Methods previously developed for studying the optical properties of solid metals were modified to permit their use for studying liquid Hg and liquid Ga. Reflectivities were measured at an angle of incidence of 45° at glass-metal, quartz-metal, and NaCl-metal interfaces in the wavelength range of 0.23 µ to 13 µ. In a second type of experiment the phase change accompanying reflection at normal incidence at a mica-metal interface was measured in the range 0.4µ to 0.87µ. In this shorter wavelength range the two measured quantities, reflectivity and phase change, were used to compute the optical constants <i>n</i> and <i>k</i>. The values thus obtained agreed to within the experimental accuracy with those calculated with the Drude free electron theory. The fact that the experimentally determined reflectivity for the complete range of 0.23 µ to 13 µ agreed closely with that predicted by the Drude theory strongly suggests that the theory applies throughout this entire wavelength range.
L. G. SCHULZ, "Experimental Study of the Optical Properties of Liquid Hg and Liquid Ga in the Wavelength Range of 0.23µ to 13µ," J. Opt. Soc. Am. 47, 64-69 (1957)