The infra-red spectrum of water

The Lambert absorption coefficient of water has been measured in the far infra-red spectral region 800 to 50 cm-1. The results, along with earlier measurements in the near infra-red, provide values of the imaginary part k of the refractive index over the spectral range 4400 to 50 cm-1. Kramers-Kronig techniques have been used to obtain values of the corresponding real part n of the refractive index over this spectral range. The values of these constants provide a complete quantitative description of the optical properties of water in the infra-red.