Work

Swift heavy ion processing of CH3CN ices: Structure and implications for Titan’s lower atmosphere nitrile chemistry

Year: 2026

Type: article

Abstract: Swift heavy ion irradiation of pure CH 3 CN ice was investigated to evaluate the influence of the initial ice morphology on its radiolytic evolution under astrophysically relevant conditions. Two deposition protocols were compared: (i) CH 3 CN ice deposited and irradiated at 50 K, and (ii) CH 3 CN ice deposited at 130 K, subsequently cooled to 10 K prior to irradiation, thereby preserving the structural organization established during deposition. In situ FTIR spectroscopy revealed efficient destruction of CH 3 CN and the formation of HCN, HC 3 N, CH 3 NC, NH 3 , and imine-like compounds. The thermally organized ice exhibited a distinct infrared spectral evolution, enhanced destruction, and differences in the stabilization of daughter species compared with the amorphous ice. Destruction cross sections of ( 2.85 ± 0.52 ) × 1 0 − 12 and ( 4.65 ± 0.43 ) × 1 0 − 12 cm 2 were determined for the amorphous and thermally organized ices, respectively. These results demonstrate that the thermal history of CH 3 CN ice, through its influence on the initial ice morphology, strongly affects radical diffusion, recombination, and product formation during irradiation. The present measurements provide benchmark radiochemical data for acetonitrile and establish a basis for future investigations of more realistic nitrile-bearing astrophysical ice analogues relevant to Titan and other outer Solar System environments.

Source: Icarus

DOI: 10.1016/j.icarus.2026.117287