Optical constants of carbon dioxide ice

Laboratory measurements of the absorption coefficient and refractive index of solid CO2 are reviewed for all parts of the electromagnetic spectrum from the ultraviolet to the microwave with emphasis on values for temperatures above 77 K. The available measurements in some cases require reinterpretation. A compilation of the spectral absorption coefficient is made for 52-nm to 160-nm wavelength, and the complex refractive index is then computed by Kramers-Kronig analysis. The uncertainty in imaginary refractive index is discussed; it varies greatly with wavelength. The real part of the refractive index is close to 1.4 for all parts of the spectrum except near strong absorption bands and is accurate to + or - 0.05 outside those bands. No measurements of absorption are available for 180-330-nm, 1.0-2.5-micron, and 25-micron-25-mm wavelength, except in the strong narrow absorption lines.