Frequency dependence in a liquid's complex refractive index measured with infrared spectroradiometry

A laboratory measurement of wavelength dependence in the real n(lambda) and the imaginary k(lambda) parts of a liquid's complex refractive index is pr esented. A known heat flow through the liquid-gas interface is generated wh ile a high-resolution infrared radiance spectrum is taken simultaneously. W avelength variations of the absorption coefficient allow the emerging radia tion to sense subsurface temperature gradients. This technique is valid onl y at intervals at which the absorption coefficient is sufficiently low to a llow subsurface temperatures to be measured. Knowledge of a liquid's therma l conductivity, specific heat, and light transmission spaed is required. Me asurement error depends on radiance measurement error and the minimization of atmospheric parameters.