Literature data on the broadband (THz-IR) optical properties of H₂O ices as compared to the inferred model (Eq. (3) and Appendix A, Tables A.1-A.3). (a)-(c): literature data on the refractive index n and absorption coefficient α (by field, in both the linear and logarithmic scale), respectively, for the Ih ice overlapped with the model. The legend indicates the ice deposition (or warming-up) temperature and the corresponding reference. The bold text denotes the densest ice samples. The vertical arrows indicate the absorption bands assigned to the different vibrational modes. (d)-(f) and (g)-(i): similar datasets for the Ic and ASW ices, respectively.