Swift Heavy Ion-Induced Chemistry of CH ₃ CN Ices at 10 and 80 K

High Resolution Image Download MS PowerPoint Slide Acetonitrile (CH 3 CN) is a key nitrogen-bearing molecule detected in a variety of astrophysical environments and is considered a potential precursor of prebiotic compounds. The study aimed to investigate the stability and radiation chemistry of 56 Fe 10+ ions at the Grand Accélérateur National d’Ions Lourds (GANIL). In situ FTIR spectroscopy revealed efficient molecular destruction accompanied by the formation of several nitrogen-bearing species, including HCN, H 2 C═C═NH, CH 2 CHNC, CH 3 CH═NH, H 2 C═NH, NCCN, and NH 3 with possible contributions from the C–H such as CH 4 and C–H stretching of HC 3 N and, to a lesser extent, the N–H stretch of ketenimine (H 2 C═C═NH). The apparent destruction cross section of CH 3 CN was found to be (2.3 ± 0.8) × 10 –12 cm 2 at 10 K and (5.6 ± 1.0)×10 –12 cm 2 at 80 K, indicating more extensive radiolytic processing at higher temperatures. Enhanced radical mobility at 80 K promotes hydrogenation and polymerization, leading to a refractory C–N–rich residue, whereas at 10 K intramolecular isomerization dominates. These results demonstrate that swift heavy-ion irradiation of nitrile ices efficiently produces small nitriles, isonitriles, and polyimines of astrochemical interest, supporting the role of CH 3 CN as a hidden precursor to prebiotic organic matter in interstellar and planetary ices.