Left: OH dangling bond baseline corrected absorbance spectra for different Ne⁶⁺ irradiation fluences (from top to bottom: 0, 5, 10, 20, 40, 60, 80, 100, 200, 400, 600, 800, 10³, 2 × 10³, 4 × 10³, 6 × 10³ in units of 10⁹ ions/cm²). The two bands at about 3720 and 3695 cm^-1 correspond to 2- and 3-coordinated water molecules, respectively (see Sect. 4.3 for details). Right: evolution of the OH-db integrated absorbance as a function of the fluence (squares) and corresponding fitted exponential decay law (triangles).