Wavelength-dependent refractive index of H₂O ice. Panels a and b show the real and imaginary parts of the complex refractive index derived in this paper (H₂O at 30 K) adopting n_700nm = 1.16 (black) and n_700nm = 1.32 (blue) compared to literature values from Hudgins et al. (1993) given by the purple line (H₂O at 40 K), and from Mastrapa et al. (2009), shown by the orange line (H₂O at 25 K). The inset in panel b displays an illustration of the water vibrational modes and their corresponding motion, except the O–H combination mode at 4.5 µm. Each mode is indicated at the top of the bands.