# Swift Heavy Ion-Induced Chemistry of CH3CN Ices at 10 and 80 K

## TL;DR

This study explores how acetonitrile ice changes when exposed to heavy ions at low temperatures, revealing new nitrogen-rich compounds relevant to space chemistry.

## Contribution

The paper presents new insights into the radiolytic processing of acetonitrile under swift heavy-ion irradiation at 10 and 80 K.

## Key findings

- In situ FTIR spectroscopy detected the formation of nitrogen-bearing species like HCN, H2C=C=NH, and NH3.
- Destruction cross sections of CH3CN were higher at 80 K, indicating more radiolytic processing at elevated temperatures.
- At 10 K, intramolecular isomerization dominates, while at 80 K, hydrogenation and polymerization lead to C–N–rich residues.

## Abstract

Acetonitrile (CH3CN) 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 56Fe10+ 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, H2CCNH, CH2CHNC, CH3CHNH, H2CNH,
NCCN, and NH3 with possible contributions from the C–H
such as CH4 and C–H stretching of HC3N and, to a lesser extent, the N–H stretch of ketenimine (H2CCNH). The apparent destruction cross section
of CH3CN was found to be (2.3 ± 0.8) × 10–12 cm2 at 10 K and (5.6 ± 1.0)×10–12 cm2 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 CH3CN as a hidden precursor to prebiotic organic matter in interstellar
and planetary ices.