The Optical Constants of Water and Sea Water in the Infrared

Abstract

Abstract : Optical Constants of Water in the Infrared: The results of earlier studies of reflection and absorption in various spectral regions are reviewed and then used to provide values of the complex index of refraction N = n + ik of water at 27 C in the spectral range 1/5000-10 cm, corresponding to wavelengths in the range 2 micrometer to 1 mm. Values of n, k, and the Lambert absorption coefficient alpha, which are presented graphically and in tabular form, should prove useful in studies of the scattering of infrared radiation by water droplets in the atmosphere and in studies of radiative heat balance at water surfaces. Optical Properties of Sea Water in the Infrared: Quantitative measurements of the ratio of the infrared spectral reflectance of standard sea water at near-normal incidence to the corresponding spectral reflectance of pure water at 27 C were made. The infrared spectral reflectance of standard sea water was determined from the measured ratio and the known optical constants for pure water. The real n(v) and the imaginary k(v) parts of the complex index of refraction of standard sea water were then determined by Kramer-Kronig methods. The results obtained for the standard sea water are compared with previous results obtained for pure water and with previous studies of sea water.