Sample d: IR spectrum from 5000 to 600 cm^-1 of N₂:CH₄; 23μm thickness (top). From bottom to top, initial deposited ice sample (red), after a fluence of 1.7 × 10¹¹ ions cm^-2 (purple) and 2.2 × 10¹³ ions cm^-2 (green). The final dose is 18 eV molecule^-1. The final spectra indicates the presence of solid water. Spectra were shifted for clarity. Evolution of the column density of selected molecules in the sample during the irradiation as a function of the deposited dose (bottom). As a result of a technical incident, there is no point between 1 and 18 eV molecule^-1.