Stopping power of ions in the ice films. Left axis and solid lines: Evolution of the electronic stopping power of ions used in the experimental sessions as a function of their penetration depth in a ¹⁴N₂-¹²CH₄ (9:1) IF, modeled with the SRIM code. Right axis and dashed lines: evolution of the nuclear over electronic stopping powers ratio as function of the penetration depths in the IFs. Filled circles indicate the size of the IFs irradiated during the experiments.