The normal-incidence spectral reflectance of ice at -7° C has been measured in the range 300–5000 cm<sup>-1</sup>. A Kramers-Kronig phase-shift analysis of the measured spectral reflectance has been employed to provide values of the real and imaginary parts of the refractive index. The resulting values of these optical constants are suitable for use in Mie-theory computations of scattering by ice particles in planetary atmospheres. The optical constants of ice at -7° C are compared in detail with those of liquid water at several temperatures and with those recently determined for ice at -170° C.
Joel W. Schaaf and Dudley Williams, "Optical constants of ice in the infrared," J. Opt. Soc. Am. 63, 726-732 (1973)