30 · openalex publication_date 2018/12/03 · arxiv updated 2018/12/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
ABSTRACT We report the first detection in the interstellar medium (ISM) of the Z-isomer of cyanomethanimine (HNCHCN), an HCN dimer proposed as precursor of adenine. We identified six transitions of Z-cyanomethanimine, along with five transitions of E-cyanomethanimine, using IRAM 30m observations towards the Galactic Centre quiescent molecular cloud G + 0.693. The Z-isomer has a column density of (2.0 ± 0.6) × 1014 cm−2 and an abundance of 1.5 × 10−9. The relative abundance ratio between the isomers is [Z/E]∼6. This value cannot be explained by the two chemical formation routes previously proposed (gas phase and grain surface), which predicts abundances ratios between 0.9 and 1.5. The observed [Z/E] ratio is in good agreement with thermodynamic equilibrium at the gas kinetic temperature (130−210 K). Since isomerization is not possible in the ISM, the two species may be formed at high temperature. New chemical models, including surface chemistry on dust grains and gas-phase reactions, should be explored to explain our findings. Whatever the formation mechanism, the high abundance of Z-HNCHCN shows that precursors of adenine are efficiently formed in the ISM.