Aliphatic C-H destruction cross section σ_d as function of the electronic cross section S_e for the different ion/energy irradiation of the a-C:H samples. The values corresponding to the C-H stretching modes at 3.4 μm (in black), the CH₂ bending mode at 6.85 μm (in red), and the CH₃ bending mode at 7.25 μm (in green) are represented for both a-C:H 1 (filled dots) and a-C:H 2 (squares). The best fit and the fits with extreme values of α are plotted (the corresponding values of α are written). The coloured arrows represent the S_e range of the few major cosmic ray elements.