New accurate values of the imaginary part, k, of the refractive index of water at T=22° supercooled water at T=-8° and polycrystalline ice at T=-25° are reported. The k spectrum for water in the spectral region 0.65-2.5 µm is found to be in excellent agreement with those of previous studies. The k values for polycrystalline ice in the 1.44-2.50 µm region eliminate the large uncertainties existing among previously published conflicting sets of data. The imaginary part of refractive index of supercooled water shows a systematic shift of absorption peaks toward the longer wavelengths compared with that of water at warmer temperatures.

L. Kou, D. Labrie, P. Chylek, "Refractive indices of water and ice in the 0.65-2.5 µm spectral range," Appl. Opt.,32, 3531-3540 (1993).